GroupDIY

Project Specific Discussions => Dynamic Processors => Topic started by: Gustav on June 13, 2015, 03:43:45 AM

Title: Build Thread:MS76
Post by: Gustav on June 13, 2015, 03:43:45 AM
I am not done finding applications for the small MS circuit, and I figured, I could use it for linking two 1176 and get rid of any L/R tracking errors (would be M/S tracing errors, which I find to be less critical). I realise this introduces other challenges, but I think its a neat trick. Theres also every mod I could think of/find implemented.

Rev 2 boads for sale.
Documents in the bottom.

https://pcbgrinder.com/index.php?route=product/product&path=59_69&product_id=205

This is a new project, so there is no FAQ and maybe some possible issues I haven't even thought about, but Ill do my best to help out if you have any questions, or if some error I did not catch shows up. This is how these things usually work....

Gustav
Title: Re: MS76
Post by: XAXAU on June 15, 2015, 08:00:38 AM
I'm loving this! MS is so useful in this comp and also if you have a bunch of mono units and your MS Matrice!:)

Please don't skimp out on the mojo in this unit! :P
Title: Re: MS76
Post by: Gustav on June 15, 2015, 01:25:43 PM
I'm loving this! MS is so useful in this comp and also if you have a bunch of mono units and your MS Matrice!:)

Please don't skimp out on the mojo in this unit! :P

Thanks!

For starters, I would be ecstatic to get it working. The circuit is the same as the usual 1176,  so the sound of it should be a given :)

I went through the boards with the layout gurus at Printline today, and after correcting an issue or ten,  Will have board before the end of the week if all goes well.

Gustav
Title: Re: MS76
Post by: XAXAU on June 15, 2015, 04:41:27 PM
Sorry for asking but is it a rev. F sort of or?
Title: Re: MS76
Post by: Gustav on June 17, 2015, 01:48:14 AM
Sorry for asking but is it a rev. F sort of or?

I can't say I know, but arent the differences after revision A just in the transformers (A being class A, later revisions being class AB)?

In that case, its not really any specific revision, since the whole input and output stage is changed in this, adding the THAT circuits for input and output, and/or optional Lundahl footprint on the output.

The schematic Ive been working from was drawn up from the G1176.

Gustav
Title: Re: MS76
Post by: XAXAU on June 20, 2015, 11:17:13 AM
Rev F uses AB output transformer and in rev G they ditched the input transformer.

http://www.uaudio.com/blog/1176-la2a-hardware-revision-history

Would it be possible to make a footprint for lundahl trafo on the input as well or is it too much work? Trafo = mojo!:)
Title: Re: MS76
Post by: Gustav on June 20, 2015, 12:35:54 PM
Would it be possible to make a footprint for lundahl trafo on the input as well or is it too much work? Trafo = mojo!:)

I may have gotten a batch with the mojo missing, but I never found the input trafo added anything significant on the G1176. If your findings have been different, you can hardwire a trafo easily.

I made sure to add a layer of mojo to the PCB layer 3, though (you should be able to see it on the board layout), so I can assure you, it was not skimped on for the slightest.  :)

Gustav
Title: Re: MS76
Post by: Gustav on June 23, 2015, 04:36:23 AM
Small update.

Went over the boards a few more times, and finally started production. Factory is closed Wednesday, so hopefully I'll have them thursday.

Gustav
Title: Re: MS76
Post by: tata on July 05, 2015, 02:15:18 AM
Gustav, can you pls shed some light on the signal route / phase when Blend is engaged and M/S processing is fully OFF?

so far what i think : signal is "in phase" at the out of the debalancer stage, but then it flips at the CLEAN-L(/R), right? (after the buffer / inverting stage). then it flips back at "BLEND-L(R)" and stays the same at the balancing stage / output.

the "DIRTY" signal is "in phase" at LM-OUT, but then it flips at "BLEND-L(R)" and stays flipped?

thanks

Title: Re: MS76
Post by: Gustav on July 05, 2015, 01:19:06 PM
Gustav, can you pls shed some light on the signal route / phase when Blend is engaged and M/S processing is fully OFF?

so far what i think : signal is "in phase" at the out of the debalancer stage, but then it flips at the CLEAN-L(/R), right? (after the buffer / inverting stage). then it flips back at "BLEND-L(R)" and stays the same at the balancing stage / output.

the "DIRTY" signal is "in phase" at LM-OUT, but then it flips at "BLEND-L(R)" and stays flipped?

thanks

Note that the buffer tapping the clean blend is non-inverted.

And sorry, I dont understand the observation you made on "dirty" tap. It just reroutes the signal to one pin of the blend circuit, same place is comes back.  Make sure you see that the MS is switched in two locations as well (I am just taking a guess it might be relevant).

