GSSL HELP THREAD!!!

[Harpo]

I just started putting together the new GSSL SC from Gustav,

Two separate projects (the GSSL circuit and the still called "Super Sidechain" SCF with the missing word 'Filter'). Your questions relate to the GSSL, not to the Super Sidechain Filter board.

there are two 27k resistors with an * , one 47k* and a 120k*

described in the legend of the GSSL schematic, pg.1,2,3.

Do these have something to do with the SC?

No. The SCF board is a different addon circuit with its main purpose of applying a HPF at the audio signal for the control path before it reaches the GSSLs sidechain.

Do you normally populate them if you are using the SC, or the reverse?

Depending on VCAs used, values might change, but the GSSL will not work without these parts populated.

 

[Jimmy1980]

So, I figured out how to read all of the voltages. Everything looks good throughout the board except for pin 4 on my input 5543's and left vca 5543, and both pin 4 on my output 5532's. I'm only measuring about 2v on each of these pins when I believe I should be measuring -15v.

Assuming typo 5543 for the NE5534 (single opamp chip, not a VCA), you either measured the wrong pin for V DC in respect to 0V reference voltage or the battery in your multimeter might be low, giving silly readouts. All NE5532 and NE5534 opamps use the same +/-15VDC supply rail voltages. Measuring the NE5534s between the chips pin 4 and 7 will give the same 30VDC readout as well as when measuring the dual opamp chips NE5532s between pin 4 and 8.

Thanks Harpo, yes that was a typo.

After further troubleshooting, I've got my voltages measuring correctly across all ICs, but now I'm hearing crazy amounts of distortion on both channels when I run audio through it. Also my right channel has a lot of system noise. I'll try reading back through this thread for an answer to this problem, but if you happen to know off hand what the problem might be, it might save me a week of reading back through this thread (appreciate all of the info tho).

Cheers,

 

[johnnyscotch]

Thanks for your response, actually I'm specifically referring to Gustavs new board which has the side chain built right onto the main PCB.

There's no mention of the * in the posted build guide.

Thanks

I just started putting together the new GSSL SC from Gustav,

Two separate projects (the GSSL circuit and the still called "Super Sidechain" SCF with the missing word 'Filter'). Your questions relate to the GSSL, not to the Super Sidechain Filter board.

there are two 27k resistors with an * , one 47k* and a 120k*

described in the legend of the GSSL schematic, pg.1,2,3.

Do these have something to do with the SC?

No. The SCF board is a different addon circuit with its main purpose of applying a HPF at the audio signal for the control path before it reaches the GSSLs sidechain.

Do you normally populate them if you are using the SC, or the reverse?

Depending on VCAs used, values might change, but the GSSL will not work without these parts populated.

 

[Harpo]

actually I'm specifically referring to Gustavs new board which has the side chain built right onto the main PCB.

Like every other compressor, so has the GSSL (and ever had) a sidechain. The latest revision has a provision for a single frequency -6dB/oct slope highpass filter on board in front of the sidechain.

There's no mention of the * in the posted build guide.

That's why I said 'described in the legend of the GSSL schematic, pg.1,2,3', maybe take a look. On the pcbgrinder shop page is a link 'board layout' supplying same information in the legends.

 

[johnnyscotch]

thanks!

actually I'm specifically referring to Gustavs new board which has the side chain built right onto the main PCB.

Like every other compressor, so has the GSSL (and ever had) a sidechain. The latest revision has a provision for a single frequency -6dB/oct slope highpass filter on board in front of the sidechain.

There's no mention of the * in the posted build guide.

That's why I said 'described in the legend of the GSSL schematic, pg.1,2,3', maybe take a look. On the pcbgrinder shop page is a link 'board layout' supplying same information in the legends.

 

[Jimmy1980]

Hey all,

I'm still trying to troubleshoot my distortion problem present on both channels. I'm starting to think the problem may be in the output section. When the compressor is powered off I can send 0.775vac (1k tone at 0dbu) from my DAW and 0.775vac will show up on the output XLR pins (I'm not sure if this should be happening). When the power is on I'm getting about 5vac at the XLR output pins. This confuses me as it seems like I'm getting a much louder signal on the output compared to the input. Could this explain why everything I run through it sounds distorted? Am I clipping something in the output section?

