GroupDIY

Project Specific Discussions => Dynamic Processors => Topic started by: fripholm on June 16, 2017, 12:00:44 PM

Title: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 16, 2017, 12:00:44 PM
(http://www.ttx-sound.net/foren/IMG_7840.JPG)

As requested, this is the support thread for my Zener Limiter boards.

The boards are available at the moment! I'm also offering my bipolar PSU board. If you're interested in either the Limiter and/or PSU boards, email me for details to fripholm(AT)gmail(DOT)com - make sure to include your Groupdiy name and your country.

Black Market thread: FS: PCBs for TG1 Zener Limiter (https://groupdiy.com/index.php?topic=65505.0)
Manual, updated 2017/11/06 (Bypass relay wiring added): TTx Zener Guide (http://www.dropbox.com/s/9kkpxcxr0hebzp0/TTx%20Zener%20TG%20Guide.zip?dl=0)

The guide includes BOM, schematic, an optional DIY PSU, general build and fine tuning instructions, a front panel design etc. - I will update that archive occassionally, when issues come up that I think are worth to be included or need to be corrected. Please make sure you have downloaded and read the most recent guide before posting here for support.

BTW: the PSU I'm offering is the same that is mentioned in the guide as a PCB for self-etching. The layout, BOM and schematics are identical.

Feel free to also share stories and/or pictures of your builds, finished or while still in progress :D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 16, 2017, 12:38:24 PM
I will start off this thread by replying to orangechili's post from the Black Market thread: https://groupdiy.com/index.php?topic=65505.msg838542#msg838542

Quote
I built both boards with a 22ohm resistor from the output + to the primary high on the output transformer. I may up the resistor value and see if that helps. It's like a big jump near the end of rotation on the output and input pots.

Then there's the meter that basically stays put after getting hit with compression...

What's hard is I have the same issue on both boards.

hmmm, none of my builts have showed the issues you describe.  :(

Regarding the big volume jump, does this happen, when the unit is in bypass or with the compressor engaged? The I/O pots should have no function when in bypass - if they have, some of the wiring in the bypass section may be wrong. I've just checked with the guide, that the drawings are correct and yes, they should be.

Can you hear the compressor's release action when compressing audio or isn't it releasing at all like the meter? Do you have an oscilloscope to check a few voltages while compressing audio?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 03:00:34 PM
After further examination I believe the compression circuit in both channels is not working right. That may explain the meter weirdness. THD and bypass seem to work decent, the loud rise of volume pops was just me talking into a mic and it clipping in comp and limit modes with the controls cranked...

I don't really hear it compressing much on either channel. As I raise input and output controls the volume just rises, not really hearing compression although the meter stays stuck and dimes after signal is inputed in comp mode . I'm gonna go through the wiring in the compression circuit again(rotary switches, etc)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 03:20:49 PM
And yes the input and output controls have no function in bypass mode.

Re-checking compression wiring now(mode, attack, release) and will report back
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 03:35:25 PM
Checked the mode, sc high pass, attack and release off board wiring and all correct according to the diagram in the guide. I was hoping for there to be an issue in the mode wiring which seems like it would cause the issue I'm experiencing but no luck...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 03:48:10 PM
I should mention I used a standard pot for the release control without the auto release function. I also connected the input transformer secondary ground to the open ground point where the open auto release pads are. It all returns to chassis ground(verified with my continuity meter)

I'd be curious to see if others have built these and are having a similar issue
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 16, 2017, 04:13:27 PM
The release pot is in series with R51 that goes to ground when auto release is OFF or not used, like in your case. When this connection doesn't exist, the control voltage doesn't have a path to ground and gets stuck - which might explain your issue.

Check if the middle pad of the auto release is jumpered to ground next to it.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 04:50:46 PM
The middle auto release pad does not jumper to ground. I was probing around looking for an open ground point on the board when I found the open 'auto release pad'. I'll see if moving the Input Tx's secondary low wire to a different ground point fixes the issue.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 05:03:29 PM
I moved the wire to another ground point. Still the same as before. It seems like it's barely compressing at all while looking at my daw's meter. I notice a tiny bit of peak reduction in the limit mode with the input and output controls all the way up.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 16, 2017, 05:16:17 PM
No, it's not the input transformer wire that needs to be moved. The middle pad of AUTO RELEASE (which is the ground side of R51) needs to be connected to ground.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 05:44:22 PM
Ok, thank you for that! The meter now works as expected!!! I'm going to start going through the calibration process. I'm noticing a ton of distortion in THD mode on both channels. If you or someone has a video of one of your units working that would be helpful as well.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 16, 2017, 05:50:14 PM
Any recommended values for R86 and R87 for use with a 4:1 input transformer would be greatly appreciated as well! I'm noting quite a bit of  volume reduction in bypass modes with the 4:1 step-down
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on June 16, 2017, 07:29:20 PM
Just when I was about to ask some questions in the BM  thread you opened this build thread! Fantastic! Thumbs up!

I'm in the process of working on dual channel TTx TG1.
I've stuffed boards except putting resistors that need calibrating. I've omitted hold control but have resistor in place of where it should go if basic compression works as it should and I plan to add it later. My build has no bypass and no input transformer - I permanently connected input to the board and jumpered bypass switch pads in permanent ON position. I have relay board near in/out connectors that will handle bypassing.

Now my issue is that both channels distort heavily in any mode. No compression at all! I've triple checked wiring (especially around HPF and Mode switches) and it seems okay. Meter is dead also.
Then I went to cross reference my build with schematics from Fester's TG1. I checked voltage on D2 and D4 input and it's around 13vdc. In Fester's that would be T_B. and T_C and they should be 10.6vdc.
Also, on Q1 emitter there's 6.8vdc (don't know what should expect here)
I had no more time to investigate further...

It's Murphy's law that you find your mistake just after asking for help!
I found what I did wrong - diodes D6 and D7 were orientated wrong. Now it's working almost as it should. I hear compression and limiting. THD mode is really distorted! I was expecting less distortion but it's cool.
I still have to go through calibration. Drivers for my oscilloscope are quirky and I have to fix that in order to go further.
But before I must say that I hear a lot of white(ish) noise when unit is compressing. Maybe it's too much compression that's pulling out this noise. I'll get back to that after I calibrate.

I'm still running my unit with unbalanced input. Is there anything I should change if I decide to leave it unbalanced? Maybe add an input pad?
If I decide to use 2:1 transformer what impedance should I go for?

Fripholm, during the hunt for error a BIG BIG help would be if you could publish pcb's silkscreen layer or hi-res photo of the board so we can all read component designations. Once the board is stuffed it's almost impossible to find certain components since they cover the silkscreen (yeah... I forgot to scan the board before stuffing... dohh me...)

:)

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 17, 2017, 02:13:22 AM
Any recommended values for R86 and R87 for use with a 4:1 input transformer would be greatly appreciated as well! I'm noting quite a bit of  volume reduction in bypass modes with the 4:1 step-down

I've already answered that in the Black Market thread, yesterday:

Quote
try 1.8k and 2.2k for R86 and R87, respectively.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 17, 2017, 03:35:46 AM
OK, I've updated the manual with infos about omitting the Auto Release function and added the board's silkscreen layer for reference. Just re-download the ZIP archive linked  above in the first post.

Recently I have finished upgrading my stereo unit with 24-way stepped attenuators for input and output (Elma type 04). The resistor values I'm using for the switches have been added to the guide as well.


I'm still running my unit with unbalanced input. Is there anything I should change if I decide to leave it unbalanced? Maybe add an input pad?

If you have Fester's schematic, you could use the resistor values from the original for the input pad. It gives about 9~10dB attenuation. The component numbers are R78, R79, R80 and cap C24, which translates to R1, R2 and C3 on my board. You just have to connect Fester's R80 in series to my C3 (changed to 150p) for the same 'frequency characteristic correction' as there's no equivalent for the original R80 on my boards - although the correction itself is still there.

Using the input pad should also lower the amount of distortion. However, don't expect THD mode to be subtle - it's brutally awesome 8)

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: innercityman on June 17, 2017, 06:01:37 AM
Really nice,
I was waiting for this support thread since I bought my pair of TG1 pcbs. Now I'll be more confident on starting building it up.

Thank you !
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 17, 2017, 01:50:31 PM
Hi Fripholm,

Thank you so much! Sorry I missed your answer in the BM thread
Quote
 try 1.8k and 2.2k for R86 and R87, respectively.


That definitely made it louder in bypass mode with the 4:1 input TX. I'm still about 3db quieter in my daw though. Is there another value(s) I can try to gain that 3db back? Getting closer!

I'm trying to use s(m)exoscope to do the CV fine tuning but notice no change in the waveform view when turning the trimmer. I've tried adjust the waveform view specs etc. Is there a good oscilloscope software someone can recommend for a mac?

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mro on June 17, 2017, 02:23:00 PM
maybe https://www.meldaproduction.com/MOscilloscope ?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 17, 2017, 02:33:47 PM
That definitely made it louder in bypass mode with the 4:1 input TX. I'm still about 3db quieter in my daw though. Is there another value(s) I can try to gain that 3db back? Getting closer!

I'm trying to use s(m)exoscope to do the CV fine tuning but notice no change in the waveform view when turning the trimmer. I've tried adjust the waveform view specs etc. Is there a good oscilloscope software someone can recommend for a mac?

Maybe you're losing dBs through your output transformer? Is it a 1:1? How much quieter is the signal when you just connect a cable from output to input on your audio interface?

R86 and R87 just form a simple voltage divider. I'd recommend you temporarily try a 5k trimmer or pot in place of R86 and R87. Adjust the trimmer/pot for unity gain, carefully remove it and measure both halves - find resistors with the closest measured values; there you have your new R86 and R87.

S(m)exoscope should get you close enough. Set the TIME knob at 0.002 or even lower.

AFAIK, MOscilloscope can't be set to display a longer timeline.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 17, 2017, 03:25:49 PM
Thanks for the oscilloscope tips guys! I managed to use the trial version of blue cat oscilloscope multi and get the CV tuning calibrated with that in the loop mode.

The output tx is 1:1 600ohm:600 ohm
My input tx is 10k:600 ohm

I'll try the 5k trimmer and report back what values i get. I figure it will be helpful for anyone who wants to try a 4:1 on the input iron.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on June 17, 2017, 05:07:27 PM
I'm in the process of calibrating my dual unit.
It's been slow since I don't have a lot of spare time.

What I noticed is that I have a lot of noise, both hum on 50hz and pink noise when going straight to output transformer without any series load. My output transformers are 10k:10k edcor. If I strap 100R to primary then the noise drops. I tried lower values like 22r and 47r but they don't work in my case. Also I need to figure out what is the best way to ground the unit. Usually I go for pin 1 to chassis but it seems that going unbalanced in likes better if I ground the pcb from pin 1 and remove pin1 to chassis link.
But I'm still reluctant if I should stay unbalanced or if I should get some input transformers...
And I'm thinking I should try 600:600 transformer for output... but that's a drag since I already mounted 10k edcors in chassis and wired them.

Soundwise, this compressor is rough. Sounds fantastic!

:)

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Rob Flinn on June 17, 2017, 08:45:16 PM
I'm in the process of calibrating my dual unit.
It's been slow since I don't have a lot of spare time.

What I noticed is that I have a lot of noise, both hum on 50hz and pink noise when going straight to output transformer without any series load. My output transformers are 10k:10k edcor. If I strap 100R to primary then the noise drops. I tried lower values like 22r and 47r but they don't work in my case. Also I need to figure out what is the best way to ground the unit. Usually I go for pin 1 to chassis but it seems that going unbalanced in likes better if I ground the pcb from pin 1 and remove pin1 to chassis link.
But I'm still reluctant if I should stay unbalanced or if I should get some input transformers...
And I'm thinking I should try 600:600 transformer for output... but that's a drag since I already mounted 10k edcors in chassis and wired them.

Soundwise, this compressor is rough. Sounds fantastic!

:)

Luka

You would more normally be using a 10k:10k on input and something like a 600:600 on an output.  Hi  Z in & Low Z out
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 18, 2017, 06:08:40 AM
What I noticed is that I have a lot of noise, both hum on 50hz and pink noise when going straight to output transformer without any series load. My output transformers are 10k:10k edcor. If I strap 100R to primary then the noise drops. I tried lower values like 22r and 47r but they don't work in my case.

Are you sure it's pink noise you're getting, not white?

The (optional) series resistor has nothing to do with noise, it's there to prevent the output stage from oscillating (when this happens, it sounds like tuning an old radio). Your 100R might be large enough for dropping the audio signal as well as the noise, so you won't improve anything there.

The circuit itself is very noisy by today's standards. It's much noisier than my 1176 for example for similar in / out and compression levels, but it's still workable. From my simulations most of the noise comes from the inherent high impedance of the Zener pairs, so there's no way to lower it - but this noise is WHITE, not pink!

You shouldn't be getting 50Hz hum, however. Try shorting the input and see if it goes away. Going un-balanced into the unit can pick up noise like this but you may also have a ground loop somewhere. My units do not hum at all.

These are the noise plots of both the 1176 (purple) and one of my Zeners (white). Input signal on both is an 800Hz sine wave at 0 dBu with 4dB of compression, output levels adjusted to be the same going back into the audio interface. The spikes at 50, 100 and 150 Hz are from the 1176.

(http://www.ttx-sound.net/foren/1176vsZener.JPG)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on June 18, 2017, 12:27:44 PM
This is becoming a great resource! I notice a little more white noise in one channel than the other but its within an acceptable range.

I do notice a tiny difference between comp and lim modes between the channels. In one of the limit modes it doesn't compress as hard as the other channel. Fripholm, do you know what the AOT resistors for comp and limit would be located on your boards? (AOT 3 &4, 5 & 6 on the other build here)

I also notice a TON of compression even with the 4:1 step down transformer so tweaking those AOT resistors or adding the input pad may help me there. THD mode is way louder than comp and limit modes. I'm already at 20db compression on my meter with the input control up halfway. I know this thing likes to squash things to oblivion, I just want to see if there's a way to control it a little bit more.

It sounds amazing btw!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on June 18, 2017, 01:37:08 PM
Are you sure it's pink noise you're getting, not white?

It's white! Sorry!

Quote
The (optional) series resistor has nothing to do with noise, it's there to prevent the output stage from oscillating (when this happens, it sounds like tuning an old radio). Your 100R might be large enough for dropping the audio signal as well as the noise, so you won't improve anything there.

I have probed signal from various points (before resistor, before transformer, after the transformer) and it's definitely not dropping any level with 100r. I'll try to lower the value a bit. I went from 47r to 100r - haven't tried some values in between!

Quote
The circuit itself is very noisy by today's standards. It's much noisier than my 1176 for example for similar in / out and compression levels, but it's still workable. From my simulations most of the noise comes from the inherent high impedance of the Zener pairs, so there's no way to lower it - but this noise is WHITE, not pink!

You shouldn't be getting 50Hz hum, however. Try shorting the input and see if it goes away. Going un-balanced into the unit can pick up noise like this but you may also have a ground loop somewhere. My units do not hum at all.

I need to work on it a bit more. I did suspect it's a ground loop. Just had no time to work on it more.

Quote
These are the noise plots of both the 1176 (purple) and one of my Zeners (white). Input signal on both is an 800Hz sine wave at 0 dBu with 4dB of compression, output levels adjusted to be the same going back into the audio interface. The spikes at 50, 100 and 150 Hz are from the 1176.

(http://i1094.photobucket.com/albums/i455/fripholm/1176vsZener.jpg)

Thanks for those plots!
I had my 50hz at around -80dbFS when measured in computer. But I'm sure I'll fix that.
White noise was at about -95 to -100dbFS (I don't remeber exactly)

I'm out of town until tomorrow so I have to wait a bit to continue debugging this thing.
But it's worth it! I've already built couple 1176's, pye comp, prr176, la-4 and clx160vu and this comp is fine complement in my arsenal! :) :)

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 18, 2017, 02:37:46 PM
I do notice a tiny difference between comp and lim modes between the channels. In one of the limit modes it doesn't compress as hard as the other channel. Fripholm, do you know what the AOT resistors for comp and limit would be located on your boards? (AOT 3 &4, 5 & 6 on the other build here)

I also notice a TON of compression even with the 4:1 step down transformer so tweaking those AOT resistors or adding the input pad may help me there. THD mode is way louder than comp and limit modes. I'm already at 20db compression on my meter with the input control up halfway. I know this thing likes to squash things to oblivion, I just want to see if there's a way to control it a little bit more.

AOT3 is R40 on my boards and AOT5 matches R39. According to Fester's descriptions, AOT4 and 6 were not used in the TG1, so I omitted them.

I've already taken measures to raise the threshold a bit, but you're right; it still is a lot of compression. R56 (for THD adjust) is also part of this, as it somehow adjusts the output level. Remember, this is a feedback compressor and more level means more compression. You have to find some kind of middle way (don't know if this is the right term in English) between distortion, noise and output level. I didn't have to mess with AOT3 or 5 on my stereo unit. It tracked pretty well from the beginning - maybe it was just luck, I don't know...

The output level of your audio interface into the Zener is also important; maybe it's set very high? Mine is set to +13dBu and with the input control up halfway I have about 12~16dB of compression with a 2:1 input iron.

THD mode basically shorts the input to the sidechain and no compression occurs anymore - what had been tucked down by 20dB with compression now becomes 20dB louder - and distorted. You just have to keep this in mind when switching THD mode in...  :P
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on June 24, 2017, 10:48:07 PM
Hey guys, I'm having an issue where my V+ stays at 28V for about 2-3 seconds, and then drops significantly. If I disconnect R75, then my V+ stays constant at 28V.  Could this be related to current? Or could this have something to do with faulty transistors at Q13/Q12?

Thanks!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on June 25, 2017, 03:25:03 AM
You may have confused the PNP (Q12) and NPN (Q13) transistors? Check their orientation as well...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mrscary on June 29, 2017, 09:12:45 AM
Does anyone have a mouser cart for this one? :D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on June 29, 2017, 03:15:57 PM
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=43808877-780f-4c00-b8a5-f1825d02c11d

I would double check it and also make sure that nothing is now on back order. This is what I used initially and I'm pretty sure I didn't forget anything.

I do not believe I added parts for the hold control option.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: innercityman on June 30, 2017, 01:39:11 AM
Quote
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=43808877-780f-4c00-b8a5-f1825d02c11d

I would double check it and also make sure that nothing is now on back order. This is what I used initially and I'm pretty sure I didn't forget anything.

Big thanks for that !
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mrscary on June 30, 2017, 12:27:05 PM
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=43808877-780f-4c00-b8a5-f1825d02c11d

I would double check it and also make sure that nothing is now on back order. This is what I used initially and I'm pretty sure I didn't forget anything.

I do not believe I added parts for the hold control option.

Thanks!

Paul

Thanks so much! Wow this makes things so much easier :D

This is for 2 boards, right?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on June 30, 2017, 01:08:27 PM
I'm in the process of calibrating my dual unit.
It's been slow since I don't have a lot of spare time.

What I noticed is that I have a lot of noise, both hum on 50hz and pink noise when going straight to output transformer without any series load. My output transformers are 10k:10k edcor. If I strap 100R to primary then the noise drops. I tried lower values like 22r and 47r but they don't work in my case. Also I need to figure out what is the best way to ground the unit. Usually I go for pin 1 to chassis but it seems that going unbalanced in likes better if I ground the pcb from pin 1 and remove pin1 to chassis link.
But I'm still reluctant if I should stay unbalanced or if I should get some input transformers...
And I'm thinking I should try 600:600 transformer for output... but that's a drag since I already mounted 10k edcors in chassis and wired them.

Soundwise, this compressor is rough. Sounds fantastic!

:)

Luka

You might have noisy zeners. I've got the same issue and the difference in the noise floor between different zeners can be as much as 20 dB.

I describe the issue here as well:
https://groupdiy.com/index.php?topic=37400.msg839788#msg839788
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on July 02, 2017, 01:32:56 PM
Ok I'm back, fun little project!

-I think a 10k log pot seems more natural on the input control instead of the 10k linear, compression curve seems better to me like this
-I tried the original input pad on one channel and like the gain structure on the original board design better. Would be cool to make it switchable I suppose...

And questions
1. I notice the with the input and output controls all the way down the signal does not get reduced to zero. I still hear signal coming thru. Is there a way to remedy this? Maybe experiment with R93(120ohm) for the input and R94(1k) for the output?
2.What components on the board should I modify to use these meters? They look similar enough to the Sifam ones for me. Here are the specs on the  meter
http://www.ebay.com/itm/TR-57-Panel-VU-Meter-Level-DB-Meter-Audio-Mixer-Tube-Power-Meter-w-Backlight-/192017460667


I am still fighting some slight excess noise but plan on tidying up some more connections with shielded wire, etc.

It's coming along nice!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on July 02, 2017, 06:39:57 PM
You might have noisy zeners. I've got the same issue and the difference in the noise floor between different zeners can be as much as 20 dB.

I describe the issue here as well:
https://groupdiy.com/index.php?topic=37400.msg839788#msg839788

Thanks for that Ilya!
It crossed my mind that it could be that when I first read about your issues with zeners.
Unfortunately I didn't have time to work more on my build. It's been busy few days.
I'll see if I can get different zeners and try them.

1. I notice the with the input and output controls all the way down the signal does not get reduced to zero. I still hear signal coming thru. Is there a way to remedy this? Maybe experiment with R93(120ohm) for the input and R94(1k) for the output?

I also noticed that. But I don't mind! If I'm going to use it in the mix it will surely be at some decent level so I don't care what level it is when it is completely CCW on ins an outs. But if you want I guess that you can lower those values or maybe omit those resistors and have it completely grounded and silent. Let's see what Fripholm has to say on this.

:)

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on July 03, 2017, 03:39:47 AM
1. I notice the with the input and output controls all the way down the signal does not get reduced to zero. I still hear signal coming thru. Is there a way to remedy this? Maybe experiment with R93(120ohm) for the input and R94(1k) for the output?

Of course you're free to just jumper these resistors to ground if you want zero compression or zero output. Personally I really can't imagine a situation where one would need zero output from a compressor. The input control adjusts for the amount of compression (obviously no compression occurs with it all the way down to zero) and the output control is the makeup gain to get about the same level out that went in - zero wouldn't make sense here as well  ;)

IMHO the resistors provide a good range of control, but I realize that there are a million workflows and it's easy enough to modify things.  :)

Quote
2.What components on the board should I modify to use these meters? They look similar enough to the Sifam ones for me. Here are the specs on the  meter
http://www.ebay.com/itm/TR-57-Panel-VU-Meter-Level-DB-Meter-Audio-Mixer-Tube-Power-Meter-w-Backlight-/192017460667

It says 150uA for full deflection, which is much less than the meters it was designed for, so I would probably try and add a series resistor to lower the current.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on August 30, 2017, 01:15:06 PM
Hello.

The last piece of the puzzle I need to build my stereo version of this is transformers. I'm wanting to use Sowters, and after discussing appropriate transformers for this type of project, they recommended the 9970 for the input and 9980 on the output. I was told they could add a lead so the 9970 could be wired 1:3.5 (backwards for input). I'm trying to make this build really special, so I don't mind spending a bit more for the cost of iron for this project. I just want to make sure these transformers would be suitable for this build.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on August 31, 2017, 06:33:15 AM
I'm wanting to use Sowters, and after discussing appropriate transformers for this type of project, they recommended the 9970 for the input and 9980 on the output. I was told they could add a lead so the 9970 could be wired 1:3.5 (backwards for input). I'm trying to make this build really special, so I don't mind spending a bit more for the cost of iron for this project. I just want to make sure these transformers would be suitable for this build.