Honestly, I am not 100% sure I nailed the blend (Its actually #1 on my "check if you screwed this up" list. #2 is my implementation, using a doubler to provide 30V, so I could use a 2x15V trafo). I went through it quite a few times, sometimes thinking I had it, but then changing the phase on the buffer back again, and again. I had a unit in for service to compare some issues to, but I gave it back before I checked the blend phase/realised I am a bit lost understanding how the signal is inverted (or if its not) in the AB stage, and I actually had an opamp providing the 12dB of gain at some point as well in the schematic, which would've been easier to see for me.

Theres always errors on a first rev board, so in the spirit of moving ahead, my plan ended up being - Measure the phase on the blend, hack and correct the board, make any needed changes to a second revision board. Factory is closed for the holidays ,so this way I have something to work with, make needed revisions, make a new board after the holidays.

If it weren't for the German postal workers, I would have had it fired up by now!

Gustav
Title: Re: MS76
Post by: Gustav on July 05, 2015, 01:37:11 PM
Current status...

I am a few trimmers, transistors and a 7910 short of placing all components.

Gustav
Title: Re: MS76
Post by: tata on July 05, 2015, 02:53:08 PM

Note that the buffer tapping the clean blend is non-inverted.


Gustav

right.. my bad. learning every day.
thanks

but signal is polarity flipped after the Blend stage, right?

german post sucks these weeks, 30+ days and i still didnt get my pack.. :(  (normally 4 days)
Title: Re: MS76
Post by: tata on July 05, 2015, 02:57:30 PM
btw if you're still refining your PCB - don't you think adding multipads for diff. sized (electrolytic) capacitors and for 3/8" trimmers is a good idea?
Title: Re: MS76
Post by: Gustav on July 06, 2015, 02:19:20 AM

Note that the buffer tapping the clean blend is non-inverted.


Gustav

right.. my bad. learning every day.
thanks

but signal is polarity flipped after the Blend stage, right?


There is an inverting opamp after the blend. Please refer back to my last post for a longer answer on the phase relations through the blend. I could start going over it again, and I probably messed it up, but I think going into the details is a waste of time, when the method for testing and correcting is so simple.

I just experienced working with someone who checked these things 100 times on schematic level, but still ended up with these "wrap your head around it" errors. Its easy for me to shoot out a board, check it, and correct it, since I work at a PCB manufacturing plant.

I dont see it as beneficial to add multipads to my board designs, sorry.

Gustav
Title: Re: MS76
Post by: tata on July 06, 2015, 04:55:34 AM
i refer back to your last post, but i read you are uncertain..

i see the inverting opamp in the Blend stage, and then signal goes to the out trafo / 1646 - noninverting, right?

so the final out is flipped?  (M/S off)
Title: Re: MS76
Post by: Gustav on July 06, 2015, 05:42:59 AM
i refer back to your last post, but i read you are uncertain..

Exactly!

"Honestly, I am not 100% sure I nailed the blend (Its actually #1 on my "check if you screwed this up" list. "

"Theres always errors on a first rev board, so in the spirit of moving ahead, my plan ended up being - Measure the phase on the blend, hack and correct the board, make any needed changes to a second revision board. Factory is closed for the holidays ,so this way I have something to work with, make needed revisions, make a new board after the holidays. "

The loop back you mention, yes, you are correct.


Gustav

Title: Re: MS76
Post by: tata on July 06, 2015, 06:39:27 AM
so a blend circuit that keeps the phase consists of : 2x (noninverting) input buffers, an inverting summing amp and an inverting buffer? is this right?

if yes, how about designing a separate PCB like this, so we could add it to any gears? (a FET Grinder and a Phat Phet are waiting for it here :) )
Title: Re: MS76
Post by: Gustav on July 06, 2015, 08:13:33 AM
so a blend circuit that keeps the phase consists of : 2x (noninverting) input buffers, an inverting summing amp and an inverting buffer? is this right?

For this circuit, its obvious I have something to check, and 99.99999% certain I have something to correct, but I feel like I have replied to that a number of times now. I may be confused because I am not concerned about it other than measuring and correcting for this circuit, while you may be interested in using it elsewhere!?

For any implementation, it would depend on the phase relation where you draw the clean/dirty signals and where you feed back the blend, of course.

if yes, how about designing a separate PCB like this, so we could add it to any gears? (a FET Grinder and a Phat Phet are waiting for it here :) )

If you want to do it in a stand-alone unit, I would recommend a line receiver to the blend pot to summing amp to a line driver.  However you invert/non-invert any or each stage doesnt really matter as long as it adds up correctly.

In that case, you are drawing the signal at the balanced input and output of your hardware and sending it out.

