GSSL HELP THREAD!!!

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Script

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Yes. Trimmer before input of VCA.

I skipped the one(s) on the output. Calibrate with SC in bypass or threshold set to no compression happening.

Remember that unit loses 6dB when connected via unbalanced cables.
 

babaorum

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Hello
I have finished my GSSL and it works fine except a breath on one of the outputs, here a little video to illustrate. I already checked the cables and it provides obviously from a specific output of the GSSL , how could I fix this issue ? do you think it can be the internal XLR wiring ? I tried too to exchange the THAT on the board but it's the same issue.
View attachment IMG_9509.MOV
 

Gustav

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Hello
I have finished my GSSL and it works fine except a breath on one of the outputs, here a little video to illustrate. I already checked the cables and it provides obviously from a specific output of the GSSL , how could I fix this issue ? do you think it can be the internal XLR wiring ? I tried too to exchange the THAT on the board but it's the same issue.
View attachment 83293

"Breath" is a little hard to interpret, and personally, I have no idea what I am looking for on your video.

Its always more helpful to state the problem in a clear language, and drop the videos - someone else may be able to help, based on what you have posted, but trying to make it easier to help..

Gustav
 

babaorum

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How can I say ... ? 'background noise' or 'hum' maybe (sorry I'm frenchy), (you have mostly to listen than looking for on the video, we can see that there is noise on the second channel of the console of my audio interface while no input signal into the GSSL)
 
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Script

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Yeah, unclear. Some kind of hiss ?
How loud is that ?

You tested with pulled input cables ? Ground loop somewhere ? What makes you think it's the output ?
 

babaorum

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a chug not a buzz (so I don't think it's a pb of Ground) here amplifiered (in the screenshot) inputs pulled or not it's the same that's why I told output issue but it's maybe in the input stage (internally) because when I put compressor in action the make up increase or decrease the noise.GSSL_noise.png
 

deuce42

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Hi guys, I'm am just stumped with a build. Unit is not compressing.

I am getting a strange reverse polarity reading in the side chain chips TL074 and TL072 unless I'm missing something? For the record, all diodes, electrolytic capacitors, and chips are mounted in their correct direction.

For voltages, I seem to have reverse voltages in the TL074 and TL072 - ie:

TL074:

Pin 4 and pin 5 ends up -12V where as I think it should be +12v.
Pin 11 and pin 5 ends up + 12V. Again I would think the should be reversed , eg -12v

TL072:

Pin 8 and pin 5 should end up -12V,
Pin 4 and 5 end up +12V.

Also in terms of measuring the Makeup Gain and Threshold pots I seem to have something bizarre:

Makup Gain pot: 0.8V on the lugs which doesn't make sense.

Threshold pot: Again 0.8v.

I've tried to audio probe the circuit and get signal coming out of the Ne5532, Ne5534 and the TL074 and THAT chips, although it is a kind of buzzy signal if that make sense

I've read so much and just can't work out what is wrong with this build.

Cheers
 

Gustav

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Makup Gain pot: 0.8V on the lugs which doesn't make sense.

Threshold pot: Again 0.8v.

I've tried to audio probe the circuit and get signal coming out of the Ne5532, Ne5534 and the TL074 and THAT chips, although it is a kind of buzzy signal if that make sense

I've read so much and just can't work out what is wrong with this build.

Cheers

Go to the "source", and check for voltages.


Gustav
 

Gustav

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Thanks Gustav. Supply voltage in the power supply seems to check out fine. I'm just stumped
output on the 12V regulators as well?

If so, yes, the 0.8 on the control board is really odd, since thats a direct line. Check wiring of the 10 pin connector!

Gustav
 

deuce42

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Thanks Gustav. Yes the 12v regs come out with 12v and -12 respectively.

Now when I retest it I get -12v on one side of the Threshold pot but the other side (ie the one that goes to the 47k resistor) measures 0.16v!

