GSSL HELP THREAD!!!

[Holiveira]

I went over my problem. I could not see what the problem is.

I saw the 2180 datasheet and saw that the gain G = (Pin 2 - Pin 3) / 0.0061.

I decided to increase the tension in 2180 (sidechain), i lowers the R470 which connects to Pin 3 of  2180 in sidechain . And I got a result, now when I move the treshold I see the difference.


The tension in F: -0.55v > -12.3v

Does the problem is here...?

I read that the voltage should be 0.23v > -12v

thanks
Hugo

lowering the 470 is unlikely to help unless the wrong value for the 470R or 47R was there to start with.

Point F is a simple potential divider. min is -12v. If you move the pot to the other exteme it's Rpot/(Rpot+47k) * 24V -12V
So if if you want a slightly higher threshold then you could play with the 47K resistor at point F.

But I don't think that's your problem.

Sounds like your SC amp may be giving too much gain and acting more like a comparator, than a non linear amplifier.
You probably need to look earlier in the side chain for the problem.

Turn your attack time to fast and release time to slow.

Can you see your input signal on pin7 of the TL074 with theshold min and threshold max?

Can you see -ve spikes at point C when the input signal is loud, and otherwise 0V when the signal is quiet?

What about pin 10 of the TL074 = point O?: a spike negative which then decays over time?

Have you checked your tantalum caps in the side chain are the right way around?
And the 1n4148 diodes too?
What about checking the wiring of your ratio board?

I've done the measurements:

TL074 pin 7:
  treshold min (-20) -10.88
  treshold max (+20) -10.88

with 68ohm instead of 470

  treshold min (-20) -10.88
  treshold max (+20) -0.06

In "C":
With input signal loud:
-9.78

below:-2v

No Input Signal: 0V

  Pin 10 of the TL074:

When I vary the treshold of min to max or max to min, there is a peak voltage which discharges slowly

Thanks

 

[Enchilada]

OK, my makeup gain was cutting out intermittently. I tested the cable connecting the control PCB to the main PCB, the wire connecting the "+" pin was shifty so I re-soldered it and now it's fine.

Threshold is still not doing anything though. Here are the voltages while passing audio from all the pins of my TL074. Voltages don't change if the threshold turned up or down:

1) 0.07V 2) 0V 3) 0V 4) 11.97V 5) 0V 6) 0V 7) 0V 8.) -0.4V to -0.68V 9) -0.35 to -0.5V 10) -0.2V to -0.6V 11) -11.96V 12) 0V 13) 0.01V 14) 0.31V to 0.34V

I've checked every single resistor and there are no problems. I've also checked every solder joint and have yet to find a cold joint.

Just for reference, here are the voltages from my 10 pin connector to the control PCB":
+) 11.99VV F) 0V E) 0V G) -0.05V D) -0.6V -) -11.96 0) 0V A) 0V B) 0.66V C) 0V

The weird thing is before I fully fixed the connector cable, I could have sworn I was getting 6.9V on pin E. Perhaps I was measuring wrong.

Any  ideas would be greatly appreciated

Another thing I've noticed is that there is a significantly loud hum coming through the speakers approx 5 seconds after I cut the audio input. Happens both when the bypass is on and off. As soon as I hit play, the hum goes away, then when I pause again it is back after approx 5 seconds. I haven't connected a ground to 0V or to one of the XLR pins so that could be the cause. just thought I would mention it just in case it is related.

Also, I have wired up the bypass switch as per Keith's instructions.

 

[Enchilada]

Also, a quick not about my ratio switch. When passing audio through my GSSL, the meter shows less gain reduction as I turn the switch clockwise. It does sound like it is hitting the peaks harder though. I've assumed that it is doing this because as I turn the ratio up, the GLLS's threshold goes down on its own.

Is that correct?

 

[gyraf]

yes

 

[Enchilada]

yes

Awesome, thanks for the info. Any thoughts on my threshold not doing anything? Any tips on where to start testing to see if I can solve th problem?

Thanks,

Kris

 

[artosaudio]

Ik guys, I detached my supersidechain board, and for the first time I see (not hear) something that looks like compression.