Someone already did a project like that. Try searching "crush n blend".

Hope that helps!

Gustav
Title: Re: MS76
Post by: Gustav on July 07, 2015, 02:01:45 PM
One mistake when drawing up the PSU schematic, one cut trace, one jumper.

Had to stack a few capacitors on the 30V rail, because I only had 25V i in the drawers

I am sure this PSU will need to be refined, but I have the voltages I need.

Hope to have transistors before end of the week, so I can smoke test the main board.

Gustav
Title: Re: MS76
Post by: Gustav on July 09, 2015, 07:39:53 AM

Honestly, I am not 100% sure I nailed the blend (Its actually #1 on my "check if you screwed this up" list. #2 is my implementation, using a doubler to provide 30V, so I could use a 2x15V trafo).

Any comments on this spur of the moment doubler I decided to try? There are an awful lot of transistors in there dependent on the 30V supply, and I have a little cold feet powering it up after reading up on it a little.

When I did it, I thought the only implication would be doubling the current draw, but after reading this - http://www.electronics-tutorials.ws/blog/voltage-multiplier-circuit.html I have no real sense what the implications would be if the supply is starved.

If its just a matter of ripple, I dont really care. For now, checking functionality and correcting the schematic is good and fine, and when thats established, I can work on a  better supply for rev 2. Im more worried about frying something than usual, though.

Its ready for me to hit the power button, so feedback would be appreciated. Otherwise, Ill play it safe and breadboard a supply without the doubler using a 2x24V transformer.

Edit:Tried adding the doubler as is. Voltages stable, no smoke.

Gustav
Title: Re: MS76
Post by: Gustav on July 11, 2015, 03:05:20 AM
Errata

Correct bridge to doubler.
Invert phase on blend output.
Reverse bypass switch

Ill post the corrected schematic when I have double checked everything.

Gustav
Title: Re: MS76
Post by: Gustav on July 14, 2015, 01:28:50 PM
Finished and calibrated the rev1 today.

Full list of errata for rev 2.

- Correct holes for meter mounting.
- Shorten Att/rel mount PCB
- Correct error in PSU
- ALL marked on/off/on, should be on/on.
- In/Output pot bank reversed for reverse mounting
- Blend circuit inverted.

Will rip up and reroute the main board properly.

rev 2 boards will start manufacturing July 27th. Shouldn't be more than a week or two underway after that.

Let me know if theres any interest for the first run..

Gustav
Title: Re: Build Thread:MS76
Post by: Gustav on August 01, 2015, 08:02:25 AM
Rev 2 boards will be ready Tuesday.

Gustav
Title: Re: Build Thread:MS76
Post by: gaetan on August 21, 2015, 08:22:01 AM
Gustav, this thing is genius!

Blend in M/S mode gives so many option, overall it sounds beautiful, i'll try to post sound examples soon.

I have to say, the calibration was a bit of a nightmare but it is worth doing it, i would suggest anyone doing the build to use precision trimmers for Qbias, Zero and Trk.


Title: Re: Build Thread:MS76
Post by: Gustav on August 21, 2015, 02:06:51 PM
Gustav, this thing is genius!

Blend in M/S mode gives so many option, overall it sounds beautiful, i'll try to post sound examples soon.

I have to say, the calibration was a bit of a nightmare but it is worth doing it, i would suggest anyone doing the build to use precision trimmers for Qbias, Zero and Trk.

Thanks :)

Calibration is 100% identical to the standard 1176 calibration. Ill write it up when I have an assembly guide ready.

Just remember to switch off MS and "all" before doing it, and you can follow any calibration procedure for the 1176.

Gustav
Title: Re: Build Thread:MS76
Post by: miszt on November 27, 2015, 01:36:49 PM
love the idea of this, i do allot of M/S compression in software, think this will be my next project!

what comes with the component kit? is it everything except the rack/front panel and power transformer? or are there other things I'd need to get? (apart from nuts/bolts/wires)
Title: Re: Build Thread:MS76
Post by: Gustav on November 27, 2015, 02:01:59 PM
love the idea of this, i do allot of M/S compression in software, think this will be my next project!

what comes with the component kit? is it everything except the rack/front panel and power transformer? or are there other things I'd need to get? (apart from nuts/bolts/wires)

Thanks :)

The content of the kit is explained on the site pcbgrinder.com in the components kit section.

Gustav
Title: Re: Build Thread:MS76
Post by: miszt on November 29, 2015, 06:27:16 AM
thanks for the reply Gustav!

I did read it through, I was bit a confused tho, as you put "mounting hardware" and "mounting, hardware" on different kits, wasn't sure which was the typo and what you specifically meant? I think it means everything but the panel/rack/power trafo, but i don't want to assume, i'd rather order everything from one place in one go...
Title: Re: Build Thread:MS76
Post by: Gustav on November 29, 2015, 07:10:26 AM
thanks for the reply Gustav!