I think a 1:3.5 (wired backwards) for input might be suitable. You just have to fiddle with R86 and R87, which control the bypassed level for unity gain - as discussed earlier in the thread.
For the output iron however, I don't see any benefit from using a high turns ratio. The output stage is perfectly capable of driving 600 ohms directly up to 25 Volts p-p (~21 dBu), so a step up is not needed if you just want to drive an ordinary line input. A step down of 7:1 would give you less than 5 dBu of maximum output level. A 1:1 or thereabouts would be more than appropriate. Sowter also offers a replacement for the TG12345 output amp transformer (Sowter 1365, turns ratio 1:1.77) which is the same price as the 9980/70 and might be better suited than those, IMHO. They also have a TG input transformer (1295, 1:3.16), which might be interesting when wired backwards.

HTH

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on August 31, 2017, 12:44:51 PM
Thanks for the response. I was a little confused with their initial recommendations for what I was asking. The 1365 and 1295 seem to make more sense. I'll look over these and make an order.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: innercityman on September 04, 2017, 03:58:45 AM
Hi guys,

I'm about to start this build and I'd like to install the AL 20 vintage mirrored meters like the ones that Chandler use on their TG version. What resistor values need to be changed ?

Thanks for your help.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 04, 2017, 11:01:38 AM
Hi guys,

I'm about to start this build and I'd like to install the AL 20 vintage mirrored meters like the ones that Chandler use on their TG version. What resistor values need to be changed ?

Thanks for your help.

Would to love to know as well. I am using these same ones in my build.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 04, 2017, 12:32:49 PM
I'm about to start this build and I'd like to install the AL 20 vintage mirrored meters like the ones that Chandler use on their TG version. What resistor values need to be changed ?

As far as I know, the original used an Ammeter with 2.4mA full scale deflection which was connected across diode D5. If Chandler really used VU meters (as opposed to an Ammeter) for their units then I would think there might be more involved than just the tweaking of some resistor values. Maybe there's some additional circuitry for the meters?! I don't know.

This is an older post of someone trying to use VU meters which seemed like a lot of hassle:
https://groupdiy.com/index.php?topic=37400.msg754309#msg754309
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 06, 2017, 02:38:52 AM
I've just tried it with a standard Sifam AL29 VU meter and it works - kind of...  8)

With the currently implemented metering circuit, the needle of the AL29 maxes out at about the third of the scale with more than 20 dB of compression. Connected across D5 (as in the original), the needle's travel is even lower. At least it moves with the compression  :o

There might still be a way to use a VU meter, but you definitely have to come up with a custom scale and replace the original one. As it is, the voltage drop across diode D15 is too low for full scale deflection but if you connect two diodes in series it might be enough. A shunt resistor/poti across the meter could be used for fine tuning. It works fine when simulated but still needs to be tested in the actual circuit.

Are the AL20 really available as a mirrored version, I mean mechanically mirrored?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: kante1603 on September 06, 2017, 03:38:50 AM

Are the AL20 really available as a mirrored version, I mean mechanically mirrored?
Hello,


yes,but very expensive,here's a link:


https://www.don-audio.com/Sifam-AL20-6-7-Retro-VU-Meter-Set


Best regards,


Udo.



Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 06, 2017, 04:12:15 AM
yes, but very expensive.

Thanks and yes, that's a lot of money - but very nice nevertheless. They even have a custom scale.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: kante1603 on September 06, 2017, 04:33:12 AM
Yes,looks like they're the replacement parts for chandler limitters.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on September 06, 2017, 04:41:58 AM
Yes,looks like they're the replacement parts for chandler limitters.

I doubt Chandler uses VUs. Should be mA meters. And yes, these are a hell of a price.....
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: kante1603 on September 06, 2017, 05:24:32 AM
I doubt Chandler uses VUs. Should be mA meters. And yes, these are a hell of a price.....
Not sure if these are vu meters.On the manufacturers page there are quite a few meters from the series "20" to find.When going through the options (use the meter selector "ALL") you'll find some of them to be available as VU,A,mA,dc etc.Same for direction,you can choose the zero position to be left,centered,right etc.
The inlay must be done yourself of course.
DonAudio just writes that these are VU,but they state them to be replacements for Chandler.Maybe ask them......?

Just thinking......

Best regards,


Udo.



Edited because of font size issues.


Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on September 06, 2017, 05:29:25 AM
I'm not a VU-meter fetishist  :D
I'm using LED meters in my build for both level and GR. Much cheaper and less internal "real estate".
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Aniol1349 on September 06, 2017, 08:20:27 AM
Really excited with this project. I'm just waiting for a new batch of PCBs :)

Have anyone actually finished a unit? Maybe someone could share some photos/audio.
and yes I would be tempted to get myself a pair of those beautiful meters!

btw. really well documented build guide as well

Take it easy everyone!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 06, 2017, 09:01:52 AM
Not sure if these are vu meters.On the manufacturers page there are quite a few meters from the series "20" to find.When going through the options (use the meter selector "ALL") you'll find some of them to be available as VU,A,mA,dc etc.Same for direction,you can choose the zero position to be left,centered,right etc.
The inlay must be done yourself of course.
DonAudio just writes that these are VU,but they state them to be replacements for Chandler.Maybe ask them......?

Just thinking......



Best regards,


Udo.



Edited because of font size issues.


I emailed the guys at Don Audio to get some further information and I'll let you all know what they say. I have already ordered a set and are in the pile of parts I have for this project. Still a month out from finishing it up.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 06, 2017, 10:18:33 AM
Response from the Aaron at Don Audio is a VU driver circuit is needed to get these particular meters to work with a design that uses 1mA.


Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on September 06, 2017, 10:26:56 AM
I wonder if removing the internal bridge rectifier and stuffing some resistors in series/parallel will do the trick...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 06, 2017, 03:32:58 PM
Have anyone actually finished a unit? Maybe someone could share some photos/audio.

I'm curious as well! Any finished units out there or photos of your work in progress?! ???
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on September 06, 2017, 03:57:40 PM
I'm curious as well! Any finished units out there or photos of your work in progress?! ???

Here is my WIP in a very early state ;)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 07, 2017, 04:09:53 AM
I'm curious as well! Any finished units out there or photos of your work in progress?! ???

I just ordered transformers so it will be a couple of weeks before I finish. I have the boards populated with case, switches, and connectors on standby till I get home.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 07, 2017, 05:16:19 AM
Within the last weeks it has come to my attention that someone has been making and is selling clones of my boards. And yours, ToBSn, seems to be one of those. I'm in contact with a couple of members who purchased copies, which had been offered at another forum outside of GDIY. And occasionally, I have seen some of the clones showing up here in the Black Market again.

I was never asked for permission nor permitted the cloning of my PCBs, but I really hope they are electrically okay. If you find out you have a clone and they are not okay, please don't blame me!

From ToBSn's photo I can tell that the silkscreen looks slightly fuzzy and the solder pads seem somewhat irregular (maybe from scanning?!). But the most obvious difference is the rotation of R90 by 180 degrees (it's upside down) and one of the PCB manufacturer's imprints is in the free space around the output stage. Mine never were that way! Maybe the cloner deliberately rotated the resistor to be able to differentiate clone from original. This person must have had at least one original, as I've never sent out the Gerbers to anyone. And as I said before, the fine quality of my boards allowed for some abuse of the solder pads for testing around with different values. Obviously, wether this is also true for the clones can't be judged from a photo...

I have only ever offered the boards here on groupdiy and I will keep it that way. If you find these offered anywhere else and/or in larger quantities, they are most likely clones.

Just wanted to let you guys know. Take care.  :)

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: kante1603 on September 07, 2017, 05:44:13 AM
Oh no,not again! >:(
Thanks for letting us know,and please decent fellows: Do not support thieves!


Best regards,


Udo.


Edited central point to bold letters....   
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: rock soderstrom on September 07, 2017, 06:01:37 AM
 :(
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: TwentyTrees on September 07, 2017, 06:42:36 AM
Dang, that's awful! Poor show, mystery thief, poor show.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on September 07, 2017, 09:22:16 AM
 ??? :o :-\ :-[ >:(

WTF?! That´s feels sad.

@fripholm
Thanks for the info.
Need to check how to continue...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 10, 2017, 05:34:35 PM
I wonder if removing the internal bridge rectifier and stuffing some resistors in series/parallel will do the trick...

If you are using JLM's VU buffers there are parts to omit/jumper for internally rectified VU meters. I have some of these I built but never used so I'm planning on installing them in this project. I just have to mess around with the trimmer so the meter displays the gain reduction accurately, or at least as much as can be.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mro on September 15, 2017, 09:02:58 PM
Within the last weeks it has come to my attention that someone has been making and is selling clones of my boards. And yours, ToBSn, seems to be one of those. I'm in contact with a couple of members who purchased copies, which had been offered at another forum outside of GDIY. And occasionally, I have seen some of the clones showing up here in the Black Market again.

I was never asked for permission nor permitted the cloning of my PCBs, but I really hope they are electrically okay. If you find out you have a clone and they are not okay, please don't blame me!

From ToBSn's photo I can tell that the silkscreen looks slightly fuzzy and the solder pads seem somewhat irregular (maybe from scanning?!). But the most obvious difference is the rotation of R90 by 180 degrees (it's upside down) and one of the PCB manufacturer's imprints is in the free space around the output stage. Mine never were that way! Maybe the cloner deliberately rotated the resistor to be able to differentiate clone from original. This person must have had at least one original, as I've never sent out the Gerbers to anyone. And as I said before, the fine quality of my boards allowed for some abuse of the solder pads for testing around with different values. Obviously, wether this is also true for the clones can't be judged from a photo...

I have only ever offered the boards here on groupdiy and I will keep it that way. If you find these offered anywhere else and/or in larger quantities, they are most likely clones.

Just wanted to let you guys know. Take care.  :)

I have the exact same boards as ToBSn. Had them from a member here, as he had 'bought more than he needed'. Boards were listed on black market.
Stupid of me for sure, but it just never crossed my mind that anyone can get that low in this particular comunity.
Up untill recently I was finishing racking some Tab and Neumann modules and never got around with those.
Now as I was to start with the bould I was checking this thread and found those 'great news'. Not sure if the build is worth the hassle under these circumstances.
I'll contact the seller and ask what are his thoughts on this :/ 
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Rob Flinn on September 18, 2017, 04:29:08 AM
As I mentioned before, using a black solder mask makes boards a bit more difficult to copy.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: warpie on September 18, 2017, 06:43:45 AM
Within the last weeks it has come to my attention that someone has been making and is selling clones of my boards. And yours, ToBSn, seems to be one of those. I'm in contact with a couple of members who purchased copies, which had been offered at another forum outside of GDIY. And occasionally, I have seen some of the clones showing up here in the Black Market again.

I was never asked for permission nor permitted the cloning of my PCBs, but I really hope they are electrically okay. If you find out you have a clone and they are not okay, please don't blame me!

From ToBSn's photo I can tell that the silkscreen looks slightly fuzzy and the solder pads seem somewhat irregular (maybe from scanning?!). But the most obvious difference is the rotation of R90 by 180 degrees (it's upside down) and one of the PCB manufacturer's imprints is in the free space around the output stage. Mine never were that way! Maybe the cloner deliberately rotated the resistor to be able to differentiate clone from original. This person must have had at least one original, as I've never sent out the Gerbers to anyone. And as I said before, the fine quality of my boards allowed for some abuse of the solder pads for testing around with different values. Obviously, wether this is also true for the clones can't be judged from a photo...

I have only ever offered the boards here on groupdiy and I will keep it that way. If you find these offered anywhere else and/or in larger quantities, they are most likely clones.

Just wanted to let you guys know. Take care.  :)

Got mine from this thread (https://groupdiy.com/index.php?topic=65875.msg834548#msg834548) and the R90 is indeed upside down. Not cool...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mro on September 18, 2017, 07:14:47 AM
yes,
C6 is C3 and D13 is rotated.
I guess more bugs to come  :P
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 18, 2017, 07:21:10 AM
Got mine from this thread (https://groupdiy.com/index.php?topic=65875.msg834548#msg834548) and the R90 is indeed upside down. Not cool...

This is not cool indeed and I know how this may look, but as far as I know that member also bought those PCBs from someone else outside of groupdiy. Please don't jump to any conclusions here as we don't know the whole picture.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: warpie on September 18, 2017, 07:27:26 AM
This is not cool indeed and I know how this may look, but as far as I know that member also bought those PCBs from someone else outside of groupdiy. Please don't jump to any conclusions here as we don't know the whole picture.

Sorry, it wasn't my intention to accuse Chrion. I've dealt with Nicolas many times in the past. I just thought I'd mention where I got mine from.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Hobbyist on September 18, 2017, 07:55:49 AM
Sorry, it wasn't my intention to accuse Chrion. I've dealt with Nicolas many times in the past. I just thought I'd mention where I got mine from.

Have to admit, I also bought from Chrion.., thought they were on sale for the purpose he mentioned. They look exactly the same as the layout on the pdf to me... but not cool if they're copies  :(
I always make 2 units of my DIY projects as a learn process, so I definitely don't want to miss the second batch, with the PSU board.   :)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on September 19, 2017, 07:08:07 PM
After one step backward.
I think the copies are okay. Except for the board marking bugs, we can give them a chance.
Have ordered a second "original" set from fripholm.
We can only be sure when we have originals to compare. We'll see.

Finally, it's sad for fripholm who took the time and created the boards and very detailed and cool manual.

So, let´s become this thread back to a cool build thread.

Just think about extending the sidechain with a few extra steps and using the lorilin rotary and adding a small PCB on the back.
What do you think? Any suggestions for improvements?


Thanks!
ToBSn
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: desol on September 20, 2017, 03:32:13 PM
It is not cool at all, because he stated he purchased more original copies and was selling them. Instead, he copied a layout and then lied about how he acquired them. Not very good at all...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mro on September 20, 2017, 03:46:20 PM
It is not cool at all, because he stated he purchased more original copies and was selling them. Instead, he copied a layout and then lied about how he acquired them. Not very good at all...
He seemed to be a nice guy but what he did is just sh*t! He confirmed he also has the original PCBs from friphorn.
So:
a) he knew he purchased copies and didn't menton about it
b) didn't notice they differ from the originals
You choose what is more likely.
But I agree with ToBSn. Let's leave this subject behind and focus on the subject.
If there are any legal options for friphorn to follow let him handle it.

Best to all,
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 21, 2017, 04:03:23 AM
But I agree with ToBSn. Let's leave this subject behind and focus on the subject.

+1
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Hobbyist on September 21, 2017, 05:00:20 AM
Just think about extending the sidechain with a few extra steps and using the lorilin rotary and adding a small PCB on the back.

That would be awesome !   :D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on September 23, 2017, 10:54:22 AM
So, the pcb layout is ready.
Wima FKP2, FKS2, MKP2 or MKS2 can be used. It´s up to you.

There are two options.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 25, 2017, 04:51:48 AM
New batch available!  :)

See here for details: Black Market Thread (https://groupdiy.com/index.php?topic=65505.msg849046#msg849046)

(http://www.ttx-sound.net/foren/IMG_7865.jpg)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 30, 2017, 01:15:57 AM
Sowter sent me notification that my transformers are on the way. I have the case and am awaiting a PSU board. Any other guys here finish building one of these? Also, does anyone know of a LED/digital replacement for the 1mA meter used in this project? I'm ordering one more board to build some sort of channel strip in a single space rack and the metering section would have to be something compact like LED to get everything to fit.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mro on September 30, 2017, 05:08:29 AM
I'm ordering one more board to build some sort of channel strip in a single space rack and the metering section would have to be something compact like LED to get everything to fit.


Maybe an edgewise meter?  At least that's my plan for this build.
Which softers did you order?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 30, 2017, 10:23:54 AM
1365 and 1708.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: desol on October 01, 2017, 12:24:35 AM
Does anyone have any clips of this unit working hard on various sources...drum room, acoustic guitar, vocals? Cheers.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 01, 2017, 06:35:02 AM
Does anyone have any clips of this unit working hard on various sources...drum room, acoustic guitar, vocals? Cheers.

Here are a few quick tests on different sources: HQ-MP3s 256kBit (https://www.dropbox.com/s/5kc2637wi8cim3c/TG_Zener_Audio.zip?dl=0)

These are not necessarily examples for tasteful compression - just me abusing the units I have 8)

The 'Drums' and 'Acoustic Guitar' files have been processed with my stereo unit. The clicks you're hearing within these files is me actually toggling BYPASS while audio is running. I change a few settings in between; input, attack, (auto)release etc., and activate the compression again on the next downbeat. Note that the room mic is not active in the drums example, just the overheads and close mics. No additional processing apart from a bit of EQ here and there. The files are not level matched.

For the vocals I have used my mono desktop unit on Comp, Lim and THD settings - the original is included as well. Again, except for a bit of EQ and reverb, there's no additional processing - but I've tried to level match them as good as it gets.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: desol on October 01, 2017, 10:04:59 AM
Thanks Fripholm! That's exactly what I was looking for.

The unit sounds pretty good actually. I was a bit skeptical at first but, hpmh...not bad...and I know these are just basic examples to start.

Cheers and thanks!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 01, 2017, 06:40:04 PM
Hi everyone!

First of all, thanks to fripholm for this project. Just placed the order for my boards and now I'm trying to get my ducks in a row in the mean-time by putting together some mouser carts and whatnot.

My questions probably have obvious answers. I've built a few kits so far, but I'm still somewhat a beginner and want to make sure I'm getting the right parts.

First question, is this a suitable power transformer for American voltage/ current?
https://www.parts-express.com/avel-lindberg-y236653-250va-30v-30v-toroidal-transformer--122-630
I know from the BOM that it needs 2x30V secondaries which this has, but I'm unfamiliar with transformers as of writing this post, so the rest is greek to me.

Second, also dealing with transformers, this time the input/output. I'd like to use Sowters if only because I have no gear that uses their transformers. There are other posts in the thread that mention which Sowters to use, but I just figured if anyone had any suggestions or advice, I'd love to hear it. I'd also be interested in Cinemag or Ed Anderson transformers as a substitute.

Lastly, regarding the BOM for the power supply, I have no idea what kind of bridge rectifier to get. I'm very unfamiliar with this kind of component, and I'm having little luck with google searches.

Thanks in advance! Really looking forward to this build, I'm hoping to have all my parts sourced by the time my boards get here.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on October 01, 2017, 07:54:25 PM
First question, is this a suitable power transformer for American voltage/ current?
https://www.parts-express.com/avel-lindberg-y236653-250va-30v-30v-toroidal-transformer--122-630
I know from the BOM that it needs 2x30V secondaries which this has, but I'm unfamiliar with transformers as of writing this post, so the rest is greek to me.

Second, also dealing with transformers, this time the input/output. I'd like to use Sowters if only because I have no gear that uses their transformers. There are other posts in the thread that mention which Sowters to use, but I just figured if anyone had any suggestions or advice, I'd love to hear it. I'd also be interested in Cinemag or Ed Anderson transformers as a substitute.

Hi JCN1218,

250VA (4.17A) is a lot and is´s not needed.
Try to find one between 50VA and 120VA and save money. ;)
Like 546-1182K15

If you want to go with the sowter´s.
I think this guy´s will do the job:
For input 2:1 (High-Z) 9165 or 1380
For output 1:1 1460
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 01, 2017, 07:58:01 PM
Thanks, ToBSn!

I thought that that number on the power trafo, seemed high, I just didn't know what to make of it.
I'll be sure to check out those sowters too.

Thanks again! Really appreciate the quick reply!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 02, 2017, 03:30:46 AM
Lastly, regarding the BOM for the power supply, I have no idea what kind of bridge rectifier to get.

This one should get you started: Through Hole KBP Bridge Rectifier (http://www.mouser.de/ProductDetail/Diodes-Incorporated/KBP204G/?qs=sGAEpiMZZMtQ8nqTKtFS%2fNgL6ac11fJuOgO4GrxUCBM%3d)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 02, 2017, 11:16:08 PM
Awesome! Thanks so much, Fripholm. Now I'll be ready to order the PSU components when the boards arrive. I'll have to start putting a cart together for the rest of the materials soon.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 04, 2017, 04:26:19 PM
Hi again, back with some more questions as I await the arrival of the boards.

I've been doing a lot of research and some comparative shopping regarding input/ output transformers. David from Cinemag has gone above and beyond as far as customer service is concerned. He recommended the CMOB-2S for output, which seems to fit all the requirements. He then said this about the input transformer:

"The input stage, I think comes through C3/R1 (???  I cannot quite make out the part numbers) at the upper left-hand corner of the schematic.  It looks like there is a 3.8K resistor across a level pot which then goes to C1/2.2u.  That creates a fairly low input impedance.  To do that right, you need a pretty big input transformer such as the CMLI-4x150D.  $111.14  If R3 could be eliminated, you could use the CMLI-15/15B which is $53.04.  Keep in mind that it looks like the design calls out this network for pre-emphasis purposes."

Just wondering if those suggestions would fit the bill. I'm leaning more toward cinemag at the moment since the cost would be considerably lower.
I was also doing some research and I found a pic of the Chandler TG1 opened up. I saw that it was using Carnhill VTB9046 input transformer as well as Carnhill output, though I couldn't clearly see the model number. Anyway, I was wondering if anyone has used Carnhills in their TG1 build.

I also noticed a lot of mention of the Sifam AL20 mirrored meters a few pages back in the thread. I was wondering if anyone has managed to get them to work with this build yet, since I was thinking about getting a pair myself, but I'm hesitant to drop that kind of cash if they're not going to function correctly.

So that's it for now. Sorry if I'm asking too many questions, I just want to be as close to 100% sure as I can get before a buy anything for this build. Thanks again to everyone in this thread for being so helpful so far, I really appreciate it!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 05, 2017, 03:47:48 AM
You don't necessarily need a BIG input transformer - big, as in size - you need one with a turns ratio of 2:1 or even 4:1 - not 1:1, as recommended by Cinemag. If however, the secondary of the CMLI-4x150D can be wired in parallel (primary stays in series as per the datasheet) you would have a 2:1, which is fine.

He's right, the input impedance is rather low but one of the purposes of the transformer is to raise the impedance as 'seen' from the outside. Impedance ratio of a transformer is turns ratio squared, so 2:1 makes for 4 times the impedance - 3.8k-ish times 4 is more than 15k - exactly what you want.

Another purpose of the input transformer is to lower the signal (by 6dB for a 2:1) to an acceptable level. This particular circuit either distorts heavily or will be in extreme compression most of the time, when the level is too high.

The Carnhill might be a perfect fit as it can be wired for both 2:1 and 4:1 - personally I would go for the M-version with the mu-metal can. But as it doesn't have mounting holes, it needs to be mounted to a PCB or perfboard with a 5.08mm (0.2") spacing.

HTH
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: TwentyTrees on October 05, 2017, 05:14:54 AM
Side-note on the Carnhills, they're excellent and I've just finished a 2254 build stuffed full of them. They actually have mounting holes on the opposite side to the pins - just undo the screws on the top and there you go!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 05, 2017, 10:10:14 AM
Awesome! Can't thank you guys enough for how helpful you've been. I think I'll go Carnhills then for this project. I was just using them in my EZ1290 build, so I'm pretty familiar with how they work too. Plus it'll also save me some funds for other parts of the project.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on October 10, 2017, 03:07:52 PM
Hi,

Side chain pcb´s available here [Black Market] (https://groupdiy.com/index.php?topic=67086.0)  :)


Edit:

Some additional infos:

To calculate your own frequencies you can use this tool: Calculator RC (http://www.sengpielaudio.com/calculator-RCpad.htm)
RC-Filter 51kΩ [R48,R49] and Cap = Corner frequency.
I think the following values make sense.
You can also increase the frequency spacing, is a matter of taste.


