GSSL HELP THREAD!!!

[tabuckner]

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.

Not entirely sure what you mean by copy/pasted text blocks. I assumed that a few thousandths of a volt would be negligible. The voltages I measured were only at most .02V deviance from the values listed above. Maybe I'm misunderstanding you in some way. If so, please help me understand as I'm very appreciative of any credible information you can offer me.

Your different from previous measurements readings at the TL072 indicate a maybe low battery in your multimeter (pin 5 probably only a typo).

I'll be sure to check them again today, although I'm fairly certain that pin 5 was not a typo. This is why I brought the information to you. It seemed very strange that the voltage would be so low. I'll post my findings after checking them again in the hopes you can lend me a hand.

Will your anti-latch fix work or be necessitated by a Revision 11 Board?

Thanks again for helping me out, Harpo! I really do appreciate it very much.

 

[axl]

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.

Sorry the battery of my multimeter was the problem but at maximum makeup still have 50hz noise at -64dbfs on my frequency analyzer and i don't think this is normal....
Any way i found this anti-latching mod on this post made up for old pcb
http://www.hausverwaltung-heger.de/al_leck_trick/GSSL_anti-latchup.gif

I've try to done it on the new pcb and now the latching problem (after hours of test
) seems gone for ever!!!

Hope have done all correct!

Anyway after change caps and rectifier can't believe the hum still at -64db

I found another problem on my unit after today tests   the unit basically work in mono !!!!!! doesn't matter what you put inside both channel the result is a compressed mono sum!!!! if i send for example a 100hz on the left and a 105hz on the right i get a modulated sine on the output of L and R
I've looked a lot today into this topic but I've found nothing.... if someone can help will be nice!!
Thanks again Harpo and sorry to have messed up a bit.

 

[thepraqtice]

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

Hi Gustav,

No problem. Please don't be too offended by the wiring, it's not as messy as it looks from photos. It's just hooked up so I can make sure everything's working ok and can take boards out easily if I need to... I do plan to make it look much neater.

Yes, first build for a bit of rack gear with balanced connections and built in power transformer. I've only made much simpler things like eurorack modules, guitar pedals, simple studio problem solvers etc in the past.

Didn't get the gssl circuit up and going on it's own first as I'd damaged the boards slightly at a couple of points with a violent solder pump, you can see in the photo the red cable from the spdt switch goes to top of 15k above left vca instead of 47k. I damaged the point at the 47k where that was supposed to go, so instead of installing the resistors and testing gssl without extra boards, I took both 47k resistors out and tried to wire it as it would be with filters and turbo and hope for best...

The problem seems to be in the signal chain somewhere. Left channel works perfect in mono, all ssc frequencies and ext. seem to do what they're supposed to with low frequencies in turbo or gssl. Right channel the same. The problem seems to be the left signal is getting into right channel somewhere before the VCA's which prevents it from operating in stereo. When there's a signal in left input it comes out left clean but also very loudly through right channel. With VCA's in the signal from left input distorts right VCA to saturation. With VCA's bypassed with wire, the left signal comes out of the right output very loud but doesn't distort so I presume left channel signal is getting into right channel somewhere before the VCA's.

The problem is there whether compressor is in or out, turbo or gssl mode and at all sidechain frequencies, external in and bypassed. The VCA CV's (Pin 3) measure the same mV's on both L + R with a mono test tone through both L + R so I didn't think it would be a problem with the summing/filter/cv generating part of the circuit creating an offset. So maybe a solder blob somewhere after the signal gets split to go to SSC boards and before the signal goes through the VCA's? Or issue with input/output grounding maybe?

Many thanks,

Sam

 

[Marod3ur]

Hello,

now i messered the output marked on the picture. I think this is the power for the point "ON" on the control board. But why we have here a diode? The diode is it what prevents it's a voltage on the control board. Is here a issue or do i have a thinking error?

May be for you its a easy thing but for now i don't realy know what the problem is.

Thank you!

