GSSL HELP THREAD!!!

[rapidcore]

RapidCore - 6dB points towards a balancing problem:
- Check that your in- and output signals (including e.g. cables) are balanced (or both NOT).
- Check level after input debalancing circuit.
- Check that both output driver opamps delivers signal.

/Jakob E.

Thanks Jakob. There was a problem with output opamp socket - fixed.
Last step to do is wiring of ground.
Is there any best solution for wiring signal and ground cables, pcb and chasis?
There are few schemas on forum, but still not sure which one is correct/best.

 

[Sisu MT]

You have AC on VCA IN ?

Any chance you had the VCA installed with wrong orientation and then powered ? If so, likely fried.

Checked for shorted solder joints around VCA ? Connectivity ?

I've replaced all the VCA's (3 x 2181), 5532's, 5534's, TL072 and TL074 and the THR POT (50k). Also double check all component values and micro examination of solder joints and traces and all looks proper. Still no compression, so I'm going back and retesting. on the Sidechain VCA input, still only get .1-.3 VAC with music playing. On output of sidechain VCA, only get .01 VAC. It's a new VCA and they were all installed correctly, so it has to be something before the VCA is amiss. Any ideas where i can test next? Thank-you very much!

 

[Script]

There isn't much between unit's input-buffer output and sidechain VCAs input.

2x47k connect well and correct value (not 470k).

The 100p cap on the SC VCA input (on schematic in third row on left, the cap before 15k to ground) is correct value too (100p = 101 written on component).

You implemented all changes for respective VCA (2181 A/B/C) as described by Matt Fischer.

Pin 5 of SC VCA measures -2.85 DC.

 

[gyraf]

(you are aware you need to measure after vca output opamp, not after vca itself?)

 

[Script]

(Yes, measure after inverting buffer.) I just saw. Sorry, my bad.

If it's none of the above, running out of ideas. The Att and Rel rotaries are wired correctly (connectivity to pole)? But I assume you have checked that.

 

[Davey78]

Hi guys, after some weeks of problems and research in this thread I finally managed to get my first unit going (more or less). Still not sure it sounds as it should but will get into those details later on (waiting for a little oscilloscope atm). One question at this point - after I switch it off, I get a delayed short "unloading" noise in my output (capacitator problems )? It happens everytime after use. Release is on shortest setting. Any ideas?

 

[gyraf]

..just don't shut it off while using it..?

 

[Sisu MT]

There isn't much between unit's input-buffer output and sidechain VCAs input.

2x47k connect well and correct value (not 470k).

The 100p cap on the SC VCA input (on schematic in third row on left, the cap before 15k to ground) is correct value too (100p = 101 written on component).

You implemented all changes for respective VCA (2181 A/B/C) as described by Matt Fischer.

Pin 5 of SC VCA measures -2.85 DC.

2x47k confirmed ok value and connectivity.

all 100p caps confirmed correct value (101)

Reviewed Mr Fischer's site again and all changes are all correct for 2181LC

Pin 5 on both output VCA's reach -2.85 VDC

 

[Sisu MT]

(Yes, measure after inverting buffer.) I just saw. Sorry, my bad.

If it's none of the above, running out of ideas. The Att and Rel rotaries are wired correctly (connectivity to pole)? But I assume you have checked that.

Here's an idea..the lorlin 4x3 rotary switches i'm using at THR shows the A and C poles diagonal from each other (attached Lorlin datasheet), but the GSSL schemo shows A and B diagonal. I wonder if I'm connecting to the wrong pole. Will play with this.

 

[Sisu MT]

Currently, the only ground to chassis I've done is from the IEC. Since i haven't sent a ground to chassis from the XLR's or PCBs...could that be the cause of no compression?

 

[Davey78]

..just don't shut it off while using it..?

Well I dont shut it off while using it... When I shut it off after using it.

 

[Davey78]

Here's an idea..the lorlin 4x3 rotary switches i'm using at THR shows the A and C poles diagonal from each other (attached Lorlin datasheet), but the GSSL schemo shows A and B diagonal. I wonder if I'm connecting to the wrong pole. Will play with this.

Just a beginner myself Sisu and didnt read your whole situation so you might have tried that already. But I had that makeup gain works/no compression problem too. I tried a lot of suggestions I found in this thread. Although my bypass seemed to work and was connected as it should, first thing I did was to bridge its (jumper A/2 and Com/ON on the board). Suddenly I could see the my VU meter react for the first time. Strangely just in the lowest ratio setting and no audible compression/attack/release but a first reacion. Later I found out that the 47k resistor on the control board was dead. I took it out and bridged it (because I had none left) and suddenly it worked. VU meter far too sensitive, but everything was working for the first time.
Oh and the switch poles shouldnt make a difference, as they have the same symetrical positions..

 

[Script]

Might check connectivity thru those rotaries -- not on switch pins but between the components they're connecting (I do by default with any switch on installation.)

How is VDC on pin 5 of the sidechain VCA (-2.85) ?

