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gyraf

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still unclear what exactly you measure, sorry

you put in say 1.2V AC (what waveform, freq, measured how?), set the unit to compress say 4dB, adjust makeup gain to 1.2V again - now what channel difference do you see? This is a real-world condition, and all that matters.

If you're within 2% here, all is well

There may be several border conditions like clipping points for various parts of control or audio chain that could influence balance but that are not relevant for our use-case

/Jakob E.
 

Gustav

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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.

I find it really difficult to follow your methodology,taking out and putting in VCAs one at a time. For example, I am confused wether you are treating the SC identically to the signal path VCAs.

Just to get a really clear picture. Could you...

1. Place all 3 VCAs in the circuit, send a 1Khz sine at 0dBU/0.775VAC to the unit, make sure treshold is set to max, and measure output (from the unit, not the VCA) at max and minimum gain at left and right respectively.

Id like to establish a base reading with known variables, at a familiar range, and see if we have discrepancies.

2. Swap the two VCAs on the left and right channel with each other, then measure output at max and minimum gain under the same conditions as before.

Id like to see if any discrepancies uncovered in step 1 follow the VCA, to make sure if the VCA is indeed the culprit.

Gustav
 
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Harpo

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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.
From your pic, the sidechain-VCA seems to be fitted with reversed orientation. The VCA most likely won't survive this, once powered on. A broken chip will give you unpredictable, if any readouts.
 

Gustav

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From your pic, the sidechain-VCA seems to be fitted with reversed orientation. The VCA most likely won't survive this, once powered on. A broken chip will give you unpredictable, if any readouts.
good eye

Gustav
 

joshk34`

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I find it really difficult to follow your methodology,taking out and putting in VCAs one at a time. For example, I am confused wether you are treating the SC identically to the signal path VCAs.

Just to get a really clear picture. Could you...

1. Place all 3 VCAs in the circuit, send a 1Khz sine at 0dBU/0.775VAC to the unit, make sure treshold is set to max, and measure output (from the unit, not the VCA) at max and minimum gain at left and right respectively.

Id like to establish a base reading with known variables, at a familiar range, and see if we have discrepancies.

2. Swap the two VCAs on the left and right channel with each other, then measure output at max and minimum gain under the same conditions as before.

Id like to see if any discrepancies uncovered in step 1 follow the VCA, to make sure if the VCA is indeed the culprit.

Gustav
Can do

Step 1: Left: .84 VAC to 6.106 VAC
Right: 6.69 VAC to 9.01 VAC

Step 2: With the VCA's swapped left and right
Left: 6.70 VAC to 9.00 VAC
Right: .875. VAC to 6.13 VAC

Thanks for pointing out the VCA, Harpo. I did have it reversed, but never turned it on like that. Just hastily put it back in at the end of the night and fixed it before powering on.
 

Gustav

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Can do

Step 1: Left: .84 VAC to 6.106 VAC
Right: 6.69 VAC to 9.01 VAC

Step 2: With the VCA's swapped left and right
Left: 6.70 VAC to 9.00 VAC
Right: .875. VAC to 6.13 VAC

Thanks for pointing out the VCA, Harpo. I did have it reversed, but never turned it on like that. Just hastily put it back in at the end of the night and fixed it before powering on.

We expect roughly 20dB gain, which is not really spot on at all, but close enough on the VCA on the left at step 1, and on the right at step 2 (comes to about 17?)

There is something wrong with the other VCA - I dont think Ive seen a broken one act like that, or maybe I never measured it quite so in depth, because it was just obviously off without going to such lenghts. Is the unit compressing and everything on the bad channel, just gaining excessively?

I only see bad VCAs, when I have put them in reversed - happens for the best of us. If you suspect other issues could be at play, you could ask the tech help at THAT. They are usually quite responsive.

Gustav
 

joshk34`

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We expect roughly 20dB gain, which is not really spot on at all, but close enough on the VCA on the left at step 1, and on the right at step 2 (comes to about 17?)

There is something wrong with the other VCA - I dont think Ive seen a broken one act like that, or maybe I never measured it quite so in depth, because it was just obviously off without going to such lenghts. Is the unit compressing and everything on the bad channel, just gaining excessively?

I only see bad VCAs, when I have put them in reversed - happens for the best of us. If you suspect other issues could be at play, you could ask the tech help at THAT. They are usually quite responsive.

Gustav
Thanks for the advice. I ended up ordering some more VCA's, but they don't arrive until November. Meanwhile, I finally got some time to dig in again, and it's not just the VCA's. The device doesn't seem to be compressing. While it passes signal, with the aforementioned errors, I ran program material through the "good" VCA and no matter what the controls were set at, the device did not compress at all. In fact, if I volume match it, it nulled with the GSSL in and out of bypass. The output volume seems to be the only thing that's working and will be affected whether the bypass switch in engaged. Ah well, back to the drawing board.
 
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