GSSL HELP THREAD!!!

[Harpo]

...I have signal on the SC side of the resistor but nothing on the VCA side... however, wouldn't I have to have signal there to be seeing signal at the output?...

Signal voltage - no. VCAs are current-in / current-out devices.

The threshold pot swings the voltage at Pin 2 of the TL072 from +3V to -3V.  Seems to be working.

Seems to be not working. Opamps inverting input Pin 2 is a summing node at virtual ground. You might have a broken TL072 or pin 3 is missing connection to 0V (solder missing or chip leg not in socket?). Your +/-3V further implies, you left out the 47k between ccw side of threshold pot and +12V. Look out for shorts or wrong part values. If you have fitted a trimmer for meter calibration, watch out for trimmers initial setting about centered.

 

[spica]

...I have signal on the SC side of the resistor but nothing on the VCA side... however, wouldn't I have to have signal there to be seeing signal at the output?...

Signal voltage - no. VCAs are current-in / current-out devices.

The threshold pot swings the voltage at Pin 2 of the TL072 from +3V to -3V.  Seems to be working.

Seems to be not working. Opamps inverting input Pin 2 is a summing node at virtual ground. You might have a broken TL072 or pin 3 is missing connection to 0V (solder missing or chip leg not in socket?). Your +/-3V further implies, you left out the 47k between ccw side of threshold pot and +12V. Look out for shorts or wrong part values. If you have fitted a trimmer for meter calibration, watch out for trimmers initial setting about centered.

Thanks, Harpo.  I may have misspoke.  Pin 2 of the TL072 is 0V-ish and doesn't seem to change with the threshold pot.  I am measuring +/- 3V at the Pin 1 side of the cap between pins 1 and 2.  I must have thought I was measuring the other side of the cap.  Pin 3's connection to ground is good. 

I did leave out the 47k resistor between the ccw side of the threshold pot and +12V.  I used a trimmer on the first one I built and found I didn't need it so I left it out on this one.  I may have to snag the first one back from my friend's studio to compare component values. 

Good point about the trimmer - I am using a trimmer for the meter calibration and it was set a little low. 

 

[guze]

I need to order a toroidal for my gssl, is it better a 18v, 15v, or it doesn't matter?
Thanks

 

[guze]

I need to make the order...

 

[spica]

Found the problem... finally.  Pin D didn't have a good connection between the main board and control board... Makes sense.  Probably should've been easier to find.  :-[

At least I shook the rust off the bit of troubleshooting skills I had... and learned a couple things. 

 

[spica]

I need to order a toroidal for my gssl, is it better a 18v, 15v, or it doesn't matter?
Thanks

It doesn't matter. 

 

[marcfrom]

More you use highter voltage accepted by the circuit, more the noise floor will be low.

But, i've build many GSSL with a 2X15V toroid transformer and +15V/-15V regulators, the result was very good!

This is my favorite:

http://www.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=TE62063-ND

 

[electrisizer]

hi spica  - my main problem is solved too - distortion is away since going to TO220 for the 78 and the 79.

one thing left - i have a bit of hum on the left channel.

i mesured a RMS of about 90dB for the right and 82 dB for the left channel in bypass mode at +4 dBu line leveling.

i think both not the best results.... but ive got to find the reason for the difference. perhaps a grounding problem...

whats your RMS? any tips for little hum noise? (peak between 100-200hz)

 

[Harpo]

I need to order a toroidal for my gssl, is it better a 18v, 15v, or it doesn't matter?
Thanks

It doesn't matter. 

Sorry to disagree.
Mains voltage isn't a constant and might vary +/-10%. He didn't say what VA rating this toroid would be and an idealing transformer will have a higher than the rated output voltage. He didn't say if he wants to build a standard GSSL or also likes to have a Turbo or other options supplied from this transformer and the maybe onboard psu with 78L12/79L12 voltage regulators (we're not talking about the 7815/7915 regulators). Without connected load and in a high mains scenario, these +/-12V regulators might have 30V raw DC connected to their input with a 2x18VAC secondaries mains transformer in front. Have a look at the datasheet of these regulators to see, they are at least close to the edge of their abs.max.rating. With load connected, a operating/not idealing standard GSSL config, coming with a single TL074,TL072,THAT2180 and LED, might draw about 30-40mA from these rail voltages. With the 10R in front of these regulators for a slight voltage drop, this is also the max.current, these regulators could supply with some heatsinking, but will be sufficient. This will probably be not sufficient with the additional current demand of a Turbo board or whatever else connected. If you already have a dual 18VAC or 36VAC CT transformer and want to use the onboard psu, you'd better feed these 78L12/79L12 from the regulated +/-15VDC rails instead, leaving enough safety margin for their typ.1.7V dropout voltage.
A dual 15VAC or 30VAC CT mains transformer will give you less limitations and keeps it way cooler. YMMV.