My meter is fully functional and shows the exact gain reduction when I turn the threshold. However the output stays exactly the same wether I'm slamming it or not. Ratio shows nothing, attack and release however seem to do something...

no make-up

Does this ring a bell to anyone?

 

[Holiveira]

I have  other problem in my gssl. When I switching the release, I hear a plok. I've checked the lorlin and he is ok. I checked the continuity between the SW4 and each capacitor  (switching positions) and is ok.

This is normal?

thanks

 

[Harpo]

OK, my makeup gain was cutting out intermittently. I tested the cable connecting the control PCB to the main PCB, the wire connecting the "+" pin was shifty so I re-soldered it and now it's fine.

Threshold is still not doing anything though. Here are the voltages while passing audio from all the pins of my TL074. Voltages don't change if the threshold turned up or down:

Maybe pots broken from your questionable idea to solder the wires into the holes of the pots rivets. There is a reason, these pots solder pins have a specific length. Your method set this length to zero, leaving you with an unreliable and overheated contact.

The weird thing is before I fully fixed the connector cable, I could have sworn I was getting 6.9V on pin E. Perhaps I was measuring wrong.

For reasons why, see previous guess, a short next to 'E' at the connector cable, you simply turned the makeup pot full ccw, or you measured wrong.

 

[MeToo2]

I've done the measurements:

TL074 pin 7:
  treshold min (-20) -10.88
  treshold max (+20) -10.88

This looks wrong at first glance. I'll have to measure mine and get back to you. But it looks like a large DC offset on the sidechain VCA.

Is there any DC at the 47K on the sidechain input (point on the schematic with an arrow marked "SC In" & "L" and "R")?

I made the recommended changes for this VCA from this site: http://diy.fischerworks.com/gssl_vca.shtml
  and i  removed the 10k and 47R resistors from sidechain.

You say in an earlier post that you "removed the 10k and 47R resistors" from the That 2180 sidechain.
Did you remove the 47R from pin 4? [not needed because you are using pre-trimmed That 2180's]
Did you leave the 47R on pin 3 in place? [still needed as a voltage divider to reduce sidechain sensitivity]

 

[artosaudio]

Anyone got a suggestion.

Where does my signal go wrong. Threshold+meter fully functional, ratio does something although not 2/4/10 so it seems. Output stays the same no matter what I do, compres/bypass/makeup. And make up does absolutely nothing.

I double checked and resoldered the control Molex connector points and double checked on shorts, nothing suspicious there.

Starting to learn something about the signalflow though, that can't be bad... (think positive)

The unit seems in sort of a semi-bypass mode...

 

[Holiveira]

I've done the measurements:

TL074 pin 7:
  treshold min (-20) -10.88
  treshold max (+20) -10.88

This looks wrong at first glance. I'll have to measure mine and get back to you. But it looks like a large DC offset on the sidechain VCA.

Is there any DC at the 47K on the sidechain input (point on the schematic with an arrow marked "SC In" & "L" and "R")?

I made the recommended changes for this VCA from this site: http://diy.fischerworks.com/gssl_vca.shtml
  and i  removed the 10k and 47R resistors from sidechain.

You say in an earlier post that you "removed the 10k and 47R resistors" from the That 2180 sidechain.
Did you remove the 47R from pin 4? [not needed because you are using pre-trimmed That 2180's]
Did you leave the 47R on pin 3 in place? [still needed as a voltage divider to reduce sidechain sensitivity]

Thanks for your help,

I put all the resistances in the sidechain. Now I have only the changes in VCAs (2180). and put the 470R

I have 47K in the "L" and "R". I removed them to turn the SSC.

The voltage at pin 7 of the TL074 is the treshold to -10.85 min or max. With audio input, the voltage is -0.5 ...- 1.1 V with max treshold. with the treshold is -7.9 ...- 9.8V min.

I still have the problem. and when I switch the release I hear a click

 

[MeToo2]

Thanks for your help,

I put all the resistances in the sidechain. Now I have only the changes in VCAs (2180). and put the 470R

I have 47K in the "L" and "R". I removed them to turn the SSC.