 

[Harpo]

Taylor, I edited your previous post to show the relation to my copy/paste remark and differences are far exceeding 'a few thousandths of a volt'. Knowing wich voltage regulator from the bipolar +/-15VDC or +/-12VDC rails might be latching helps for an easier fix.
>>>My voltages across sockets  at the sockets pin in respect to 0V reference voltage with ICs in place are as follows:
Input:
Left 5534
-Pin 4: -12.9V should read -15VDC
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch) should read +15VDC. The 7815 voltage regulator might be latching
Right 5534
-Pin 4: -12.9V should read -15VDC
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch) should read +15VDC

Output
Left 5532
-Pin 4: -12.9V should read -15VDC
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch) pin 8 should read +15VDC
Right 5532
-Pin 4: -12.9V should read -15VDC
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch) pin 8 should read +15VDC

VCAs:
Left 5534
-Pin 4: -12.9V should read -15VDC
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)should read +15VDC
Right 5534
-Pin 4: -12.9V should read -15VDC
-Pin 7: -0.8V (this doesn't seem right, I'm just not sure what component(s) could be causing the mismatch)should read +15VDC

TL072CP
Pin 4: -11.8V should read -12VDC
Pin 5: -1.3v (again very strange...) pin 5 should read 0VDC. Pin 8 should read +12VDC. If your pin 5 reading was ment to be the pin 8 reading, the 78L12 voltage regulator might be latching <<<<

>>Will your anti-latch fix work or be necessitated by a Revision 11 Board?
Might be the easiest fix if your brand of voltage regulators misbehave (your 78L12 and 79L12 vregs might be damaged from your 1st.mixed up soldering). See previous post by member axl for placement and orientation of these diodes for all related bipolar rail voltages for a rev.11 pcb. The 7812 for relais and light power will not latch up.
Good luck

 

[Harpo]

...but at maximum makeup still have 50hz noise at -64dbfs on my frequency analyzer and i don't think this is normal....

Hum at whatever AC voltage your converter translates to a dBFS number and level was boosted by about 20dB. There is no dBFS relation to the analogue world without reference level.  I already asked for your AC voltage signal level when measuring between input XLR pins 2/3.
Dominant 50Hz is local AC mains frequency before rectification. Do you use shielded mic cables inside your unit or tightly twisted wires for your hot/cold XLR connections so the balanced line receivers have a better chance to cancel out common mode induced garbage? Keep AC mains and transformer secondary wires as far away from audio as possible. Distance is your friend. Rotate the toroidal transformer for least radiating garbage, largest field for usual radiating where secondary wires are leaving the transformer.

Anyway after change caps and rectifier can't believe the hum still at -64db

Nothing to do with your 1000uF caps and rectifier.

I found another problem on my unit after today tests   the unit basically work in mono !!!!!! doesn't matter what you put inside both channel the result is a compressed mono sum!!!! if i send for example a 100hz on the left and a 105hz on the right i get a modulated sine on the output of L and R

Again what is your feeding signal level in AC voltage, dBV or dBu when the result is a compressed mono sum?
Modulated sine is usual behaviour for a compressing GSSL with different frequency sine feed (signal is summed before it gets rectified and timed, so every 5 sec. there will be full cancelation of summed L/R sidechain signal from opposite polarity for your 100/105Hz sine example values). The Turbo circuit addon will fix this behaviour.

 

[axl]

...but at maximum makeup still have 50hz noise at -64dbfs on my frequency analyzer and i don't think this is normal....

Hum at whatever AC voltage your converter translates to a dBFS number and level was boosted by about 20dB. There is no dBFS relation to the analogue world without reference level.  I already asked for your AC voltage signal level when measuring between input XLR pins 2/3.
Dominant 50Hz is local AC mains frequency before rectification. Do you use shielded mic cables inside your unit or tightly twisted wires for your hot/cold XLR connections so the balanced line receivers have a better chance to cancel out common mode induced garbage? Keep AC mains and transformer secondary wires as far away from audio as possible. Distance is your friend. Rotate the toroidal transformer for least radiating garbage, largest field for usual radiating where secondary wires are leaving the transformer.

Anyway after change caps and rectifier can't believe the hum still at -64db

Nothing to do with your 1000uF caps and rectifier.

