GSSL HELP THREAD!!!

[Harpo]

Are the black can DBX202 known working? There are some changes needed to make it work.
Last pages of this thread
or this thread might help you.

 

[synnys]

I made more than one gssl, and they all had (have) the following symptoms:

sometimes when i power up the unit it doesnt work, the panelmeter leds do go on but the power led doesn't.
Just flipping the power switch one or two times, always resolves this issue. But i've read other people are having the exact same issue.

I this a design flaw? Can it be fixed? if yes, how?

Would love to hear some thoughts or ideas...

 

[audiophreak]

Are the black can DBX202 known working? There are some changes needed to make it work.
Last pages of this thread
or this thread might help you.

  " Are the black can DBX202 known working? " That's a very good question  ... I've built a few GSSLs (  most with your invaluable help ) , now I'm gonna try and help someone , and have had no experience with the DBX 202s , so I giess I will de-solder them, test +/- power , then empty ICs , if everything is ok , then put ICs and DBX 202s in and see what happens 
 
  The Links you posted  have some great info  -  Thanks so much Harpo , would not have been able to get my units up and running without your help 

 

[masterboyle]

Hi,
I'm having some trouble with the left channel to My GSSL. The signal thru the unit is not at unity gain, while the right side is. I have added 50K trimpots in place of the unity gain resistors ebfore the audio VCAs, and the right side was easy to calibrate for unity this way. This is the first time testing after assembly, so its not like it was working and now is problematic.
I Started tracing signal levels with a test tone feeding the unit. The
right side is fine and producing unity gain through to the output. So
I started at the left input side. Getting a reading on the actual
solder pad where signal comes onto the pcb the signal is at unity, so
I know it's not an issue with one side of the audio interface creating
the tone being too low.
But by the time I'm at pin 2 and 3 of the input IC the signal is
already very attenuated by maybe 6-10dB. There's not really much before those IC pins. Could it
be a something in the input decoupling /filtering network? Resistor
out of spec? Cap reversed in polarity? What do you think?
Thanks,
Brian

 

[synnys]

when i turn on my ssl, (no sound and no controls are working)

the power led doesn't work, the panelmeter led does work

and i measure about either 2,6volt or -2,2volt on the meter. that changes randomly when when i power up the unit.

about an hour ago it did actually pass sound quite nice, althoufg no comrpession or controls were working,

i replaced both 074 and 072 and know the aobve iss the only thing that happens...

Somebody got a clue where to start troubleshooting?  my power transformer gives me 2x16volt..

 

[synnys]

got sound again after replacing the 074. still no compression or working controls though.

 

[Harpo]

The right side is fine and producing unity gain through to the output. So I started at the left input side. Getting a reading on the actual solder pad where signal comes onto the pcb the signal is at unity, so I know it's not an issue with one side of the audio interface creating the tone being too low.
But by the time I'm at pin 2 and 3 of the input IC the signal is already very attenuated by maybe 6-10dB. There's not really much before those IC pins. Could it
be a something in the input decoupling /filtering network? Resistor out of spec? Cap reversed in polarity? What do you think?

With signal at right side GSSL input measure AC voltage at right side balancing line receiver NE5534 pin6. Write this number down. Disconnect your signal feed from right side GSSL input and plug it into the left side GSSL input. Measure AC voltage at left side balancing line receiver NE5534 pin 6. Does the measurement match your noted measurement from right side? Yes -> input stage is OK, if problem still exist, it will be in a following stage. No -> check for shorts, same 22K resistor values or replace the broken opamp. Fault returns when connecting the other side signal feed as well? Check for broken or shorted XLR cable.

 

[Harpo]

when i turn on my ssl, (no sound and no controls are working)
the power led doesn't work, the panelmeter led does work
and i measure about either 2,6volt or -2,2volt on the meter. that changes randomly when when i power up the unit.

Make sure, all supply rails +/-15V and +/-12V are working.
A voltage regulator might be hanging on startup (most often the 7815). Using a different brand most often helps. A diode between regulator output and 0V, anode side to the lower voltage rail (0V for the positive rails regulators or -12V/-15V for the negative rails regulators), might fix this latching as well.
For your 'still no compression or working controls', double check for shorts, parts values and parts orientation.

 

[synnys]

So i placed the motherboard into a working ssl and it works just fine. So i just ruled out any problems on the motherboard. which is a step in the right way i suppose.

I checked all resistors and caps polarities on the control pcb and sidechainboard, all soldering is done accurate and seems fine as well..

any tips on how to proceed??

The weird thing is that i build two ssl's synchronous at the same time and they both have exact the same problem.. no compression and no makeup gain and no controls whatsoever....

pulling my hair out at the moment pfff

 

[Harpo]

.. no compression and no makeup gain and no controls whatsoever....