 

[marcfrom]

My GSSL is equiped of this 25VA transformer:

http://www.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=TE62063-ND

There is inside:

4x 12v relais for true bypass
1x turbo board
5x Leds
2x Dbx202x
1x second 12V PSU connected on the same transformer (dedicate to relais and leds)
1x 12v incandescent (meter)
1x Sifam 29Wf meter

And it's really enought powerful, and it seems at ease!!! 8)

 

[guze]

I ordered a 15v 30va. It's going to have a turbo board and probably the CRC board.
Thanks

 

[marcfrom]

I forgot, my units has a CRC board too. ;D

 

[wordave]

Hi!

What is the chance of a mono GSSL build? Does anyone have the schematic/PCB lay outs with just the left channel? Tried doing this myself but quickly got confused and some of the signal paths.

Going to get going with this project pretty soon, I don't know wether to be laughing or crying!

Cheers,
Dave

 

[ytsestef]

Hi!

What is the chance of a mono GSSL build? Does anyone have the schematic/PCB lay outs with just the left channel? Tried doing this myself but quickly got confused and some of the signal paths.

Going to get going with this project pretty soon, I don't know wether to be laughing or crying!

Cheers,
Dave

It's quite complicated, from what I know, which is probably why you got confused. As Jakob himself once said: "Just build a GSSL and use one channel only".

 

[imo]

I was going through a Gssl that i built a couple of years ago, tidying it up before lending it to a friend. I noticed the 12V rails were latching, did some troubleshooting and found that it was the 7812 that would occasionally latch on power-up.
My comp has the turbo board and 2 led meter lights. I did some Lab "searching" and discovered that this is a common problem and that many people have gone to offboard supplies in the last couple of years.
Before i try to lash a separate board together for this, is it worth it tossing another 7812 in, or am i up against the limit of the reg? It seems that many people have built much more elaborate boards with no trouble.
Ian

 

[ptron]

hey guys! im building 2 units with crc board and supersidechain board from barclaycon  planning on one illuminated switch for bypass 1led for on off switch and 2 for the meter.

im almost there with the material and component finding but the transformer is an enigma for me (most of this is but i hope i get thru! )

anyways.. my question is this is 10va +/-15vdc enough or should i get another one a bit bigger?
and if anyone has a partnumber for mouser would be great mouser is the only one that i can find in mexico

thanks for your help!
patricio

 

[Harpo]

What is the chance of a mono GSSL build? Does anyone have the schematic/PCB lay outs with just the left channel?

Umm, left channel only,... ??? Schematic with just the right channel would be a lot easier. Print out the page, cut off the top 5 cm, leave out the left channel 47k in front the sidechain VCA and replace the right channel 47k in front of the sidechain VCA with a 33k resistor. Done. Pcb layout? Just don't stuff the parts that were cut off from previous schematic print. :

 

[sdR]

What is the chance of a mono GSSL build? Does anyone have the schematic/PCB lay outs with just the left channel?

Umm, left channel only,... Huh Schematic with just the right channel would be a lot easier. Wink Print out the page, cut off the top 5 cm, leave out the left channel 47k in front the sidechain VCA and replace the right channel 47k in front of the sidechain VCA with a 33k resistor. Done. Pcb layout? Just don't stuff the parts that were cut off from previous schematic print. Roll Eyes

I'm also looking for how to do a 2*Mono GSSL Clone !

With a 33k resistor, will the input voltage be enough to have a good response in the sidechain ? any other components to change ??

 

[Alessio]

Hello everyone,
I finally finished my two units with turbo and double ssc.
Everything is working but I have a little problem:
When I move the rotary switch for the "release" I can hear a little POP in the speaker.
I use this switch: Digikey number CKC7004-ND
This is a NON-SHORTING switch, as I understand the contact is "break before make" why I hear the POP?
Do I need a shorting switch? Can be a "ground" problem?

Thank you very much,


Alessio

 

[marcfrom]

Non-shorting is correct !!!

Maybe the swith is defective, try another one.

I usually use :

http://export.farnell.com/lorlin/ck1030/switch-2pole-6-pos-metric/dp/1123706