[BUILD] fripholm's TG1 Zener Limiter boards - support thread

JMan

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Hey all, I’m slowly but surely getting my boards stuffed, and now thinking about the next steps.  I’ve read through Fripholm’s fabulous build guide numerous times, and I have to say I really appreciate how thorough it is!

I’m looking at transformers for my next purchase, and I’m hoping to get some thoughts from you all, as this is actually my first build that uses audio transformers and I’m feeling that newbie uncertainty.  I’m currently thinking about the Carnhill 9046 wired for 2:1 on input, and Sowter 1460 600:600 on output (links below.  I found both of these mentioned much earlier in the thread).

Very curious to hear your thoughts on these, or if you have better suggestions — I’ve seen that people have used other xfmrs throughout this thread, and I’m open to guidance!

Carnhill: http://www.audiomaintenance.com/acatalog/CA%2d18%2dVTB9046M%5fextended%5finfo%2ehtml

Sowter: https://www.sowter.co.uk/cgi-bin/ss000001.pl?page=search&SS=1460&PR=-1&TB=O&ACTION=Go%21
 

Potato Cakes

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JMan said:
Hey all, I’m slowly but surely getting my boards stuffed, and now thinking about the next steps.  I’ve read through Fripholm’s fabulous build guide numerous times, and I have to say I really appreciate how thorough it is!

I’m looking at transformers for my next purchase, and I’m hoping to get some thoughts from you all, as this is actually my first build that uses audio transformers and I’m feeling that newbie uncertainty.  I’m currently thinking about the Carnhill 9046 wired for 2:1 on input, and Sowter 1460 600:600 on output (links below.  I found both of these mentioned much earlier in the thread).

Very curious to hear your thoughts on these, or if you have better suggestions — I’ve seen that people have used other xfmrs throughout this thread, and I’m open to guidance!

Carnhill: http://www.audiomaintenance.com/acatalog/CA%2d18%2dVTB9046M%5fextended%5finfo%2ehtml

Sowter: https://www.sowter.co.uk/cgi-bin/ss000001.pl?page=search&SS=1460&PR=-1&TB=O&ACTION=Go%21

I put Sowters in mine. A bit more expensive and there was a several week lead time although Don Audio sometimes has various Sowter transformers in stock. Carnhills are more readily available and less expensive. Both will sound great.

Thanks!

Paul
 

JMan

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Potato Cakes said:
I put Sowters in mine. A bit more expensive and there was a several week lead time although Don Audio sometimes has various Sowter transformers in stock. Carnhills are more readily available and less expensive. Both will sound great.

Thanks!

Paul

Hey Paul,

Thanks for your input! 

Do you recall which models of Sowters you used?  (I know it's gotta be here in the thread somewhere, I just haven't been able to go back and find it).

Since this is my first time using audio transformers, I'm hoping that whatever I end up choosing will be pretty straightforward to implement, as I want to save any more complicated adjustments and alterations for future projects when I have a little experience.
 

Potato Cakes

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JMan said:
Hey Paul,

Thanks for your input! 

Do you recall which models of Sowters you used?  (I know it's gotta be here in the thread somewhere, I just haven't been able to go back and find it).

Since this is my first time using audio transformers, I'm hoping that whatever I end up choosing will be pretty straightforward to implement, as I want to save any more complicated adjustments and alterations for future projects when I have a little experience.

1295 for the input and 1365 for the out.
 

dunk91

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Ok, so I've finished my unit and powered it up,  many things work as expected, many not.
Actually to keep boards debug easy I've bypassed input and output xformers and inject unbalanced signal on Byp1 and check output header with my oscilloscope. So bypass work as it should, in\out switches idem.

In THD mode I get a lot of distorsion, I can adjust level with r22 and r56 but distorsion is fixed, (I put a sine and get out a dirty square, no matter how I set both trimmers, only level change)

In Comp mode gain reduction never happen and again the signal gets louder and distorder (not a square but a very distorted sine this time)

In Limit mode sound is pretty clean and gain reduction seems to work correctly

I've checked mode\SC wiring and I can assure it's legit, I've also  tried to bypass switches and hardwire the the mode\SC header in all 3 positions and it behave the same as with switches installed.

Attack, release and sidechain hpf appear to work properly (only in limit mode of course)

Also I've got a ton of background noise, but this can be the opened case, messy wiring due to debug etc, I'll face this later.
I've tried both 1n751 and 1n5231, no big changes.
Already checked transistors and diodes orientation, resistors and cap value but nothing strange spotted.

More to this if I try to calibrate meters I get only 1mm of needle travel around middle trimmer range, for 95% of it's run it does nothing.

Now the only thing that buzz me is that I've used 1n483 instead of 1n4153, but I don't think they could lead to this beahviours, could they?
Any tip welcome, I can't think anything else to check  :'(

P.s.: Problems are common to both boards
 

ToBSn

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Sounds like a grounding issue.

If I remember correctly I had a similar problem when I had the boards running on my desk without a case.
 

dunk91

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Yep I was thinking about grounding too, but I've star grounded everything to the chassis, where main inlet earth and psu output gnd are joined togheter. Here also are connected both boards ground (one gnd path for each board), internal cables shieldings, connector's pin 1 etc etc.

ToBSn said:
Sounds like a grounding issue.

