GSSL HELP THREAD!!!

[thepraqtice]

Either faulty right side audio-VCA or a solder bridge at the VCA on pcb. You could confirm this by swapping left side with right side audio-VCA. With faulty VCA, distortion will follow the faulty part. Distortion still at right side, use a magnifying glass to spot and remove the solder bridge.

I tried swapping VCA's and distortion stays on same side. Then tried looking for solder bridges and couldn't find any. Tried resoldering all points around VCA's and opamps with a very small soldering iron tip and went light on solder to avoid bridges. Distortion is still there as before.

If I take out right VCA with no jumper, just leaving left VCA in and send a mono signal through both inputs the output level is about equal on both L+R outputs with no distortion... If I take out the left VCA with no jumper, only leaving right VCA in. I have about the same amount of signal as before on the right output with no distortion, but no signal at all through the left output.

I pulled out both VCA's again and replaced with jumpers again and it seems like I must have missed this the first time. With a mono test tone the signal on the right side is significantly higher than the left signal although there is no saturating distortion which I presume must be the VCA's overdriving/saturating from signal being too high on right side before it goes through the VCA's...

I checked again with jumpers. A hard right panned signal only comes out of right output and a hard left panned signal comes out of both left and right outputs. the right out even seems to be a bit higher than left output with a hard left panned signal.

I tried swapping input opamps, no change. Switched opamps in VCA section, no change. Swapped output opamps and  still no change of sides.

Very confusing. Do you think the left signal must be bleeding into the right channel somehow and the addition of the extra left signal going through right is making VCA's saturate on right side? Presumably this is happening before the VCA's, so maybe somewhere in the input section? If so it's seems like it's well connected... :-\

 

[thepraqtice]

Another thing I've noticed that might be worth adding/mentioning is when I listen to left or right channel individually (so I can't hear main distortion problem), the 600ms, 1.2s and Auto release settings all add audible distortion to the signal with some fairly high frequency harmonics.

.1 and .3s release settings compress very clean with no audible distortion as expected.

I have already clipped Pin 4 from the VCA's which are THAT 2180B

Many thanks for your help again,

Sam

 

[Harpo]

I checked again with jumpers. A hard right panned signal only comes out of right output and a hard left panned signal comes out of both left and right outputs. the right out even seems to be a bit higher than left output with a hard left panned signal.

Can you show some pics from your complete build, especially showing the hookup wiering of gssl/turbo mode switch, sscf boards, turbo board, main board and trace side of control board (not your hookup overview pic from some posts ago). There must be something wrong at input side of your sscf boards connection or the summing opamp of the sscf board where both L/R signals connect is broken or is missing supply voltages. You have removed the 47K summing resistors from GSSL main board ? Ratio connections from turbo board connect to free pole/throw connections at ratio-switch on control pcb ?

 

[Harpo]

some time's as i said the psu works, but in this case i've just audio passing into the compressor with a huge distortion and controls doesn't works, if i bypass the unit it's going in MUTE!
when i move release the led inside the meter start flashing (usually is not working) for an half second and makeup seems working only for 3db!!!

Between which power rails is your meter illumination powered and what is the resistor value to limit the LED current ?

I've checked the control board but seems all ok! right resistors right oriented capacitor, right oriented switch, threshold makeup and bypass seems well connected.

Did you fit the jumper/wire link right side next to the M+ marking on control pcb ?

Right now I'm feeding it with 0dbfs 100hz on both channels with unbalanced connections.

0dBFS could be any voltage. What is your multimeter readout when measuring AC voltage between input+/- ?
Unbalanced connection with output- not shortet to 0V reference voltage ?

 

[axl]

some time's as i said the psu works, but in this case i've just audio passing into the compressor with a huge distortion and controls doesn't works, if i bypass the unit it's going in MUTE!
when i move release the led inside the meter start flashing (usually is not working) for an half second and makeup seems working only for 3db!!!

Between which power rails is your meter illumination powered and what is the resistor value to limit the LED current ?

I've checked the control board but seems all ok! right resistors right oriented capacitor, right oriented switch, threshold makeup and bypass seems well connected.

Did you fit the jumper/wire link right side next to the M+ marking on control pcb ?

Right now I'm feeding it with 0dbfs 100hz on both channels with unbalanced connections.