When the compressor is powered on, I can trace the 0.775vac cleanly to the left and right 2181 IC's in the VCA sections where I find a slight bump up to around 1.1 vac on pin 8. This continues on to the two 15k resistors in the output section where after the two 15k resistors I'm reading around 5vac. This seems like a pretty large jump up in volume.

These are my approx VAC readings at my output NE5532 pins from my +XLR pins:

Pin 1- 7.12vac
Pin 2- 0.775vac
Pin 3- 0.775vac
Pin 4- 0.775vac
Pin 5- 0.843vac
Pin 6- 1.131vac
Pin 7- 5.78vac
Pin 8- 0.775vac

I'm also getting a constant static sound on the right channel when the power is on.

I've gone up and down the PCB looking for shorts but can't find any. All of the DC voltage rails are good too.

Thanks,

 

[Jimmy1980]

Update:

I removed the 2180's from the left VCA section and jumped pins 1 and 8, which made the left channel sounds great but no compression. It also put my 0.775vac from my left input XLR to my output XLR properly. Haven't tried this with the right VCA yet but I assume it would be the same result. This led me to a possible short in the sidechain's 2180; I'm getting continuity between pin 2 of the sidechain's 2180 and the 470R. Looking and the schematic, I don't think there should be continuity here? Can anyone confirm continuity between these two? All of the solder joints look great. I'd be surprise if there's a short there seeing as they are positioned far from each other.

Thanks,

 

[rearturo]

Hi everyone

It's my first post here and I'm a beginner in DIY stuff and electronics.

I recently finished building my GssL kit... thanks to Gustav for all the parts and help.

I tried to look for my problem in this thread but there's a lot of pages to go through and I didn't find anything similar to my query so far so here's my problem..

I hooked up my GssL to a mixer.. I managed to get an input signal and the meter seemed to read as it should, even when i moved the threshold. However my compressor was breaking my ISR signal, i.e. no output was coming out of it.
One thing that I noticed was that the IC on the left  from the input XLR was getting hot very quickly (in about 20 sec)... I'm pretty sure that's not right.

Anyone helpful can maybe guide me at least from where to start or maybe can share some ideas please?

I checked the transformer before powering it and I was reading 15.4VAC on both wires (i.e. black and yellow, against the centre tap of the transformer - it's connected in series and I'm in Germany).

Would really appreciate if anyone can maybe at least guide me from where to start or maybe can share some ideas please...I'm doing this project as part of my diploma thesis and would love to have it working

Thank you!

 

[weiss]

I hooked up my GssL to a mixer.. I managed to get an input signal and the meter seemed to read as it should, even when i moved the threshold. However my compressor was breaking my ISR signal, i.e. no output was coming out of it.
One thing that I noticed was that the IC on the left  from the input XLR was getting hot very quickly (in about 20 sec)... I'm pretty sure that's not right.

Anyone helpful can maybe guide me at least from where to start or maybe can share some ideas please?

I checked the transformer before powering it and I was reading 15.4VAC on both wires (i.e. black and yellow, against the centre tap of the transformer - it's connected in series and I'm in Germany).

i cannot tell from the photo, but check your soldering on the back, your ic's (value and orientation) and your 10 ohms resistors..

 

[rearturo]

i cannot tell from the photo, but check your soldering on the back, your ic's (value and orientation) and your 10 ohms resistors..

Thanks weiss... i'll have a look into it but i think my soldering should be fine.. i have some bridges, but it's only where the soldering pads were connected to each other.. that's ok right?
Not sure if it can really help but i attached a photo of the back just in case ...

Thanks again

 

[Harpo]

I hooked up my GssL to a mixer.

How in detail ? Balanced/unbalanced ? Separate XLRs or TRS sockets or a single TRS insert socket for unbalanced operation in your mixer ?
The GSSL has electronic balanced inputs (2 conductors+shield) and electronic balanced non floating outputs (2 conductors+shield).

I managed to get an input signal and the meter seemed to read as it should

probably the GSSLs gain reduction meter, not a signal level showing VU meter ...

However my compressor was breaking my ISR signal, i.e. no output was coming out of it.

maybe outputs connected wrong.

One thing that I noticed was that the IC on the left  from the input XLR was getting hot very quickly

Be more specific. From your 'no output' you might be talking about the NE5532s.
If you shorted the output signal that connects to NE5532-pin7 to 0V reference voltage (inside the GSSL or in your insert jack wiring) would have this hot IC no output effect. Hot IC and distorted signal could be NE5532-pin1 shorted to 0V reference voltage instead. There are more ...