I did read it through, I was bit a confused tho, as you put "mounting hardware" and "mounting, hardware" on different kits, wasn't sure which was the typo and what you specifically meant? I think it means everything but the panel/rack/power trafo, but i don't want to assume, i'd rather order everything from one place in one go...

"What's not in the components kit?

A case & mounting hardware (Info in the Cases & panels section with a full list of suggested mounting hardware)"


I give a very specific reference for a very specific list for a very specific design for each project, but of course, it will vary with the way you design your case and panel, and with the project in question.

It may be more abstract than I realise, but it seems to make sense for most people...

Gustav
Title: Re: Build Thread:MS76
Post by: miszt on November 29, 2015, 02:17:09 PM
maybe its just me, but because the GSSL description says "mounting, hardware", I couldn't be certain... but ok i guess my first assumption was right!

what does the transformer option involve? do I just need to get the transformers, or other components aswell?
Title: Re: Build Thread:MS76
Post by: Gustav on November 29, 2015, 02:24:14 PM
maybe its just me, but because the GSSL description says "mounting, hardware", I couldn't be certain... but ok i guess my first assumption was right!

what does the transformer option involve? do I just need to get the transformers, or other components aswell?

Hi Miszt.

Would you mind sending me a mail with any questions you may have about the kits? I think this thread would be better off reserved for build issues rather than a direct conversation between the two of us, answering questions directed at me specifically :)

As a response to your last question here - just the transformers.

If you really want to go deep into the shopping list and make sure you cross every t and dot every i, get the schematic on the site and work through it...that should do it!

Hope that helps!

Gustav
Title: Re: Build Thread:MS76
Post by: rprimmett on December 17, 2015, 03:03:32 PM
Hi there, could anyone tell me the requirements/specs for the vu meters.

Cheers
Title: Re: Build Thread:MS76
Post by: rprimmett on December 18, 2015, 02:25:53 PM
Never mind on the meters, I caved and bought the ones from pcbgrinder. :)

What pots do you use for this build, I noticed that the panel holes are 10mm diam. cut out, which is much larger than a standard Alpha pot?


Title: Re: Build Thread:MS76
Post by: Gustav on December 19, 2015, 01:06:36 AM
Never mind on the meters, I caved and bought the ones from pcbgrinder. :)

What pots do you use for this build, I noticed that the panel holes are 10mm diam. cut out, which is much larger than a standard Alpha pot?


Hi Rimmett.

VU meters should just be VU meters. Ballistics are usually better on the more expensive meters, but any VU should do.

If you are doing your own shopping - For pots, it is way easier to find a pot and adjust the hole on the panel layout, than stick with the (somewhat random) hole size and chase a pot.

Gustav
Title: Re: Build Thread:MS76
Post by: rprimmett on January 04, 2016, 09:39:30 AM
Can anyone advise are the resistors 1/4w or 1/2w
Title: Re: Build Thread:MS76
Post by: rprimmett on January 06, 2016, 09:29:18 AM
Can anyone advise are the resistors 1/4w or 1/2w

bump, looking to get going on this, anyone....

I ask because the silkscreen seems large for 1/4w
Title: Re: Build Thread:MS76
Post by: Gustav on January 07, 2016, 03:53:40 AM
Can anyone advise are the resistors 1/4w or 1/2w

bump, looking to get going on this, anyone....

I ask because the silkscreen seems large for 1/4w

1/4 watt is fine.  Not sure why you'd think the silk screen seems large for that. For reference, its whats used in the assembly guide.

Gustav
Title: Re: Build Thread:MS76
Post by: rprimmett on January 07, 2016, 08:34:44 PM
Thanks Gustav, I build a lot of euorack modular stuff and I guess due to form factor restrictions the footprints seem smaller (just what I'm used to). I'm glad to hear that I can just pick parts out of my inventory  ;D
Title: Re: Build Thread:MS76
Post by: hugo on February 27, 2016, 06:10:18 AM
Hi All,
My name is Hugo, i'm from France and it is my first post on this forum, even if it helped me a lot on the past ; thanks all for your contributions.

I just finished my MS76 and not any problem, it works well....but i have some general questions about troubleshooting some details...i think gustav has a lot of questions to answer so if anybody can answers, it would be great.