0dBFS could be any voltage. What is your multimeter readout when measuring AC voltage between input+/- ?
Unbalanced connection with output- not shortet to 0V reference voltage ?

Hi Harpo!
Thanks for the fast repl. I figure out!!!!!!
I have totally inverted the connection between motherboard and control board now it's work and compressing nice!!!!!!

I have just one issue not solved it's something with the psu, some times i power on but the 7815 put out -0.7 V!
If i shut down the unit for an instant the meter needle crank all up and the light flash!
Then i power the unit on again and it's working but i have 50hz @ -70db!!! i've checked with the meter and i have discovered this:
-The - rail works fine at the -15v bridge i have -14.9v dc and 0ac
-The + rail have some problem i get +14.8v (and that's fine ) but if i measure in ac it's show 35v!!!!!!!!!!!!
Now i have already change the 7815 but nothing happen the problem persist, should have to change the 2 1000uf caps on the + rail ?????

 

[Marod3ur]

Hello dear DIY community...

i'm a new member from germany. I came from a little german DIY forum but i need some more help with my GSSL...

Finally, I have finished the GSSL. The compressor will however not work properly. I have two Problems:

1st:
If I give a sine wave on the compressor, I have a signal at the outputs. With the make-up gain I can control the volume as desired. With the bypass, I can disable the make up gain. But i have no compression on the signal. After a search i found out that the sidechain vca have no input signal. In the picture you can see that i measured 3,8 V AC at this 47k resistors. But behind these i am not able to measure anything. Do you have an explaination for this and can give me some advice?

What could I check yet?

2nd:
Almost every time, I must turn the compressor twice to get a signal at the outputs. Otherwise I get a compression of 16db at the meter and no signal at the outputs. What could be the cause and is this may be in connection with my first issue?

Thank you for your help and bye

 

[Marod3ur]

Here just a picture of the main pcb of the GSSL. May be there is something wrong...

i know there are no ICs

 

[gyraf]

1 - The 47K resistors are voltage-to-current conversion, looking into a virtual-ground (inverting amplifier) input - you should not have signal after these.

Check for AC signal AFTER the associated opamp - that is, at the sidechain-insert jumper. Then check for DC signal after your bypass switch, at the input to attack time switch. (does your GR-meter indicate as expected?)

If I should guess, I'd aim at either a bad *HPF link, or a wrong wired bypass switch.

2 - Need to switch on twice points to regulator latch-up (as described many times before in this thread). Find out what voltage is missing when it misbehaves, and change the related regulator to a different brand.

Jakob E.

 

[Marod3ur]

Hello and thank you for your fast answer...

do you mean this IC marked on the picture?

On pin 1 i messered 0 - 6,2 V AC (Treshold)
On pin 7 i messered 0 - 1,92 V DC (Make Up)

I think this is ok...I checked the DC signal at the input of bypass...nothing here. I checked the corresponding pin at the TL074 -> No Signal.

The HPF link I've newly soldered. No effect...

I have just a value on the meter if the regulator are working not correct. After switching on and off there is no value...

Thank you for your help!

 

[Marod3ur]

Oh...now i see that the pin on the TL074 that i have messered is an input...i keep looking

 

[thomasdf]

Hi to all of you GSSL lovers

I think I will buy Gustav's kit one pretty soon to put across my 2bus as I need some of that specifig "glue"
I have one question tho : I don't need a complicated side chain filter board, can I put a very simple passive hi pass filter instead or will I lose too much level? (I can adjust the threshold accordingly). Is it too much of a hassle? I was think of cutting under 120hz with the flip of a switch.

Thanks in advance

Thomas

 

[gyraf]

Hi Thomas,

That is easy enough - you just insert (and short by your switch) a capacitor at the sidechain insert point.

No loss of signal, other than for the obvious out-of-band frequencies.

Jakob E.

 

[thomasdf]

oh ok that's cool then, thanks Jakob. For some reason I thought I had to use a RC filter. I still need to find the proper cap value, knowing that my slope will be quite soft right?

edit: non sidechain related question : I have a 1mA 300mV meter that I'd like to use for that project. Can I use it to show a 0 to 10dB gain reduction range but in a precise way (I can graduate it in the proper way) as I mostly use the SSL to compress less than 7 dBs... ?