Off and 5 selectable frequencies:
 

 
Off
1
2
3
4
5

 
-
47nF
33nF
22nF
15nF
10nF
@ -3db
-
~70Hz
~100Hz
~150Hz
~200Hz
~320Hz
 

 

 
Off
1
2
3
4
5

 
-
68nF
47nF
33nF
22nF
15nF
@ -3db
-
~45Hz
~70Hz
~100Hz
~150Hz
~200Hz
 





6 selectable frequencies + Off with extra dptp[on/on] to switch the high pass on/off:

 

 
1
2
3
4
5
6

 
68nF
47nF
33nF
22nF
15nF
10nF
@ -3db
~45Hz
~70Hz
~100Hz
~150Hz
~200Hz
~320Hz
 

 

 
1
2
3
4
5
6

 
100nF
68nF
47nF
33nF
22nF
15nF
@ -3db
~30Hz
~45Hz
~70Hz
~100Hz
~150Hz
~200Hz
 



ToBSn
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 10, 2017, 03:33:04 PM
Hi,

Side chain pcb´s available here [Black Market] (https://groupdiy.com/index.php?topic=67086.0)  :)




ToBSn

Awesome! Would love to have some more side-chain options. PM sent
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: MrBlomski on October 12, 2017, 05:41:13 AM
Side-note on the Carnhills, they're excellent and I've just finished a 2254 build stuffed full of them. They actually have mounting holes on the opposite side to the pins - just undo the screws on the top and there you go!

Do I see the DB54?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: TwentyTrees on October 12, 2017, 09:09:36 AM
You certainly do! I'll do a proper build report at some point in the DB54 build thread, but it's a very enjoyable build and sounds fantastic.

I've not got going on this zener limiter yet, but I'm looking forward to two apparently very different flavours of diode compression!

Do I see the DB54?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: MrBlomski on October 12, 2017, 03:17:25 PM
You certainly do! I'll do a proper build report at some point in the DB54 build thread, but it's a very enjoyable build and sounds fantastic.

I've not got going on this zener limiter yet, but I'm looking forward to two apparently very different flavours of diode compression!

I am also building them :D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Hobbyist on October 16, 2017, 03:27:15 AM
Hi,

Side chain pcb´s available here [Black Market] (https://groupdiy.com/index.php?topic=67086.0)  :)




PM send  ;)

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on October 19, 2017, 09:44:41 PM
Making progress!

I am waiting on push button switches and a fancy IEC inlet. I have everything else.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: kante1603 on October 20, 2017, 12:47:50 AM
Making progress!

I am waiting on push button switches and a fancy IEC inlet. I have everything else.

Thanks!

Paul
Very nice.
I see squared holes for the pushbutton switches,are these the ones from frank or can you tell us the type?
For the meters,are these the ones from DonAudio?Did you get them to work already?
Best regards,


Udo.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on October 20, 2017, 02:06:00 AM
Very nice.
I see squared holes for the pushbutton switches,are these the ones from frank or can you tell us the type?
For the meters,are these the ones from DonAudio?Did you get them to work already?
Best regards,


Udo.

Those are for the switches from Don Audio. Same with the meters. I haven't been able to power anything up as I forgot to order the IEC inlet and I used the switches I had for a GSSL I sold.

I did ask Aaron about using these meters in place of a 1mA version that this design uses, and he said to use a VU meter driver that are commonly found on ebay. I have a pair of VU meter buffers that I built from JLM audio but never installed, however I don't think it's the same thing. I'd have to look over that particular schematic some more and see if it will work. Hopefully will have this finished at the end of next week.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 20, 2017, 04:09:19 AM
Making progress!

I am waiting on push button switches and a fancy IEC inlet. I have everything else.

Thanks!

Paul

Very nice progress. Looking great!

Keep us posted how those meters work in the circuit.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on October 31, 2017, 05:14:24 PM
For the Bypass illuminated push button switches, how did you go about wiring your LEDs? I normally take the unused side of the switch and route the VDC from there to the + side of the LED, but for this bypass it is using both sides of the switch. Is it safe to incorporate the VDC with the audio or do need need blocking capacitors? Or do something else?

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 01, 2017, 04:58:10 AM
For the Bypass illuminated push button switches, how did you go about wiring your LEDs? I normally take the unused side of the switch and route the VDC from there to the + side of the LED, but for this bypass it is using both sides of the switch. Is it safe to incorporate the VDC with the audio or do need need blocking capacitors? Or do something else?

Thanks!

Paul

On my stereo build I have used one side of the switch for the LED and the other to trigger a relay which is used for bypass. Both are getting the +28 volts directly from the PSU. I'm using 24V relays and >10k resistors for the LEDs - the switches are the same ones from don audio, that you are using.

The mono desktop unit just has a simple 2PDT toggle switch, that directly switches BYPASS in or out (no LED). Under some circumstances I'm getting a loud thump when the switch is toggled. It might be a good idea to use a make-before-break switch to avoid this, but I haven't found one.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 01, 2017, 11:29:55 AM
Yes, of course, a relay! I did something like this on another build but I guess I completely forgot about it. Sorry for the silly question.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 02, 2017, 05:46:03 AM
Here's more pics of progress...

Wiring explosion!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 02, 2017, 05:48:56 AM
Another one
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 02, 2017, 05:58:38 AM
Starting to look like something now.

I thought I had all the parts but it turns out that I don't have the right power transformer or IEC panel mount inlet. All the 2x30V transformers I've found on mouser are made by Hammond and are 80VA, costing around $60 each. Has anybody found a suitable Triad product for this build?

I was hoping to at least power it up before I headed out of town, but now it will be two weeks before that happens.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 02, 2017, 06:20:25 AM
Has anybody found a suitable Triad product for this build?

The Triad VPT30-1670 might work.

Looking good!  :D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 02, 2017, 06:48:23 AM
It looks like that is 2x15 (30V secondaries in series). That's the one I originally bought.

I'll keep looking.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 02, 2017, 07:36:38 AM
It looks like that is 2x15 (30V secondaries in series).

Ooops, you're right.

**nevermind** 8)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 04, 2017, 04:14:19 PM
Hey everybody. My build is going along well, boards are populated and my enclosure is all put together. Just waiting on all my transformers at the moment. While I'm waiting for them, I was looking over the schematic and I'm just wondering what kind of grounding scheme to go for. Are there any points on the boards that should be connected to star ground for example, or is the grounding taken care of with the other off board connections.
Also, I'm unsure how to socket the trimmers during the calibration steps. What should I do with the wiper leg? I can't tell from the pic in the build guide.

I'll post some pics of my progress soon. Thanks again to everyone for being so helpful!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 04, 2017, 06:19:14 PM
Wiper has to in one socket and then either of the other legs in another. Extend by soldering trimmed lead pieces from resistors if needed. Just make sure you measure the resistance on the legs that where in the sockets when calculating permanent values.

For grounding, I use Ian Thompson's Grounding 101 for any and all builds that I do and they always turn out very quiet if the rest of the build is correct. Do a search for it and read it.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 04, 2017, 09:22:33 PM
Awesome! Thanks for the tip. I'll be sure to check it out while I wait for my transformers to get in.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 05, 2017, 01:48:30 PM
So far, my build seems to be going very well, so I figured I post up some progress pics.

(https://i1.wp.com/dmsoundstudios.files.wordpress.com/2017/11/2017-11-02-15-30-11-1.jpg?ssl=1&w=450)

Here's the back of the front panel. It's almost fully wired up with the exception of the auto-release switches and hold pots. Thanks again to ToBSn for the nifty side-chain boards.

(https://i2.wp.com/dmsoundstudios.files.wordpress.com/2017/11/2017-11-05-12-31-48.jpg?ssl=1&w=450)

Here's the inside of the case as of now. Power supply isn't installed yet due to lack of power transformer. I have it in a really shallow 3U case with the boards stacked on top of each other. The reason being that my GSSL has a big bolt sticking out the bottom of its case about 6" from the front panel, so I can't rack it above anything that has a case deeper than about 6". I figured this was good opportunity to make something that could live under my GSSL. I'm going to be mounting my input and output transformers on the outside like an LA2A  since I have limited space inside the box.

(https://i1.wp.com/dmsoundstudios.files.wordpress.com/2017/11/2017-11-05-12-34-25.jpg?ssl=1&w=450)

Here's the front panel with all the goodies on it. I actually don't have the meters properly mounted yet, I was hoping they'd come with mounting hardware but I had to order some after the fact. Should be getting here tomorrow. This is my first custom front panel from Front Panels Express and I'm really happy with how it turned out. It definitely has the biggest cool-factor of anything in my rack so far. I'll be leaving it there until I get the transformers in, at which point I can work on it more. Power trafo should get in this week, the audio ones I ended up ordering from Sowter so I could mount them externally. They haven't even shipped yet, so it might be a while before I can start testing. Calibrating this beast, especially with the stacked boards, is certainly going to be a fun challenge.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on November 05, 2017, 07:17:19 PM
Hey guys,

very cool. Good work!  :D

I´m currently working on my front panel design...
Not finished yet, just a good start to experiment.  ;D
 
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: TwentyTrees on November 06, 2017, 02:23:41 AM
LOVE that design - sleek! Those toggle switches work really well, is there a link you can share?

Hey guys,

very cool. Good work!  :D

I´m currently working on my front panel design...
Not finished yet, just a good start to experiment.  ;D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 06, 2017, 04:08:19 AM
Just so people are aware, you can get DC mA versions of the retro style Sifam meters that are sold by Don Audio:

https://sites.google.com/site/diypartsstore/catalog/pcb-transistors-op-amps-pots

The catch is you have to buy their TG boards with the purchase. I still haven't been able to order the correct power transformer to power up my build and work on getting the VU version I have to track correctly. So if there are some people waiting for those results to determine if they want to go this metering route, you might want to consider the DC mA version.

I've order somethings before from them in the past and I didn't have any issues.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: innercityman on November 06, 2017, 04:12:17 AM
Yeah, I visited their page when searching infos on the TG1 and I wondered what's the difference between their TG1 kit and Fripholm's one ?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 06, 2017, 08:47:07 AM
Concerning the illuminated push button bypass wiring. I saw in an earlier post something about using a relay to trigger the bypass and wiring the led to one side of the switch. I've never worked with relays before. If anyone would be willing to explain that setup a little more in detail or perhaps post a crude wiring diagram it would be highly appreciated.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 06, 2017, 11:37:54 AM
Relay is a basically a switch activated by power. One side of the push button is going to send power to the relay (make sure it's rated for the VDC you are using) and the relay switches the two things you need on/off (LED power, bypass, what ever you decide). You can do some searches for relays in a GSSL and it should give you an idea, although some of those images have been taken down.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 06, 2017, 11:43:13 AM
Yeah, I visited their page when searching infos on the TG1 and I wondered what's the difference between their TG1 kit and Fripholm's one ?

It seems the switches are on PCBs, so you would be committed how you want to do your panel layout. My thought is that if someone wanted these style of meters but were unsure about making the VU version work, then this would be a faster way to get DC mA versions than to order custom from Sifam.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 06, 2017, 12:54:00 PM
Concerning the illuminated push button bypass wiring. I saw in an earlier post something about using a relay to trigger the bypass and wiring the led to one side of the switch. I've never worked with relays before. If anyone would be willing to explain that setup a little more in detail or perhaps post a crude wiring diagram it would be highly appreciated.

I've just updated the guide with a wiring diagram. Just re-download (link in first post) and see page 2 of the guide.

My relays are mounted on perf board with a 2.54 grid, powered directly by the +28Volts from the PSU board - GND also directly from there, not the limiter board. Most relays can operate at up to 150% of their rated coil voltage, so a 24V relay should be fine. In this case I preferred to power the relay when in Bypass. This way, no current is drawn in normal operation, which could lead to higher supply ripple. Don't forget the flyback diode in parallel to the coil.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 06, 2017, 01:03:02 PM
I still haven't been able to order the correct power transformer to power up my build

Paul, have you seen this: https://www.alliedelec.com/block-usa-rkd-60-2x30/70632313/
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 06, 2017, 01:21:56 PM
Thanks so much guys! I'm definitely learning a lot building this project, it's been a blast so far. Can't wait to have it up and running
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 06, 2017, 01:30:53 PM
Paul, have you seen this: https://www.alliedelec.com/block-usa-rkd-60-2x30/70632313/

I have not. I was going to just order the Hammond, but I this would be a much better option. I'm just waiting till I get back. I head over on that side of the pond for 9 days then I'll be able to get back on this upon my return.

Thanks for the info!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Rob Flinn on November 06, 2017, 02:10:02 PM
Yeah, I visited their page when searching infos on the TG1 and I wondered what's the difference between their TG1 kit and Fripholm's one ?

There are more options for switching iron in and out or having op amp based balanced in and out.  Essentially it is an i/o board with bypass and relays on to perform this switching.  It's quite a tricky board to get your head round if for example you want op amp in & transformer out permanently.  It also has options for the hold function on elma switches.   You can build it like an original TG or the chandler version.

(you might ask whey you would want to swiitch the iron out.  I used Gardners transformers & there is not a massive difference between either option)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 06, 2017, 06:29:05 PM
So while I wait on parts, I tested to see if the meters I acquired were indeed of the VU variety, but it seems they are DC meters. Whether they are 1 or 2.4mA I do not know (Don Audio lists them as replacements for the Chandler Limiter meters). But I do know that they do not respond to AC current coming direct from my signal generator, except I can actually hear the 1kHz tone in the meter itself. I did this same test with a known VU meter and the needle responded as expected. If I get the inclination I'll open up a GSSL and test that circuit with these meters and see what happens. So we may not have to much of anything to get these to track correctly with the TG1 boards.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 06, 2017, 06:35:08 PM
That would be awesome news! Thanks for going the extra mile Paul, keep us posted

Edit:
I emailed Frank from Curious Audio, the site selling the DC mA sifams you had linked to. If the Don audio meters are the same, then they are 2.4 mA meters.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 06, 2017, 09:07:39 PM
All righty, here's what I have found.

I connected the Sifam to the GSSL and it is indeed a DC meter, but I believe it is 2.4mA. The scale is also curious as there is an indicator line below 0 on the scale, and there is not enough movement on the mechanical zero adjustment to get it up to that "0" mark.

The signal I used to get 8dB of reduction on the 1mA meter hits about 2dB on the Sifam (with the needle resting at the mark below "0"). This is part of the story where I don't know exactly how to proceed as I am not familiar with the history of these units or how they behave. It still may track better with this TG1 circuit, but I won't be able to test any of that for another week. I don't know if using a VU driver will still help solve this problem. Maybe there is are some things that can be swapped out in the metering section of the boards to make it work better with the Sifams.

Okay, you guys' turn...

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on November 07, 2017, 03:05:45 AM
@TwentyTrees
LOVE that design - sleek! Those toggle switches work really well, is there a link you can share?
Thanks. :)
Yeah, also like the toggle switches. These are from Miyama.
Currently doing the Design in Illustrator and C4D.
When i´m sure i will port this to a frontpanel-designer layout.


@Paul
Okay, you guys' turn...
R91/R92 is good start i think.
Lower R91 and/or R92 may can help to fix this issue.

Don´t know how much, just an idea.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 07, 2017, 04:40:21 AM
Okay, you guys' turn...

In addition to what ToBSn said, try two diodes in series instead of just D15. This increases the voltage drop through the meter's resistance and raises the current - in theory (LTSpice, that is)  ::)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on November 09, 2017, 05:37:09 PM
New layout – in stereo...

Took´s 3 hours to render on my 9 years old machine.  :o
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on November 09, 2017, 06:07:06 PM
In addition to what ToBSn said, try two diodes in series instead of just D15. This increases the voltage drop through the meter's resistance and raises the current - in theory (LTSpice, that is)  ::)

I'll definitely give these changes a whack and see what happens.

I did reach out to Sifam about this and they said they could make these meters 1mA if need be (same model and layout). Lead time would be 5 weeks. I'm still over on the other side of the pond at the moment, but as soon as I get home I'll be able to mess around with the resistor and diode suggestions. If I can't figure something out I'll just get order new ones from Sifam.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 10, 2017, 08:17:41 PM
Power transformer just arrived today, and I got an email from Sowter that my in/out transformers are on their way! Can't wait for them to arrive so I can finally power up and test this compressor. Hopefully we can get these meters to work since I already have the pair of them. Nice to know that Sifam offers the 1mA version though if all else fails.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 23, 2017, 03:32:26 PM
Powered up today for the first time, got my PSU to the proper voltage output without problems. Unfortunately when I try sending a test tone through, I get no output. I feel like signal isn't even reaching the board. I double checked my bypass switch and switched it on and off a few times, but still nothing. Any ideas?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 24, 2017, 04:06:43 AM
Unfortunately when I try sending a test tone through, I get no output. I feel like signal isn't even reaching the board. I double checked my bypass switch and switched it on and off a few times, but still nothing. Any ideas?

I'd definitely start to double/triple check the wiring. The bypass switch connects the input transformer with the output stage (when bypass is switched in), which means that the output stage is always in the signal chain. If there's no output, something is wrong there. Do you have an oscilloscope to trace the signal? Makes things much easier.  :)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 24, 2017, 05:38:08 PM
I'd definitely start to double/triple check the wiring. The bypass switch connects the input transformer with the output stage (when bypass is switched in), which means that the output stage is always in the signal chain. If there's no output, something is wrong there. Do you have an oscilloscope to trace the signal? Makes things much easier.  :)

I have an oscilloscope in my DAW, although I'm not sure how to use it to trace the signal. I checked my switch wiring again and thought I had found the problem. I'm using the push-buttons from don-audio, currently without the lights and relays since I'm waiting to find out what resistors I'll need before placing another mouser order. Anyway, I had initially thought that the tabs labeled C were the poles, but I think I was mistaken, so I just fixed it. I'm still not getting any output. I'm very confident that the wires from the switch to the board are correct at this point. Maybe the switch is bad?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on November 25, 2017, 02:18:53 AM
Measure the switch with DMM. This will resolve any questions regarding where is what contact.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 25, 2017, 07:37:52 AM
I have an oscilloscope in my DAW, although I'm not sure how to use it to trace the signal.

Don't just use your interface's line inputs, the DC in some spots could hurt your interface and/or speakers if you're not careful.

I have a cheap USB oscilloscope from PICO (about 120 bucks). One of the best investments I've ever made. You'll learn a lot just by (carefully) probing around in circuits. And there are even cheaper alternatives that do the job quite well. Do a search here, this topic comes up frequently.

For now just follow Ilya's advice and check continuity with your DMM, so you can rule out the switch as the problem.

You could also inject your test signal directly into the pad pictured below. It shouldn't have DC on it (measure it to be sure).

(http://www.ttx-sound.net/foren/outputstagetest.jpg)

This bypasses the switch and output pot completely and goes directly to the output stage, to allow you to check if it's working properly.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 25, 2017, 08:38:22 AM
Thanks for the advice everyone!

I think I may definitely have to invest in an oscilloscope, although in the coming days I'll see what I can do to get this thing working without one.

I did check the switch the other night. It does work, and I actually had it wired up correctly the first time. I tend to get ahead of myself with trouble shooting, so now I'll have to go fix the switch wiring again.

I'll have to check my switch wiring again, I feel like I must have it wired incorrectly but I just can't see my mistake. Maybe I'll have a friend or my dad take a quick look at it. Fresh eyes are usually a big help.

I'll be sure to try putting the input signal right into that middle pad as well if I still can't figure out the switch.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 26, 2017, 04:56:35 PM
Tried putting signal right into that middle pad of the bypass 2 section. Still nothing  :( I guess there must be a problem in the output stage. There must be one in the output stages of both boards too, because the second board is experiencing the same problems. I looked at the schematic for the output stage. If Q12 or Q13 were installed backwards, would that be possibly causing my problems? I'm using the BD139&140. I remember during install having some trouble figuring out which way they should be placed, especially the BD139. It's the only thing I can think of right now as far as trouble shooting is concerned.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 26, 2017, 05:38:59 PM
The three dots/notches on the BD139/140 should be facing outwards. Look at the photo in the guide, top of page 5.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 27, 2017, 04:23:32 PM
Well, the 139 was indeed backwards. It's now oriented correctly. Unfortunately, it hasn't solved my problems. I'm still getting no output, even when directly sending the signal to the middle pad of bypass 2.

I'm not sure what else could be wrong at this point. Thanks for everyone's help so far, please let me know if you have any ideas as to what else might be wrong.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 28, 2017, 05:04:32 AM
I'm pretty sure you have done this before, but just to be sure: check the orientation of all the transistors, diodes and polarized caps. Make sure the NPN and PNP transistors are in their correct spots, Qxx are PNP (BC559, 560 etc.),  Txx are NPN (BC550).

Try to fix the output stage first. It's a pretty simple circuit block with just a handful of parts.

What's the voltage at the top (+) of C29? It should read about 12 Volts. Maybe something burnt out due to the incorrectly installed BD139...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 28, 2017, 09:39:56 AM
Yeah, the first thing I did once I saw it wasn't working was to check my transistors.

I did just do a quick test on the top of C29 and I'm not getting a DC voltage reading at all really, so something must have burned up due to the flipped BD139. Now I just have to track down the malfunctioning part(s). I haven't seen any smoke or anything during any power ups so far.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: AD797 on December 01, 2017, 10:51:22 PM
(http://www.bilder-upload.eu/thumb/31893b-1512186801.jpg) (http://www.bilder-upload.eu/show.php?file=31893b-1512186801.jpg)

omg... the transfomer i got are that big!!!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: MrBlomski on December 02, 2017, 04:23:45 AM
What are these monsters?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: AD797 on December 02, 2017, 08:39:13 AM
it´s a Sedlbauer LÜ81, it´s 8:1, 4:1 and 2:1 in one monster...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Murdock on December 05, 2017, 12:50:04 PM
Hey, sorry if this has already been asked. But what would be the drawbacks of using a 24V PSU instead of the 28V?
I have a really good 24V PSU which I use for a lot of my modules. Would be great if I could also use it for this compressor... Could I make any changes to the circuit to accommodate a 24V supply?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 06, 2017, 04:13:24 AM
Could I make any changes to the circuit to accommodate a 24V supply?

I don't know your 24V supply, but maybe it's easier to modify your PSU's circuit to deliver the 28 Volts?! If it's based on linear regulators, the output voltage is just a matter of a couple of resistors or maybe there's even a trimmer...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Murdock on December 06, 2017, 06:02:18 AM
I don't know your 24V supply, but maybe it's easier to modify your PSU's circuit to deliver the 28 Volts?! If it's based on linear regulators, the output voltage is just a matter of a couple of resistors or maybe there's even a trimmer...


Hey, thanks for the fast reply!
But I don't want to modify my 24v supply as I Use it for most of my German broadcast modules which need 24V... so I assume It's not a good idea to run the TG1 with 24V then? Probably less headroom, right?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 06, 2017, 06:36:39 AM


Hey, thanks for the fast reply!
Probably less headroom, right?

That would be one thing. There are also transistor regulators on board that provide another bipolar +/-20Volts for the compressor stage to work properly.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 14, 2017, 06:58:10 AM
So the power transformer is on backorder, even though I was certain it was in stock when I ordered from Allied. So unless I want to wait a month, I'll have to find something else.

