All-discrete GSSL signal path upgrade

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Blahpstick

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DrywOwens said:
It works great now. I do have one question though - it seems inserting the compressor in bypass yields a significant level drop. Has anyone else experienced this?

I am experiencing the same problem.  I've been dealing with it by using the true bypass when the unit is powered off, but I'm worried about stressing out the power supply board by always switching it on and off trying to get comparable levels.  Has anybody figured out how to keep the 10-11 dB drop from happening when the unit is on and bypassed?
 

andow

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Blahpstick said:
I am experiencing the same problem.  I've been dealing with it by using the true bypass when the unit is powered off, but I'm worried about stressing out the power supply board by always switching it on and off trying to get comparable levels.  Has anybody figured out how to keep the 10-11 dB drop from happening when the unit is on and bypassed?

I don't have this problem with mine...
 

Blahpstick

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andow said:
I don't have this problem with mine...

Did you mod a real Gyraf kit?  Owens modded his Stam Audio SA4000 and I modded a Serpent Audio SB4000, so it seems that there is a difference and I'm curious if anybody has pinpointed those differences between the Serpent and Stam versions of the board.
 

andow

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I used a board from PCB Grinder.

Did you remove the feedback resistor of the output stage from the main pcb? If you use the same resistor in parallel you'll get 6dB less gain.
 

Blahpstick

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andow said:
I used a board from PCB Grinder.

Awesome, I love PCB grinder

andow said:
Did you remove the feedback resistor of the output stage from the main pcb? If you use the same resistor in parallel you'll get 6dB less gain.

Yes, I did. The drop in level (about 11 dB) is only when the compressor is in bypass.  Yet, when the unit is powered off, it passes signal at unity.

Thanks for taking the time to try, Andow! Got any other ideas by chance?
 

DrywOwens

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A new problem has cropped up that I haven't experienced before. For seemingly no reason, the compressor's right channel will sometimes cut the signal and make a strange popping and crackling noise. If I wait it out, it eventually goes back to normal. Does anyone have any ideas as to how I can troubleshoot this?
 

hikowinter

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Aug 22, 2013
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I finished the Cavendish mod but level dropped -6db.
I used 2503 Litz transfomers, 5k resistor and 5k trimmer and DOAs are DIY JE-990.

Anyone knows?
 

hikowinter

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hikowinter said:
I finished the Cavendish mod but level dropped -6db.
I used 2503 Litz transfomers, 5k resistor and 5k trimmer and DOAs are DIY JE-990.

Anyone knows?
Is this mod unbalanced output?
 

andow

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hikowinter said:
I finished the Cavendish mod but level dropped -6db.
I used 2503 Litz transfomers, 5k resistor and 5k trimmer and DOAs are DIY JE-990.

Anyone knows?

andow said:
Did you remove the feedback resistor of the output stage from the main pcb? If you use the same resistor in parallel you'll get 6dB less gain.
 

hikowinter

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andow said:
Did you remove the feedback resistor of the output stage from the main pcb? If you use the same resistor in parallel you'll get 6dB less gain.
Yeah, I removed 15k feedback resistors.
Should I use 10k resistor and 10k Trim pot?
 

andow

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hikowinter said:
Yeah, I removed 15k feedback resistors.
Should I use 10k resistor and 10k Trim pot?

If you have the same gain on both channels, everything is probably wired correct. So to increase gain you will have to raise the feedback resistance...
 

hikowinter

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Potato Cakes said:
No. Hence the 2503 output transformer.

Transformer input leads are Brown/Red, output are Green/Grey. The Blue/Violet leads put together are not connected to ground on pcb.
Isn't  this output balanced?
Am I wrong?
 

Potato Cakes

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Your first question asked if it was unbalanced. That answer is no. So the answer to is it balanced is yes.

Does the output level change when you adjust the trimmers?

Thanks!

Paul
 

hikowinter

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Potato Cakes said:
Your first question asked if it was unbalanced. That answer is no. So the answer to is it balanced is yes.

Does the output level change when you adjust the trimmers?

Thanks!

Paul

Yes, I can adjust the trimmers.
 

Potato Cakes

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Another thing would be your XLR wiring. The pinout for the output connections matches the GSSL board, so if you inadvertently swapped + and ground, that would give you -6dB.

Thanks!

Paul
 

hikowinter

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Potato Cakes said:
Can you achieve unity gain by adjusting them?

Potato Cakes said:
Another thing would be your XLR wiring. The pinout for the output connections matches the GSSL board, so if you inadvertently swapped + and ground, that would give you -6dB.

Thanks!

Paul

Maybe the pinout for the output connections to XLR would be ok.

I tried to connect to unbalanced input setting gear and I could get +6dB gain , but level was low to unity gain.
And then I changed 5k resistor to 10k, trim pot left 5k as it is.
I could achieve unity gain by adjusting Trimmer.

Is that correct?
 

Potato Cakes

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That's the what the trimmer is there to do. If you have proper gain through the unit and everything else checks out (distortion, polarity, etc.) then you're done.

Thanks!

Paul
 

hikowinter

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Potato Cakes said:
That's the what the trimmer is there to do. If you have proper gain through the unit and everything else checks out (distortion, polarity, etc.) then you're done.

Thanks!

Paul

OKay, I'll try.

Thanks, Paul!
 

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