I found another problem on my unit after today tests   the unit basically work in mono !!!!!! doesn't matter what you put inside both channel the result is a compressed mono sum!!!! if i send for example a 100hz on the left and a 105hz on the right i get a modulated sine on the output of L and R

Again what is your feeding signal level in AC voltage, dBV or dBu when the result is a compressed mono sum?
Modulated sine is usual behaviour for a compressing GSSL with different frequency sine feed (signal is summed before it gets rectified and timed, so every 5 sec. there will be full cancelation of summed L/R sidechain signal from opposite polarity for your 100/105Hz sine example values). The Turbo circuit addon will fix this behaviour.

Hi Harpo!
Yes I use tightly not twisted wires, you think there's a lot of difference to use a mic cable? it's only 5cm long.

Here the measurement you required feeding the inputs with 100hz from my audio card:

INPUT LEFT    pin 2/3  -  3,410V  (12.87 Dbu right?)
INPUT RIGHT  pin 2/3  -  3,397V  (12.84 Dbu right?)

And here there is a picture of my gssl so you can see better the placement of the trafo, if you have any suggestion let me know!

I don't think to well understad you when you talk about gssl behaviour ....So it's normal to have dual mono out ????? if i put a drum loop for example i lost all the stereophony!!!!! can't work that way right????

 

[tabuckner]

Harpo,

Thank you so very much for such a detailed explanation of what I should be getting. You've set quite a bit straight in my mind. I will report back with my findings soon.

I think you are correct in that the voltage regulators might be the root of the error. Would I be better off trying the anti latch fix or just replacing the regulators altogether? Is there a way to test the 7815 at the component rather than at the sockets with reference to ground? By than I mean, can I test the rails on the regulators with reference to ground to discern whether they are latching or malfunctioning in a way that would warrant replacement?

Thank you again for all of your help. I wish I could express my gratitude in a more personal way.

Thank you sir,
Taylor

 

[axl]

Harpo,

Thank you so very much for such a detailed explanation of what I should be getting. You've set quite a bit straight in my mind. I will report back with my findings soon.

I think you are correct in that the voltage regulators might be the root of the error. Would I be better off trying the anti latch fix or just replacing the regulators altogether? Is there a way to test the 7815 at the component rather than at the sockets with reference to ground? By than I mean, can I test the rails on the regulators with reference to ground to discern whether they are latching or malfunctioning in a way that would warrant replacement?

Thank you again for all of your help. I wish I could express my gratitude in a more personal way.

Thank you sir,
Taylor

Hi Tab i'm not expert in anyway but i've solved your same problem adding 2 100nf caps and 4 1n4007 diodes under the pcb as you can see in the picture i've posted above.
Before do that try to use different brand regulator.
To test the regulator just set your multimeter on dc, plug one probe on the gnd, and the other to the output leg (see data sheet) of the regulator.

 

[tabuckner]

Thanks, axl!

Should have checked the thread before I left for my local components store. I'll try a new regulator when I get the parts in from Mouser and let you know what I find. Thanks again for the suggestion regarding the fix. Just saved the picture in case.

Taylor

 

[Harpo]

Yes I use tightly not twisted wires, you think there's a lot of difference to use a mic cable? it's only 5cm long.

probably not. Rotating the transformer for least radiating garbage would be my next step, not knowing your soldering station behaviour (mine would radiate more than your measurement) or the proximity of your -whatever it might be- lighting source above the open case lid, so the circuit is without shielding. Did you ever try to measure with case shut ?

Here the measurement you required feeding the inputs with 100hz from my audio card:
INPUT LEFT    pin 2/3  -  3,410V  (12.87 Dbu right?)
INPUT RIGHT  pin 2/3  -  3,397V  (12.84 Dbu right?)

dBu numbers are correct and for usual analog operation these levels will cause heavy compression.

I don't think to well understad you when you talk about gssl behaviour ....So it's normal to have dual mono out ????? if i put a drum loop for example i lost all the stereophony!!!!! can't work that way right????