Curious to see if other people have this up and running yet.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on December 14, 2017, 05:32:03 PM
I have the 2x24V 0.5A transformers in stock if you need it.  I'm using them for my 12413 modules.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 15, 2017, 02:31:25 AM
Thanks for letting me know. I'll keep this in mind if I get stuck.

thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 15, 2017, 03:36:50 AM
Yes, someone pointed out the other day, that a 2x24V power transformer would also work in this case.

Curious to see if other people have this up and running yet.

Yup, me too!  ;D
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 19, 2017, 08:42:32 AM
Hammond Power transformer ordered from mouser. Should be here in a couple of days. I will report back after calibration.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Mike Havok on December 24, 2017, 08:23:20 PM
Hi people, just got my boards today (christmas present from my wife)

I was wondering, is there a way of increasing the treble boost in the input stage? Either with a switch or pot?

Really looking forward to getting stuck into building this (thanks Thomas!)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 25, 2017, 05:00:58 AM
I was wondering, is there a way of increasing the treble boost in the input stage? Either with a switch or pot?

I'm glad, the boards made it in time before xmas :)

You could make R1 and C3 switchable for different options. With the given values it's only a slight boost - about 1dB at 20kHz, originally intended as 'frequency correction' according to the circuit description of the original.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 25, 2017, 06:23:46 PM
So I'm having a bit of trouble trying to get power to the relays I'm using for to do the switching and LEDs for the push button DPDTs. It seems that when I try to put a diode (1N4148) across the contacts that receive power it burns up the 22R resistor on the PSU. I guess I can just wire the relays without the diodes but I thought it was go practice to do so for circuit protection. The diode was wired with the anode on the +V side and the cathode to the side connected to ground. I don't recall having this trouble on other builds.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 26, 2017, 02:07:56 AM
Okay, finally powered it up with out letting out any magic smoke.

So both channels are really noisy with the circuit in, very similar to radio interference and perfectly clean bypassed, I know getting through the transformer part of the wiring is fine. This happens on both channels. Channel 2 has about 15 less gain than channel 1 and when I do the fine tuning step 1 the waveform on the oscilloscope looks very different. Noise is present with BYP1 (input transformer to board) disconnected but with BYP2 still connected. With BYP disconnected it goes away. Level differences do not change with swapping transformer, BYP 1,2, input or output connections.

Transformers being used are Sowter 1295 for the input (wired backwards for 3:1, no attenuation taps) and 1365 for the output. There is +8dB of gain when compressor is bypassed.

The fancy meters seem to track pretty good and there is plenty of travel in the gain reduction trimmer to get it where you want.

The stereo linking works but when disengaged the lower output channel shows less gain reduction then none when the mode is switched back and forth. It is almost as if there is a residual charge on the gain reduction part of the circuit then it is dissipated when switching between compressor and limiter.

From what I can test, this thing gets really aggressive, but is able to sound much more smoothed out with the slower attack and Sidechain HPF.

Currently both channels have trimmers in place for R8 to do the fine tuning 1 step and socketed resistors per the BOM for R56 and R22.

I am very close to a working unit, I just need to figure out this noise issue and gain difference before I can go any further.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 26, 2017, 02:15:58 AM
I forgot to mention that I am using stepped controls for everything except the release. Adjusting the output creates massive pops no matter what level is being used. This does not occur for the input.

Also on the meter there is a line below 0. The mechanical adjustment will only get you right to the actual zero line. I'm not sure if this is the correct way to setup this meter.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: warpie on December 26, 2017, 05:23:48 AM
I forgot to mention that I am using stepped controls for everything except the release. Adjusting the output creates massive pops no matter what level is being used. This does not occur for the input.

You might have to use MBB switches or try adding 1M (or higher) resistors between each pin of the switch.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on December 26, 2017, 05:54:14 AM
Pops generally mean there's DC in the switching circuit. This should not be the case because the output attenuator is between the blocking caps. I suppose the output stage has something wrong. Check DC voltages before and after the attenuator and see if there's any.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 26, 2017, 06:03:29 AM
The diode was wired with the anode on the +V side and the cathode to the side connected to ground. I don't recall having this trouble on other builds.

In this case the cathode (the side with the black bar on it) goes to V+ and anode to GND. The other way around you essentially short out the power supply.

So both channels are really noisy with the circuit in, very similar to radio interference and perfectly clean bypassed, I know getting through the transformer part of the wiring is fine. This happens on both channels.

It seems, your output stage is oscillating! Try a series resistor between the output connector and the transformer primary, anywhere from 22 to 100 ohms.

Quote
Channel 2 has about 15 less gain than channel 1 and when I do the fine tuning step 1 the waveform on the oscilloscope looks very different. Noise is present with BYP1 (input transformer to board) disconnected but with BYP2 still connected. With BYP disconnected it goes away. Level differences do not change with swapping transformer, BYP 1,2, input or output connections.

Is there a level difference when the unit is in bypass?

If it's only different, when the compressor is in, then you need to do 'fine tuning step 2'. In this case, I would try and fine tune both channels (as opposed to just one, as stated in the guide) because of the large difference of 15dB - one channel goes up by ~7dB, the other is adjusted down by ~7dB.

Quote
Transformers being used are Sowter 1295 for the input (wired backwards for 3:1, no attenuation taps) and 1365 for the output. There is +8dB of gain when compressor is bypassed.

When you've successfully completed the above steps, this difference should have become much smaller. The resistors R86 and/or R87 do the fine tuning. Originally, the values of these are for use with a 2:1 input transformer.

Quote
The stereo linking works but when disengaged the lower output channel shows less gain reduction then none when the mode is switched back and forth. It is almost as if there is a residual charge on the gain reduction part of the circuit then it is dissipated when switching between compressor and limiter.

As this is a feedback compressor whose sidechain is fed by the output signal, it's normal that the quieter channel compresses less. When link is engaged, the higher control voltage takes over and controls both channels.

Again, complete the above steps and this will also go away...  8)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 26, 2017, 10:00:56 AM
Thanks for the reply!

I had wired the diode this way as that is what I had seen on other designs and it worked for me in the past. Right now I'm running without till I sort out the rest of the issues.

I had read in the instructions regarding oscillating, but it did not think that was the sound I was hearing. I'll give the resistors ago.

I figured the gain difference was related to fine tuning step 2, but I was put off by the noise and I had thought there was a problem with the input stage of the lower level channel. Plus the way the drum tracks looked on the scope from one channel to another. And it was pretty late so my brain was shutting down.

I'll report back with my findings. Looking forward to sharing some photos and impressions.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 26, 2017, 12:19:45 PM
You might have to use MBB switches or try adding 1M (or higher) resistors between each pin of the switch.

I thought about having to use different switches. Thought about having to use either DC blocking caps or the 1M resistors as you mentioned.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 26, 2017, 12:22:20 PM
Pops generally mean there's DC in the switching circuit. This should not be the case because the output attenuator is between the blocking caps. I suppose the output stage has something wrong. Check DC voltages before and after the attenuator and see if there's any.

Haven't measured for VDC around the switch but it is definitely there. This is also happening with switching the circuit in and out. It will pop on the side that is being switched then both sides will pop when switched out.

Quite maddening.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 26, 2017, 12:35:27 PM
I had wired the diode this way as that is what I had seen on other designs and it worked for me in the past.

I'm sure you knew this, but maybe it's also interesting for others; see here for an awesome and simple explanation why the flyback diode on a relay coil is a great idea: https://www.youtube.com/watch?v=c6I7Ycbv8B8

And before you order different switches or make any other changes, try and make your output stage work properly. I have seen this circuit do the weirdest things and I spent days troubleshooting before I realized it was just the output stage oscillating.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 26, 2017, 12:39:53 PM
In this case the cathode (the side with the black bar on it) goes to V+ and anode to GND. The other way around you essentially short out the power supply.

It seems, your output stage is oscillating! Try a series resistor between the output connector and the transformer primary, anywhere from 22 to 100 ohms.

Is there a level difference when the unit is in bypass?

There is no level difference when in bypass. And it's definitely a radio station and not oscillating as I just added 100 ohm resistors per the guide. When push on either of the BYP2 connections or touch the back of the output pot the radio signal comes in loud and clear. Even the side that has the lower level will transmit the radio signal about the same level as the other channel. I swapped the connection for balanced cable from the output pot header to the stepped switch and same result. I even changed the switch to a 10k pot per the BOM and no change. The shield was attached to the side that connects to R94 which ties to ground. The Sowter 1365's that I am using for the output have a connection that ties to it's electrostatic screens but there is no change with it connected to ground or not.

I know it's something to do with what I've done, but I'm a bit stumped. I'm afraid I'm going to have to pull it all apart and stare at the board until I find something.

Until I fix this interference issue I won't be able to proceed with trying to solve the other guys. It's something obvious and stupid on my part as it usually is, but I hide my stupidity very well it seems.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on December 26, 2017, 03:30:36 PM
...it's definitely a radio station and not oscillating as I just added 100 ohm resistors per the guide. When push on either of the BYP2 connections or touch the back of the output pot the radio signal comes in loud and clear.

Ok, does it sound similar to this MP3 file (http://www.ttx-sound.net/foren/osc.mp3) ?

This happens, when I un-plug the connector for the output gain pot/switch, which leaves the output stage's input open. It starts to oscillate far above the audio band at around 120 kHz (as seen on the oscilloscope) and what can be heard are some kind of side effects within the audible spectrum that sound like tuning an old radio and a lot of noise.

You are right, this can't be fixed by just a series resistor - must be something else.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on December 27, 2017, 01:09:48 PM
It does make that noise when the output pot is disconnected, but the frequency shifting noise disappears when it is attached. Plus, when I touch the back of the output pot or press on the middle of the board at the output pot header, an AM radio station comes in very clear playing classic country music. I've been looking at the schematic to try to see where it could be. The only times I've had this happen is with a bad cable connection, which they all seem fine as the functions all seem to work with the exception of the loud popping in regards to the stepped output pot. I'm afraid I'm going to have to pull everything apart and start staring at solder joints....

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 04, 2018, 11:57:28 AM
Can you verify the correct wiring of the input and output pots? Now I have both poles (using stepped switches) going to the center header pin. I believe all other header wiring is correct as the functions sound like they are working properly.

I was hoping that I messed up the bypass wiring to the relays I am using, but those seem to be correct. I thought I had an issue with the transformer wiring, but that is also correct as it is clean when bypassed and the signal is always passing through those. I was for some reason missing R86 as that would account for the large increase in gain which didn't make sense as  the input transformer I'm using is 3:1 and the output is 1:1.7.

I'll start doing some component checking in the meantime.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 04, 2018, 12:41:50 PM
Also, R66 and R71 both have asterisks by them, but no mention of why in the manual. I this something that needs to be adjusted as well?

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on January 04, 2018, 04:16:44 PM
Can you verify the correct wiring of the input and output pots? Now I have both poles (using stepped switches) going to the center header pin. I believe all other header wiring is correct as the functions sound like they are working properly.

Yes, the poles (or wipers, when using a pot) of both the input and output controls go the center header.

Quote
Also, R66 and R71 both have asterisks by them, but no mention of why in the manual. I this something that needs to be adjusted as well?

The asterisks are leftovers from an earlier version of the boards, which I never sold to anyone. Both resistors adjust the positive and negative subrails. If you have about +/-20 volts there, you're fine (eg. measured at the top of R28 and the bottom of R29). I never had to change these.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 04, 2018, 11:28:07 PM
Thanks for the response. I was hoping again that I found the cause to my build woes. I think that is something related to the output pot as I get massive pops when I change settings and if this was a case of what happens with stepped output switches you would have reported this.

Whatever it is, I've manage to do it on both boards. I hope to poke around some more this weekend. I really had high hopes for this one as did some of my best soldering work on this board, so it was quite the let down when it was so noisy. If there are any bits of advice or ideas about places to check please let me know.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on January 05, 2018, 03:50:59 AM
Have you checked for DC on the output of the compressor stage, as suggested by Ilya? What kind of switches are you using?

The topmost pin (square) of the 'outputgain' header is the unattenuated output of the comp stage. Disconnect the switch and measure - it shouldn't have DC on it.

If it does not, you could also connect your soundcard directly (turn your monitors down!!) and listen to the signal . This way the output stage is out of the equation. Is the noise already there?

Here's one easy way to do it:

(http://www.ttx-sound.net/foren/alliclips.jpg)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 05, 2018, 02:31:32 PM
All righty....

Did the tests as prescribed and here's what I got.

When I first power up the device, there is about 10VDC on the unattenuated output header pin then it drops off immediately at a moderately fast rate down to about 0.01 and stays there. On power down, it does the same thing except with a negative voltage.

The noise is present with jumpers connected as described to just the unattenuated header pin and a ground reference. It is worth noting that the noise follows the compressor when there is signal at the input. When I ran program through it, the noise is attenuated with the input audio being at a higher level. The noise then returns as the compressor releases. So I believe the output stage is fine and that it is somewhere before the compressor.

The boards in the build are V2.0 and not the current V2.1.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 05, 2018, 03:39:26 PM
The switches being used are Lorlin. It appears the ones I have for the output are not make before break. When I turn the switch to the point before it clicks to the next position, I get +3.5VDC at the pole of the switch, which would explain the loud pops when I turn the knob. I do have some of the nicer Elna switches, but I was hoping to save those for a mastering compressor I am hoping to build later this year. I might have to order some Grayhills.

I have a V2.1 board that I am going to use for a channel strip idea that I could build and see if I get the same results. I just don't know if I have enough parts.

I'll stare more at this guy later tonight and see if I can try to narrow down the noise even further. If I figure out the noise part, then I can finish tweaking and get my being awesome award. Like I said, it's working, it's just that something is contaminating audio before it hits the compressor stage. The noise also does not change level with any adjustments to the input control.

Of all the troubleshooting adventures I've had, this might be the most exciting.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on January 06, 2018, 04:07:32 AM
When I first power up the device, there is about 10VDC on the unattenuated output header pin then it drops off immediately at a moderately fast rate down to about 0.01 and stays there. On power down, it does the same thing except with a negative voltage.

Mine also does that, when the switch is not connected, so I would consider it normal 8)

Quote
The noise is present with jumpers connected as described to just the unattenuated header pin and a ground reference. It is worth noting that the noise follows the compressor when there is signal at the input. When I ran program through it, the noise is attenuated with the input audio being at a higher level. The noise then returns as the compressor releases. So I believe the output stage is fine and that it is somewhere before the compressor.

I didn't run into this problem, but in one of the other threads about the TG someone mentioned that Zener diodes can be pretty noisy at times. However, I doubt they pick up radio stations, as in your case.

IIRC it was Ilya, maybe he can chime in.

Quote
The boards in the build are V2.0 and not the current V2.1.

Don't worry about the version number. There were only minor cosmetic changes, nothing electronics related.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 06, 2018, 10:32:47 AM
So the noise sounds like the oscillating noise that you posted, but then goes away when I touch the resistors on the output switch (or the wiper if it's a potentiometer) and becomes a radio station.

My next plan is to pull C11 and C12 and try to isolate the source of the problem to one half of the schematic. I don't feel that it's the Zeners as it's unlikely with modern manufacturing that a whole run would be bad, plus then they would have to be matched. But the problem is on two boards, so it's not impossible.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 09, 2018, 01:52:38 AM
Also, can I bypass the Zeners and still get audio and not cause a meltdown? Trying to make a list of all the things to try when I get back to it tomorrow.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on January 09, 2018, 04:55:59 AM
My next plan is to pull C11 and C12 and try to isolate the source of the problem to one half of the schematic.

If you want to bypass the sidechain completely, you also want to short out the bases of T7 and T8, or SCIn1+2. This way, the sidechain circuit won't get any input signal.

Also, can I bypass the Zeners and still get audio and not cause a meltdown?

The quick and dirty way: you could replace the Zeners D1, D2 and D3, D4 by a 120k resistor for each pair. This makes T1 and T2 act as an ordinary long tail pair without compression capabilities. Works in theory - without guarantee...  :o

(http://www.ttx-sound.net/foren/quickdirty.jpg)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Mike Havok on January 12, 2018, 03:18:17 PM
Would this be a suitable power transformer?

http://www.mouser.com/ds/2/410/media-1067235.pdf

https://www.mouser.co.uk/ProductDetail/Triad-Magnetics/VPT30-1670/?qs=wkKrz7WmEgMzASoQ2znXHg==

And does someone have a link to a suitable bridge rectifier on Mouser?

Thanks
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 12, 2018, 07:21:34 PM
It is not.

It needs to be 2x30V. The one listed is 2x15V

Here's a whole list of rectifiers:

https://www.mouser.com/Search/Refine.aspx?Keyword=2KBP

I used the Vishay 200V 2A version.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Mike Havok on January 12, 2018, 08:41:30 PM
Thanks Paul, gone for that Vishay 200V 2A.

This is the right trafo then isn't it?

https://uk.rs-online.com/web/p/toroidal-transformers/1233098/
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 12, 2018, 09:30:14 PM
Correct.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 12, 2018, 10:27:49 PM
Did all the things to by bypass the compressor settings and the diodes and still the same noise. Still completely clean when bypassed. Giving it a second listen, I would say it does like the MP3 you posted, without the sweeping frequency noise in the background. When I pull my output pot connection is does make the same sound. So I'm guessing it is something in the output stage, but what is escaping me. I'll start looking over the BOM and see if I misplaced anything, which is what it must be at this point.


Still getting loud pops when switching in/out. I am using the same square push button switches from Don Audio as you have in your stereo build.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 13, 2018, 12:17:23 AM
I replaced the Zeners with the 120k resistors and it is now clean, though it does sound broken in Comp and Limit modes, which I think is to be expected without D1-D4. The channel used is the one that needs major adjustments to the THD section as running audio through in this mode is much more distorted that what I think this is intended to be. Nonetheless, with no audio program playing it is very quiet. So now I need to find some more suitable Zeners than what I have. Any recommendations on which brands/part numbers would be best?

One thing I am noticing with the dynamics section is it bottoms out the compressor on the first big transient it sees from a drum kit, pinning the meter. Then the gain reduction stabilizes from there until the next quiet passage then repeats as above. I do not know if this will go away with properly working Zeners.

On a side note, the radio station thing happens regardless if it is working properly. If you touch the top of the capacitor behind the output header you turn the unit into a fixed AM radio preamp.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 13, 2018, 12:27:58 AM
The Zeners I am using are Central Semiconductor 1N751A TR.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on January 13, 2018, 05:50:08 AM
I replaced the Zeners with the 120k resistors and it is now clean, though it does sound broken in Comp and Limit modes, which I think is to be expected without D1-D4.

Exactly, as this was supposed to be a test with the sidechain bypassed. But good to know it's clean. Are you still getting the loud pops on switching, when the diodes are out of the circuit?

Quote
So now I need to find some more suitable Zeners than what I have. Any recommendations on which brands/part numbers would be best?

These are the ones I'm using (they are dirt cheap, so take a lot of them): http://uk.farnell.com/multicomp/1n751a/zener-diode-0-5w-5-1v-do-35/dp/1861484

Edit: Newark in the US sells them as well.

Quote
One thing I am noticing with the dynamics section is it bottoms out the compressor on the first big transient it sees from a drum kit, pinning the meter. Then the gain reduction stabilizes from there until the next quiet passage then repeats as above.

This can happen, when the control voltage feeds through to your audio signal. Have you checked, whether your audio looks like described in the guide "Fine Tuning, step 1"?

Also, have you done any mods, like the hold control? If so, I would suggest you remove it for the moment, as this makes troubleshooting even harder.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on January 13, 2018, 09:05:25 AM
I haven't been able to do the Fine tuning I on this board as the output was so lo and the distortion so high I couldn't get a good enough image on the scope to do this step. The other board I was able to do this step, but didnt really go much further as I was trying to solve the noise issue. I'm not going to worry about it until the diodes are changed out.

I do not have any mods. Everything is as per build guide.

I'm hoping to get the parts by the end of next week before I head out of town.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on January 14, 2018, 02:10:24 PM
So now I need to find some more suitable Zeners than what I have. Any recommendations on which brands/part numbers would be best?

Haven't continued my build yet. But stocked 3 different zeners.
My plan was to add some socket and try out which ones sound best.

Got the diodes from MultiComp, FairChild and also from Diotec "ZPD5B1"
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: core13 on January 18, 2018, 07:28:15 PM
Hello
I will build it soon and I have little question. maybe it's a dumb question but I don't know where to search
concerning bypass pushbutton what do I need concerning lamp voltage please? 12v is fine?
what is the one on this picture?
http://www.ttx-sound.net/foren/IMG_7840.JPG
is it possible to wire it like the original for comp1 comp 2 and limit and have a dedicated switch for thd?

thank you
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on January 19, 2018, 03:04:57 AM
concerning bypass pushbutton what do I need concerning lamp voltage please? 12v is fine?
what is the one on this picture?

https://www.don-audio.com/Classic-British-Console-Pushbutton-Switch-Illuminated-Yellow

This is the switch. They are illuminated with an LED, so you can use a wide range of voltages as long as you connect an appropriate resistor in series to limit the current.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mrdarwin on January 27, 2018, 02:57:27 PM
Hi!
Considering to build this machine...
a simple question:
Every DIY versions of this limiter need matched 1N751A, but can we use any 5.1v zener diode here?
Because all bom are available where I buy my components except 1N751A...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Mike Havok on January 27, 2018, 07:23:05 PM
Hi!
Considering to build this machine...
a simple question:
Every DIY versions of this limiter need matched 1N751A, but can we use any 5.1v zener diode here?
Because all bom are available where I buy my components except 1N751A...

I've ordered 500 Fairchild 1N751A's and I wont need that many so I could sell you some for a reasonable price if you wanted?. I'm in the UK but shipping wont be much I don't think
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: dogvoid on January 31, 2018, 01:06:23 PM
Hello everybody!!

Waiting for PCB;)

I found a very good option as audio transformers Carnhill

Input: VTB9046 2: 1
Output: VTB9070 1: 1.7

Does anyone know anything about it?

On the other hand, I have seen in other models a HI / LOW switch. I must review the scheme, but I think it is a switch that cancels or activates the pass through the input transformer, some information?

Thanks !!!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: mro on January 31, 2018, 04:01:54 PM
Hi,

Carnhills are excellent. F.E. Chandler uses them in their clones.
I was thinking VTB9046 and VTB2281 for the output.
Best contact [email protected] He sells them. A very helpful guy.
The I/O transformers bypass was a feature offered in some other TG1 clone project here on groupdiy.

Best,
P
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on January 31, 2018, 08:48:43 PM
It's been months this unit was left untouched on my bench (literally)!
I'm rebuilding my studio so I had no time to work on it.

Today I went to check out what is going on and try to pass some signals.
What I noticed is that it has pink noise combined with signal ONLY when gain reduction is happening. I don't know if it's the same issue Potato Cakes has since on my unit there's no radio signal in the noise. This is just pink(ish) noise.

I didn't try to see what's up with channel two. My diy time today was a bit limited.

I noticed that it has nothing to do with R22 and R7/R8 trimmers. The amount of noise is the same regardless of the trimmer position. But it has to do with the amount of low end in the incoming signal. I filtered the incoming signal (HPF in the plugin playing the test loop) and if it had no low end then the noise would disappear. It would still compress but without noise in that case. But that would be some heavy high passing, like everything below 500hz!
Also, I couldn't get R7/R8 to flatten the waveform. No matter what, some dc was always there.

I'll continue some other day, probably this weekend, when I have more free time.

Just felt need to report my current status for now

:)

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 01, 2018, 04:36:05 AM
Got a chance to circle back and work on this.