If I remember correctly I had a similar problem when I had the boards running on my desk without a case.
 

fripholm

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Have you tried the recommended (fixed) value of 12k for R22 and replaced trimmer FT2A with a jumper?  There's a lot of interaction between what the trimmers for R22 and R56 do and the window is pretty small where the circuit behaves correctly.

Are there any other mods like the hold circuit at this point? What's the test signal level going into the board? It has to be pretty low for it not to distort - usually the 2:1 input transformer takes care of this.
 

dunk91

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Yes, I've started with r22 12k and r56 1k, no ft2a on my board, I'm on 2.1 version.
Also no hold added, just auto release.
I'm using an 1Vpp sine, it should be fine also without a 2:1 on input, right?

May I ask you I you know a valid reason for comp mode to not work when limit seems fine? (beside bad wiring, wich I should have excluded hardwiring various mode)

Thanks BTW  :)


fripholm said:
Have you tried the recommended (fixed) value of 12k for R22 and replaced trimmer FT2A with a jumper?  There's a lot of interaction between what the trimmers for R22 and R56 do and the window is pretty small where the circuit behaves correctly.

Are there any other mods like the hold circuit at this point? What's the test signal level going into the board? It has to be pretty low for it not to distort - usually the 2:1 input transformer takes care of this.
 

fripholm

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dunk91 said:
I'm using an 1Vpp sine, it should be fine also without a 2:1 on input, right?

1Vpp input signal is pretty high if hard wired and not further attenuated by the input control but COMP mode should still work.

May I ask you I you know a valid reason for comp mode to not work when limit seems fine? (beside bad wiring, wich I should have excluded hardwiring various mode)

No idea, sorry. Have you tried to lower R56 below 1k. When I had the finished boards from another forum member on the bench here for troubleshooting, it turned out that it had to be 820 ohms on both. He also had some strange issues that we were able to fix by this change.
 

dunk91

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Actually when I try to calibrate unit and setting r56 I'll end having something around 750 ohm on trimmer, so it seems in line with what you are saying.
Well I'll keep trying to sort this out, I'll let it alone a couple of days then start again with fresh mind and report back!


fripholm said:
1Vpp input signal is pretty high if hard wired and not further attenuated by the input control but COMP mode should still work.

No idea, sorry. Have you tried to lower R56 below 1k. When I had the finished boards from another forum member on the bench here for troubleshooting, it turned out that it had to be 820 ohms on both. He also had some strange issues that we were able to fix by this change.
 

dunk91

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Well well, maybe we have our culprit...
All bc559 are B not C, Low low hfe. Will swap them all and hope to get it right  :-X
 

JMan

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Hey all,

I'm still waffling back and forth on what transformers to go with.  In the meantime, I'm picking up some rotary switches (Elma Type 04) for the Input/Output controls from Don Audio.  I want to make sure I've got the right thing -- 1 Wafer 1x24 Shorting 15˙

Does this look right?  I'm fairly confident, but since this project is presenting me with a lot of firsts and these switches are pricey, I have no shame about triple-ultra-checking.
 

Potato Cakes

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JMan said:
Hey all,

I'm still waffling back and forth on what transformers to go with.  In the meantime, I'm picking up some rotary switches (Elma Type 04) for the Input/Output controls from Don Audio.  I want to make sure I've got the right thing -- 1 Wafer 1x24 Shorting 15˙

Does this look right?  I'm fairly confident, but since this project is presenting me with a lot of firsts and these switches are pricey, I have no shame about triple-ultra-checking.

I'm using 1x12 single deck Lorlin switches except for the release which I used a potentiometer per the manual's recommendation. The ones you're ordering would be great for super fancy precision control for something super fancy precise. This circuit is really great but I wouldn't use it for something that requires more exact control over program material, so you can save yourself some money on the control switches if you want.

Thanks!

Paul
 

dunk91

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If you want save some money you can always get the cheaper uraltone rotary switches (uraltone doesn't carry them anymore but you can find them @ don audio) wich cost a fraction of elma's and are pretty decent :)

JMan said:
Hey all,

I'm still waffling back and forth on what transformers to go with.  In the meantime, I'm picking up some rotary switches (Elma Type 04) for the Input/Output controls from Don Audio.  I want to make sure I've got the right thing -- 1 Wafer 1x24 Shorting 15˙

Does this look right?  I'm fairly confident, but since this project is presenting me with a lot of firsts and these switches are pricey, I have no shame about triple-ultra-checking.
 

JMan

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Thanks for your input, guys!  :)

Are these the uraltone ones (I couldn't find any branded as such)?  In which case, I'd just ignore the second wafer, right?
https://www.don-audio.com/Rotary-Switch-2024-2-Pole-24-Position
 

dunk91

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Yes, they are! Just use one wafer only and you are fine; elma of course is another league, but those aren't bad at all ;)

JMan said:
Thanks for your input, guys!  :)

Are these the uraltone ones (I couldn't find any branded as such)?  In which case, I'd just ignore the second wafer, right?
https://www.don-audio.com/Rotary-Switch-2024-2-Pole-24-Position
 

fripholm

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tomas1808 said:
Is there a trace layout file available to DIY a TG1 board?

No, but you can buy boards from me. They are available and according to 'Deutsche Post' shipping to Uruguay is no problem. See first post on how to contact me.

Thanks!
 

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