GSSL HELP THREAD!!!

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Harpo

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Well after a year after ordering I think I got mine up and running. After a lot of troubleshooting, having to source new VCA’s after the THAT’s that came with it were faulty, drilling out a couple pads to make the DBX’s fit and soldering components to the bottom, and replacing a voltage regulator I shorted….Signal is finally passing, the meter is moving, and it’s definitely compressing. So a small victory for my second build, and I do feel pretty damn great. Had a couple questions though and I apologize if I missed them in the thread: There’s definitely a significant volume boost when running signal through, even with no compression and the output at the minimum. Also, it doesn’t quite have the snap that I’ve known from SSL’s, not that I’m trying to have an exact copy. The compression feels spongy and can’t seem to find the happy medium between barely noticeable and way too much. I’m firmly willing to admit I’m way overthinking this with my head so far deep into getting this things up and running, but something just isn’t sitting right and I can’t quite put my finger on it. Anyone else have similar experiences. That said, definitely took a major step forward with this build. Couldn’t have done it without the resources and great advice here. Going to play with this a while before potentially adding a cavendish.
Using DBX202 VCA's (never seen these with lables attached in opposite directions), to what value resistors did you change in order to adapt for the lesser allowed input current (the 27k voltage to current converters in front of the VCAs are now FI 100k..?), the corresponding feedback resistors in the VCAs following I2V converters (the 15k now are FI 50k with paralleled compensation caps 100pF decreased to FI 33pF...?), the VCAs different control law -50mV/dB for the DBX202C from GSSL-schematic (missing the appendix 'C') vs. -6mV/dB for the DBX202 is adapted by...?, just to name a few...
 

craigmorris74

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I really appreciate your help!

When the needle slams to the right, it doesn't pass audio. Sometimes when you turn the switch just right, or thump the knob, the meter settles back to normal, and it passes audio. If you do go from 2:1 to 4:1 and the unit behaves normally, if you ever so slightly touch the ratio switch the problem comes back.

Strangely, with the meter pegged and the unit not passing audio, there is continuity between the pole of the switch and the 1.8M resistor it's connected to. The resistor doesn't show continuity to the nearest resistor and diode, which indicates there isn't a solder bridge.
Checking in again to report that I've measured the switch connections, confirmed that the two resistors at the 4:1 position measure 1.8M and 510K. Also checked that there are no soldering errors causing unwanted connections. I'm still getting so much compression in 4:1 that no audio comes through. Is there anything past the ratio circuitry that would affect one ratio like this? I don't see how, so the only thing that seems like it could cause the problem would be a faulty switch, even though it is measuring as I'd expect it to.
 

Script

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Sometimes when you turn the switch just right, or thump the knob, the meter settles back to normal
Sounds erratic.

- Connectivity of switch is continuously good when 'thumping' and wiggling the rotary switch knob?
- All solder joints are rock solid ?
- A single wire strain sticking out at either end of 10-pin connector causing wrong on/off connection?
- 12V rails are generally stable ?
- Diode in RAT section measures good ?
 

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craigmorris74

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Sounds erratic.

- Connectivity of switch is continuously good when 'thumping' and wiggling the rotary switch knob?
- All solder joints are rock solid ?
- A single wire strain sticking out at either end of 10-pin connector causing wrong on/off connection?
- 12V rails are generally stable ?
- Diode in RAT section measures good ?
Thanks again for replying
-I haven't gotten a single bad connectivity reading from the switch
-I have reflowed all of the joints around the switch
-I'll check around the 10 pin connector
-12V rails read good
-I haven't measured the diode-I'll swap it and see what happens-if it were bad, wouldn't it affect my 2:1 ratio as well?

I think the thing that doesn't make sense is why is it only affecting 4:1. 2:1 and 10:1 perform pefectly.
 

Script

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Tricky. You use Lorlin (or like) soldered to sub board ? Painful to replace. Here's what I might try -- just an idea and might be wrong cos it's late over here .

That Lorlin uses only one pole thrown to three positions, but two resistors for 4:1. To bypass the rotary, could desolder one lead of the 10:1 resistor (1M2?) -- the side connecting to the rotary -- and then set rotary to 10:1 so that RAT is completely open and hopefully doesn't connect at all. Easy to check.

Then use alligator clip to bridge from pole to 2:1, then 10:1, and finally 4:1 resistor junction.

If everything is fine in all three RAT positions, you do indeed have a faulty rotary (maybe MBB type that doesn't 'break' properly). If still bad, problem is elsewhere -- but then it'd save the pain of desoldering that rotary.

Makes sense ? Really late here, sorry.
 

craigmorris74

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Tricky. You use Lorlin (or like) soldered to sub board ? Painful to replace. Here's what I might try -- just an idea and might be wrong cos it's late over here .