I pulled the diodes and matched 8 different pairs out of the new batch of 1N715As I used the two that measured the highest voltages, which I don't think actually matters. One of the channels is now clean but the other still has the same noise. However the channel that is clean still has several issues. I can't seem to get any of the fine tuning steps to actually do anything. Adjusting the trimmer does not change the waveform to what is supposed to look correct. I can adjust this properly on the noisy channel. I also cannot seem to do a proper adjustment on for fine tuning II. I do not have a distortion meter, but when I look at 1k on the scope I can see all the THD bumps on the sine wave, but adjusting R22 does not change any level of the distortion. I do not know if this is related to the fact that I cannot perform fine tuning I. The compression circuit is working, but it does have some weird things happening like when it comes to a quiet passage in the program material, the gain reduction circuit is being maxed out by several low frequency pulses about 2 seconds apart, then disappears. It does not do this with the side chain HPF. The noisy channel does not have this problem.

Another weird thing is that I get a pop on both outputs when I bypass either channel, but not when I engage the compression. I am using the square push button switches from Don Audio to control a pair of relays.

For now, I need to fix the noise that still persists on one of the boards. Then I can focus more on the other guy. But I am a bit surprised of how much trouble I am having with the quiet channel. I'll get back on it tomorrow. I hope.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 01, 2018, 05:44:48 AM
I was about to go to bed. Then my OCD flared up....

SO... I went back to the "clean channel." After poking around some more I found that I had to make adjustments to R56 as well because when I turning the trimmer for fine tuning I, I would lose audio, and I remembered something being said about that one time at that party with R56, so I trimmed that guy to where the audio came back and then I could finish adjusting the other trimmer to figure out R7 and R8. I still don't know if I am doing Fine Tuning II correctly. The highest value trimmer I have is 20k and not 50k as instructed in the manual. I do have some 100k pots that I could use, but I don't know if I will be able to make an accurate enough adjustment to my liking. I'm more curious if will be able to see this change on the oscilloscope and I currently don't. I do know the compression and limiting and the THD all sound correct with no weird jumping in the gain reduction circuit or the distortion being so great it sounds broken.

There is actually some noise, but it is way, way quieter. And giving it another listening it is indeed a radio station and not oscillation. When I press on the Bypass 2 header it comes in loud and clear. But to hear the noise I have to really open up the volume on my studio monitors, so I doubt it will actually be heard in any track I use to process with this. I do have this problem with tube mics if the cover is left off, but I don't recall having this problem on any of the rack gear I have built unless there was an unshielded connection there should have been one. Maybe it will be even quieter when I close the top lid and put in a rack.

I have gray hill switches to replace the Lorlins that are currently being used for the output gain, which causes loud pops when I make an adjustment. However I am using Lorlins for the input gain and they are totally fine.

The relays that are controlled by the bypass push button switches still cause a loud pop when I engage/disengage the circuit. I have used the same relays before on many other builds and have never heard anything like this when they switch. The Link push button is fine, but it is not controlling a relay like the bypasses.

The fancy 2.4mA meters that I got from Don Audio are working very nicely. I reread the meter calibration and realized that when the unit is off, the meter should sit on the line below 0 and when it is on R88 should be adjusted so it moves to the 0 line. I haven't done a thorough accuracy test, but from what I hear from the compressor and what I see on the meter seem to match up pretty good.

We're very close now.


Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 01, 2018, 05:28:04 PM
I need to change R86 and R87 to increase output so it is at unity gain on bypass. I found the formula for doing so, and if I decrease R1 and increase R2 I get the Vout value that I need, but I don't know if this is the correct approach or if I just change one value or if it even matters that much when dealing with low voltages.


Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 01, 2018, 09:11:54 PM
I got one channel up an running pretty good. The other is still very noisy even though I changed the diodes. I sorted out getting unity gain in bypass for both channels and they both compress and limit properly, but I could not closely match the THD because of the excessive noise. I did do a full swap of control and transformer connections and the noise stayed with the board. I was hoping for something easy, but it seems that problems have been getting very good at hide and seek these days.

I'll try pulling diodes again and see what happens. I find it very unlikely that diodes from two completely different matched pairs from different manufacturers made at different times would still be the issue.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 02, 2018, 01:12:09 AM
I changed the diodes again and touched up some solder joints. One or the other sorted out the noise, but now I am have a very difficult time matching the THD between the channels. I had put the first one the scope and was able to get the distortion per harmonic to fall off nicely and still be able to have unity gain with input and output knobs in the middle. I can get the other to kinda do the same, but at much lower volume. I've been messing around with trimmers for the last several hours and the best I can do is still +2dB of the channel I am trying to emulate, but the distortion characteristics as per the scope is still way off, and this is with R56 at 0.4ohms and R22 being over 30k.

The "good" channel wound up having R22 being 13k3 and R56 being 240.

I've managed to break a trimmer leg and socket in the process. The really sucks. The one channel is exactly how I want it but I may have to compromise it so I can have them both be the same. It's getting late again and I'm starting to get angry as I have been working on the noise problem most of day and I should be done with this by now and moved on to my last build. 

Anybody else run into difficulty with matching channels' THD?

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 02, 2018, 03:34:06 AM
Nice progress, Paul!! :)
Does that mean you have fixed the noise issue for good? What was it?

I wouldn't try to be too fastidious with the THD adjustment. As long as the onset of distortion is at about the same level for both channels it is good. Could be a zillion reasons why the Xth harmonic is higher on one channel or the other - component tolerances, temperature, phase of the moon... ;)

One my stereo unit, channel two has more 2nd harmonic in THD mode, but the two together sound great on stereo signals, so why bother. Interestingly, in COMP mode with link on, there's almost no difference between the two channels with regards to the amount of harmonics.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 02, 2018, 07:15:04 AM
Thanks!

I have no idea what was causing it, actually. I replaced the diodes and touched up some solder joints and then it was fine. There is still radio interference if I touch the cable going to the Bypass 2 header. I think the wires for this connection need to be shielded. I had a similar issue on some SSL preamps I built.

Swapped out the Grayhills for the Lorlins for the output switches but still have loud pops. I did some experimenting and found that a electrolytic cap with the + side on the pole and the - side on the 1st position that it solved that issue. I still have loud pops switching the circuit in and out. I might do something similar there. I still need to redo the resistor values for both input and output switches.

I think I have a pretty good THD procedure figured out, but I won't really know till I go back and redo the CV and THD adjustment on the channel that was good. After fighting with this for the last 15 hours, I thought I had it all good to go, but when I doubled checked my work, I saw that the "good" channel had a slightly sagging waveform when doing the drum loop test and it a little too clean in the THD mode. But that will wait till tomorrow. It's 6am here and I'd like to get a couple hours of sleep before I get up and get back at it. Once I confirm the THD setup procedure works, I'll share it here.

I will say if there is another batch of boards you wind up making, you might want to see if you can have the solder pads made out of a little more durable material. Or at least out of a metal/alloy that allows removing solder a little easier. For some reason, the pads are stubborn and hold on solder, requiring longer time that heat needs to be applied to fully clean it out. It's not a huge deal for me or should it be for anyone else who has the skills necessary to construct and troubleshoot this project, but it would make swapping out parts when tweaking a little faster. I already have another board that I'm going to cram into some sort of channel strip, so I'm set for this PCB. But maybe others might appreciate it.

The 2.4mA fancy meters do track very well with this circuit when using program material. The Stereo Link function also works very well.

This project has been quite the unexpected workout, but I'm glad I did and to have another high end piece of gear to add to my studio.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 02, 2018, 03:51:26 PM
I may have found a workaround for the loud pops when switching the bypass!

My desktop unit (it just has a toggle switch, no relays) also did this with the output gain control at certain positions. I just connected a 100k resistor from the middle pin of BYP2 to ground. A convenient spot for this might be the topmost pad of C34 (which is the middle pin of BYP2) connected to one of the ground pads of R94/R30. You could even remove C34 completely and use its pad for the resistor. This cap was a first and desperate attempt to minimize the pops, but as you can see, most of the time it didn't really work...

This got rid of the pops when switching in and out. Now there's merely a small click sound like my stereo rack unit does. I wonder why the relays in that unit don't cause popping sounds...

I will add this to the guide if someone can confirm it's working for them, too. Sorry for the inconvenience  :-[
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 02, 2018, 04:32:10 PM
Thanks for info. I was going to do something similar, but this info will save me time. And don't worry, this is DIY! It's all part of the love/hate emotional roller coaster that is inherent in this process. Hopefully I'll have this wrapped up today minus the power transformer that I've been waiting to arrive.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 02, 2018, 11:33:39 PM
I tried the 100k resistor thingy and it's still popping. What's interesting is that it will pop on the respective channel when engaging and then pop again on both channels when disengaging. For a quick test, I grabbed a random resistor and connected it to the middle position and ground and that solved the problem when engaging but still pops when disengaging. Right now I'm going to work on redoing the input and output gain resistors resistors and replace the connection to Bypass 2 with balanced line.  After that I'll mess around with the popping issue.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 03, 2018, 05:22:06 AM
I've got the output gain resistors replaced with the new values and it's approximately 2.5-3dB steps over 11 positions. Now I need to redo the input ones as now I want them to be more consistent as well. I was initially lazy at first and just did the 10k pot as per the BOM and divided into 11 steps. But what i discovered with output pot is that it worked best with my transformers using a 20k. So I attached a variable pot and turned till I had a 2.5dB difference, recorded the resistance, and repeated. I really should find the formula for just doing the math.

I replaced the wire for the Bypass 2 switch for shielded cable, but it didn't change anything as when I touch those wires, the same AM radio station comes through clearly. The output gain wires do the same thing as well, but at a lower volume.

When I redid the fine tuning I on one of the boards, I couldn't get it to track right till I got it to 2ohms, which I feel means something else it wrong, however the image is correct. The only side affect that I noticed is that with just using tone, when the other channel is at -4dB of reduction, this one is at 0, but it matches the other channel very closely after that. I feel this may have something to do with the abnormally low values for R7 and R8. This is board that I thought I had figured out the first time then when I double checked after calculating for the parallel resistors I saw that the drum loop wave form was askew.  I guess I can stand to have to desolder it one... more.. time....

For the other board I have, thing I may just mount the trimmers permanently. For future revisions, it might be a good idea to have a third solder pad to mount trimmers that way tweaking this will be much easier to do.

After all of this then fix the switch pops and we're good to go. This definitely will not be used in instances where exact calibration and finesse are the goal. I was really hoping that this would be done today (technically yesterday) as I really didn't have that much left to do, or at least I thought. Kinda bummed it will require another day of poking around.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 03, 2018, 08:55:06 PM
I've gone back to the initial setup and I think I have something wrong with the board that has unreasonably low values for R7 and R8. I've put R22 and R56 back to stock values and the board that seems problematic is 18dB lower than the other channel, which is the same when I first started testing. During the the fine tuning I, the gain reduction goes from nothing to maxing the meters out. This and the gain reduction is what causes me to think there is something else wrong. I thought I was about done but this might take one more day of poking around. I know it's not the diodes as I've swapped those out a couple of times and still get the same results.

I still get unity gain when channels are bypassed.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 04, 2018, 12:25:48 PM
Found some more things that will hopefully narrow down where this problem with the huge gain difference.

Swapped boards with the control connections one more time to be certain that it is the board and not a wiring issue. Problem moves with the board. Both boards still have unity gain when bypassed.

With both in compress and same setting, if I short R56 on the bad channel temporarily, the gain is then about 1dB off, which is more of what I would be expecting with two boards built with the exact same components. When I bypass then engage the compressor the gain issue returns. In THD mode, shorting R56 does not move the output levels up to match the working channel. It seems similar to when a power regulator has a latching issue if there are too many capacitors for the PSU to support.

When running the drum loop, the problem channel goes from no compression to maxed out compression (needle pegging on the beats), and the output level goes from lower output signal to much higher output, almost a 25dB swing. The HPF Sidechain affects the dB reduction (as far as the meter is concerned) as one would expect.

With both channels set to compress, bypassing the circuit on the good channel creates pops on the output of both channels, but only the meter of the bad channel pegs with this pop. When circuit is bypassed on the the bad channel, it still pops on both channels but the meter of the good channel does not move. I pulled the header with the link connection on the bad channel and the meter does not move when doing the above procedure, but there still is popping on both channels. When engaging the circuit, there is only popping on the respective channel. What may be needed is putting DC blocking caps to the output transformer as I'm sure the popping can't be good for it.

I'm going to start testing voltages around R56 and see if anything will show up. My focus right now is the gain issue. What ever is causing the output level problem is affecting the fine tuning I procedure and how the compression circuit is behaving.

The one thing that is really confusing is the pops on both channels when only one side is disengaged. The only connection between the two other than tying to a star ground is the link control, which is bypassed and is not making that connection in the first place. Plus, this still happens then link header is disconnected from the board. But for now, this and the radio station thing will have to wait.

Comments and suggestions are very welcome indeed.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 04, 2018, 01:00:39 PM
Correction, I do see the DC blocking cap before the output transformer. So I really don't know what's going on with the popping.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 04, 2018, 04:31:49 PM
Here are some DC voltages, I've just measured from my stereo unit, set to COMP with no input signal. If they differed from the two channels, I've included the other channel in blue. Let me know if you need more.

Regarding the relays: I'm using Fujitsu NA24WK and there are no popping sounds when they switch, just a tiny click.

Hope this helps.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 04, 2018, 06:36:31 PM
This does help, thanks. I started comparing DC voltages and they seem the same for the most part. I started checking AC with signal applied and I am only able to get a reading on some of the transistors in the gain reduction section. When I try to get a reading in the input section, the meter shows VAC for a second then falls off rapidly, even though signal is still present on both channels. I can measure audio signal up to Q1 and that's where I can't seem to get a steady voltage for my DMM to read. This applies to both channels.

I think I have a bad transistor in the input section of the trouble channel that is acting like an expander that opens up after I hit it with enough signal. It's going to be mostly guessing as I get a little lost trying to follow the audio path amongst all the transistors. This will just have to be a painful trial and error session.

I'm using OMRON G5V-2-DC24 relays. I have used them for pretty much every build that as needed relays, so this popping is a first for me. Plus, I am mostly baffled this happens on both channels when either one is disengaged.

Thanks!

Paul

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 04, 2018, 09:10:03 PM
I didn't have any BC559 left so I used some 560Cs for the suspect input PNP transistors but to no avail. I've gone over solder joint and checked voltages, and triple checked the control connections by swapping headers but still nothing. All the voltages in the input section matches pretty good with each other. The diodes and transistors in the compression section are different because they are not getting enough signal to do anything. When I crank the input signal to were it opens up whatever is choking the signal and the circuit is compressing, those voltages then match the other channel when equal compression is shown on the meters. Once the signal is passing, I can then turn down the input signal to where I read 4dB of reduction on the meter then past that, the signal falls off and I have to repeat the above procedure. I also found is when testing voltages, on certain points it will make the meter spike and then the compression is happening until the signal falls below that certain magical level. At this point I'm just guessing. I don't know if it's a faulty diode or transistor, and I'm not aware of diodes having this particular characteristic. My options are to replace all diodes and transistors on this board or build up the other board I I've been saving for another project and throw the bad one away.

I'll start with the diodes. Then we'll try with the transistors. This is becoming very frustrating....

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 04, 2018, 11:56:14 PM
Seems I don't have the diodes or the BC559s to make the swap. I'll have to make an order then wait. So hilarious.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 05, 2018, 02:55:44 AM
Indeed, sounds like a zener diode slipped into the place of an ordinary diode or something like that. Sometimes they are hard to tell apart.

FWIW, what does your grounding scheme look like?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 05, 2018, 11:21:05 AM
I've been following Ian's Grounding 101 for all my builds and it works really great. So no shared grounding between boards. So PSU, both boards, and any transformers that need to all tie to the star ground separately. If there is a ground plane connection and a 0V on a board those are connected separately as well.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 08, 2018, 06:53:29 AM
All righty then,

I went ahead and built out the extra board I had laying around, put it in and it closely matched the other one right out the gate, like I knew it should since all the parts were the same. This wound up being easier than trying to replace parts on the other one. The boards are obviously fine, I just either have a bad part or I missed finding a misplaced one and I felt a fresh start, at least for my time and sanity would be best. Maybe some day I'll feel the need to replacing all of the diodes and transistors on the board I messed up to get it working. But not today.

So now that I have both working close to each other, I have a bit more precise way to match the distortion for both channels. For measuring I used the Blue Cat free analyzer that shows distortion. After you do the Fine Tuning I step and install the properly calculated values for R7 and R8, put trimmers on R56 and R22 for both channels as per the instructions starting with the stock BOM values. Make sure match the values between the corresponding resistor numbers. Set the release for both channels to full CW and with the auto release engaged (if installed) as I found that the amount of distortion and which harmonics are emphasized changes with the position of the Release. In this position, I found it easier to match both with having a descending level of odd harmonics, which is what I preferred in this circuit. I put the Attack full CCW for both just to be sure, but this doesn't actually seem to change distortion levels. Both input and output controls are set to 12 o'clock. Because I said so.

Now we fire up the tone generator and route signal through the Blue Cat analyzer while also keeping an eye on the output level. For me, the distortion for both were already pretty close, with one channel about 2dB lower in volume. This is where your skills of finesse and patience will be needed. As per the build manual, R22 will change the distortion and the peak to peak output, and R56 will change output while having a different effect on distortion. Pretty sweet, right? The idea is to get the distortion waveforms to match and to have the same output, and this will require you to make slow adjustments and making a mental note of what is affecting what. Patience and finesse. So as in the build manual, you start by determining which one is least distorted or the you like the best. You might know this from simply looking at the waveform. Or you may have to turn off your generator and play some program through it (don't change the settings on the panel!) and listen to which one sounds "better". Then you go back and match the waveform and level of the "bad" channel to the good one. What you might run into, as I did, is that the channel having R22 and R56 being adjusted to match the other may not be able to get enough level so both outputs are even. For me this meant 0.5dB, which is fine when listening back but not when you are OCD about matching meters and numbers. If this is the case, you would lower R56 just enough on the higher output channel so that both have equal output and then double check your waveform.

Playing back program material in THD mode retained the stereo image much better than before without any noticeable shift to instruments that are meant to be centered. And if you want to change the harmonic content of the distortion, you can change this after the fact by adjusting the Release control and engaging the Auto Release if that is installed, so you are not stuck with the attributes of the distortion after you close the lid.

This circuit reminds me to a fair degree of sameness to a Chandler Zener Limiter that I rented years ago. Not particularly suited for mastering/program material (which is what I rented the Zener to do but was able to smoothly do), but definitely for some aggressive drum bus and guitar/bass tracks. I haven't messed with vocal tracks through this yet.

It should be noted that I went overboard matching D1/D3 and D2/D4 and kept them within 0.001VDC of each other for both 1k and 10k measurements and not too far from that between the pairs themselves.

Last couple of things for me to work out: I still get pops with switching the relays as before. It spikes the meter, but the actual sound is more like a clock switching noise and not a tremendous explosion as the display would suggest. Still needs to be sorted. The additional 100k from the middle pin Bypass 2 header to ground didn't seem to do anything for me in this regard. I also have the radio station thing to sort out. One channel has slightly more interference and after swapping positions inside the case, it was clear it has to do with what is mounted on the board and not the switches or cabling. One thought is that when I did my distortion calibration I was at too high of a level that is raising the noise floor. I get about +7dB from unity with the THD engaged and both input and output knobs set to 12 o'clock. I am using stepped controls with 11 positions. I could readjust R56 to be at unity and lower the S/N ratio in theory, but that wouldn't solve the mystery of the radio interference. However, in its current state the static interference is pretty faint and can only be heard when there is no signal being generated and the volume of the speakers are turned up. In use, I don't even hear it when it's processing audio and even if I don't figure this out it will still be for processing tracks. So for now, I've put the lid on it and I'll get back to tinkering with it after I finish the last build I have on my bench.

If anyone has any suggestions for trying to sort out the faint radio static I would appreciate it. I know it's somewhere between the bypass connections, as it is perfectly clean when the circuit is disengaged.

Really great project and I'm glad I finally got my mine up and running.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Neko Neko on February 12, 2018, 06:57:14 PM
Just starting my build. Excited to get going on this one!

Have a few questions before I start.

1. Can I get away with 5:1 for the input transformers? I've read that 4:1 input transformers are ok to use with a few resistors to change. 

2.  Hold control, worth adding? Was going to add it via on off on toggle and two set resistors instead of a pot. Struggling to see how useful it would be or exactly what it's doing. Some people refer to it as a kind of threshold control.

3. Side chain hpf caps.  How to calculate the cap values for the hpf, I would like to add more frequencies.

4. Good source of the 1n4153? I have only found one source and have to buy 100 at a high price.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 15, 2018, 03:08:39 PM
Member ToBSn has made a small helper board for the sidechain filter which he offers in the Black Market. I think he also mentioned values for different frequencies. Do a search in this thread, as well as for the hold control.

There's nothing special about the 1N4153 in this circuit. It's just a general purpose diode after all. Mouser lists the 1N483B as a more modern substitute which is also end of life, but they still have plenty of them in stock. I'm pretty sure you could also use an ordinary 1N4148 or 1N914.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Neko Neko on February 16, 2018, 06:18:05 AM
Member ToBSn has made a small helper board for the sidechain filter which he offers in the Black Market. I think he also mentioned values for different frequencies. Do a search in this thread, as well as for the hold control.

There's nothing special about the 1N4153 in this circuit. It's just a general purpose diode after all. Mouser lists the 1N483B as a more modern substitute which is also end of life, but they still have plenty of them in stock. I'm pretty sure you could also use an ordinary 1N4148 or 1N914.

Thanks for the info Fripholm!

I ended up ordering the 1n4153 anyway so could be good to have aorund for synths or something.

Thanks for the info on HPF, thats all i needed.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 17, 2018, 04:35:09 PM
I readjusted R56 to lower the output and more closely match unity gain when both the input and output are at 12 o'clock, hoping that decreasing the level would also lower the level of the static interference. That was not the case. I did notice that increasing the input gain decreases the noise about 5 dB. Also, to triple check that it was radio noise and not oscillation, I pulled the connector for BYP2 and I could hear a sweeping noise and see that sweep occur on the scope as it changed frequencies, so what I am experiencing is definitely not oscillation. The noise on one channel is 7-10 dB louder than the other, and this seems to move with the board and I have confirmed it is not the transformers or the switch wiring. And as before, the radio signal has something do with the wiring connected to the BYP2 switch, as when I touch is the radio station signal comes in loud and clear. I've used normal twisted pair and individual shielded cables, so maybe there is some other combination that I need to try. I am using a shielded cable to go from the transformer to the switch for BYP1. Touching this cable does not affect the radio station signal like it does with BYP2. I have a couple of ideas to try for testing to see if I can mitigate this noise.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 17, 2018, 10:59:43 PM
I think I am out of ideas. I've done more testing, but I can't seem to sort out this radio interference. I did find that even when the circuit is bypassed, I can still get radio when I touch the cable going to BYP2. I also found that when the circuit is in, if touch the side of R59 that connects to T15 I can make the radio station come in clearly, but not when touching the other side that connecting to ground. I even made a jumper to connect BYP2 to itself with a shielded cable without the need for a switch and still the same results. I tried to insert WIMA film caps of various values in places I thought that would help filter RF but to no avail. I would like to see if anyone who has a working unit that has is quiet when the circuit is engaged if they can cause a radio station to transmit through the output by squeezing the cable or cables that connect to BYP2. Or if they have any ideas on how to filter the RF or anyone is using all shielded cables to make their connections.

Another fun thing that I found which I didn't notice before is that the release control changes the output level when doing THD, or at least when running tone. I mentioned before that it affects the distortion characteristics but didn't also realize it was changing the level. Very bizarre.