The voltage at pin 7 of the TL074 is the treshold to -10.85 min or max. With audio input, the voltage is -0.5 ...- 1.1 V with max treshold. with the treshold is -7.9 ...- 9.8V min.

I still have the problem. and when I switch the release I hear a click

First you said you removed 47R and 10K resistors. Now you say "I put all the resistances in the sidechain."
Can you please be more precise about which resistors around the That 2180 you removed or fitted?
Or make a photograph. There are 2*47R next to the 2180. One should be removed in your case (pin 4). One should NOT be removed (pin 3)

I would remove the SSC until you get the basic GSSL working, unless you have an oscilloscope and a signal generator.

There are too many variables and possible mistakes on the wiring of the SSC otherwise.

My DC and AC voltages, relative to chassis ground. Note I was intentionally using a voltmeter for AC readings not my oscilloscope, so it may not be reading true RMS.
But I wanted something that you could easily compare.

Test 1: attack 1, ratio 4, release .6, make up mid, SSC off, threshold min (-20), no signal in
Vin +ve phase -150mV DC 0mV AC
Vin -ve phase 350mV DC 1mV AC
SC IN @47K 0.0mV DC 0mV AC
pin 7 TL074 1.1mV DC 0.0mV AC
pin 1 tl072 -2.86VDC 0V AC
GR 0db

Test 2: attack 1, ratio 4, release .6, make up mid, SSC off, threshold min (-20), -10dBm 600R 820Hz signal in
Vin +ve phase -150mV DC 473mV AC
Vin -ve phase 350mV DC 1mV AC
SC IN @47K 0.6mV DC 473mV AC
pin 7 TL074 -5.5mV DC 309mV AC
pin 1 tl072 -4.28VDC 0V AC
GR ±-20 on meter

Test 3: attack 1, ratio 4, release .6, make up mid, SSC off, threshold max (+20), no signal in
Vin +ve phase -150mV DC 0mV AC
Vin -ve phase 350mV DC 1mV AC
SC IN @47K 0.3mV DC 0mV AC
pin 7 TL074 -4.7mV DC 0.0mV AC
pin 1 tl072 +2.85VDC 0V AC
GR 0

Test 4: attack 1, ratio 4, release .6, make up mid, SSC off, threshold max (+20), -10dBm 600R 820Hz signal in
Vin +ve phase -150mV DC 473mV AC
Vin -ve phase 350mV DC 1mV AC
SC IN @47K 0.5mV DC 473mV AC
pin 7 TL074 -5.1mV DC 0.0mV AC
pin 1 tl072 +2.84VDC 0V AC
GR 0

You can see that I do NOT have a high DC offset on pin 7 of the TL074 as I suspected.

 

[artosaudio]

One problem solved, another occurs...

I resoldered almost everything and now instead of a non working gssl (execpt for the meter wich seemed to be working fine, but none was audible) I now have a perfectly working gssl on one channel, everything works (threshold make-up ratio etc) but the other channel wether in bypass or not distorts like hell. I also have something like 5 volts ac on the left 5532 output (pin5) wich makes sense. Offcourse I doublechecked for shorts and blobs but nothing suspicious. This must be something rather simple, since I didn't have a distortion problem before (also not in bypass)

Anybody, I would be jumping around in my house if this unit was finally working!

 

[MeToo2]

One problem solved, another occurs...

I resoldered almost everything and now instead of a non working gssl (execpt for the meter wich seemed to be working fine, but none was audible) I now have a perfectly working gssl on one channel, everything works (threshold make-up ratio etc) but the other channel wether in bypass or not distorts like hell. I also have something like 5 volts ac on the left 5532 output (pin5) wich makes sense. Offcourse I doublechecked for shorts and blobs but nothing suspicious. This must be something rather simple, since I didn't have a distortion problem before (also not in bypass)

Anybody, I would be jumping around in my house if this unit was finally working!