- Left and right are not really matched, which transistors can i change to have the same gain and compression on both channels ? during the calibration, it seems that the input of right channel is lower than the left one. I can measure HFE but not sure about which transistors to change for a complete matching of gain and compression.
- The blend is working well, but it affects the L/R balance..i saw some posts about it, is there one solution ?.
- When i switch to dual mono, i really don't have the same sound than in stereo mode, is it normal ?
- In the stereo mode, with both vu meter on "GR", the left moves good whereas the right one do not move, or just a little bit, is it normal, or may i have the same gain reduction tracking on both channels  (the signal sent to the left is the same as the signal sent to the right) ?
Title: Re: Build Thread:MS76
Post by: Gustav on February 27, 2016, 06:13:22 AM
Hi All,
My name is Hugo, i'm from France and it is my first post on this forum, even if it helped me a lot on the past ; thanks all for your contributions.

I just finished my MS76 and not any problem, it works well....but i have some general questions about troubleshooting some details...i think gustav has a lot of questions to answer so if anybody can answers, it would be great.

- Left and right are not really matched, which transistors can i change to have the same gain and compression on both channels ? during the calibration, it seems that the input of right channel is lower than the left one. I can measure HFE but not sure about which transistors to change for a complete matching of gain and compression.
- The blend is working well, but it affects the L/R balance..i saw some posts about it, is there one solution ?.
- When i switch to dual mono, i really don't have the same sound than in stereo mode, is it normal ?
- In the stereo mode, with both vu meter on "GR", the left moves good whereas the right one do not move, or just a little bit, is it normal, or may i have the same gain reduction tracking on both channels  (the signal sent to the left is the same as the signal sent to the right) ?

I replied to your mail, but will reply here as well.

I think most of the problems can be boiled down to the misunderstanding that the unit has a stereo mode. You can either use is in dual mono or M/S. In M/S mode, you can do stereo track processing, but one channel will be referenced to the M content, while the other will be linked to the S content.

I hope that clears up some issues.

Edit:And as mentioned in the calibration guide, its important that the unit is not in M/S link mode while you calibrate.

Gustav
Title: Re: Build Thread:MS76
Post by: hugo on February 27, 2016, 06:48:42 AM
Thanks a lot Gustav, really sorry about this misunderstanding. This unit is really great ! During the cakibration it was in dual mono, but 2n5457 are not matched on my unit...i think about taking 4x2n5457 matched on hairball (fairchild old series). On the datasheet it seems that i have to put those transistors reversed ( DSG to GSD), am i right ?
Title: Re: Build Thread:MS76
Post by: Gustav on February 27, 2016, 07:06:06 AM
Thanks a lot Gustav, really sorry about this misunderstanding. This unit is really great ! During the cakibration it was in dual mono, but 2n5457 are not matched on my unit...i think about taking 4x2n5457 matched on hairball (fairchild old series). On the datasheet it seems that i have to put those transistors reversed ( DSG to GSD), am i right ?

I am not sure whats giving you the matching problems, but if you feel trying the Hairball transistors will work better for your build, you can give it a try.

The board is designed for the 2N5457. I am not aware that different pin-outs for that part exist (see attached for reference), but if you have become aware of a difference in the part you intend to use, you should adjust it, of course..

Gustav
Title: Re: Build Thread:MS76
Post by: hugo on February 28, 2016, 06:32:34 AM
Thanks a lot for that great support, everything is working fine now, good matching between 2 channels, i love this gear ! Will post some pictures.. i really think about taking the veca to replace my gssl now...
Title: Re: Build Thread:MS76
Post by: Gustav on February 28, 2016, 07:02:26 AM
Thanks a lot for that great support, everything is working fine now, good matching between 2 channels, i love this gear ! Will post some pictures.. i really think about taking the veca to replace my gssl now...

Great news!

In my experience, is always best to complete basic trouble shooting and zoom in on any problems before starting to think about redesigning. These projects are thoroughly tested.

Gustav
Title: Re: Build Thread:MS76
Post by: rprimmett on April 30, 2016, 11:08:07 PM
Can someone tell me the value of the blend pot, I must be missing it somewhere?
Title: Re: Build Thread:MS76
Post by: Gustav on April 30, 2016, 11:51:03 PM
Can someone tell me the value of the blend pot, I must be missing it somewhere?

A linear 10K.


Gustav
Title: Re: Build Thread:MS76
Post by: rprimmett on May 17, 2016, 10:31:43 PM
Gustav, thanks for support on this build. I think its all working, one question though. When the blend is at 100% I dont have any signal, is this normal?

(http://s32.postimg.org/geysudclh/IMG_6147.jpg)

(http://s32.postimg.org/4vlzw5ssl/IMG_6146.jpg)

Ryan
Title: Re: Build Thread:MS76
Post by: Gustav on May 18, 2016, 01:32:10 AM
When the blend is at 100% I dont have any signal, is this normal?

Hi Ryan.