I'm going to give it some more thought and also see if anyone has any fresh ideas I can try before I commit to giving up. It works as is and the noise floor is low enough that it won't matter when this unit is applied to louder instrument tracks. I just want to understand what is going on for the sake of increasing my own knowledge, but if it's not to be then so be it.

Thanks!

Paul

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on February 18, 2018, 03:37:41 AM
This doesn't seem right. The circuit shouldn't rectify AM/FM if built correctly. There's a mistake somewhere. And release shouldn't affect the output level at all. You need to start looking from there and try to find the error. Don't give up!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 18, 2018, 04:47:30 AM
I would like to see if anyone who has a working unit that has is quiet when the circuit is engaged if they can cause a radio station to transmit through the output by squeezing the cable or cables that connect to BYP2. Or if they have any ideas on how to filter the RF or anyone is using all shielded cables to make their connections.

Tried this but I still can only get the noise that I posted as a sample a few weeks ago. That only happens when the output gain pot/switch is removed from the connector. With everything connected I'm not able to reproduce this.

Maybe you have a radio station nearby which transmits on that particular frequency?

Quote
if touch the side of R59 that connects to T15 I can make the radio station come in clearly, but not when touching the other side that connecting to ground.

T15 is in the output stage, R59 in the sidechain and they don't connect. Which ones do you really mean? ;)


Quote
Another fun thing that I found which I didn't notice before is that the release control changes the output level when doing THD, or at least when running tone. I mentioned before that it affects the distortion characteristics but didn't also realize it was changing the level. Very bizarre.

That's odd, I didn't notice this before but you are right. The release control affects the distortion AND level. On mine, it's a level change of about 1 dB over the pot's travel.


Quote
I'm going to give it some more thought and also see if anyone has any fresh ideas I can try before I commit to giving up. It works as is and the noise floor is low enough that it won't matter when this unit is applied to louder instrument tracks. I just want to understand what is going on for the sake of increasing my own knowledge, but if it's not to be then so be it.

I think I've already mentioned it, C34 (next to BYP2) does not work the way I intended it to work. It usually is shorted when the circuit is engaged - but have you tried removing it completely?

C6 and C7 control the HF response of the compressor circuit. Maybe try increasing the value of one of them or both - up to 270p shouldn't affect the audio band. C6 should have the most impact. You could also temporarily short out R1 which (in combination with C3) slightly lifts high frequencies before it hits the input.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 18, 2018, 09:34:18 AM
Radio station only happens in other builds when I have an unbalanced cable when I should have a balanaced or on mic builds when the cover is removed. This current issue is new. I had just finished another compressor build with some different mods and during the troubleshooting/testing phase it did not have a radio station pick up, even with extreme output gain settings. So I'm a bit baffled to the say the least.

I meant T13 and not T15. Sorry.

Earlier I noted the change in distortion, but did not mention any gain difference as it was only about 1dB like you mentioned. Now when I'm testing it drops significantly when turning the release control, so I'm like "what is going on now?!" I've been constantly connecting an disconnecting the headers, so I don't know if something is starting to fail. This is happening on both channels.

I haven't tried removing C34 yet. I'll mess around with C6 and 7 and see what's going on.

I know all of these problems are my doing and lately I've been discovering all kinds of fun issues with recent builds, so I place the blame on myself. I'm just frustrated because after solving all kinds of different problems, this one in particular doesn't make any sense.

I'll make the changes and report back.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 18, 2018, 11:16:06 AM
A discovery about the Release affecting output gain. I had previously adjusted R56 to get the gain back down to unity when in THD mode. When I did this, that's when I started having a 40dB of gain drop with turning the release control down. I put it back to where it was and now I just have the 1dB drop as before. When I adjust R56 to a lower value, it eventually lowers the the level down to where I want it to be but it kills the distortion, however the release doesn't drop the output level. You can see in the attached image what you get when R56 is adjusted too low. So I will have to set everything back to where I have 8-10 of gain increase in THD mode with both input and output set to 12 o'clock and just figure out where the controls need to be set in order to get unity gain.

You'll note all the noise I am getting that I'm currently fighting. When I pull the output control I get this plus a spike that moves back and forth that looks like a shark fin which corresponds to the sweeping frequency due to oscillation.

I also removed C34 and changed both C6 and C7 to 220pF but that made no change in the RF interference.

My next move is to make sure all the connections that are going to ground are indeed doing that. I might also have to replace the input and output gain pot connections to shielded cable. I did already try this with the output pot, but not both.

I am going to figure this out!! Maybe!!

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 18, 2018, 12:52:52 PM
I've rigged up a step to pick off audio from different points in the circuit with tone being injected to see where noise it being amplified. A couple of observations:

- Noise at D5 is approximately 90dB lower than the signal peak. Before it was about 60dB. The noise level changes with the input gain setting

-Noise at R25/27 is about 100dB lower than signal peak when gain is set to 12 o'clock. The noise level at this point does not change with the input gain setting.

-BYP2 gives me only noise at the middle and engaged (side next to T13) pins and the level of that noise jumps intermittently.

Somehow the noise is being boosted by the time it gets to the output pot. If I could just maintain the 90dB difference like I get at D5 then I would be fine.

Time to go back to poking around.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 18, 2018, 06:49:07 PM
Tried some more things. Unless I my brain can come up with any more ideas, I think I'm done poking around for now. Here's where I ended up:

-Changed output/input pot and BYP2 connections with single, balanced, shielded cable. I the radio station no longer comes in clear when I touch the cable to BYP2, though the noise as before is the same.

-With a normal DPDT switch for the bypass, I had to use 8.2k resistor connected between the pole of BYP2 and ground and I was able to stop it from popping when engaging/disengaging. However, with the relay this would stop the popping when engaging but not disengaging. I also noticed at this point that I was no longer getting pops on both channels as before. I thought that it was something with how the relay was getting power and how much, so I lowered the voltage going to the relay down to 16V, but it did not fix the disengage problem. I did lead me to discover that doing this I no longer needed the resistor on the pole of BYP2 to ground to stop the pops while engaging. For the pops disengaging, I found that the level of the popping was inversely proportional to the output gain setting. Also, pops themselves contain higher frequencies, and can be lowered using a 48dB slope/octave LPF at around 16kHz. I still can't figure out how to get it to not generate an audio spike while disengaging with a relay. It happens to fast for me to get a voltage reading.

-The noise is being picked up somewhere after the input controls and before the BYP2 connection. It is present when I only have power, the output pot, and BYP2 connected with the circuit engaged. To reiterate, it's level is not affected by anything other than the output pot. This is with both stepped and variable controls. The places where I can pick off an audio signal after the output pot does show that I am getting noise but at a lower level. I just haven't been able to see exactly where in the signal flow of the schematic it gets introduced in the circuit. When I first started I thought I was D1-D4, but I'm pretty sure it's not those considering they been changed twice within the same manufacturer and a third time with a different one.

I think what I may do next is remove the connection between R30 and the output and start at the top and work my way from the input and see if I can find where the noise originates, although I don't know exactly what to do in the event I find the culprit.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on February 18, 2018, 07:00:29 PM
What kind of a noise it is? I had several noisy zener batches both from the same and different manufacturers. Are you using 751 zener? I had Fairchild 751 that were fine and another ones from Fairchild that were noisy. Try another zeners and see if the noise changes. You don't even have to match zeners for this check.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 18, 2018, 10:11:52 PM
What kind of a noise it is? I had several noisy zener batches both from the same and different manufacturers. Are you using 751 zener? I had Fairchild 751 that were fine and another ones from Fairchild that were noisy. Try another zeners and see if the noise changes. You don't even have to match zeners for this check.

I sounds to be radio interference. I have used zeners from MulitComp and Central Semiconductor. As I have stated earlier that I have swapped these out three times now, so I have a pretty good feeling that it is something else. I will, however, try it one more time because you brought it up.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on February 19, 2018, 01:57:08 AM
Radio interference is not relevant to zeners. If you get high level of white or pink noise than you can swap zeners to see if they are the culprit.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 19, 2018, 12:31:55 PM
I have replaced the zeners several times but will try one more time. If you had seen previously, when I touched certain cables I would get a radio station playing through very loud and clear, and just sitting idle the noise has the characteristic of being an RF signal that is very weak and not as consistent as white noise.

I'll try try pulling them later tonight and see what happens. If it is the zeners I might have to see about purchasing some tested matched pairs as I've already tried several different sets across different manufacturers.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Rob Flinn on February 19, 2018, 12:46:19 PM
I have replaced the zeners several times but will try one more time. If you had seen previously, when I touched certain cables I would get a radio station playing through very loud and clear, and just sitting idle the noise has the characteristic of being an RF signal that is very weak and not as consistent as white noise.

I'll try try pulling them later tonight and see what happens. If it is the zeners I might have to see about purchasing some tested matched pairs as I've already tried several different sets across different manufacturers.

Thanks!

Paul

Simple question:

Are you using screened cable everywhere with the screen connected to Earth on every cable ?    I found this made quite a lot of difference with stray noises.   It's not sufficient to use just twisted pairs for this box.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 20, 2018, 12:31:39 AM
I am not currently doing so but I was thinking that might be another thing I could do. After doing all the header wiring, I've only changing the wiring slowly as I'm lazy and didn't want to redo all those connections. But I may not have a choice.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 20, 2018, 03:43:10 AM
To what Rob said I might add, that it's even more effective to connect the cable's shield on only one side to ground.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 20, 2018, 11:15:14 PM
I pulled the zeners again and did 120k resistor bypass trick again and the noise was lowered by about 20dB, but then I found out the overall output was down by the same amount so there wasn't any actual improvement. I did notice at this point the radio station issue returned when touching the BYP2 cable when the zeners are bypassed. I put the zeners back in and made sure the input cable was connected to ground on one end all the way to the bypass header. I also pulled C11 and C12 as well as shorting SC1 and 2 to bypass the sidechain part of the circuit with no change. Signal is still clean when bypassed. So I know that it's not in the sidechain, in the output section past the output pot, or before C1. It seems that a gain stage before the output pot is boosting this noise and sending it downstream. Guess I'll have to go back to trying to pick off signal in the circuit and see if can find a change in noise level. I think for now I'm going to say it's not wiring that is inducing this unwanted signal.

At this point all I am looking to achieve is lowering the noise a bit more. It's still low enough to be quite usable for the large majority of types of instruments that I would use this to process. Its just that I have not had this type of issue on any of the dozens of other builds, even with in circuits designed significantly impart it's own characteristics to the audio signal. My problem is that while chasing this down I have maxed out my understanding of audio circuitry. I'll focus on just trying to find where the noise starts and see if anyone has anyone can provide some insight to this situation.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on February 21, 2018, 12:21:43 AM
You may try a couple more things. Inject test signal directly into output pot. This will confirm if the issue is in the output stage or not.
If it's the output stage, build this circuit in a simulator and check against the real one. This may give you some clues on what is wrong with your build.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 21, 2018, 03:49:40 AM
I pulled R30 and C8 and wired in a test lead to where it connects those components to the CW connection of the output pot. I found that I start picking up noise where T1 connects to D2 and where T2 connects to D4. I have to short the base and emitter of both of T1 and T2 to get enough signal to make a comparison, which is clean. The signal on both sides of D5 is also clean. I had already pulled D1-D4 out and did the bypass with the 120k and I still had noise. Is it possible that both T1 and T2 are bad? Keep in mind that this is the third board I've built with different parts from different manufacturers and I've had this noise problem on all of them, with the first attempt having higher noise than the others. Not saying it's impossible that they are all bad, but it's highly unlikely. My other thought is to reinstall R30 and C8 and remove T3 and T4 and see I get a cleaner signal when injecting tone after those parts, but before I do a bunch more unsoldering, I'm hoping someone here can offer some better suggestions that would prevent me from needlessly hacking away on this board.

I now know for certain that the output section is functioning properly. I also believe the wiring is not the culprit as well. This time.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 24, 2018, 04:13:39 AM
Paul, this one struck my mind the other day: Have you ever tried this without an input transformer, going directly into the input pin unbalanced? Does that help with the noise?

Maybe your input transformer is ringing heavily at HF and you need a zobel network across the secondary. Look up the datasheet of the transformer and/or experiment with different values.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 24, 2018, 10:30:16 PM
I have been thinking about this too, but if it's clean in bypass, wouldn't that mean the transformer is not at fault? Or am I incorrect thinking about it this way? If it's because I need a zobel network, then that would be great news indeed!

And thanks for all your help on this project. I know the dangers of offering a PCB to the public, and I appreciate you taking the time for your assistance.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on February 25, 2018, 03:41:00 AM
I have been thinking about this too, but if it's clean in bypass, wouldn't that mean the transformer is not at fault? Or am I incorrect thinking about it this way? If it's because I need a zobel network, then that would be great news indeed!

And thanks for all your help on this project. I know the dangers of offering a PCB to the public, and I appreciate you taking the time for your assistance.

You're welcome!

Maybe there's some HF interaction with the compressor and/or sidechain stage at work here that's way over our heads  :D

I would try it anyway - it's just a resistor and a small cap. You could also temporarily connect just a cap (start with a film cap, 100n~1uF) across the secondary. Depending on your input transformer, this filters out high frequencies completely and could give you a hint whether you're on the right track...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 28, 2018, 06:58:12 PM
It appears that a Zobel network is not the answer. The noise is still present when the input transformer is disconnected.

I did some more testing. I pulled T1-T4 and soldered C8 and R30 back in place. I picked the signal at R93 after the input gain pot and started injecting tone downstream and found that at the anode of D2 and 4 no noise added but there was at the anode of D1 and 3. This carried downstream and then the noise went away where R30 and C8 connect and go to the output pot. So I guess my next course of action would be to pull D1 and D3 and check again. I'll do that a little bit later as I need a break from pulling the board out of the case and desoldering parts. If it does turn out to be the diodes I will find that to be very hilarious.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 28, 2018, 10:27:33 PM
So after pulling D1 and D3, I find that I still get noise when I touch the test probe on the cathode side of the respective diode connections and it continues like before and stops at R30. The noise occurs even when there is no tone being generated and goes away when the probe is removed. So I put D1 and D3 as well as T1-4 and made an unbalanced cable to go directly to BYP1 and used a jumper to make the appropriate connection to BYP2 to take the relay out and the input transformer out of the chain but I still get the same noise results. The attached picture shows the noise when idle and with tone the 1kHz peak is at -20dBFS.

I'm at a loss here. I've have some really sneaky problems that I've been able to solve in the past, but I've done everything I know to do and have maxed my abilities to understand and strategize a troubleshooting approach. If I could find out why I am getting noise when I touch the end of the probe to D1 or D3 or even when they are removed from the circuit then may I could find the culprit. I noticed that where I am injecting signal is also attached to the +20V rail, so maybe that is disrupting something.

Whatever it is, I think I've exhausted all the possibilities that I have been able to take into consideration. Somewhere after the input pot, not in the sidechain section, not the zeners and not in the output section is the answer to this mystery. The one thing that I thought might help is if the ground plane was separated from the audio ground, but if no one else is having problems like this then I don't know if it would be beneficial. I did manage to blow up D12, T15, and/or Q14 on one of the boards while I was trying to find were the noise was originating, so now that channel's output doesn't work. I'm probably going to put this one off to the side for now. Maybe later I will build one of these in reverse order of the schematic signal flow and see when I can start to make noise happen.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on February 28, 2018, 10:48:30 PM
I also noticed that on the original schematic that VT13 and VT14 (T7 and 8 respectively) are supposed to be a matched pair. Would this make any sort of difference on the current schematic?

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on March 01, 2018, 03:21:08 AM
I did some more testing. I pulled T1-T4 and soldered C8 and R30 back in place. I picked the signal at R93 after the input gain pot and started injecting tone downstream and found that at the anode of D2 and 4 no noise added but there was at the anode of D1 and 3. This carried downstream and then the noise went away where R30 and C8 connect and go to the output pot.

As I understand the circuit description of the original, only the leg with T2, D3 and D4 is directly fed with signal and is a first amplifier stage. The other leg consisting of T1, D1 and D2 is biased the same way for temperature compensation but is not fed with signal, so I think it's normal you won't get any noise added there. It's a mystery to me, that the noise disappears at the junction of R30/C8 - because that IS the output of the compressor stage which is fed to the output stage where you can clearly hear it again. Doesn't make any sense...

From looking at your frequency plot, I would say it's pretty normal. But can't say for sure as it's not obvious to what reference level your interface is set to and what the compressor's controls are set to. Digicheck's noise measurement for my Fireface UFX+ (0dBu is set to -13dBFS on both inputs and outputs) tells me, the noise of my stereo unit is at -87 dBFS (RMS a-weighted), which calculates to about -74 dBu. Your plot is between -80 and -90, which falls in line with those numbers - if the noise were not a radio station playing country music...  8)

To measure this, I inject a 0dBu signal (-13dBFS) to the input, adjust the input control until the compressor just slightly starts compressing and adjust the output control to get the same signal level back into the interface again (-13dBFS). If your interface is set to -14 or -18 or whatever, you take these numbers. This way you get consistent readings. Noise measurement is taken without input signal of course.

What happens, if you close the lid or you cover the board with a huge steel cooking pot or something similar? Does that keep the radio station out?



Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 01, 2018, 05:43:38 AM
The noise doesn't seem to go away with the lid closed as I thought the same thing. The station only comes in clear when I hold the cable to the BYP2 connection, which is made less of a problem since I switched to shielded cable for this connection. The noise that you see on in the photo is all static but I do seem to hear way background a radio signal. At least I'm almost really sure.

I'll do your test with setting the compressor and see how that impacts the noise level. For over all output when adjusting the distortion, my meters in logic would read about -7dbFS and with no signal the noise would read about -65dB. I will have to double check but I remember it being close to that. None of the other builds I've completed have had this much noise unless something was wrong, so that has prompted me to really tear into this guy and try find out why this one has a higher noise floor.

I am a little baffled as well at the R30/C8 being cleaner than the points proceeding it. I also think I might have spent so much time repeating the process of removing the PCB from the case, soldering/desoldering, then testing again, I start to loose track of where I am. I might need to set this to the side for a while as I am starting to make things worse working on this guy. I think one thing I might is separating the audio ground from the top ground plane and have two connections going to the star ground from the PCB.

Maybe if you get an chance you could post a screen shot of your analyzer with and without signal to see what kind of noise readings you are getting.

Thanks!

Paul

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on March 01, 2018, 07:13:03 AM
I'm usually using Voxengo's GlissEQ as my analyzer, but their SPAN has the same flexible and very detailed frequency plot and it's free. I'd strongly encourage you to download and install it. It's very important to use the same analyzer settings, so we can compare apples to apples. Here's the spectrum preset (http://www.ttx-sound.net/foren/spectrum-presets-user.zip) I'm using (called "Measurement"). Unzip this file to your Voxengo user folder after installing. On Windows it's at C:\Users\YOUR USERNAME\AppData\Roaming\Voxengo\ - don't kow where it goes on Mac. Make sure to reload the plugin after copying the file...

This is the plot with signal @ -13dBFS:
(http://www.ttx-sound.net/foren/withsig.jpg)

No signal, only left channel shown:
(http://www.ttx-sound.net/foren/nosig.jpg)

I just realised, that I've made a mistake in my earlier post. The real noise numbers from Digicheck should be -80.4 dBFS (RMS A-weighted) which is about -67dBu.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on March 10, 2018, 01:50:02 PM
Hi Paul,

I built a 2nd stereo unit recently that had a similar issue to yours. The right side was quite noisy only when engaged, in bypass mode it was silent.

I took the board out, touched up solder joints and any potential micro bridges, etc. I also swapped out the 4 751 zeners too and the noise floor issue was dramatically lowered. I'm not sure exactly what did the trick but figured I would mention what worked for me...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 10, 2018, 07:53:26 PM
Just getting back to this.

I did the prescribed steps for setting up the input/output gains and have attached a pic of what it looks like in SPAN. The preset you attached wasn't recognized, but I was able to copy settings from the screen shot you provided.

The channel used is the noisier of the two by about 5-6dB. I have confirmed noise level difference is related to the board and not the proximity to the PSU or power transformer. I put all the connections back to how they are prescribed in the build manual after doing dozens of tests and soldering/resoldering parts many times with no change to the noise level.

I have changed the 751A's out several times as well as using shielded cable and bypassing the input transformer. So as far as I can tell, the unit is working properly, just seems to have more noise than what would be expected using modern components. I'd like to put this to rest this week before I leave on tour, because when I get back, I plan on finally organizing everything in a proper studio setup and get back to making music. I'm planning on using this in the setup, but I would rather not have to factor in the noise level every time I use it.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 10, 2018, 07:54:22 PM
I have attached a screen shot of it bypassed with no signal for reference.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 10, 2018, 08:18:02 PM
My next line of thinking is if there are other models of zeners that can be used that would give equivalent or even better results both in noise and subjective audio qualities? I don't need this to sound exactly like the TG Limiter on which this circuit is based. If there have been reports of the 751A causing noise in this and other similar PCB designs, then maybe finding a suitable alternative(s) would alleviate this "problem" all together.

On a quick glance, it seems that the 1N5231 seems to be a likely candidate for this application and is RoHS for those that care or need to care about this. The DIY-Racked version of this circuit even lists it as an alternative in the BOM.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on March 11, 2018, 08:59:18 AM
My next line of thinking is if there are other models of zeners that can be used that would give equivalent or even better results both in noise and subjective audio qualities?

...snip....

On a quick glance, it seems that the 1N5231 seems to be a likely candidate for this application and is RoHS for those that care or need to care about this. The DIY-Racked version of this circuit even lists it as an alternative in the BOM.
Are your zeners from the same batch or from different? If from the same, it's highly unlikely that they are the culprit (since you have one channel working fine).

I'd swap zeners between the channels and see if the noise issue moves with them. Don't remember if you've done this already or not. The circuit should NOT rectify radio, but with noisy zeners you can have drastically higher noise floor, but no radio.

1N5231 may be actually even better than 1N751. At least according to my notes. Definitely try them out. ROHS has nothing to do with zeners suitability. But different manufacturers can have different processes, so get the same model from different manufacturers if you can.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 11, 2018, 10:28:47 AM
I have swapped zeners several times from different manufacturers. And even though the channel not being tested is quieter, it's only a little less. The mention of RoHS was only referring to accessibility in places where "the State knows best" and not in terms of performance.

I might order some this week and see if they make a difference.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 13, 2018, 01:50:30 AM
I ordered some 1N5231 and wi ll report when I get them installed.

One thing I thought about is somehow shifting the inherent gain characteristics for the input and output to lower the noise floor. So if a different input transformer ratio is used to increase the signal level going into the unit, then changing the values for where the threshold of the compressor is higher (different value for the threshold control and or fixed resistor in line with the pot) to where the same or similar gain reduction is taking place at similar positions of the potentiometer in relation to CW/CCW and then reducing the level before it hits the output control to get the level leaving the unit to be the same as before, then we should get a much better S/N ratio. I don't know much of the history of the original circuit, but if it is true the sound is in the zeners, then how we do the gain structure around them shouldn't matter too much.

