Yes, this circuit has been built a couple of thousand times and was found working
Earlier in this thread we have already discussed that biasing thing - it has to do with reducing distortion as per THAT's vca usage application notes
/Jakob E.
GSSL HELP THREAD!!!
- Thread starter hairyandy
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Help Support GroupDIY Audio Forum:
Yes, this circuit has been built a couple of thousand times and was found working
Earlier in this thread we have already discussed that biasing thing - it has to do with reducing distortion as per THAT's vca usage application notes
/Jakob E.
front247
Member
I have been using my GSSL for over two years and everything has worked well from the very beginning, the system is quiet, almost inaudible, no noise or buzzing, it compresses both channels perfectly, the bypass works great... but from the very beginning there is one small problem: the right R channel is quieter by exactly 4 dB, generally it didn't bother me because I always equalized the levels on the sources, but now I have some free time and it doesn't bother me. XLR inputs and outputs checked, all op amps checked, working and replaced, vco - checked and replaced, working, the entire audio input and output path checked element by element - everything is working. I've lost ideas at this point... the rest of the system, as I read, influences the signal but only controls it. What else can cause one channel to be 4 decibels quieter? Do you have any idea where to look?
Read (precise) voldtages at control-inputs to the two main vcs's?
I am assuming it is 4db lower in bypass right? I had a similar issue and what I did was run a 1khz sine wave with both input and output connected and started at the output XLR connectors and checked voltage back towards the inputs following the signal path and see where the voltage changes. Sounds like you've got an incorrect resistor in the signal path or short somewhere if I had to guess.
front247
Member
Hello
I measured the voltages: input -15.24V +15.24V
At the outputs of the potentiometers to the VCO - right channel - 3.20V, left channel 3.19V.
On operational amplifiers Left channel - 0.62V and -0.63V. Voltages measured within the VCA circuits
front247
Member
Today I will do the same, I will pass sine waves and look for the path, thank you for the tip, although, as I wrote, I measured the voltages and measured all the elements where the analog signal goes and there is perfect symmetry, I selected the resistors so that they are identical, the capacitors too, but I will check, thank you for the tip
I have a 4 dB drop on the right channel all the time, both during compression and bypass.update: I passed a 1kHz sine signal through the signal path: at the inputs I have: 28mV and 28.4mV but... I checked how the cables are connected to each other without GSSL and they have a perfect 28mV for both channels. I don't know if .4 mV is a lot...? I went further and at the input of the ne5532 opamp I already have 6.8mV - R channel and 6.2mV - L channel... at the input of the operational amplifiers after the capacitor I already have 1.2mV left channel and 1.8mV right channel. So there is a difference, but I don't know if it is so big that it affects the 4 dB drop? I can't compare it, but there is a difference. But I don't know what causes it, because from the very beginning the left channel is getting bigger and bigger.I followed the entire signal chain and the output of one of the VCAs is 10.8mV and the output of the other is 6.2mV, so this is a significant difference, I only increased the sine input signal a bit... but at the outputs of 22uf capacitors, from which the signal through the res\ The 27K ystor goes into the VCO and is respectively: 1.8mV and the second one is 1.2mV. I replaced the VCA channels, I have the 2181 and it is identical, so the VCOs are functional, I think, there is also this difference at the JRC 5584 outputs, but... at the inputs it is much smaller, i.e. 6.8 mV and at the other 6.3 mV... but it is I also swapped places and it's exactly the same, so I don't know where the signal is lost... I have no idea how to check it to locate the element of the audio track that is responsible for it. I will also add as a side note that when changing the settings of the attack and realise controls, the difference increases slightly to about 6 dB at extreme attack and release settings. But the problem, in my opinion, definitely lies in the signal path.
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