GSSL HELP THREAD!!!

[micah421]

I feel like I've narrowed down the issue. If while the SSC is connected, the unit passes audio, the bypass and makeup gain works and the power for the led works, Then it must have something to do with COM, ON, OFF, POTA, POTB section.

... then you proved that it has nothing "to do with COM, ON, OFF, POTA, POTB section" as this part of circuit is obviously working fine.
I already suggested how to proceed. Maybe you give it a try to see where and why your filter board is interrupting your signal. Owning a multimeter only makes sense when you use it. YMMV.

The Main board connections (+15v,-15v, 0v, L, R, Ret) seem to be working. That sends and returns the audio path and feeds power the SSC board power, correct or am I wrong?

I thought the COM, ON, OFF, POTA, POTB section deals with the Threshold, Ratio, Attack, Release controls.

 

[Harpo]

The Main board connections (+15v,-15v, 0v, L, R, Ret) seem to be working. That sends and returns the audio path and feeds power the SSC board power, correct or am I wrong?

What is the AC voltage at differential line receiver NE5534-pin6 on main board with an audio test signal connected to one (L or R, not both) of the XLR-input connectors? Maybe 1.23VAC as an example value (we have no idea of your secret test frequency amplitude). Note this number.
You removed the 47K summing resistors on main board that get substituted by your filter board ? ('super sidechain' is the least important part of the boards name).
What is the AC voltage at SSCF board next to input connector NE5532-pin7? Is this readout about half the value of previous example readout=0.615VAC?
Yes? Move on, else check why signal doesn't arrive here. (Broken wire, broken pcb trace, broken opamp, opamp not pushed into its socket, opamp missing power supply DC voltages at pin4 and 8, wrong resistor values, ...)
Depending on frequency of your test signal and lorlin switch filter setting (we have no idea of your secret test frequency number and the purpose of this filter board is to decrease the signal amplitude below the selected HPF cutoff with a -6dB/oct.slope), same or slightly lower AC voltage as previous measurement should show up on your lorlin switch pole.
Yes? Move on, else check why your lorlin switch doesn't connect.
Same AC voltage as previous measurement should show up on same (the opamp located next to SSCF input connector) NE5532-pin1.
Yes? Move on, else check for wrong 12K resistor values.
SSCF output connects to the right side (VCA side) of the removed 47K resistors on main board ?
With 1kHz signal feed and lorlin switch set for position TL, measure AC voltage as described in 1st step and adjust TL trimmer for half this measured readout.
With lorlin switch set for position TM adjust TM trimmer for same readout.
Disconnect XLR-input connector and plug it to the other input to check for same readout of last TM measurement in order to prove both sides behave the same.
Done.

I thought the COM, ON, OFF, POTA, POTB section deals with the Threshold, Ratio, Attack, Release controls.

In no way. All connections are for the substitution of the original lorlin bypass switch.

 

[SEED78]

is there any real difference in sound between the 2150B VCA and the 2150A VCA?

AFAIK a DBX 2150B has never existed.
Could it be you're taking about THAT 2180A/B differences. Just look up this parts datasheet and have an eye on noise and THD numbers. Maybe this matters to you and if so, you probably won't go in the opposite direction with a DBX202C at a later step.

Is there not a DBX 2150A ?
http://www.studioelectronics.biz/sunshop/images/products/large_1333_dbx.2150.JPG

 

[matta]

... but the threshold seems to make no difference to the audio even when 'off' it seems to be compressing pretty hard, though it is 'working' in that it is working as a voltage divider, at point F I measure -11.99VDC with the threshold fully CW and 0.652VDC when fully CCW.

Double check the supposed to be 220K resistor value going thru a hopefully fitted jumper to TL072-pin2 (resistor closest to pin8 of the sidechain VCA) ?

Thanks Harpo, it's 220K, read as such, but lifted to triple check, as well as the jumper to the TL072-pin 2. Any more thoughts?

Thanks in advance

Matt

 

[Harpo]

Thanks Harpo, it's 220K, read as such, but lifted to triple check, as well as the jumper to the TL072-pin 2. Any more thoughts?

Essentially check resistor values in the sidechain section as the most likely cause of misbehaviour, especially the 100K next to the 220K, the 56K feedback resistor between TL072-pins1/2, the 100R+470R series resistors in the voltage divider between TL072-pin1 and sidechain-VCA pin3 with the 47R shunt resistor between sidechain-VCA pin3 and 0V.