Blend should work as  a "crossfader" between the clean and compressed signal, so one end 100% compressed, other end 100% clean. Which end is what will depend on the orientation of your wiring on the pot.

It could be a number of things, including some weird combinations of what you are feeding the unit, and what your settings are.

1. Make sure you are in dual mode (in MS mode, if you only send signal into the M channel, you will have no "clean" signal on the S channel blend knob, but depending on your settings, you can have signal on the compressed end of the S channels blend knob (check this signal flow).

https://pcbgrinder.com/image/cache/catalog/FLOW/MS76FLOW-900x900.gif

In short - make sure you are not in MS mode, and check one channel at a time.

2. Starting with the left channel in split mode, check for signal on the points where the clean and compressed signals are tapped from, then trace them to the pot.

3. In single channel mode, you will always have the clean signal on the blend pot, but the compressed signal will only be there if you are actually sending it through the unit (in/output pot can cut it off).


Thats should get you started.

Gustav
Title: Re: Build Thread:MS76
Post by: rprimmett on May 19, 2016, 03:09:34 PM
Gustav, do you have a description of what each test point is and what I should see there.
Title: Re: Build Thread:MS76
Post by: Gustav on May 19, 2016, 04:49:15 PM
Gustav, do you have a description of what each test point is and what I should see there.

Test points are spread through the signal path. They are marked, but not named appropriately in the schematic.

What you should see depends on what you put in, and they are just handy for poking around with a scope.

Gustav
Title: Re: Build Thread:MS76
Post by: frederickalonso on September 08, 2016, 01:42:45 AM
Also big thanks to Gustav, great documentation!

Everything works fine, soft compression dynamics like I like them.
In M/S mode my mono is not complete in the center, so I will try to insert Lundahl transformers to solve this.

Hope it works..

(https://www.instagram.com/p/BJSjXvwjWCb/?taken-by=alonso.frederick)

Video:
https://www.instagram.com/p/BJSwyLeDlLs/?taken-by=alonso.frederick
Title: Re: Build Thread:MS76
Post by: Gustav on September 08, 2016, 02:03:55 AM
Also big thanks to Gustav, great documentation!

Everything works fine, soft compression dynamics like I like them.
In M/S mode my mono is not complete in the center, so I will try to insert Lundahl transformers to solve this.

Hope it works..

(https://www.instagram.com/p/BJSjXvwjWCb/?taken-by=alonso.frederick)

Video:
https://www.instagram.com/p/BJSwyLeDlLs/?taken-by=alonso.frederick

Well done, Frederick!

If you dont mind, can you tell me how you are measuring that mono is not completely down center in MS, have you traced it back, and how much is it?

In theory, anything that is M content will per definition be center, anything that is not will per definition be S, even if they are not in complete balance as far as what you are putting into the unit.

I usually have to have a unit on the bench to double check, but I dont see how mid shift could happen anywhere but after the decoding, and I dont see how it could be fixed by swapping the IC outputs to transformers.

Hope to understand this, and see if we can get you 100% there!

Gustav
Title: Re: Build Thread:MS76
Post by: frederickalonso on September 08, 2016, 02:28:06 AM
Also big thanks to Gustav, great documentation!

Everything works fine, soft compression dynamics like I like them.
In M/S mode my mono is not complete in the center, so I will try to insert Lundahl transformers to solve this.

Hope it works..

(https://www.instagram.com/p/BJSjXvwjWCb/?taken-by=alonso.frederick)

Video:
https://www.instagram.com/p/BJSwyLeDlLs/?taken-by=alonso.frederick

Well done, Frederick!

If you dont mind, can you tell me how you are measuring that mono is not completely down center in MS, have you traced it back, and how much is it?

In theory, anything that is M content will per definition be center, anything that is not will per definition be S, even if they are not in complete balance as far as what you are putting into the unit.

I usually have to have a unit on the bench to double check, but I dont see how mid shift could happen anywhere but after the decoding, and I dont see how it could be fixed by swapping the IC outputs to transformers.

Hope to understand this, and see if we can get you 100% there!

Gustav

Gustav,

I use my Waves ( Analyser vst ) on my input channels in Ableton Live. On my other gear everything is fine. If I switch the unit to dual mono everything is fine = playing a mono kick thru it and it comes back in center at both channels. If I play a full stereo track all is fine. Only M/S is a little off, don't know why. If I adjust the L/M gain (on PCB) I can fix this issue but once I switch to dual mono  and play a full stereo track the bass is more to the left. In M/S mode I tested to mute the volume from the Side (R/S) so I could see what's going on and then I  see that it's not complete center. Hope you understand what I try to write here ;-)

So in perfect stereo (dual mono) all is fine. In M/S the mono is like around 11 hour (more to the left)  instead of 12 on a clock where 12 would be the center (mono)

PS: I tried to switch the THAT's from Right to Left but all is the same.
If I know where the calculation M/S is done I can maybe adjust something or add an extra resistor maybe?


