GSSL HELP THREAD!!!

[eqp1a]

I got my friend's GSSL (w/sidechain high pass) working a bit ago thanks to help from some kind people on this thread. All of a sudden it's stopped compressing. Makeup gain still works. I'm at a loss; thoughts?

 

[darkus]

I got my friend's GSSL (w/sidechain high pass) working a bit ago thanks to help from some kind people on this thread. All of a sudden it's stopped compressing. Makeup gain still works. I'm at a loss; thoughts?

Check if the vca´s are well in their sockets.

Im building my 2nd unit. No mods. After power up, both 10R resistors burned. I then found out the short in the control board (+ and F) and bypassed the pcb as Joel did. Once again, on powerup both 10R resistors burn.

Ive checked that they are not shorted to ground but it seems like the only thing that might cause this to happen, right? What else should i check?

 

[audiophreak]

Hi All !! 
    I have built up a SSL9k and GSSL in a 1U case and having a slight problem. The 9k is working perfectly and the GSSL is also working and compressing perfectly and all controls work as they should.

  I set it up with two relays that work from a single DPDT toggle - in the normal ( non-energized state ) the un-balanced output signal from the 9k goes to the GSSL input via (+) to (+)  and (-) / ground/shield to (-) ... and GSSL  output (+)  ,  (-) non connection and 0v to ground/shield - ... -with the relays energized 9k out put is switcheed directly to un-balanced out put jack leaving the GSSL input disconnected and GSSL  output is disconnected / left hanging from output jack.

  It all works , however the problem is that with GSSL IN , signal is  -6dB - no hum or buzz or distortion , just -6dB , when switched out ( basically  just switched out of signal chain )  normal signal level from 9k .  I did use the 27k instead of the 15k , I used a members diagram (EDIT : Lucas's )  " Road Map to GSSL " to populate only the Left channel components of GSSL .

  Any Help / Suggestions Appreciated

  Thanks,
                    Chip 

 

[Gustav]

  It all works , however the problem is that with GSSL IN , signal is  -6dB - no hum or buzz or distortion , just -6dB , when switched out ( basically  just switched out of signal chain )

I have read the line a few times, and I can't tell if you have a relative signal loss of 6dB with the GssL IN or OUT.

Could you clarify?

Solution could be pretty simple (The value of the resistor you changed)...

Gustav

 

[audiophreak]

Apologies , Yes , the 6dB drop in signal level is when GSSL is switched IN signal chain. 

  I am assuming this is because I'm UN-balanced IN and OUT ??  and if so , is there a way to compensate for that ??

 

[audiophreak]

ok , I think I possibly found my answer on page 279 - Harpo's « Reply #5567 on: February 19, 2013, 08:22:19 PM » will try this

 

[audiophreak]

... is that the 15k resistor near the bottom left of the right channel VCA  section next to the 100u electro  and Left channel 5532 ?

 

[audiophreak]

Yup ... thats the one , all is good now  ;D

  Thank you Harpo and all - Search is where its at !!    ;D

 

[rainton]

short question,

I've finished another GSSL with Turbo & SSC.
It works great except one thing:
When  turn it on so the compressor is in bypass, the needle hits the very left for about 2 or 3 seconds, then it slowly returns to the "0" position.
audio wise this is accompanied by a very loud output of the GSSL for the above mentioned 2 or 3 seconds then the level returns to normal.

The strange thing is, this is only when I power on the GSSL into bypass mode. When I power it on with compressor engaged it doesn't occur - UNTIL I switch in bypass for the first time after powering on 

So it has to be something that comes before the compressor side-chain circuit.

It's a version 11 pcbs and I have to add, that instead of the 15k resistors in the output circuit I used a 10k resistor + a 10k trimmer to fine trim it to unity gain...but that couldn't be the problem could it?

Thanks for any ideas!!