I checked the transformer before powering it and I was reading 15.4VAC on both wires (i.e. black and yellow, against the centre tap of the transformer - it's connected in series and I'm in Germany).

Maybe right. Colour codes of transformer wires between different manufacturers are not standarized.
You want to know the correct operation of the +15VDC, -15VDC, +12VDC, -12VDC (and maybe the aux.+12VDC) supply rail voltages in respect to 0V reference voltage.

 

[rearturo]

How in detail ? Balanced/unbalanced ? Separate XLRs or TRS sockets or a single TRS insert socket for unbalanced operation in your mixer ?
The GSSL has electronic balanced inputs (2 conductors+shield) and electronic balanced non floating outputs (2 conductors+shield).

I used TRS (on the patch bay) to XLR balanced cables (i have XLR connections on my GssL) .. what do you mean by non floating please? .. never heard of that when it comes to balanced connections ...

probably the GSSLs gain reduction meter, not a signal level showing VU meter ...

I have a 1ma DC meter which seemed to be responding well to the incoming signal.

maybe outputs connected wrong.

Connections were fine, I had them double checked with someone else as well so I guess no problem there...

Be more specific. From your 'no output' you might be talking about the NE5532s.
If you shorted the output signal that connects to NE5532-pin7 to 0V reference voltage (inside the GSSL or in your insert jack wiring) would have this hot IC no output effect. Hot IC and distorted signal could be NE5532-pin1 shorted to 0V reference voltage instead. There are more ...

No it's the IC on the left of the input connection ... NE5534... but is it wrong to have bridge soldering if the pcb soldering pads were connected cause I'm not 100% sure about this?

Maybe right. Colour codes of transformer wires between different manufacturers are not standarized.
You want to know the correct operation of the +15VDC, -15VDC, +12VDC, -12VDC (and maybe the aux.+12VDC) supply rail voltages in respect to 0V reference voltage.

Yes, I need to do some research on how to measure these rail voltages cause unfortunately I'm not an electrical engineering and have no experience here...

Thanks a lot Harpo... much appreciated!

 

[Harpo]

I used TRS (on the patch bay) to XLR balanced cables (i have XLR connections on my GssL) .. what do you mean by non floating please? .. never heard of that when it comes to balanced connections ...

Wiring of insert jack is depending on mixer (FI Behringer, Allen&Heath,... TRS insert jack is tip=send, ring=return, or just the other way round FI Soundcraft,... TRS insert jack is ring=send, tip=return). With the other split insertwire end going to male and female XLR plugs, this makes a difference, hence my 'detailed' request.
The GSSL input exclusively operates the differential between XLR-pins2/3, so with an unbalanced signal feed you connect the TRS 'send' wire to XLR-in-pin2 and TRS shield to XLR-in-pin3. All XLR-pin1 connect to GSSL case in the shortest possible way and 0V reference voltage is connected to your case ground in one single spot.
The GSSL output is non floating balanced out. XLR-out-pin3 is the inverted signal from XLR-out-pin2, each referencing the GSSLs 0V reference voltage. If you link XLR-out-pin3 with XLR-out-pin1 (would be correct for a transformer floating output), you nearly short out this inverting opamp stage (and the chip will induce a whispering "this guy wants to fry me, don't buy his records" to every track you record for the next two weeks. ;D). For the GSSL output connecting to an unbalanced receiver (your mixers insert return jack), XLR-out-pin2 connects to the TRS 'return' wire and XLR-out-pin1 connects to wire shield. Leave XLR-out-pin3 unconnected. With given parts values and a connection for unbalanced out, you will lose 6dB, to come by by either increasing the makeup-gain pot setting for this amount, or decreasing the 27K resistors that connect to audio-VCAs-pin1 to 15K resistors (same value as feedback resistors in the VCA following current-to-voltage converter stage).
Operating the GSSL with impedance balanced output would only require two additional jumper wires and cutting two pcb traces, giving the advantage of same output level, no matter of connecting balanced or unbalanced, and not risking to short out the last opamp. A cross-coupled output stage with balanced line driver chips (THAT1646,...) on an addon pcb or piece of perfboard would be another alternative.