I could rewire my Sowter input transformers to be 1:3 then pad the signal before it hits the circuit to the desired amount. Then I would have to play with the compression circuit sensitivity and figure out where to alter the signal level before the gain pot. I would probably need someone a bit smarter to guide and give suggestions where to accomplish all of this. I'll stare at the schematic a bit more and see if I can figure out where to start.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 13, 2018, 02:10:07 AM
At a quick glance and with my child like understanding of electron behavior, It seems that increasing the values for R25 and R27 would decrease the signal feeding the side chain circuit and hopefully require more input signal to work. The place to do this would seem to be R73 and R74. For the decreasing the signal to the output pot it would seem that decreasing the value of R30 would accomplish this. I honestly don't know if there would be any adverse affects to circuit outside of my intended goals.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on March 13, 2018, 02:50:07 AM
If you increase the input level, you get higher level across the zeners. This will get you higher THD. You can increase the level only so much before you get distortion of unacceptable levels.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 13, 2018, 03:09:16 AM
If you increase the input level, you get higher level across the zeners. This will get you higher THD. You can increase the level only so much before you get distortion of unacceptable levels.

This is one of things I thought about and was afraid of happening. Maybe R14 and 15 could also be tweaked so as to not prematurely overload the zeners. I'll poke around with this after I swap zeners and see if I get better noise measurements.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on March 13, 2018, 04:12:12 AM
As Ilya said, in this circuit, noise behavior is extremely dependent on distortion behavior - there's no free lunch. When I designed the boards, one of the goals was to lower the noise floor. I actually modified the level going into the sidechain - which in turn altered the knee of the compressor and the ratio, which also needed to be compensated and so on...  :o

This is a feedback topology, where everything depends on anything else. Changing the overall behavior is not as trivial as it seems. Whoever the genius was, who designed the original, I'd bow to him ;)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 13, 2018, 10:41:17 AM
As Ilya said, in this circuit, noise behavior is extremely dependent on distortion behavior - there's no free lunch. When I designed the boards, one of the goals was to lower the noise floor. I actually modified the level going into the sidechain - which in turn altered the knee of the compressor and the ratio, which also needed to be compensated and so on...  :o

This is a feedback topology, where everything depends on anything else. Changing the overall behavior is not as trivial as it seems. Whoever the genius was, who designed the original, I'd bow to him ;)

Copy that.

Hopefully the new zeners will give me what I'm after, or at least get me closer.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: schrobbelbop on March 28, 2018, 09:40:07 AM
Hi Guys,

maybe not for this project but i'm building diy-racked's version of the zener limiter.
it's not an easy beast to manage!

i have one issue left, when linked the left channel is giving more compression then right above 6db's of compression
till 6db's it stays fine with right.

left channel CV raises at link point where the right channel stays the same.
TP-E goes down around 1.5 vdc on the left channel.

replaced and removed D-1-4
matched Q13/14

i have replaced 1n751 zeners from mousers brand to farnells (multicomp) the mouser ones are unusable (brand: Central) lotsa noise on the output.
could also be the other zeners be totally diffrent? it seems to be that when above a certain amount off compression the knee gets very steep and it turns in to infinity limiting....

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 28, 2018, 10:28:22 AM
Hi Guys,

maybe not for this project but i'm building diy-racked's version of the zener limiter.
it's not an easy beast to manage!

i have one issue left, when linked the left channel is giving more compression then right above 6db's of compression
till 6db's it stays fine with right.

left channel CV raises at link point where the right channel stays the same.
TP-E goes down around 1.5 vdc on the left channel.

replaced and removed D-1-4
matched Q13/14

i have replaced 1n751 zeners from mousers brand to farnells (multicomp) the mouser ones are unusable (brand: Central) lotsa noise on the output.
could also be the other zeners be totally diffrent? it seems to be that when above a certain amount off compression the knee gets very steep and it turns in to infinity limiting....

You are right, that is not for this project. It is best you email them directly.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Olegarich on March 30, 2018, 04:37:52 PM
Are those boards still available? wrote you a mail today.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on March 31, 2018, 04:45:03 AM
Are those boards still available? wrote you a mail today.

Sorry, I didn't get any mail from you. The boards are available!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 02, 2018, 07:54:19 PM
I'm home for a minute so I got a chance to swap out the 1N751As with 1N5231s and the noise is drastically lower. Compression and limiting seem to behave and sound as before, but i think I might have to drive it a little harder than before to get the same gain reduction. I'm not entirely sure on that one as it's been a while since I've tinkered with this. Now I just need to finish matching distortion and level between the channels and I should be good to go.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 03, 2018, 12:22:13 AM
Now both sides seem to be matched and the noise floor is down where I can finish tidying up the wiring inside and put it to use. You can see that I was able to 1kHz level and the third harmonic to match up pretty much perfectly.  I definitely didn't expect to have to experiment and solder/desolder as many times as I did, but I managed to learn a couple of things in the process. I still haven't been able to get rid of all the popping when using the switches, and maybe some day I'll get back to that. Here are some final notes regarding building these boards....

First, the circuit works exactly as is when built per the build manual. It seems to work well with the 2.4mA meters that Don Audio sells for this type of zener limiter.

Stereo matching channels is very tricky. R22 does indeed affect distortion, but so does R56 and the meter trimmer. This is also compounded when trying to match levels with R56. And you have to take into consideration that this same R56 value will affect the meter position, so when switching to compress/THD modes your metering will not be the same. For me, one of the channel's meters is slightly higher than the other in resting position after doing all of my tweaks, but the tracking above 3dB of reduction is very close. I think this board would be well served with an optional trimmer in the output stage to match levels without affecting the other aspects of the circuit. I think this would make matching much easier.

Also for the distortion calibrating, it's best to start with the attack set all the way to fast and not on auto release if you built your unit with this (I had previously stated to have the auto release engaged, but my push/pull switch was wired backwards). When you adjust R56 to give you maximum output, there is about a 1dB difference in level when the release control is adjusted as well as affecting the amount and type of distortion. However, when R56 is adjusted to match one channel to another, then the amount of output and distortion affected by the release control is quite a bit more, so it becomes necessary to have both release controls in the identical position when starting this process. I found that fully CCW (fast) is the best place to start so you have the most distortion present that can be seen on a meter as it relates to the release control. After all the tweaks are made, you can then used this control to change the distortion characteristics.

I used all stepped controls except for the release, but I feel that maybe a variable control for the output would be better when trying to use this for stereo applications and one is trying to match left and right. Even with using 1% resistors, the output levels are a bit off when both controls are set the same. Again, this may also be solved with a trimmer in the output section. This can be easily compensated in the DAW, but if you are unnecessarily obsessed with perfection when calibrating builds the slight mismatch can be off-putting.

Lastly, I don't think one should be focused on making a perfectly matched stereo unit with this circuit. I can't imagine the originals were, especially with component tolerances back then. One could match all the resistors, diodes, and transistors to 0.1% or better, but I honestly don't think it would be a good use of one's time for a dynamic processor that isn't known for precision and finesse. That's just my opinion, though.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 03, 2018, 03:25:00 AM
Tinkered with this just a little bit more before putting the lid back on for good, which gave me some new results...

I put C34 back in the one channel that was still popping (the other one I hadn't removed). Now I can see meters jumping on the inputs of my DAW when I take it in and out of circuit, but I cannot hear it whereas before it was a pretty massive sound. Not sure what I did, but somewhere in the 100+ times I took the boards apart and I managed to "fix" it.

The other thing is the linking. I had spent so much time tweaking the individual channels to match, but when I engaged the link there was about a 3dB loss on one side when just using tone. However, this is not necessarily the case when actually running program through it. I had this similar discussion with Mike at Hairball Audio when using the linking cards on his FET rack compressors and he concurred that tone and program yielded different results. So one will have to lean more on listening skills rather than having eyes glued to a set of meters, if one can imagine such a thing.

I also wound up putting both meters back to where they were for the initial calibration. After the unit being powered on for some time the resting position changed. This "warm up" time seems similar to the ez760 calibration.

If there were any future revisions, I would recommend having the option to permanently install a trimmer for R22 and a trimmer in the output section for level matching. I think with those changes R56 could just be 1k as the BOM states.

I would be interested if someone here did some transformer testing to see if there were any notable changes in audio characteristics. But emphasis on someone else doing that. I believe I have had my fill experimenting with this board.

Hopefully all of my struggles (mostly self-induced) as documented on this thread will help others who are building this circuit to complete one of these boards faster and without headaches.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on April 03, 2018, 06:07:55 AM
Great recap, Paul! Thanks for your input and persistence - much appreciated.  :)

Do you mind if I'd take some of your findings about the calibration procedure and add it to the guide?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 03, 2018, 11:58:36 AM
Great recap, Paul! Thanks for your input and persistence - much appreciated.  :)

Do you mind if I'd take some of your findings about the calibration procedure and add it to the guide?

Absolutely use any of this information that you want. I would recommend double checking my findings as I finished this up really late last night, but I did sit with this for a while doing tests with program material, so I'm confident that these results are repeatable. It might be helpful in the future to have some tips on using this in stereo operation, but I feel that if one acquires enough DIY experience to successfully build this circuit then they should be able to take into account the factors affecting the stereo linking operation.

I'd love to hear from someone who has built one of these with the hold control. I'm curious if this option would be more useful than the auto release. I have plans on building a channel strip with this as the compressor section and am thinking about going this route for the next one.

Thanks for making this project available and taking the time to provide updated information. I thought about renting a Chandler unit and making comparisons, but if someone wants a Chandler then buy one. Based off of my recollection, this unit behaves very similar, plus you get to learn stuff in the process.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on April 03, 2018, 12:19:44 PM
Having built this compressor per original schematic I can comment on hold control. I rarely leave it at maximum as in Chandler. Most of the time it is somewhere between 2/3 and 3/4 rotation where compression kicks in, but is not crushing the signal too much.
I had no difficulty matching channels. I had 4 close pairs of zeners though. I get a good match in sonic signature and THD, and tracking is very good both with link engaged and in independent operation. When linked you have to set all controls identically (except output) otherwise the units will not track properly.
The real task is finding proper zeners and matching them. Everything else is not that difficult.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on April 03, 2018, 09:18:54 PM
Paul,
Thank you for doing this in such detail. It's so inspiring to see someone go through such struggle and document every step with successful end.
I feel now that I have to find spare time to sit and finish my two channel unit! It got stuck on the bench for months since I'm too tired when I get home late and I had no energy to do my diy stuff.
:)
Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on April 08, 2018, 02:09:24 PM
Well, I had some time to play with my dual unit.
Seems that the right channel is working fine, except for some 50hz hum that is due to position of the output transformer. I'll move both transformers to a location that is not so close to psu and it's power transformer.

But I have problem with left channel.
Before I start fiddling with trimmers, I wanted to check if anyone have any idea where to look for a fault.
Audio is passing fine and it compresses (and limits) under some conditions. When the release is from 12 o'clock up to CW position it's okay. Compression is happening (though I seem to have a bit more distortion combined with some hiss whenever compression is going on, but I think it's due to trimmers being untouched). But when I shorten the release, at some point it just slams the gain reduction to max and output level drops about 20db down. And it stays like that until I move the release to some longer value past the 12 o'clock. It seems it doesn't have anything to do with attack time, it's just release related.

Any ideas where to look for a problem?

:)
Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on April 08, 2018, 03:50:01 PM
Might be that the control voltage makes it through as DC into your audio signal. When it does that, does your audio look like on the picture? If so, you might need to do Fine Tuning 1 as described in the guide.

(http://www.ttx-sound.net/foren/dc_audio.jpg)

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on April 08, 2018, 09:42:18 PM
Fripholm, I went to see what the waveform looks like and it's not raised up by DC signal.  I tried to adjust R7 but I couldn't manage to get my signal to have flats. Right channel was easy to adjust, I did that already, but on left channel it was impossible. I think it has to do with my main problem (see below)

I sorted out my initial problem with release cutting the signal if set too short! Left channel was way too low in level. So I went to increase R22 and when I got it to be the same level as right channel, all the problems with release were solved. I fiddled a bit with R22/R56 and settled on some setting that is very similar on both channels.

But I still have an issue with left channel!
Whenever there is gain reduction, there's a lot if hiss added to the signal. It happens only when there is compression going on, so it's not something with output amp stage. Also, maybe related to the same problem, when I switch to THD setting there's a lot more upper harmonics. It's like ten upper harmonics present above 1khz test tone. Regulating R22/R56 doesn't move them, just the first three or four harmonics move (as they should).
I'm thinking it's got something to do with zener diodes. Should I try to replace them? Or is it possible that it's some faulty transistor?
I'm tempted to order 1N5231 and put those on both channels since Paul reported that they lowered the noise compared to 1N751A.

Btw, tonight was the first time I was able to listen to this compressor! Even though it's still not finished, it's already KILLER sounding! I've built PYE, PRR176, Pico, clx160,  few 1176s and this one has something special in it's sound. I'm already happy with it! Can't wait to fix this hiss issue, add hold control and take it to the studio!

:)

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 16, 2018, 02:47:34 AM
Did you see my above post regarding THD? I was getting more than ten harmonics per channel. Where do you have your release control when you started matching THD? They must be in the same exact position when you start messing with R22 and R56. Plus, you really need to make sure when using trimmers for R22 and R56 that they are adjusted to the same value when starting to do any sort of matching. Remember that R56 affects the harmonic content as well as R22. It's a bit of a balancing act until you arrive at a result you like.

The hiss doesn't make any sense. Does it hiss when it is not compressing? When I had a noise issue it was ducked down when it was in gain reduction. I believe if the zeners were the issue the hiss would be present even with no signal passing through.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: shot on April 16, 2018, 04:31:23 AM
Did you see my above post regarding THD? I was getting more than ten harmonics per channel. Where do you have your release control when you started matching THD? They must be in the same exact position when you start messing with R22 and R56. Plus, you really need to make sure when using trimmers for R22 and R56 that they are adjusted to the same value when starting to do any sort of matching. Remember that R56 affects the harmonic content as well as R22. It's a bit of a balancing act until you arrive at a result you like.

Paul,
Yes, I've set trimmers on both channels to the same position at first. But my first channel was way off at that point. It was ducking the signal if release was set shorter than 12 o'clock. So I figured that it is due to R7/R8 and when I increased it enough the release problem was solved. During that process I had to trim R22 and R56 to get that channel's distortion and level closer to second channel. And during that tuning I noticed that I can't get rid of higher harmonics no matter what. And hiss issue was there all the time.

Quote
The hiss doesn't make any sense. Does it hiss when it is not compressing? When I had a noise issue it was ducked down when it was in gain reduction. I believe if the zeners were the issue the hiss would be present even with no signal passing through.

Thanks!

Paul

It's interesting - it doesn't hiss at all when there's no compression! It's just there when compression kicks in, and hiss level doesn't ride in level with amount of gain reduction. That's how I assumed it may have something to do with zeners... or not...?
And again, this happens only on the first channel! I went to measure some voltages on transistors and compare them channel to channel. It's very consistent. May be few mV off here and there but it all seems normal. So now I have no idea what to do apart from ordering new zeners and trying them. But still why would I do that if my second channel is okay, and all the components used throughout the build were from the same stock and I tried to match them whenever I could.
I have no ideas...

Luka
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on April 18, 2018, 02:58:46 AM
I've just got a report back from another guy who also used the zeners from Mouser. His stereo unit developed a massive hiss when turning the release pot clockwise. He's now replaced those with 1N751s from Farnell (Multicomp) and the hiss is gone and the unit's working as expected.

It seems, most of the noise problems arouse from those Mouser zeners (Central Semiconductor?), although the symptoms may vary a lot...

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 18, 2018, 05:24:12 PM
I've just got a report back from another guy who also used the zeners from Mouser. His stereo unit developed a massive hiss when turning the release pot clockwise. He's now replaced those with 1N751s from Farnell (Multicomp) and the hiss is gone and the unit's working as expected.

It seems, most of the noise problems arouse from those Mouser zeners (Central Semiconductor?), although the symptoms may vary a lot...

I used a number of different brands of 1N751s from Mouser and Farnell and all gave me the higher noise I was fighting. I do not recall the brand 1N5231s that I used. I'll have to the look that up if people are looking for that info.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ToBSn on April 18, 2018, 06:43:25 PM
Hi Guys,

I've found a new 1n751a  zener from RND Comps. here https://www.reichelt.de/?ACTION=3;ARTICLE=223390;SEARCH=1n751a

@Paul
Thanks for your hard work. It seems i have to read a lot for the next few days.
Is your unit up and running?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 19, 2018, 01:01:44 AM
Hi Guys,

I've found a new 1n751a  zener from RND Comps. here https://www.reichelt.de/?ACTION=3;ARTICLE=223390;SEARCH=1n751a

@Paul
Thanks for your hard work. It seems i have to read a lot for the next few days.
Is your unit up and running?

Yes it is indeed up and running. It's one of the many pieces that I've built for the reconfiguring of my studio. All the functions are working exactly as they should.

If you focus on building it exactly how it is says to do in assembly guide, you will have a properly working unit. There is quite a bit of off board wiring, so be prepared mentally for that. The boards are perfectly fine the way they are and the instructions explain very well how to customize your build with things like the hold function, etc. I just wanted people to be aware of what is going on when trying to do the stereo balance, which I would not have known about if I wasn't so obsessed with the noise I was hearing and hadn't spent all that time staring at a scope with audio passing through the unit.

Let us know how you go!

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: dogvoid on April 21, 2018, 08:44:48 PM
Hi

Finally I finished, well, the next month the input and output transformers, I think I'll put a switch to bypass these, I love how it sounds, it's wonderful!

In the end, the only zener that I have not given white noise problems I got in an old local store, and did not have many ...

After calibrating everything perfect, just following the pdf carefully.

The only problem is the baypass, I preferred to put relays with the pcb HWBP36 of Silent Arts and do direct bypass, when activating it sounds a "POP" is not a drama, but if someone knows some trick to eliminate them (they sound even with the volume to 0 input and output)

Thank you very much for offering this project, it is one of the best compressors that I have built (2 different SSL, one 1176, Gates Sta Level and Federal Compressor) sounds simply magical! I recommend it to everyone !!!

Abel
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on April 21, 2018, 09:13:19 PM
If the pop is from Volker's boards you should probably reach out to him. The pop using these boards is addressed in this thread.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: letterbeacon on April 29, 2018, 09:23:51 AM
Looks like a great project!

How is everyone using this limiter? Is anyone using it across the mix bus?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on April 30, 2018, 04:58:21 AM
The TG1 can be pretty aggressive and coloured, kind of ‚in-your-face‘. Personally, I tend to use a more transparent compressor on the mix bus but depending on your needs this might work for you as well.

I love it on close mic‘d snare, it makes them pop!  ;D Have also used it for rock piano or clean electric guitar and it works great on some vocals. Maybe it‘s the right choice for mix bus compression on some electronic genres but haven‘t tried yet.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: MrBlomski on May 07, 2018, 05:54:40 AM
@fripholm, what transformers did you use in you're build manual?
I have transformers from carnhill and I was figuring out how to use this in the stepped Elma switch version.

Cheers
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on May 07, 2018, 06:28:19 AM
I'm using Haufe transformers for input and output. The one on the input is designated as '90468' and it's a 2:1 - unfortunately I couldn't find any more info on this. On the  output is a RK310/2 which has a turns ratio of 1:1.

Unless your using something different than a turns ratio of 2:1 you should be fine by using the resistor values for the input switch provided in the guide. For the output, the kind of transformer you're using is irrelevant for the values.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: warpie on May 17, 2018, 07:06:30 AM
Does anyone know what is the input and output impedance of this circuit if I use a 2:1 and 1:2 in and out xfmrs? Thanks!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on May 17, 2018, 03:27:12 PM
Does anyone know what is the input and output impedance of this circuit if I use a 2:1 and 1:2 in and out xfmrs? Thanks!

The input impedance is about 3k which makes it about 12k when using a 2:1 transformer. The (simulated) output impedance of the output stage is less than 20 ohms which again is quadrupled (for an 1:2 xfrmr) at the secondary plus your winding resistance.

HTH
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: warpie on May 17, 2018, 04:13:08 PM
thanks fripholm  :)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: orangechili on May 27, 2018, 10:50:06 AM
@Paul,

Would you happen to know what brand 1n5231 diodes you used? It would definitely be helpful as option for others to try who get the noise issue with zeners etc.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on May 27, 2018, 05:52:32 PM
@Paul,

Would you happen to know what brand 1n5231 diodes you used? It would definitely be helpful as option for others to try who get the noise issue with zeners etc.

As I posted above, I do no recall and I cannot seem to find that order. They were either Vishay or ON/Fairchild.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: MrBlomski on August 22, 2018, 02:18:13 PM
Hello everybody!!

Waiting for PCB;)

I found a very good option as audio transformers Carnhill

Input: VTB9046 2: 1
Output: VTB9070 1: 1.7

Does anyone know anything about it?

On the other hand, I have seen in other models a HI / LOW switch. I must review the scheme, but I think it is a switch that cancels or activates the pass through the input transformer, some information?

Thanks !!!

Did you realise this? I would like to know :)


Other stuff:
I am going for matched 1n5231b

Other question:
Could some people post some front panel designs for me for inspiration?
Thanks I am a noob at designing this.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Hobbyist on August 22, 2018, 03:28:47 PM
Did you realise this? I would like to know :)


Other stuff:
I am going for matched 1n5231b

Other question:
Could some people post some front panel designs for me for inspiration?
Thanks I am a noob at designing this.

Here is the idea for my unit.

  :)

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on August 23, 2018, 03:58:59 AM
In case you didn't know, there's also an FPD file (for Front Panel Designer) with my design within the ZIP file from the first post.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 19, 2018, 12:26:47 AM
Hi all, I built my unit about a year ago, but I was having an issue where the +28v rails would suddenly drop down to about 16v dc. I've been trouble shooting this intermittently ever since, but haven't been able to figure it out. Could there be a problem with my diodes?

I just replaced all the transistors on one of my boards and am positive the output transistors are installed correctly. But I'm still getting the issue, so I doubt it's a transistor problem.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 19, 2018, 01:35:02 AM
Hi all, I built my unit about a year ago, but I was having an issue where the +28v rails would suddenly drop down to about 16v dc. I've been trouble shooting this intermittently ever since, but haven't been able to figure it out. Could there be a problem with my diodes?

I just replaced all the transistors on one of my boards and am positive the output transistors are installed correctly. But I'm still getting the issue, so I doubt it's a transistor problem.

Does it do this with nothing connected to the PSU? Are you using one or two boards? You're just going to have to do the process of elimination like everyone else has to do in this situation. PSU work properly without being connected to any TG boards? Yes - connect one board at a time and check again. No - double check your PSU soldering/component placement. Etc, etc....


Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 19, 2018, 11:44:42 AM
The PSU holds the correct voltage without the boards connected. I've actually tried a few different LM317/337 PSU circuits and even perfboarded Fripholms circuit to make sure, and they all do the same thing when I connect to either board. I even tried different power transformers. Same thing. I've quadruple checked my soldering and component placement (not my first rodeo ;). I suppose something could be in the wrong place, but it seems odd that both boards do the same thing.

As noted above there are two boards with the same behavior and the voltage drop is worse when both are connected to the PSU.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 19, 2018, 02:29:27 PM
How hot are your regulators getting? Are you using big enough heat sinks?

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 19, 2018, 03:58:13 PM
Does this only happen with the positive rail? Could you try and measure the DC current draw of the positive rail when this happens?

However, from what I'm reading, the PSU seems to be okay.

To further delimit the possible fault you could try and lift one side of either R31 and R75 - one at a time. The latter is directly between +28V from the PSU and the output stage. If that one is lifted and the voltage drop goes away, the problem most likely is within the output stage. This stage obviously can't work with the lifted resistor but it helps pinpoint the error.

R31 is part of another discrete on-board regulator that provides a +20V rail (derived from the PSU's +28V rail), that the entire compressor stage including sidechain runs on.