The GSSL is a stereo compressor, so whatever L/R side has more sidechain level above threshold will cause gain reduction of the other side as well by the same generated control voltage. Differing from a SSL compressor that operates the sidechain level and rectification of L/R seperate before timing, the GSSL sums both L/R channels in front of the sidechain, so sidechain operation isn't stereo. If FI the left side sidechain amplitude would swing positive to a +1V peak value and the right side sidechain amplitude would swing to the negative side to a -1V peak value for the same snapshot moment, the summed L+R value of the sidechain would be zero volts, generating nada control voltage for gain reduction as both levels cancel out. Similar situation, but both sides peaking in the same direction will sum up to a doubled up 2V sidechain level, causing overcompression of common (for usual centered like FI bassdrum) program material. The Turbo circuit addon will keep both L/R seperate and only the higher of two rectified control voltages is timed and controls the amount of gain reduction above threshold for both audio sides. Depending on your audio program material, one might work better than the other. Some like it switchable between GSSL-mode/Oxford-mode for this reason. I wouldn't call your previously mentioned 100Hz/105Hz sine waves a usual audio program material, but YMMV.

 

[Harpo]

Would I be better off trying the anti latch fix or just replacing the regulators altogether?

I'd try the addition of the diodes first (caps probably not needed for a rev.11 board) and only replace vregs afterwards if so required. YMMV. Your local electronics shop might only have the same brand of your already fitted vregs in store anyway and for a substitution you would look for the same type of vreg from a different brand.

 

[axl]

Yes I use tightly not twisted wires, you think there's a lot of difference to use a mic cable? it's only 5cm long.

probably not. Rotating the transformer for least radiating garbage would be my next step, not knowing your soldering station behaviour (mine would radiate more than your measurement) or the proximity of your -whatever it might be- lighting source above the open case lid, so the circuit is without shielding. Did you ever try to measure with case shut ?

Here the measurement you required feeding the inputs with 100hz from my audio card:
INPUT LEFT    pin 2/3  -  3,410V  (12.87 Dbu right?)
INPUT RIGHT  pin 2/3  -  3,397V  (12.84 Dbu right?)

dBu numbers are correct and for usual analog operation these levels will cause heavy compression.

I don't think to well understad you when you talk about gssl behaviour ....So it's normal to have dual mono out ????? if i put a drum loop for example i lost all the stereophony!!!!! can't work that way right????

The GSSL is a stereo compressor, so whatever L/R side has more sidechain level above threshold will cause gain reduction of the other side as well by the same generated control voltage. Differing from a SSL compressor that operates the sidechain level and rectification of L/R seperate before timing, the GSSL sums both L/R channels in front of the sidechain, so sidechain operation isn't stereo. If FI the left side sidechain amplitude would swing positive to a +1V peak value and the right side sidechain amplitude would swing to the negative side to a -1V peak value for the same snapshot moment, the summed L+R value of the sidechain would be zero volts, generating nada control voltage for gain reduction as both levels cancel out. Similar situation, but both sides peaking in the same direction will sum up to a doubled up 2V sidechain level, causing overcompression of common (for usual centered like FI bassdrum) program material. The Turbo circuit addon will keep both L/R seperate and only the higher of two rectified control voltages is timed and controls the amount of gain reduction above threshold for both audio sides. Depending on your audio program material, one might work better than the other. Some like it switchable between GSSL-mode/Oxford-mode for this reason. I wouldn't call your previously mentioned 100Hz/105Hz sine waves a usual audio program material, but YMMV.

Hi harpo and thanks for the tips you share with me, i will try to take measument with the case shut and let you know! i use a cheap 20€ soldering pump. really basic but always works for me!
maybe you don't understand my problem or I don't get how this things work....
Ok it's stereo and ok the same sc signal control both channel compression, this is clear to me, this mean when gssl compress change the stereo perception too of what is passing thru, but don't mean go out the same signal on both channels!!!, if i send to the comp a drum stereo buss for example with all percussion panned i get on the output all the sounds in the centre!!!
Seems like the compressor sum not only the side chain signal but even the main signal!!!!!!!!!!!!!!!!!!!!!

 

[dave293]

Hi all,

I am having a little trouble tracking down a fault with my gssl build.
My unit includes both the turbo and CRC boards and uses THAT 2180 VCA's. My power rails all seem to be correct.

While testing the voltages at my IC's and VCA prior to popping them in I have found some issues with my sidechains IC voltages.