The two VCAs in audio path are powered by 15V, so 5K1 there is correct (as per Matt Fischer). But SC VCA is powered by 12V. So 3K9 I think ?! Better check in forum again ! Not sure though whether too high a resistor there (too low VDC on pin 5) would shut down entire sidechain.

 

[Sisu MT]

Might check connectivity thru those rotaries -- not on switch pins but between the components they're connecting (I do by default with any switch on installation.)

How is VDC on pin 5 of the sidechain VCA (-2.85) ?

The two VCAs in audio path are powered by 15V, so 5K1 there is correct (as per Matt Fischer). But SC VCA is powered by 12V. So 3K9 I think ?! Better check in forum again ! Not sure though whether too high a resistor there (too low VDC on pin 5) would shut down entire sidechain.

Hold the phone! So I traced the 12V that powers the sidechain VCA and it was fine, followed it to the 5k1/3k9 resistor that goes to pin 5 on the SC VCA and turns out there was barely any voltage coming through that resistor, so double checked the value and looks like I accidentally installed a 510k resistor instead of a 5.1K!! Will swap this out and double check whether it should be the 3.9k instead also....cautiously optimistic that this could be the issue...will report back.

 

[Sisu MT]

Might check connectivity thru those rotaries -- not on switch pins but between the components they're connecting (I do by default with any switch on installation.)

How is VDC on pin 5 of the sidechain VCA (-2.85) ?

The two VCAs in audio path are powered by 15V, so 5K1 there is correct (as per Matt Fischer). But SC VCA is powered by 12V. So 3K9 I think ?! Better check in forum again ! Not sure though whether too high a resistor there (too low VDC on pin 5) would shut down entire sidechain.

WE HAVE COMPRESSION!!!! sweet crushing compression (-; Sure enough it was an incorrect resistor value. Turns out the orange on the 4 band of the 510K resistor was very brown looking which is why my earlier double checking passed over it. ugh! Anyway, audio is clearly compressing and meter is dancing like gem! Thanks so much Jakob @gyraf and @Script for your generous support helping newbs like me learn and improve our skills. So fun! I'm going to make sure everything is working as it should...then on to turbo mod and sidechain! (-;

 

[Sisu MT]

Just a beginner myself Sisu and didnt read your whole situation so you might have tried that already. But I had that makeup gain works/no compression problem too. I tried a lot of suggestions I found in this thread. Although my bypass seemed to work and was connected as it should, first thing I did was to bridge its (jumper A/2 and Com/ON on the board). Suddenly I could see the my VU meter react for the first time. Strangely just in the lowest ratio setting and no audible compression/attack/release but a first reacion. Later I found out that the 47k resistor on the control board was dead. I took it out and bridged it (because I had none left) and suddenly it worked. VU meter far too sensitive, but everything was working for the first time.
Oh and the switch poles shouldnt make a difference, as they have the same symetrical positions..

Thanks @Davey78. I tried these things out and tested my 47k resistor on the control panel, but it tested fine. I appreciate you sharing though! see my last post...overlooked an incorrect resistor value going into pin 5 on the sidechain VCA. All fixed now.

 

[Davey78]

Np great it works, I know that feeling after a long search;-)

 

[Script]

WE HAVE COMPRESSION!!!! sweet crushing compression (-; Sure enough it was an incorrect resistor value.

Great ! Took out the plugs over here and opened the windows cos now we want to hear it -- time to party. What are you having ? Strawberry beer ?
_____
P.S.. Checking resistors visually has never worked for me. Can pull IC and measure from empty socket. Works for some. Also developed habit of measuring every single resistor twice before installing.

PS2 And I'm sorry if I sent you on a wild goose chase. I'm a long-term noob myself...

 

[Sisu MT]

Great ! Took out the plugs over here and opened the windows cos now we want to hear it -- time to party. What are you having ? Strawberry beer ?
_____
P.S.. Checking resistors visually has never worked for me. Can pull IC and measure from empty socket. Works for some. Also developed habit of measuring every single resistor twice before installing.

PS2 And I'm sorry if I sent you on a wild goose chase. I'm a long-term noob myself...

Well, promptly cracked a local blackberry mead beer from here in Austin. Ah sweet victory! Went into the house and tried to explain to my wife and kids why there was a huge grin across my face. They pretended to understand as best they could, God love 'em my son'll get it tomorrow when I play him an A/B comparison...he's got the bug. No need to apologize at all! You got me here. This has been an incredible learning to start to read juice in the circuit and getting a better understanding how to do that point to point. Your lessons about checking switches and resistors twice I'll take to heart. Cheers!

 

[Harpo]

Hold the phone! So I traced the 12V that powers the sidechain VCA and it was fine, followed it to the 5k1/3k9 resistor that goes to pin 5 on the SC VCA and turns out there was barely any voltage coming through that resistor, so double checked the value and looks like I accidentally installed a 510k resistor instead of a 5.1K!! Will swap this out and double check whether it should be the 3.9k instead also....cautiously optimistic that this could be the issue...will report back.

If this was a kit and you mixed up the 510k resistor, what value resistor is placed in the ratio circuit now (close to the silkscreen label 'meter' on the control pcb)?