EDIT: solved. I forgot to cut that one pin of the 2180. As soon as I did the GSSL behaved normal

 

[Chad]

Hey there. I've just put together my GSSL, I'm having some problems.
-When the bypass switch is on I get no audio at all
-When I enable the compressor I get very Loud amplified, super distorted signal that moves the meter needle but I cannot hear the effects of any compression
-The threshold adjusts the needle but no compression.
-I'm getting good voltages on the ICs except for the pin 5 on all THAT2081Bs is showing -2.8v. Im thinking its supposed to be -15v?

I've gone over every component, and triple checked all my soldier points
Any help would be amazing
Cheers

 

[gyraf]

I'm pretty sure we've had some of these symptoms before - look through this thread for possible answers...

Jakob E.

 

[Terge]

Hi folks! I just finished building my second GSSL and I'm having problems with my -15 rail, no matter what I do and try it's -20.8 V. I've got the TL074 chip installed to have a load on the regulator but that doesnt help either.

My build has an on board +- 18V transformer.

+15, -12 and +12 measures fine, the problem is only the -15.

Do you have any pointers or tips on how to zero in what's wrong?

 

[Harpo]

Hi folks! I just finished building my second GSSL and I'm having problems with my -15 rail, no matter what I do and try it's -20.8 V.

This -15VDC rail needs a load connected. (FI a temporary connected maybe 1K5 resistor between output of this regulator and 0V reference voltage will draw 10mA to ensure this ...)

I've got the TL074 chip installed to have a load on the regulator but that doesnt help either.

The -15VDC rail needs the load. The TL074 is supplied from the +/-12VDC rails (and this chips idle current alone will hardly draw enough from its preregulators...)
Just an idea...

 

[Terge]

Eureka! Popped in the 5534's and now its a nice and even -14.9

Thanks!

Hi folks! I just finished building my second GSSL and I'm having problems with my -15 rail, no matter what I do and try it's -20.8 V.

This -15VDC rail needs a load connected. (FI a temporary connected maybe 1K5 resistor between output of this regulator and 0V reference voltage will draw 10mA to ensure this ...)

I've got the TL074 chip installed to have a load on the regulator but that doesnt help either.

The -15VDC rail needs the load. The TL074 is supplied from the +/-12VDC rails (and this chips idle current alone will hardly draw enough from its preregulators...)
Just an idea...

 

[djfatum]

8)
Another G-ssl

 

[JW]

Hey folks,

I have a GSSL that I bought off another forum member.

I noticed that the polarity flipped going through the unit. So I traced the wiring from the inputs to the 5534 chip and the outputs back to the 5532 chips.

The wiring looks correct. i.e. Input XLR pin two (hot) goes to pin 3 (non-inverting input) of the 5534 chip. XLR pin 3 (cold) goes to pin 2 of the 5534 (inverting input) http://circuits.datasheetdir.com/25/NATIONAL-NE5534-pinout.jpg

And XLR pin 2 on the output is connected to pin 1 on the 5532 (which is Output 1 on 5532 pinouts) XLR pin 3 (cold) is connected to pin 7 (output 2 on the 5532) http://module.blog.com/files/2011/10/NE5532-2.jpg

Am I to assume "Output 1" on the 5532 should be the + output? And "Output 2" should be the - output?
Anyway, that's how the Gyraf schematic has it. http://www.gyraf.dk/gy_pd/ssl/ssl_sch.gif

So. . . . seems I have a polarity swap going on somewhere else.

The unit has DBX 202's for the VCA's fwiw.

Any ideas?

Also of note, when I tried simply swapping the wires on the output XLR's the unit started behaving badly (not compressing at all until the threshold was dramatically lowered and then the signal cutting out completely for a second) This doesn't make sense. I probably did something when I was messing around with the pcb. I'm gonna go through the calibration procedure after I figure out the polarity issue.