Well I have seen some articles where it's obvious that Lundahl transformers can give a perfect focus and avoid stereo artifacts. I have a pultec EQ for example with the same Lundahl transformers and the difference I had by replacing FET outputs in this EQ with the transfo's was huge. That's why I think it will help as well.

BTW: I have had an API2500 and Elysia xpressor 500 and price/sound wise I would rate this unit  between 1400€ and above the Elysia. Seriously, I like it. Great build as well.
Title: Re: Build Thread:MS76
Post by: Gustav on September 08, 2016, 08:08:29 AM
BTW: I have had an API2500 and Elysia xpressor 500 and price/sound wise I would rate this unit  between 1400€ and above the Elysia. Seriously, I like it. Great build as well.

So happy you are into it :)

your drift of center is obviously not due to the output stage - and I can't even wrap my head around a possible error to cause it, other than something funky going on in the MS decoding. Adding the Lundahl output trafos will certainly not have any effect on it.

Please mail me, I may have an idea to check, but Ill need to add some documents, which is not so easy here.

Gustav
Title: Re: Build Thread:MS76
Post by: pstcho on September 22, 2016, 07:32:34 AM
Hi guys, question for the people having finished the unit

HOW DOES IT SOUND :p

Is it close to a classic 1176, cleaner, muddier, more/less distortion ?

( i guess i will go for a unit pretty soon )

Thanks
Title: Re: Build Thread:MS76
Post by: frederickalonso on October 06, 2016, 07:11:57 PM
Hi guys, question for the people having finished the unit

HOW DOES IT SOUND :p

Is it close to a classic 1176, cleaner, muddier, more/less distortion ?

( i guess i will go for a unit pretty soon )

Thanks

For me it sounds open and has a little but warm saturation to it.
On a complete mix you can have more click (attack) on drums or give
the bass more body. I also found out that a resistor change on the release (PCB) can give more tail to drums.

I'm thinking to build a GSSL and MS HOL from pcbgrinder as well. Not yet sure wich one will be my "sound".  If someone has examples, please share.
Title: Re: Build Thread:MS76
Post by: pstcho on October 07, 2016, 04:30:19 AM
Great, thanks for our reply !!

i guess i will go for a it pretty soon when i finish to debug my GSSL
Title: Re: Build Thread:MS76
Post by: RSRecords on June 30, 2017, 07:47:09 PM
Just finished wiring this guy up. I'm having a few issues that I can't wrap my head around.

1st Meter Level seems low. I changed the 20k resistor in for the meters back to 10K and I was able to get it to 0.

Input pot level does not affect what the Meter is reading. With the Input all the way to 0 ( counter clockwise) the meter is still reading 0 VU. Looking at the Test Point 2 I see the signal level change with the pot. Same for the Output Pot with the meter set to read the output.  Output at the xlr does change.

Any thoughts? I'm assuming its something with the meter switching but I can't find anything wrong.

Thanks for any help!
Title: Re: Build Thread:MS76
Post by: Gustav on July 01, 2017, 01:34:24 AM
Just finished wiring this guy up. I'm having a few issues that I can't wrap my head around.

1st Meter Level seems low. I changed the 20k resistor in for the meters back to 10K and I was able to get it to 0.

Not sure what you mean by "able to get it back to 0", or which resistor exactly. Could you describe the problem leading you to make the change, the reasoning for making it, and specify which 0 (0 in GR mode, 0 resting in VU mode)

Input pot level does not affect what the Meter is reading. With the Input all the way to 0 ( counter clockwise) the meter is still reading 0 VU. Looking at the Test Point 2 I see the signal level change with the pot. Same for the Output Pot with the meter set to read the output.  Output at the xlr does change.

Any thoughts? I'm assuming its something with the meter switching but I can't find anything wrong.

Thanks for any help!

I would start by tracing the signal to the meter, and also make sure the switching is actually done on the relays (check the voltage going there)

Gustav
Title: Re: Build Thread:MS76
Post by: RSRecords on July 01, 2017, 11:26:44 AM
Not sure what you mean by "able to get it back to 0", or which resistor exactly. Could you describe the problem leading you to make the change, the reasoning for making it, and specify which 0 (0 in GR mode, 0 resting in VU mode)

By 0, I meant  0vu while in VU IN mode.
I was referring to the 20k resistor in the feedback  loop of the tlo72. In the "Errata" section you say to replace it with a 10k for proper gain. I was attempting to complete the calibration but the 1st step is to set the level to zero vu in which I was unable to do. I've changed the resistor back to 10k since it did not seem to be the issue.