I am not sure this is very clear, please let me know and I can try to reformulate the question

Thanks

 

[Harpo]

oh ok that's cool then, thanks Jakob. For some reason I thought I had to use a RC filter. I still need to find the proper cap value, knowing that my slope will be quite soft right?

The 'R' from your RC filter is already there, being the two 20K resistors in parallel, connecting to a virtual ground node, so effective value is 10K. For your wanted hpf at 120Hz, the caps value (in Farad) needed for this -3dB cutoff point is 1/(2*PI()*R*freq) with R in ohm, freq in Hz and PI() 3.14159..., giving 1.326e-7F or 132.6nF. Noone builds this value, but two 68nF caps in parallel will give you a hpf at 117Hz, being pretty close to your wanted 120Hz. This is a 1st.order RC filter, so slope is -6dB/oct or -20dB/dec.

edit: non sidechain related question : I have a 1mA 300mV meter that I'd like to use for that project. Can I use it to show a 0 to 10dB gain reduction range

The amount of meter deflection shows the amount of generated VCA control voltage by the sidechain, so the question is sidechain related. You can use your 1mA meter. Maybe use a variable resistor/rheostat instead of the 2K** fixed resistor for a meter sensivity trim with trimmers initial value about 1K (the TL072 will not drive a much heavier load, so avoid a full CCW setting/shorting out of this sensivity trimmer).

 

[tabuckner]

Hello All,

I have been reading this thread for some time and finally go around to building my clone. I had everything wired up correctly--so I thought--until I went to boot the unit without having checked the voltages across empty sockets.

Sure enough, I flipped the placement of the two 12v regulators (79L12 and 78L12). I tested the unit thoroughly prior to realizing that I had made what I deem to be a potentially critical error. The symptoms of the unit prior to repair are as follows:

-Will not pass audio on either channel under any configuration
-Unit displays a nearly 0.0 dBFS (-1.1) pop upon turning the unit on
-Meter moves very slightly when turning on and switching between bypass and thru

I have switched the positioning of the 12V regulators into the proper placement and measured voltages across empty sockets. My voltages across sockets with ICs in place are as follows:

Input:
Left 5534
-Pin 4: -12.9V
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)
Right 5534
-Pin 4: -12.9V
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)

Output
Left 5532
-Pin 4: -12.9V
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)
Right 5532
-Pin 4: -12.9V
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)

VCAs:
Left 5534
-Pin 4: -12.9V
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)
Right 5534
-Pin 4: -12.9V
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)

TL072CP
Pin 4: -11.8V
Pin 5: -1.3v (again very strange...)

I tested the unit again and still exhibiting the same sort of behavior with one caveat; the meter is how halfway deflected whenever the machine is turned on. The only way to change this is to switch the unit to bypass at which point the meter will drop very slightly but still maintain a constant deflection.

I feel like I may have botched a voltage regulator at some point. I would really appreciate if someone (maybe Harpo?? ) could shed some light on these weird values and behavior of the unit.

The worst part about this whole situation is that I have to have the unit completed and functional (hopefully) in two weeks for a presentation. I have chosen to build the GSSL as my senior project of college. I'm an audio production major, not an EE so this is a little over my head. Hopefully my sob story will tug on some heart strings and remind you of your college years!

Thanks in advanced,
Taylor A.

 

[Harpo]

Taylor, please edit your copy/pasted textblocks with your real world voltage readings, IE some opamps are powered by +/-15V rails, others by +/-12V rails for usual.
Your different from previous measurements readings at the TL072 indicate a maybe low battery in your multimeter (pin 5 probably only a typo).
Fix voltage regulators latching on startup by either exchanging with different brand or try my anti-latchup fix for a previous pcb revision. Dunno what pcb revision you have, so diode placement might need adapting to differing trace layout.

 

[axl]

some time's as i said the psu works, but in this case i've just audio passing into the compressor with a huge distortion and controls doesn't works, if i bypass the unit it's going in MUTE!
when i move release the led inside the meter start flashing (usually is not working) for an half second and makeup seems working only for 3db!!!

Between which power rails is your meter illumination powered and what is the resistor value to limit the LED current ?