 

[matta]

Thanks Harpo, it's 220K, read as such, but lifted to triple check, as well as the jumper to the TL072-pin 2. Any more thoughts?

Essentially check resistor values in the sidechain section as the most likely cause of misbehaviour, especially the 100K next to the 220K, the 56K feedback resistor between TL072-pins1/2, the 100R+470R series resistors in the voltage divider between TL072-pin1 and sidechain-VCA pin3 with the 47R shunt resistor between sidechain-VCA pin3 and 0V.

Thanks Harpo, it's all good. Triple checked the values of all the components and gave a once over on soldered over the joints around the sidechain and it seems to be all good now, hooked it up to a 1mA DC meter to confirm and ran a test tone in as well, threshold is making a difference across the throw of the pot.

Cheers

Matt

 

[John Isaac]

Hello all! (Again)

Yesterday I finally threw together a bare-bones regular GSSL. I'm using one of Gustav's kits with trs jacks instead of xlr's. The unit powers on fine, both channels are showing good compression on my meter, but I'm getting very very very low output (like -60 or 70db) regardless of the makeup gain, or whether the unit is bypassed or engaged.

Before I go multimeter hunting for bad components, is there any "usual suspects" or areas of the board I should be aware of? Is this a common issue?

Thanks in advance!

 

[gyraf]

..not trying to patronize, but have you read through this thread?

Jakob E.

 

[John Isaac]

..not trying to patronize, but have you read through this thread?

Jakob E.

Please, patronize away!

I've done a few more searches since my last post and have been making progress. Please understand, as a frustrated, solder-burned, trainee, it's temping to shoot off a quick question instead of tackling a 316 page thread. In my defense, I've been working on this GSSL since december and this is only my second question asked.  ;D

Thank you for being patient with all the many newcomers like myself!

 

[gyraf]

Try putting in a wire link instead of audio VCA's (description earlier here) - that will show you if you have a problem in control sidechain or audio path.

Jakob E.

 

[SSLtech]

A quick random guess, but do you happen to have mono (tip-sleeve) plugs in the outputs? -If so, and you can load down the outputs...

But otherwise, link pin 1 to pin 8 and check for unity-gain audio.

 

[John Isaac]

Thanks again all! I'm working on it.

 

[micah421]

Finally done! Ended up adding the Turbo(switchable). I ditched the SSC for now.

 

[Jeffhucik]

Hi,
  I am taking on my first GSSL build. I only learned of this build a few days ago and have done research over the past days. Don't wan to take up too much of people's time(I'm sure you have more important questions to answer) but is there any thing I can be told to expect during the build? Common problems? I am buying off of PCB grinders BOM. One thing I noticed I no trim pots for the VCA's on his list.. Thanks a lot
Jeff

 

[Gustav]

.One thing I noticed I no trim pots for the VCA's on his list..

I already answered your mail, but in case you missed it - the VCAs on my BOM are pre-trimmed, which means you don't need the trimmers.

Any common problems should be covered in this thread.

Gustav

 

[Jeffhucik]

For the VCA the part number 2181"brings up a "trimable" unit. Part number 2180 brings up "pre trimmed". Which is best? Your list says 2181. Also for the multi position switched is "shortening" or "non shortening" circuits best?

 

[melomane]

Hello there
I have a big problem with my GSSL.
All is ok, just the Gain Reduction very low!
The threshold range is also very low...
Nobody have the same problem?
Thanks 

 

[gyraf]

check resistor values (for order of magnitude) in sidechain - after time constants, all the way up to sidechain VCA

Jakob E.

 

[melomane]

Thank you Jakob 
I just check all the resistors (humpf), all is right

Maybe you can see something wrong on this pictures?
I use Pushbutton switch for Power and Bypass + GSSL Pcbgrinder kit.

LMK, thanks!

 

[Gustav]

You replaced a 1K resistor with a bridge on the control board (top right corner on your picture). Im sorry to say, I can't find it on the schematic, so I am not sure if it could be the cause.


It traces directly back to the 47K going to +12 from the make-up gain, so it should probably have been pencilled in between the threshold pot pin 3 and +12 in the schematic.

I am not smart enough to figure out how it would add much to a 50K pot other than making sure it can't be dialed all the way back to zero, but I would at least try putting it in, since its connected to the function giving you problems.

Gustav