There's nothing else that is directly connected to the 28 Volts rail (except for maybe R66 and R64, which I suppose are 100k and 10k respectively?) which would be able to cause a voltage drop like you describe.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 19, 2018, 07:33:30 PM
Thanks for the help guys.

There must be a problem with the output circuit because the voltage drop doesn't occur when R75 is lifted (it looks like I already tried this some time ago, but I must have thought there was some other problem). Leaving R75 in the circuit and lifting R31 still resulted in the drop.

R75 is a little scratched up, probably from my previous troubleshooting attempts, so it might be good to replace that regardless.

pictures of output transistors and R75
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 20, 2018, 04:03:17 AM
Firstly, what's the current draw with and without R75 in the circuit?

I see, you're using 3055/2955 transistors for your output stage. Have you tried the circuit with BD139/140?

I've put the additional footprints for 3055 and 2955 on the board to have options, but have never actually tried it with those nor do I know of anyone who has (ANYONE??). They're pretty similar though and theoretically should work but it's worth a try and change these to BD139/140 - if you happen to have them at hand. Or maybe one of them is faulty...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on September 20, 2018, 06:17:52 AM
I've put the additional footprints for 3055 and 2955 on the board to have options, but have never actually tried it with those nor do I know of anyone who has (ANYONE??). They're pretty similar though and theoretically should work but it's worth a try and change these to BD139/140 - if you happen to have them at hand. Or maybe one of them is faulty...

My stereo unit that I wrote about earlier in this thread is using 3055's and 2955's with no problems. I double checked to make sure I was using the correct footprints before soldering them in place.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 20, 2018, 10:35:14 AM
I'll check the current draw when I get home from work, but I initially used BD139/140 and switched thinking that it might be the issue (it wasn't lol).
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 20, 2018, 07:33:33 PM
Silly question: how do I measure the current draw of the circuit?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on September 20, 2018, 10:54:43 PM
Silly question: how do I measure the current draw of the circuit?

You can put a DMM in series with either voltage rail right after PSU. DMM will show you current consumption on that rail. Make sure to put your DMM in current mode.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 20, 2018, 11:56:08 PM
That makes sense, thanks!

So with R75 the DC current on the +positive rail is around 0.04 amps (although it starts around 0.07 amps and then drops quickly).
Without R75 the DC current is around 0.02 amps.

In both cases the negative rail is around 0.03 amps.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on September 21, 2018, 12:43:59 AM
Those bands on the resistors are hard to decipher from that one pic.... maybe test the values of them to be sure if you haven't already?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on September 21, 2018, 02:02:41 AM
That makes sense, thanks!

So with R75 the DC current on the +positive rail is around 0.04 amps (although it starts around 0.07 amps and then drops quickly).
Without R75 the DC current is around 0.02 amps.

In both cases the negative rail is around 0.03 amps.

The current seems too low. As if the output stage is not working.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 21, 2018, 04:42:01 AM
So with R75 the DC current on the +positive rail is around 0.04 amps (although it starts around 0.07 amps and then drops quickly).
Without R75 the DC current is around 0.02 amps.

In both cases the negative rail is around 0.03 amps.

On my stereo unit each channel draws about 60mA from the positive rail (starting from 70mA then dropping quickly). The negative rail is ~30mA - just like yours.

The output stage in a properly working unit draws ~40mA from the positive rail, which means that without R75 your reading of the remaining 20mA is correct.

All of this doesn't explain the voltage drop you're getting. I was expecting excessive current draw - but nope  ???

What are the DC voltages at either end of resistor R3 on the PSU board with R75 in circuit?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 21, 2018, 07:57:13 PM
I'm not using the same PSU circuit at this point and there doesn't seem to be a corresponding resistor (the copy of your circuit I perfboarded  is in another piece of gear :/), but checking the positive voltage before it hits the regulator and after the diode bridge is ~36v and I'm getting ~ -44v on the negative rail before the regulator.  I'm getting around 60vac from the transformer.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on September 21, 2018, 09:19:23 PM
Got a schematic of the supply your using??
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 21, 2018, 10:36:18 PM
I don't have a schematic handy, but I landed on a Chinese kit off of ebay.

https://www.ebay.com/p/PCB-Board-for-Lm317-Lm337-Adjustable-Power-Supply-Voltage-Regulator-Bare-Rf4/6006632706?iid=172179466048
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 22, 2018, 04:49:32 AM
Looks pretty standard to me - without the extra filter resistor (which R3 is). 36 Volts on the positive rail should also give enough margin to properly regulate down to 28 at low currents like you've measured. But it's still quite a lot lower than the negative rail... weird  :o

What's the power rating of your transformer (in VA)?

Quote
I'm getting around 60vac from the transformer.

Is this between both AC wires or between AC and center tap/GND ? If it's the latter, it seems quite high...

What happens, if you temporarily adjust the PSU down to like 24 Volts on each rail to give the regulator even more margin? Does it still drop?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 22, 2018, 12:21:04 PM
Transformer is 50VA (antek as-0528)

60v is between the two ends (transformer is wired in series) so the former

Adjusting down to 24v it still drops to around 16v.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on September 22, 2018, 02:02:31 PM
I'm guessing the reg heat sinks are good enough ???seems like a bit of voltage to drop ....IDK..... you said the original supply acted the same???so it must be something else???

What does R75 measure??? looks like it's 59 ohm from pic???
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 22, 2018, 02:34:05 PM
R75 is 56 ohms on both boards.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on September 22, 2018, 03:39:58 PM
Looking at the photo it seems you are using metal locking washers for the standoffs. Have you made sure they are not piercing any traces on the top and/or bottom layer? The positive rail runs in close proximity to one of the holes.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on September 22, 2018, 03:48:07 PM
I think I remember someone somewhere having some issue that was weird like this and they had the transformer primary wired up goofy or something.........just throwing stuff out there.....
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on September 22, 2018, 05:35:41 PM
So I just now tried this with a bench power supply, wired it backwards and quickly blew up c25 on one board. I though "ah ha!" and then realized I wired it backwards...

Tried with the other board and the bench supply set to +/- 28 v like I''d want with a draw of  0.03 amps on the negative rail and .06 amps on the positive, so I guess there must be something off with the power supply circuit somewhere. I'll email fripholm and get a copy of his psu pcb just so there's not weird variables in this.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on October 09, 2018, 02:42:36 PM
Quick update: I received the PSU board from frip and got that working with a brand new power transformer, but I'm still running into the same issue with my TTx boards. One actually got worse (negative rail gets higher while the positive rail gets lower), but I think it's because I flipped the polarity during the bench test as noted in the post above.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 09, 2018, 03:49:50 PM
Sorry to hear that!

Maybe something else blew up on that board during the bench test with the polarity flipped. Most likely candidates are C21 and C26 and/or the transistors in the output stage. But you should first fix your PSU problem with the good board before troubleshooting this.

As I suggested earlier by email, you could try a TL783 on the PSU board as the positive regulator.

Could you post a bird's eye photo of your limiter boards? A few more eyes might see something you missed...
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on October 09, 2018, 07:41:46 PM
I replaced C12 and C26 on both boards and they're behaving the same again.

Picture attached.

I'll order a tl783 and take a look at that.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 09, 2018, 10:35:55 PM
So the bench power supply still gives the right readings on both boards  but the new psu does not??


how do you have your transformer wired? Have a diagram??? I know you mentioned series earlier.... ??


Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on October 09, 2018, 11:12:47 PM
So with the antek transformer I had red-red and black-black connected to the 120V source (IEC jack, on/off switch etc), and then I had the secondaries in series - middle blue and green connected and the outer blue and green going to the power supply board ac inputs.

To rule out any weirdness with wiring, I switched to a simpler transformer (https://www.digikey.com/product-detail/en/hammond-manufacturing/187D56/HM4759-ND/2358269) with a single set of primaries/secondaries, and yeah, same issue, even with Frip's psu board.

The bench is working with the both boards just fine. I'd assume there's some sort of hefty regulation happening there.

Fuse should be slow blow, correct?

It seems like there some component on each board that's having some sort of gradual short?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 09, 2018, 11:39:27 PM
what is the current draw from these boards anyway? Did you measure that one resistor voltage drop now that you have frip's board?? The one after the bridge I think it was???

ll///you didn't wire the center tap to the psu board???
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 10, 2018, 01:58:38 AM
ll///you didn't wire the center tap to the psu board???

Yes, the transformer's secondary center tap must connect to GND on the PSU board - at connector "AC" next to the AC label.

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Hobbyist on October 10, 2018, 02:33:25 AM
Hello,

This is what i did and works great, have perfect 28- and 28+ .
I made also the mistake with wiring the secondaries wrong.

Connect 0v to ac



Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: brewbacca on October 10, 2018, 11:13:37 PM
The missing center tap connection was the issue. I have a steady +/- 28V. Thanks guys!

I'm betting I'll have some issues getting my meters to work (they're the 2.4ma sifam that some other people in the thread have), but that will have to wait for a bit.

Thanks again everybody!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on October 11, 2018, 12:24:13 AM
I have the fancy 2.4mA meters and they worked great after I did the calibration as per the instruction and then a little tweaking to my liking. I found that the gain reduction amount printed on the meter is pretty close, but it still should only be viewed as a guide for what is happening and not as a true representation of math and science.

Thanks!

Paul
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 28, 2018, 09:11:42 AM
Hi again everyone!

Took a little break from this project after it gave me a lot of trouble. I've got three almost complete projects on the bench right now though, and ideally I'd like to get them all working before I start any other projects.

Fripholm was nice enough to send me the LTspice files for the output section to help me do some initial troubleshooting. I found out that Q13 on the main board was installed incorrectly. After I fixed that, I couldn't find any problems with the output section of the main board, nothing seemed to be fried and voltage reading were just fine, however, to this day, I'm still not getting any kind of output. Fripholm's last email to me said to check my output transformer with a TS cable. I only really have TRS available to use with the test tones from my DAW, but I tried putting the input leads on all the combinations I could think of and still nothing.

I'm using a sowter 1365e, which are pretty pricey, so I'm hoping that they're not dead and I just have something wired up wrong. Could that flopped Q13 have damaged them enough so they aren't functioning?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 28, 2018, 09:38:47 AM
Yeah, the first thing I did once I saw it wasn't working was to check my transistors.

I did just do a quick test on the top of C29 and I'm not getting a DC voltage reading at all really, so something must have burned up due to the flipped BD139. Now I just have to track down the malfunctioning part(s). I haven't seen any smoke or anything during any power ups so far.

So what has happened since this post?? I was trying to follow your progress but it sorta dropped off until now......
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 28, 2018, 02:22:16 PM
Fripholm's last email to me said to check my output transformer with a TS cable. I only really have TRS available to use with the test tones from my DAW, but I tried putting the input leads on all the combinations I could think of and still nothing.

I'm using a sowter 1365e, which are pretty pricey, so I'm hoping that they're not dead and I just have something wired up wrong. Could that flopped Q13 have damaged them enough so they aren't functioning?

You can also use TRS cables for the test. Make sure to disconnect the transformer from the circuit before testing. You basically connect your interface's output via TRS to the primary of the transformer and the transformer's secondary to the input of the interface. If you're getting a clean signal, the transformer is fine. If your interface has balanced I/O, you connect TIP to the PLUS side and RING to MINUS, SLEEVE goes to the transformer's chassis or shield if that wire exists.

You wrote this in an email back in November 2017:
Quote
-I'm using Sowter 1365 for output tx, the wiring scheme is Primary: Brown+, Blue-. Secondary: Green+, Grey-. It also has a black wire for electrostatic shield.

According to this, output cable TIP is BROWN, RING is BLUE - input cable TIP is GREEN and RING is GREY. BLACK goes to any SLEEVE. But before, make sure you're getting an input signal when one of the TRS cables goes straight from output to an input on your interface.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 29, 2018, 04:25:25 PM
So what has happened since this post?? I was trying to follow your progress but it sorta dropped off until now......

Unfortunately, due to a combination of me being busy and just kind of generally discouraged about the project, not much. I've been recording a lot recently though, and this piece of gear is one of my bucket list items, so I'm feeling inspired to give it another try.

Your post did remind me of the C29. I just checked it again on my one board and I was reading very low VDC, but about 17.8VAC, which if I recall, was about what I kept getting at my output for whatever reason. Maybe there's a clue in there somewhere.

Edit:
Just rechecked my output transformers. No signal whatsoever when touching the primaries to a TRS cable as fripholm instructed. The secondaries are soldered to my XLR connector, so I was connecting back to my interface via a microphone cable. I managed to place the TRS so the tip and ring touched on pin 2 and ground and my test signal came through. This is true on both output transformers.

So I guess they're shot? It seems strange that they'd be so delicate, I once accidentally sent phantom power into an output transformer via a patch-bay misunderstanding and it's still kicking. But, then again, maybe I'm just in denial. Either way, I'm sure that's not the only issue that I'm facing with this project at the moment.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on October 29, 2018, 04:44:35 PM
A wild guess. Maybe the actual pinout of the transformers differs from what is there in the datasheet? You may try to check the windings with a DMM and see if they are not open. You can also check a signal with a scope before the transformer (AC coupled). This will show if you're getting anything from your output stage at all.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 29, 2018, 05:02:49 PM
So I had a thought just now. My test signal was very low for my ears sake. Around -20dB. I cranked it up to -9dB and hey, a signal! It's a very low signal though. Tried it with some actual audio and got similar results. Sounds fine through the monitors, albeit incredibly quiet. The 1365e transformers I'm using are advertised as being 1:1.77 ratio, so I was expecting a volume increase. Maybe I got a batch with the color inverted? That being said, the signal I'm getting out of them is quite weak, so I'm not sure that's a good sign or not.

Edit:

Alright, I'm at a loss. Wired it up in reverse, since I realized I could actually do that. Got a signal, though still more quiet than I'd expect. I recorded some measurements and figured that for science, I should really see what my dB drop is when wired normally. Hooked it back up as I had been before, and suddenly I'm getting a full strength signal! Outputting -21dB from my interface and getting about -17dB back from the transformer. I have no idea why it suddenly decided to start working.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 29, 2018, 07:03:20 PM


Your post did remind me of the C29. I just checked it again on my one board and I was reading very low VDC, but about 17.8VAC, which if I recall, was about what I kept getting at my output for whatever reason. Maybe there's a clue in there somewhere.




Well I'm not sure about this piece without looking but ac voltage  shouldn't usually be around unless it's an audio signal.......and never that high even so.........

Something might be up for sure.........I don't know yet

calling fripholm.. 

is there a voltage reference schematic for this floating around????
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 29, 2018, 07:33:08 PM
Just did some more tests, I've been given new life for this project now that I know the output transformers work. Checking the voltages again and honestly, everything seems like it should be working. However, for some reason I keep getting a reading of 17.6VAC everywhere! Like, literally everywhere, even at the outputs of my power supply, leading me to believe that it has to be stemming from there, which is a shame since that's the one part of this build that I thought I had working.

Here are my thoughts:
1. Could be a grounding issue, despite my readings telling me everything is referencing ground. In my emails with fripholm he mentioned moving my star-ground point for the PSU to the output. I never got around to it, but I definitely will do that ASAP.

2. I never isolated my regulators on my power supply, which are attached to those large heatsinks. I never knew it was a thing that needed to be done. Not sure if it would be causing a problem like this, but I do have a couple of the insulator kits for those TO-220 regulators, so I should probably go ahead and do that.

I'm not really sure what else it could be. After all, I had initially thought my PSU was operating flawlessly, but now I'm reading AC at the outputs for some reason.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 29, 2018, 07:53:06 PM
.....bridge rectifier have ac after it????

What's the reading at R3 after it??
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 29, 2018, 09:59:57 PM
I'm reading 48VDC as well as 18VAC on R3 right after the rectifier
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 29, 2018, 10:56:45 PM
I'm reading 48VDC as well as 18VAC on R3 right after the rectifier


Do you have a picture of your power supply you can post???
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 29, 2018, 11:09:56 PM
Here's about the best picture I can get. It's fripholm's PSU board.

(https://dmsoundstudios.files.wordpress.com/2018/10/2018-10-29-22-52-20.jpg?w=450)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on October 30, 2018, 12:04:02 AM
Great.... Doesn't look like your filter caps are backwards........ Can't imagine they'd be bad.....
.... I'm sure fripholm or others will have some direction to get this ball rolling.... maybe I'm looking at your issue wrong...circuit is unique to other ones.....

These things look pretty sweet..... you'll get it figured out.... don't give up....
...... 



Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Ilya on October 30, 2018, 02:23:51 AM
If you disconnect the boards from PSU do you still see AC at the PSU output (when unloaded)? If yes, that's where your problem is.
Otherwise it may be an oscillation. But it must be very huge. Do you have a scope? Can you see what that AC looks like?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on October 30, 2018, 04:50:47 AM
So far this looks like a grounding issue. Unfortunately, I'm drowning in work at the moment. Hopefully I will have some time tomorrow and can take a look at this and reply.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 30, 2018, 11:52:00 AM
If you disconnect the boards from PSU do you still see AC at the PSU output (when unloaded)? If yes, that's where your problem is.
Otherwise it may be an oscillation. But it must be very huge. Do you have a scope? Can you see what that AC looks like?

I was seeing the AC, even with the power supply unloaded. So I went and changed my PSU star ground connection from the PSU input to the PSU output, and I'm beyond thrilled to report that absolutely all AC voltage is now gone from my power supply. I plugged in a board to do a quick check, and again, no more random AC. I wish I had the rest of the day to test out my circuit and see if it'll actually pass audio now. I feel pretty silly now shelving this project for a year, only to find out it was grounding issue, the solution of which was even offered to me way back when I was having the problems in the first place  :P

Oh well! Better late than never. I'm just happy to finally be making progress on this beast again.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on October 31, 2018, 11:05:53 PM
Back again!

Got my relays wired up today, since I still hadn't taken care of that. Also wired up my meter lights, because I needed anything to lift my spirits with this project.

Wired up a board, hooked up a test signal to the input XLR, etc. No signal :(
Double checked my relays and the wiring to/ from. Everything checks out. I can read AC coming out of the input transformer, but only the one that isn't hooked up to the relay yet. The one that is attached to the relay reads no voltage at the relay connection.

I remember having this problem before, so I read back through the thread and saw to test by injecting the signal directly into the middle pad of Bypass 2. Tried that and was happy for a moment because I saw some signal coming through my interface, but when I turned the volume up I realized that it wasn't really signal coming through at all, just some very quiet noise.
Took the signal coming from the output XLR into my multimeter ad I was getting some really bizarre results. Touching the test lead to the middle pad gave me a spike of AC, but even after I took the lead off of the pad, there was still an AC signal coming from the output cable. It seemed to be fluctuating pretty rapidly, it read around 3-4VAC, but it was never audible through my interface.

So I guess I'm back to square one as far as this project goes. Seems like all of my problems are coming from the output stage. I'll have to double check my voltages now that I cleaned up the AC from my power supply.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 01, 2018, 03:42:01 AM
James, I think you have too many variables to deal with when doing the third step before the first and wire up the relays before even getting the basic functionality of the unit right. Do this when everything else is working!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: kante1603 on November 01, 2018, 04:21:43 AM
James, I think you have too many variables to deal with when doing the third step before the first and wire up the relays before even getting the basic functionality of the unit right. Do this when everything else is working!
Fripholm is right,you‘ll most likely end with a messed up unit and totally disappointed.
That is not a propper way to sort out possible issues.The key is patience and logical thinking.
Please always read carefully and follow his recommendations.Take a deep breath and start again.


Best regards,


Udo.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on November 01, 2018, 10:40:01 AM
Fripholm is right,you‘ll most likely end with a messed up unit and totally disappointed.
That is not a propper way to sort out possible issues.The key is patience and logical thinking.
Please always read carefully and follow his recommendations.Take a deep breath and start again.


Best regards,


Udo.

+1..... I was reading the guide and got scared...lol .... Definitely a lot of room for error if not paying strict attention to all the details......

JCN---- wiring looks crazy nice so,the detail is there..... I know you'll get it..... Just take as long as you need.......
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 02, 2018, 09:43:03 AM
Fair points guys! I'm not sure what it is about this project that has me so anxious to finish it. Probably just the amount of time it's been on the bench.

Anyway, took some time yesterday to take the relays out. I left the meter lights wired up, just disconnected its feed from the power supply.

Still getting the same issues from my last post. No signal reading at the pole of my switch, and when directly injecting the signal I'm still getting those strange results.

Seems like there must be an issue in the output section still, but also somewhere around the input as well.

When I get some more free time, I'm going to triple check my off-board wiring to confirm that all the pads have connectivity to the front panel components that they're supposed to be connected to.

Thanks to everyone for all the help so far. I feel pretty determined that I'll have this thing up and running soon.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: scott2000 on November 02, 2018, 10:05:40 AM
Rome wasn't built in a day........or something like that.....

There are only a handful of components in the output section so, that should be easy enough to get past. The flipping orientation or misplacing  of things (transistors) can definitely cause other issues but maybe you got lucky....

Testing transistors, diodes, reading resistances, checking for bridges or cold joints.......all doable with a simple multimeter.... Transistors and diodes are most likely culprits after wiring or user mistakes from my experience..... sometimes caps..... shouldn't take hardly any time to find anything that looks questionable....

LCR meters are nice to have to check capacitors as well...

Then, after everything checks out or is addressed you can at least be ready to test the output section like was mentioned earlier after your other issues are sorted.....????

Good luck!

Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 10, 2018, 04:29:50 PM
Hey James, any news on your build?  :)
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: JCN1218 on November 15, 2018, 09:14:00 AM
Not yet  :( Progress has been very slow, unfortunately. I've been recording/mixing my band's new album and that's been taking up most of my free time lately.

I've checked the off-board connections for most of one board so far, and it looks like I may have a mixup somewhere in the SC section, but I'm not 100% sure yet. Still need to diagnose what's going on in the output section as well. Supposed to snow here today, so maybe that'll free up some DIY time for me. I'll definitely keep you guys posted!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: fripholm on November 30, 2018, 04:49:07 AM
PRICE DROP!

Until December 31st, 2018 the price for one of my TG1 limiter boards is just 30 Euros plus shipping.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ron_swanson on February 27, 2019, 12:56:41 PM
Hi all!

Slowly working to assemble the parts to start this build. 

Sorry if this was covered earlier in this thread, I must have missed it if so... wondering what the minimum enclosure depth I should consider when using fripholm's PCB's and PSU PCB in a stereo configuration?  The PCB's are rather small, so I'm wondering if I can get away with an enclosure smaller than 14" in depth without running into access and / or power supply or wire routing noise issues?   

Thanks in advance!
Greg
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Rob Flinn on February 27, 2019, 01:36:30 PM
Hi all!

Slowly working to assemble the parts to start this build. 

Sorry if this was covered earlier in this thread, I must have missed it if so... wondering what the minimum enclosure depth I should consider when using fripholm's PCB's and PSU PCB in a stereo configuration?  The PCB's are rather small, so I'm wondering if I can get away with an enclosure smaller than 14" in depth without running into access and / or power supply or wire routing noise issues?   

Thanks in advance!
Greg

You could easily use a 14" depth rack case with room to spare.
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: ron_swanson on February 28, 2019, 11:43:00 AM
You could easily use a 14" depth rack case with room to spare.

Excellent!  Thanks, Rob!
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Voodoobeat on March 16, 2019, 02:15:11 PM
anybody acutally build a unit from ChrioN PCB copies?
Title: Re: [BUILD] fripholm's TG1 Zener Limiter boards - support thread
Post by: Potato Cakes on March 16, 2019, 02:20:40 PM
anybody acutally build a unit from ChrioN PCB copies?

This would be answered in a new thread.