It may sound obvious, but connect a mono test tone signal to both inputs and then step through the circuit measuring ac and dc voltages comparing the left with right channels until you find a point where they are different. Distortion will almost certainly be in the signal amp chain, not the side chain...... there are sample test voltages and test points earlier in this thread.

 

[artosaudio]

[/quote]It may sound obvious, but connect a mono test tone signal to both inputs and then step through the circuit measuring ac and dc voltages comparing the left with right channels until you find a point where they are different. Distortion will almost certainly be in the signal amp chain, not the side chain......
[/quote]

Thanx, I found that the values for Left and Right are the same Till the output stage, so there must be something wrong there.
However no solderblobs, doublechecked all resistorvalues...

 

[MeToo2]

Thanx, I found that the values for Left and Right are the same Till the output stage, so there must be something wrong there.
However no solderblobs, doublechecked all resistorvalues...

Well you now know where to look. From what I remember things are pretty tight on the pcb around there, so check for shorts/ capacitors inserted in the correct orientation, all the obvious things.

 

[Mastringshuset]

Hi,

First post. Have been reading and reading through this forum, but I just can't bring myself to connect the transformer before someone else tells me if I got it right or completely backwards... Don't wanna fry anything =)
Yes, I did a search, and yes, I read most of the thread.

I live in Sweden, hence my power outlet delivers 230V/50Hz.

I bought a toroidal transformer, which had no info besides a sticker on the side. According to the web shop it's 30VA.
The sticker says the following:

Primary: 230V/50Hz
Secondary: 15V/1.66A blue-grey
Secondary: 15V/1.66A red-yellow

Am I correct in thinking I should hook it up to the PCB as follows:
Pin 1: Blue
Pin 2: Grey and Yellow
Pin 3: Red

Since the colors seems to differ from trafo to trafo I can't seem to find the answer by myself.

Thanx alot for your help! =)


Best regards
//Daniel Muhr, Mastringshuset.se

 

[Harpo]

The sticker says the following:
Primary: 230V/50Hz
Secondary: 15V/1.66A blue-grey
Secondary: 15V/1.66A red-yellow

Am I correct in thinking I should hook it up to the PCB as follows:
Pin 1: Blue
Pin 2: Grey and Yellow
Pin 3: Red

Welcome Daniel.
More likely it will be blue | grey+red | yellow.
You want this dual secondary transformer behave like a center tapped transformer, so the outer connections of your combined secondary windings will be the in phase end of the first secondary winding and the out-of-phase end of the 2nd secondary winding. The transformers center tap connection will be the junction of the remaining 2 leads from both secondary windings.

 

[Mastringshuset]

The sticker says the following:
Primary: 230V/50Hz
Secondary: 15V/1.66A blue-grey
Secondary: 15V/1.66A red-yellow

Am I correct in thinking I should hook it up to the PCB as follows:
Pin 1: Blue
Pin 2: Grey and Yellow
Pin 3: Red

Welcome Daniel.
More likely it will be blue | grey+red | yellow.
You want this dual secondary transformer behave like a center tapped transformer, so the outer connections of your combined secondary windings will be the in phase end of the first secondary winding and the out-of-phase end of the 2nd secondary winding. The transformers center tap connection will be the junction of the remaining 2 leads from both secondary windings.

Hi,

Thanx, i got a similar response from Me2Too
I'll give it a try!

Thanx all for being so helpful

 

[Looksharp]

hi !
this is my first post..I don't really know much about all this wonderfull electronic diy stuff but decided to have a try with this GSSL..hey, I'm impressed about the lot of work that Mr Gyraf did..!!
...i'm a little embarassed 'cause I know all my answer will be really silly to all of you ..i can see you are all expert anyway..here is my first question: I'm goin to purchase the transformer..in the component list I read: Toroid power transformer, 2x15V/10VA or more

so lookin' at the RS site I think the one below  could be ok ( since Gyraf wrote "or more" I choosed 15 VA instead of 10...could you please tell me if it is the right one to purchase?

here is the link:
http://it.rs-online.com/web/p/trasformatori-di-toroide/6718924/

Doc. Looksharp