 

[grrrunge]

If i were you, I'd swap the input wires instead.
The inputs are going straight to a differential amplifier, which won't care if one side of the signal is eventually grounded as a result of running an unbalanced signal to it.
If you swap the output wires, you might end up grounding the output that also drives the input for the inverting amplifier, when driving an unbalanced input with the GSSL. That could result in a multitude of weird situations, though i suspect the unit would just go quiet in most cases.

 

[JW]

Thanks grrrunge,

Seems to be working now. (My other problem was something silly)

However, I have a few more questions.
Something I've noticed is my voltages look like this:

+14.7V
-15.1V

+12.1V
-12.1V

I'm a little concerned about what should be the plus 15V leg. How do I adjust this?
I'm using the original power supply that was part of the gyraf board from awhile back. I just moved those components onto some perfboard and farther away from the main compressor board. So, there aren't any trimmers to adjust the voltage rails. Where should I put them?

And I know this has been discussed before and I've read everything I can about it, but I'm still confused and wondering what is the correct value for the resistor going into the VCA when using a DBX202C gold can?

Gyraf originally had 15K, then 27K.

I've seen an SSL schematic with 15K. Can be seen on this page of this thread posted by Biasrocks http://groupdiy.com/index.php?topic=37306.0

Then there's the DBX202C notes hosted by thatcorp that call for a 50K www.thatcorp.com/datashts/dn127.pdf

And yet another value on another SSL schematic hosted on the gyraf site. This one is very hard to read but appears to be a 68.1K ?  http://www.gyraf.dk/gy_pd/ssl/ssl_82e26.gif 68.1K

 

[Gustav]

Thanks grrrunge,

Seems to be working now. (My other problem was something silly)

However, I have a few more questions.
Something I've noticed is my voltages look like this:

+14.7V
-15.1V

+12.1V
-12.1V

I'm a little concerned about what should be the plus 15V leg. How do I adjust this?

I would not worry about the small measured difference, but you could try a different regulator.

I'm still confused and wondering what is the correct value for the resistor going into the VCA when using a DBX202C gold can?

Gyraf originally had 15K, then 27K.

I've seen an SSL schematic with 15K. Can be seen on this page of this thread posted by Biasrocks http://groupdiy.com/index.php?topic=37306.0

Then there's the DBX202C notes hosted by thatcorp that call for a 50K www.thatcorp.com/datashts/dn127.pdf

And yet another value on another SSL schematic hosted on the gyraf site. This one is very hard to read but appears to be a 68.1K ?  http://www.gyraf.dk/gy_pd/ssl/ssl_82e26.gif 68.1K

In your examples, you can see the resistor value varies, but if you check the feedback resistor (above the opamp following the VCA), you will see the ratio between these values do not change. 50K/50K, 68K/68K, and originally for the Gyraf, 15K/15K THAT (example attached to post)

The resistors "program" the gain in the opamp  http://www.learningaboutelectronics.com/Articles/Op-amp-gain-calculator.php
If you plug in the values, 68K/68K, 50K/50K, 15K/15K for Rin and RF, you will get 1 every time. (Multiplied by 1, which means no gain).

The original comp schem is single ended (unbalanced input), but in order to use it as a stand-alone circuit, a differential input driver has been added. The input sums the identical content of the +/- signals (+ going to the positive input, - going to the negative).

You may have heard that summing two identical signals doubles the signal, so this is a gain factor of x 2.

In order to compensate for our gain factor of x 2 in the input, we half (x0,5) the signal by replacing the the Rin value of 15K with 27K. (Try it in the calculator).

If you got this far, you may ask why were not using a 30K value instead of 27K (Gain= RF/RIN), and I honestly didn't think of it until now. I would imagine it off-sets with the 470R going to ground on the positive input of the opamp in the GssL circuit.

It should be sufficient to put your mind at ease about the value, though!?

Gustav

 

[JW]

Gustav,

Thanks so much! Yes, that does make enough sense to put my mind at ease!