The makeup pot now has 12v but this is on the wrong side of the pot and it has no voltage on the other side of the pot.
 
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joshk34`

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Apologies if this has been mentioned before, I did a search of the thread and couldn't find what I was looking for. If I somehow missed the answer, please let me know as I've been working all day and probably am not in a solid frame on mind, haha.

I've got my GSSL, one of the last one's from PCB Grinder, wired up and am running a 1kHz sine wave into it at 1.204 Volts AC on each input.

I'm getting some massive output discrepancies that seem to vary with the VCA. I'm using THAT 21080B vca's.

With the output knob from low to high and this is read I'm getting on the output:

(Threshhold: all the way counter clockwise
Ratio: 2
Attack: all the way clockwise
Release: all the way clockwise)

VCA 1:
Right side: 6.90 VAC to 10.62 VAC
Left Side: 6.90 VAC to 10.60 VAC on the right

VCA 2:
Right Side: 1.314 VAC to 9.64 VAC
Left Side: 1.302 VAC to 9.60 VAC

VCA3:
Right Side: ~3.5 VAC to 10.70 VAC
Left SIde: ~3.37 VAC to 10.52 VAC

This is my first time working with these VCA's, is this normal behavior for them to act so differently from one another? My gut says something is wrong with them or potentially something in the circuit. I would think they would match better, especially since the circuit is trimmerless. Thanks for any help or insight
 

gyraf

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this is within 2% or so, I wouldn't expect much higher untrimmed precision than this. If you need better, look a handful of posts back for adding a trimmer

/Jakob E.
 

joshk34`

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this is within 2% or so, I wouldn't expect much higher untrimmed precision than this. If you need better, look a handful of posts back for adding a trimmer

/Jakob E.
Just making sure I was clear, as I reread my post and it might have been confusing. There was only three total VCA’s, I measured each one once on the left and once on the right to show there was essentially no difference because of something in the circuit. So, one on the low end approximately 1.3, one was 6.9 and the other was 3.5 VAC. Maybe, that is within normal tolerance, as you said, but seemed off to me so u wanted to double check. Thanks.
 

joshk34`

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I was getting some really hot output levels from a relatively small input signal. I was also noticing a discrepancy between the level coming out of the left and right channel. So, in the process of troubleshooting I removed all three VCA's from the board. And with the input signal and settings I mentioned (1.204 VAC measured from the XLR input jack), I put one of the VCA's on the board at a time. Then, I measured the output signal from the output jack. So essentially, all VCA's off the board. I put one of the VCA's back in the right channel, measured the output with the output pot all the way counter-clockwise then all the way clockwise. Then I took that same VCA and put in in the left channel and remeasured. After that I took that VCA off the board and repeated with the second VCA, then the third. Each as the only VCA on the board and that's how I got the level measurements. One at a time. The signals seem way to hot to me, and the fact that each VCA varied so wildly. Just wasn't sure if they were bad or maybe it's normal. Hope that helps. If I still haven't explained myself clearly, I can try an up load a video.
 

Script

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How about a picture of the board first ?

Are you measuring differing max ratio threshold level behaviour between different VCAs ?

How often do you need max compression from this unit? Could run material thru it to get a feel for the THR knob. What's your max THR setting in real life ?

I'd get the audio path of both channels calibrated first, meaning signal IN equals signal OUT with no compression dialled in.

Any add-ons installed like side chain filters, Turbo ?
 
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joshk34`

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Here’s a pic, no mods. Trying to get it right first. All this is what happened the first time I plugged it in, and this is PCB Grinder’s last incarnation kit, there are no trim pots. Hence why I was so curious as to why I put a 1.2 VAC signal in and with the output knob all the way counter-clockwise get up to 7 VAC on the output signal. So I can’t test it with any material, as my converters are dying as it is. My testing and troubleshooting brought me to the VCA’s as when I first fired it up I noticed radically different outputs on the left and right channel. So I took them out and tested them one by one. Thanks for the help, would love any insight.
 

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