That Lorlin uses only one pole thrown to three positions, but two resistors for 4:1. To bypass the rotary, could desolder one lead of the 10:1 resistor (1M2?) -- the side connecting to the rotary -- and then set rotary to 10:1 so that RAT is completely open and hopefully doesn't connect at all. Easy to check.

Then use alligator clip to bridge from pole to 2:1, then 10:1, and finally 4:1 resistor junction.

If everything is fine in all three RAT positions, you do indeed have a faulty rotary (maybe MBB type that doesn't 'break' properly). If still bad, problem is elsewhere -- but then it'd save the pain of desoldering that rotary.

Makes sense ? Really late here, sorry.
Yes, that makes perfect sense, thanks! I'll give it a try this afternoon.
 

craigmorris74

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Tricky. You use Lorlin (or like) soldered to sub board ? Painful to replace. Here's what I might try -- just an idea and might be wrong cos it's late over here .

That Lorlin uses only one pole thrown to three positions, but two resistors for 4:1. To bypass the rotary, could desolder one lead of the 10:1 resistor (1M2?) -- the side connecting to the rotary -- and then set rotary to 10:1 so that RAT is completely open and hopefully doesn't connect at all. Easy to check.

Then use alligator clip to bridge from pole to 2:1, then 10:1, and finally 4:1 resistor junction.

If everything is fine in all three RAT positions, you do indeed have a faulty rotary (maybe MBB type that doesn't 'break' properly). If still bad, problem is elsewhere -- but then it'd save the pain of desoldering that rotary.

Makes sense ? Really late here, sorry.
The ratio section diode checked out fine so I took the switch out of circuit as described. 4:1 was fine with alligator clips, as was 2:1. With the unit alligator clipped for 4:1, I turned the ratio switch to 4:1, and the problem came back. I think this confirms a faulty switch?
 

Script

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Still a mystery switch...

When setting to 4:1 position, does the 4:1 pin of the rotary show connectivity to the 2:1 and/or 10:1 pins ? And is there connectivity from pole to 4:1 pin at all time ?
 
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craigmorris74

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Still a mystery switch...

When setting to 4:1 position, does the 4:1 pin of the rotary show connectivity to the 2:1 and/or 10:1 pins ? And is there connectivity from pole to 4:1 pin at all time ?
it does not.

What's crazy is I've desoldered the switch, and using it with alligator clips, it seems to work fine.

I feel like I'm losing my mind
 

craigmorris74

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Ok, maybe a breakthrough here. Removed the ratio switch and hardwired it for 4:1. When I touch a multimeter lead to pad of the 50k threshold pad labelled - on the wiring diagram, the problem appears. When it touch the pad for the center leg of the 50k pot, problem goes away.

Could a bad connection from the threshold pot or meter cause a problem with 4:1?
 
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mariuo

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Just want to add my appreciation for this thread, I got my gssl working after 5 days of lurking here and tinkering.

Thanks to Gustav for the rev11 boards, gyraf for designing this fun box, and everyone that takes the time to answer and troubleshoot in this thread.

I found that it was super important to go over and check soldering, refer to schematics, and double check IC orientation before powerup!
 

Pik

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Jan 15, 2022
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Serbia
Hello guys
I've build GSSL comp with THAT 2181
Have a really strange problem
When turned on everything's working as it should, apart from channels gain difference, right channel is louder a few dB's (27K resistor I guess).
But after 3 or 4 minutes the same channel slowly starts to distort and gain reduction starts to increase (I can see it on the VU meter too). After a few more minutes it distorts like crazy, but only on the right channel. Gain reduction goes crazy too.
If I shut down the power supply just for a few seconds everything's back to normal and I have a normal working compressor for 4 minutes again, then it will start all over again. It distorts in a bypass too.
All voltages good, tried to swap VCA's, change NE5534 and 5532. No change.
Does Anybody have any ideas?
Please Help
Thanks
Pik
 

Harpo

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...
But after 3 or 4 minutes the same channel slowly starts to distort and gain reduction starts to increase (I can see it on the VU meter too). After a few more minutes it distorts like crazy, but only on the right channel. Gain reduction goes crazy too.
If I shut down the power supply just for a few seconds everything's back to normal and I have a normal working compressor for 4 minutes again, then it will start all over again. It distorts in a bypass too.
All voltages good, ...
symptoms sound like thermal protection shutdown of the 78L12 or 79L12 voltage regulators.
Measure the supposed to be +12VDC and -12VDC rails of the sidechain supply part when in fault condition.
What are your mains transformer secondary voltages ?
 