I've checked the control board but seems all ok! right resistors right oriented capacitor, right oriented switch, threshold makeup and bypass seems well connected.

Did you fit the jumper/wire link right side next to the M+ marking on control pcb ?

Right now I'm feeding it with 0dbfs 100hz on both channels with unbalanced connections.

0dBFS could be any voltage. What is your multimeter readout when measuring AC voltage between input+/- ?
Unbalanced connection with output- not shortet to 0V reference voltage ?

Hi Harpo!
Thanks for the fast repl. I figure out!!!!!!
I have totally inverted the connection between motherboard and control board now it's work and compressing nice!!!!!!

I have just one issue not solved it's something with the psu, some times i power on but the 7815 put out -0.7 V!
If i shut down the unit for an instant the meter needle crank all up and the light flash!
Then i power the unit on again and it's working but i have 50hz @ -70db!!! i've checked with the meter and i have discovered this:
-The - rail works fine at the -15v bridge i have -14.9v dc and 0ac
-The + rail have some problem i get +14.8v (and that's fine ) but if i measure in ac it's show 35v!!!!!!!!!!!!
Now i have already change the 7815 but nothing happen the problem persist, should have to change the 2 1000uf caps on the + rail ?????

Hi guys sorry if i'm boring, i've changed all the 4 1000uf cap and the rectifier, now the unit power on regular, but i'm getting 32v AC on the +15rail!!!!! what can it be????

 

[thepraqtice]

Can you show some pics from your complete build, especially showing the hookup wiering of gssl/turbo mode switch, sscf boards, turbo board, main board and trace side of control board (not your hookup overview pic from some posts ago). There must be something wrong at input side of your sscf boards connection or the summing opamp of the sscf board where both L/R signals connect is broken or is missing supply voltages. You have removed the 47K summing resistors from GSSL main board ? Ratio connections from turbo board connect to free pole/throw connections at ratio-switch on control pcb ?

Hi Harpo,

Had to borrow a camera but these should be nice big images of the compressor just now.

https://www.dropbox.com/sh/78ektzl79mns8l8/UbmpvftEI8

Wiring looks a bit messy just now, intend on tidying that up with cable ties/heatshrink etc once it's up and running. I also mounted the lorlin switch pcb in the chassis along with other pcbs to make room on front panel.

It should match that diagram from previous post here: (although not colour co-ordinated at all!)
https://dl.dropboxusercontent.com/u/4364451/GSSLTURBOSSCCRCLAYOUT.jpg

Many thanks again,

Sam

 

[Gustav]

Can you show some pics from your complete build, especially showing the hookup wiering of gssl/turbo mode switch, sscf boards, turbo board, main board and trace side of control board (not your hookup overview pic from some posts ago). There must be something wrong at input side of your sscf boards connection or the summing opamp of the sscf board where both L/R signals connect is broken or is missing supply voltages. You have removed the 47K summing resistors from GSSL main board ? Ratio connections from turbo board connect to free pole/throw connections at ratio-switch on control pcb ?

Hi Harpo,

Had to borrow a camera but these should be nice big images of the compressor just now.

https://www.dropbox.com/sh/78ektzl79mns8l8/UbmpvftEI8

Wiring looks a bit messy just now, intend on tidying that up with cable ties/heatshrink etc once it's up and running. I also mounted the lorlin switch pcb in the chassis along with other pcbs to make room on front panel.

It should match that diagram from previous post here: (although not colour co-ordinated at all!)
https://dl.dropboxusercontent.com/u/4364451/GSSLTURBOSSCCRCLAYOUT.jpg

Many thanks again,

Sam

I hope you don't mind, but for the sake of getting some basic info.

Is this your first build?

Did you put this all together before testing and powering up the unit, or did you get the standard GssL with no mods working first?

Gustav

 

[Harpo]

Hi guys sorry if i'm boring, i've changed all the 4 1000uf cap and the rectifier, now the unit power on regular, but i'm getting 32v AC on the +15rail!!!!! what can it be????

No idea why you would need to change your probably healthy 1000uF caps and the rectifier. This is in no way related to a voltage regulator latching on startup. A 32VAC readout of the +15VDC rail in respect to 0V reference voltage will either be a low battery in your multimeter or it was displaying 32 and you missed the uV or mV indication of a auto sensing multimeter reading.