If check for +12V across the makeup pot fails, mend the probably broken 12V trace on control pcb.
When not in bypass, 'E' on mainboard varies voltage between 0 .. +12V when turning the makeup pot, else check the endstop washer at the lorlin bypass switch (remove nut, remove endstop washer, dial the switch to full CCW position, put washer back in to pos.2, nut back in).
Double check the endstop washers of the other lorlin rotary switches as well.
good luck.

 

[synnys]

there's 11.96 volt on the make up pot so that's ok right?

 

[synnys]

and 23.9 volt on the threshold pot no ... hmmm odd

 

[Harpo]

Check for '+12V across the makeup pot' (no talk of pot wiper). One side of your pot is connected to 0V reference voltage, the other side to +12V.
Take your black multimeter probe and you might even weld/glue/solder the tip to this 0V reference voltage, so it doesn't move. Nearly all measurements -except your mains transformer- use this reference for probing the potential difference to this reference voltage with your red wire probe tip.
If you don't fix the 1st step, following steps don't make much sense.
Your 78L12 might be broken, the pcb trace, carrying this voltage might be broken, you connected additional load (panelmeter?,whatever) to this rail and the overloaded regulator is in thermal protection mode, the 620K at makeup pot wiper is a 620R or the 220K at threshold pot wiper is a 220R, ...

uhmmm, after previewing this message your numbers seem to have changed, except the threshold pot would read +11.96 at one end and -11.94 at the other, so you didn't place a 47K between +12V and the pots CCW end.

 

[synnys]

i got some weird voltages from my 7815/7915 so i replaced them, also replaced 072 and 074 just to be sure.

still no luck...

I'm am however getting the right voltages at threshold (12,3volt)  and makeup pot (11,9volt) now.

I've had "no compression" problems before, but the makeup gain always worked... and it isn't right now.

 

[synnys]

Couldn't find the right emoticon for "complete ashamed"...

I soldered the bypass switch incorrect resulting in an 'always-bypassed-mode'

Both units are working topnotch now. Thanks for all the help and insights Harpo! Much appreciated!

 

[Bob1991]

I bought a nice vintage panel meter to replace my standard one on my GSSL. One slight 'problem': It is a 2mA meter instead of the requested 1mA meter, so if I have 20dB compression, the meter moves only to the half (with the 2k resistor on the pcb). So I need '40dB' of compression to get the meter to fullscale movement. For 10dB (0.5mA) fullscale, you should use a 1k resistor, and for 20dB(1mA) fullscale a 2k resistor. Can I replace this 2k resistor with a 4k (or another value?) to achieve '40dB' (2mA) fullscale, or do I need to amplify in some way the meter-control circuit?
So I just want to let the 2mA meter behave like it is a 1mA one..

 

[synnys]

Hoi Bob,

Volgens mij klopt je wiskunde wel en kun je gewoon een 4k gebruiken... klinkt me logisch in de oren, probeer het gewoon uit, kan in ieder geval geen schade veroorzaken..

 

[mdmedia]

Hallo,

the GSSL is my first DIY project, so please apologize my stupid questions. I got the SSL running. All controls work as they should, but there seems to be an error at the input stage: sending an asymmetric signal to the compressor works fine, but on symmetric signals I get nothing out of the box.

I would guess that the normal and the inverted signal cancel out since something is wrong at the input stage. Could it be the case that my opamps NE5534 are blown or should I start searching somewhere else? Unfortunately I only have a multimeter, but no signal generator or something else to track the signal along the circuit. I am grateful for any suggestions!

 

[ptron]

I bought a nice vintage panel meter to replace my standard one on my GSSL. One slight 'problem': It is a 2mA meter instead of the requested 1mA meter, so if I have 20dB compression, the meter moves only to the half (with the 2k resistor on the pcb). So I need '40dB' of compression to get the meter to fullscale movement. For 10dB (0.5mA) fullscale, you should use a 1k resistor, and for 20dB(1mA) fullscale a 2k resistor. Can I replace this 2k resistor with a 4k (or another value?) to achieve '40dB' (2mA) fullscale, or do I need to amplify in some way the meter-control circuit?
So I just want to let the 2mA meter behave like it is a 1mA one..

i would think half resistance for equal behaviour? since it can handle twice the current? (not sure just wanna understand)

 

[Harpo]

.. an error at the input stage: sending an asymmetric signal to the compressor works fine, but on symmetric signals I get nothing out of the box.
..Unfortunately I only have a multimeter, but no signal generator or something else..

http://www.rme-audio.de/old/english/download/audtest.htm for wav.testfiles or http://audio.rightmark.org/downloads/rmaa6.exe might help you for your signal generator. A keyboard/organ might give you a steady signal as well, a little gaffa tape will get your hands free, so you don't have to press a key.
Input stage will be fine. The NE5534 operates the potential difference between its non-inverting and inverting input. Getting signal thru at whatever waveform assumes this stage operating as it should. More likeley you have a polarity flip at your XLR cable or GSSL in-/out wiring and you might listen to a mono summing stage (pfl ?).