Measuring the voltages with no input signal I get the following results. The threshold pot has no effects on any of these reading nor the attack and release switches. Placing a multimeter probe on the IC pins causes the voltage to gradually make their way to zero, but powering the unit up again causes them to return to these measured values. I haven't been able to find any solder bridges or wrong components yet. Can anyone offer some suggests on where to look?

TL074

Ratio 2:1

Pin 1 - 3.41v
Pin 2 - 3.61v
Pin 3 - 0v
Pin 4 - 12v
Pin 5 - 0v
Pin 6 - 3.14v
Pin 7 - 3.3v
Pin 8 - 0v
Pin 9 - 0v
Pin 10 - 0v
Pin 11 - -12v
Pin 12 - 0v
Pin 13 - 3.63v
Pin 14 - 3.91v

Sidechain 2180

Pin 1 - 0v
Pin 2 - 0v
Pin 3 - 0v
Pin 4 - 0v
Pin 5 - -12v
Pin 6 - 0v
Pin 7 - 12v
Pin 8 - 3.91v

Ratio 4:1

Pin 1 - 2.74v
Pin 2 - 2.94v
Pin 3 - 0v
Pin 4 - 12v
Pin 5 - 0v
Pin 6 - 2.25v
Pin 7 - 2.24v
Pin 8 - 0v
Pin 9 - 0v
Pin 10 - 0v
Pin 11 - -12v
Pin 12 -0v
Pin 13 - 2.93v
Pin 14 - 3.28v

Sidechain 2180

Pin 1 - 0v
Pin 2 - 0v
Pin 3 - 0v
Pin 4 - 0v
Pin 5 - -12v
Pin 6 - 0v
Pin 7 - 12v
Pin 8 - 2.22v

Ratio 10:1

Pin 1 - -0.65v
Pin 2 - -0.77v
Pin 3 - 0v
Pin 4 - 12v
Pin 5 - 0v
Pin 6 - -1.45v
Pin 7 - -1.45v
Pin 8 - 0v
Pin 9 - 0v
Pin 10 - -0.02v
Pin 11 - -12v
Pin 12 - 0v
Pin 13 -  -0.77v
Pin 14 - -0.40v

Sidechain 2180

Pin 1 - 0v
Pin 2 - 0v
Pin 3 - 0v
Pin 4 - 0v
Pin 5 - -12v
Pin 6 - 0v
Pin 7 - 12v
Pin 8 - -1.37v

Any help is appreciated, thanks in advance.

 

[axl]

SOLVED!!!!!!!!
how stupid I am!!!! i was inverted the two cold wire of the output  :
finally works!!!!!!!
Now it's time to get lower noise possible!
Harpo what about changing the toroidal with one shielded or a trafo tipe ????

 

[Harpo]

Can anyone offer some suggests on...

Your voltages (some spots are current nodes, not voltage nodes) are controlled by these chips and will be different with TL074 and THAT2180 populated.

... where to look?

Look down. For usual only blowing semiconductors rise up. (sorry, couldn't resist.. ;D)
The TL074 and THAT2180 must be somewhere  ...

 

[dave293]

Thanks Harpo!

I when I installed the IC's and VCA's the voltages looked much better.
Though when I tested the unit the left side seems to be working correctly with all controls operating as they should. However the right channel is heavily distorted and none of the controls seem to have any effect on the right side signal, fried VCA maybe?.

 

[Harpo]

I when I installed the IC's and VCA's the voltages looked much better.
Though when I tested the unit the left side seems to be working correctly with all controls operating as they should. However the right channel is heavily distorted and none of the controls seem to have any effect on the right side signal, fried VCA maybe?.

Maybe. Look for shorts and parts values at the right side probably DBX202C substitution circuit (THAT218x audio-VCA and NE5534 buffered attenuator).

 

[dave293]

Thanks, I'll check out that right DBX circuit.

Since my last post I swapped out the VCA in the turbo sidechain and now the unit has developed a problem where it seems to turn itself off after being turned on for a second or so.

 

[Harpo]

Since my last post I swapped out the VCA in the turbo sidechain and now the unit has developed a problem where it seems to turn itself off after being turned on for a second or so.

Your problem was not sidechain related (else the left side audio would have been affected as well).
Look out for shorts and correct orientation of your VCA at the Turbo board.