Pik

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symptoms sound like thermal protection shutdown of the 78L12 or 79L12 voltage regulators.
Measure the supposed to be +12VDC and -12VDC rails of the sidechain supply part when in fault condition.
What are your mains transformer secondary voltages ?
Thank you Harpo for your answer,
I've just solved my problem. Some soldering issues and some capacitors were wrong capacity.
Thank you one more time for your answer.
All best
 

craigmorris74

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benton, ky
I got my unit working, and it sounds fantastic. I'm pretty sure the ratio switch wasn't the problem. I thoroughly cleaned the control board, and made sure every solder connection was stable, and things started working. I built mine with 202X VCA's (adjusted component values according to the data sheet, and as suggested by this thread) and a Turbo board. I'm very happy with the sound.
 

rikkord

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Jan 13, 2022
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Budapest
Hi everyone, I'm new here, this is my first diy build and spent the last two weeks reading this thread, buying components, building my gssl (basic, no mod apart of the hpf on a switch with a 100nF cap) and troubleshooting.

As for my actual problem I spent a noticeable amount of time on searching for this issue already sorted out, but haven't managed to get it clear so I thought I give it a try asking it.

Audio passing through the unit is barely recognizable in the form of a heavily distorted audio signal. After a thorough check I'd say all the components are in the right direction (caps,diodes,opamps,vcas, bridge diode, voltage regulators)

So I started to measure voltages at points mentioned in the thread to check. The results seem fine at most of the measured points

at the +15V and -15V jumper = +15,28V and -15,41V
at the 7815 pin 3 = +15,26V and 7915 pin3=-15,42V
at the 7812 pin 3= 12,13V
at the 78L12 pin 1= +11,9V pin 3=14,72V
at the 79L12 pin 2= -15,03V pin 3= -12,48V
+/- 12V at TL074(pin 4 and 11) and TL072 (pin 4 and 8)
+/- 12V at sidechain VCA (pin5 after the 5k1 resistor and pin 7)
+/- 15V at Left ad Right VCA (pin 5 and pin 7)
+/- 15V at 5534 for left and right VCA (pin 4 and 7)

What I found strange, are the following values:

5534 at left and right VCA (DBX emulation circuit) has +12,8V on pin 1 and 8 - I’m not sure if this is OK
And the I/O section op amps shows this:
5534 pins - 5532pins
1 +14,85V - 1 +14,48V
2 +2,48V - 2 +2,13V
3 -1,82V - 3 +1,31V
4 +2,02V - 4 +2,03V
5 -3,88V - 5 +1,05V
6 +4,53V - 6 +0,95V
7 +15,24V - 7 +14,47V
8 -15,03V - 8 +15,24V
So I suppose the cause of the distorted sound is somewhere in the I/O section on the PCB am I right? where should I go from here?

Thanks a lot in advance and if it is an already existing and sorted problem sorry for the long post, then please turn me into right direction ( page).

David
 
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gyraf

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Hi David

You shouldn't have (significant) DC after the input de-balancing opamp - NE5534's Pin6.
Likewise, you don't want (significant) DC at the post-VCA balancing opamps NE5532's pins 1, 7..

On pin4 of the 5534, 5532 you want to have negative supply (-15V) - but your list shows +2V? Check continuity from your 7915 to these pins?

/Jakob E.
 

Sisu MT

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Jun 24, 2015
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Austin, TX
Hi there,
I just finished building my first GSSL. First power on smoked the to 100R resistors after the bridge. Realized that I'd reversed the 5534's in the VCA's. So, replaced the 100R's and repositioned the 5534s. Before populating the opamps/VCAs i tested the voltage points and all the points on the main PCB had perfect readings. First question...is it likely that inverting the 5534's damaged any other components? The unit passes clear audio and the make up gain works, but the threshold doesn't do anything and the ratio/attack/release functions when changed seem to impact the sound a bit, but only slightly.
Many thanks, Pat
 

rikkord

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Jan 13, 2022
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Budapest
Hi David

You shouldn't have (significant) DC after the input de-balancing opamp - NE5534's Pin6.
Likewise, you don't want (significant) DC at the post-VCA balancing opamps NE5532's pins 1, 7..

On pin4 of the 5534, 5532 you want to have negative supply (-15V) - but your list shows +2V? Check continuity from your 7915 to these pins?

/Jakob E.
Ok so I started to check continuity components side and got until the vca distortion trimmer and then lost it, Then from the first 5532 pin 4 to the last 5534 pin 4 (we're talking I/O section) I have continuity again. So I turned it upside down and saw something which could mean (if I'm not tottally wrong) that a part of the circuit is missing from the PCB. I attached a photo of the PCB and the PDF version, marked the route I think is missing.. Am I right on this one?
 

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