I would start by tracing the signal to the meter, and also make sure the switching is actually done on the relays (check the voltage going there)

Gustav

Voltage is at the relays and I can hear them switching. Everything looks good and I went through and reflowed the solder on the relays for good measure. I measure 12v at the relays depending on the meter selection switch.


Are test points 2 and 3 after the in and out pots respectively?



I should also note that both channels are behaving this way.



Title: Re: Build Thread:MS76
Post by: RSRecords on July 01, 2017, 12:39:29 PM
I think I figured it out.

I mis interpreted the pcb markings for the molex connectors. Since I used the molex pin numbers on the pcb to wire the control boards, its not an issue for any of them except the blend pot which isn't on a pcb. It was wired backwards.

Also, I was thinking that the input pot should affect the level shown in the VU IN mode. I don't think that is the case.

I am trying to calibrate it now; I'll update if I am successful.
Title: Re: Build Thread:MS76
Post by: Gustav on July 01, 2017, 07:30:32 PM
Blend pot should be out during calibration. Theres a relay, which will switch it out completely, regardless of the orientation of the  wiring.

VU in is just that - the level coming into the unit.

Hope you get there!

Gustav
Title: Re: Build Thread:MS76
Post by: RSRecords on July 05, 2017, 10:26:58 PM
Well seems to be working now. I'm not sure what fixed it but I went through and just reflowed most of the pcb and checked all the transistors. Everything tested fine in and out of the circuit.  Who knows! works now and sounds great!
Title: Re: Build Thread:MS76
Post by: Gustav on July 06, 2017, 02:09:19 AM
Well seems to be working now. I'm not sure what fixed it but I went through and just reflowed most of the pcb and checked all the transistors. Everything tested fine in and out of the circuit.  Who knows! works now and sounds great!

Awsome, and great design!
Title: Re: Build Thread:MS76
Post by: RSRecords on July 06, 2017, 11:42:32 AM
I kept the front panel layout the same and just changed font and color scheme inspired by the rev a blue stripe.

I've been wanting to try front panel express' print service. It came out pretty good. It's definitely more fragile as you can see some chipping around the chassis screws nothing a washer can't hide but if I were to do it again I'd probably  Hit it with a coat of lacquer or something for extra durability.
Title: Re: Build Thread:MS76
Post by: RSRecords on July 06, 2017, 07:50:34 PM
One question regarding attack and release:
Is this like an 1176 wherein the fastest setting is clockwise? I haven't had much time to experiment with it yet but I was getting the feeling the release was faster in the counter-clockwise setting.

Thanks!
Title: Re: Build Thread:MS76
Post by: Spex95 on March 10, 2018, 07:10:44 AM
Hi,
Can someone tell me the value of the out pot, I must be missing it somewhere?
Is this a linear or log pot?

Thanks!
Title: Re: Build Thread:MS76
Post by: Thijmen on November 08, 2018, 08:16:40 PM
Hi everybody,

I see some people talk about a "Errata" file/section, which i'm currently looking for. I scanned all the documents i could find over here:  https://pcbgrinder.com/index.php?route=product/product&path=59_61&product_id=64 (https://pcbgrinder.com/index.php?route=product/product&path=59_61&product_id=64):

 But i can't find anything referring to "errata".  Where can i find the Errata file/section?

Greetings,
Thijmen
Title: Re: Build Thread:MS76
Post by: noiro on November 27, 2020, 08:11:36 PM
Hi Gustav, I'm wondering about a few thing with the MS76, first it seem that the blend pot does not work at all, I disconnect the connector but it doesn't do anything, wondering if there is something wrong with my build. Everything seem to be working just fine. Is there a way to test it. I used a standard  A 10K pot, Am I missing something here? so to resume the MIX knob dry/wet simply does not do anything, the wet is always full on, no dry signal at all, i try disconnect the blend wires but still does not do anything, does not make any sense.
Title: Re: Build Thread:MS76
Post by: Gustav on November 28, 2020, 02:27:31 AM
Hi Gustav, I'm wondering about a few thing with the MS76, first it seem that the blend pot does not work at all, I disconnect the connector but it doesn't do anything, wondering if there is something wrong with my build. Everything seem to be working just fine. Is there a way to test it. I used a standard  A 10K pot, Am I missing something here? so to resume the MIX knob dry/wet simply does not do anything, the wet is always full on, no dry signal at all, i try disconnect the blend wires but still does not do anything, does not make any sense.

Hi Noiro.

I already replied to the post you made asking me on Gearslut.

https://www.gearslutz.com/board/product-alerts-older-than-2-months/1249677-pcb-grinder-new-units-amp-guides.html

You are welcome to use my mail for future questions!

[email protected]