Connections were fine, I had them double checked with someone else as well so I guess no problem there...

maybe (hence my request for detail, IE TRS-tip goes to XLR-pin???...)

but is it wrong to have bridge soldering if the pcb soldering pads were connected cause I'm not 100% sure about this?

Most often wouldn't matter only IF these pcb pads in question would be connected in short distance by a pcb trace. Have a look at the GSSLs pcb self etch file for confirmation, if pads in question should be connecting to neighbouring pads or kept separate.
Your 'IC on the left  from the input XLR was getting hot very quickly' implies a condition exceeding parts limits, maybe caused by a short (your bridging soldering pads?) or wrong parts value(s) or orientation. This chip should not even get warm.

Yes, I need to do some research on how to measure these rail voltages cause unfortunately I'm not an electrical engineering and have no experience here...

Set your multimeter for measuring DC voltages in a range higher than expected, maybe 20VDC, just in case your multimeter is not auto-sensing. Plug your black wire probe into your meters [COM] terminal. Plug your red wire probe into your meters [V,Ohm,...] terminal. With GSSL powered on, you get a sign sensitive VDC readout with your black probe wire tip pointing to 0V reference voltage (the center pin of the aux.12VDC connector might come handy, or any spot at the big filled pcb traces) and red probe wire tip pointing at a spot you want to measure in respect to this 0V reference voltage, FI NE5534-pin7 or NE5532-pin8 for +15VDC, NE5534-pin4 or NE5532-pin4 for -15VDC, TL072-pin8 for +12VDC, TL072-pin4 for -12VDC, ...

 

[Jimmy1980]

I'm still trying to get through my issue. I've gotten to the point where I think I might just have to desolder all components and redo it to see if that solves the problem as I cannot find a short anywhere.

I have extreme clipping at the output section and I'm only measuring about -2.8v dc at pin 5 of the sidechain 2180 when I believe I should be measuring -15v dc, but can't find the source of the problem. If I jump pin 1 to 8 on the 2180's in the VCA section, the signal sounds clear but I'm bypassing the compression effect.

Question: When I send 0.775 AC voltage (1k tone at 0vu) from my DAW and trace the voltage through the PCB, I've noticed I can measure 0.775 AC at ground. Even on front panel of the chassis. Is this normal?

Any help is appreciated.

Thanks,

 

[rearturo]

Set your multimeter for measuring DC voltages in a range higher than expected, maybe 20VDC, just in case your multimeter is not auto-sensing. Plug your black wire probe into your meters [COM] terminal. Plug your red wire probe into your meters [V,Ohm,...] terminal. With GSSL powered on, you get a sign sensitive VDC readout with your black probe wire tip pointing to 0V reference voltage (the center pin of the aux.12VDC connector might come handy, or any spot at the big filled pcb traces) and red probe wire tip pointing at a spot you want to measure in respect to this 0V reference voltage, FI NE5534-pin7 or NE5532-pin8 for +15VDC, NE5534-pin4 or NE5532-pin4 for -15VDC, TL072-pin8 for +12VDC, TL072-pin4 for -12VDC, ...

Thanks a lot for all the info, much appreciated! I'll start working on it and hopefully manage to find the problem

 

[emanuele.stragliotto]

Hello everyone ... I have finished the assembly of my second compressor GSSL and found some problems ... I checked all voltages ... +15v and -15v are correct ... even the 12v rail is correct ... The signal seems to pass correctly and make-up gain control works fine ... instead the compressor do not work as well as the meter that shows no signs of life...Thanks for any help...

 

[emanuele.stragliotto]

...Also noticed that disconnecting the HPF bridge nothing happens...

 

[Harpo]

The signal seems to pass correctly and make-up gain control works fine ... instead the compressor do not work as well as the meter that shows no signs of life.

Double check parts values and parts orientation in the sidechain section, as well as wiring of the bypass switch.

...Also noticed that disconnecting the HPF bridge nothing happens...

??? interrupting signalflow in a 2nd spot won't make fixing easier. You either need a bridge or a cap at the HPF* provision. Look at the pcb traces for the correct two solder pads, the jumper or cap should connect to.

 

[thomasdf]

I was wondering: is it easy to add the autofade function just like the original SSL comp (switch + rate) to that kit?
From time to time it's a pretty useful feature..
Thomas

Ok got my answer after having a closer look at the SSL central section's schematics. The autofade is a different circuit that can be cloned I guess and that is placed before the comp... Maybe it would be a good idea to place it after the compression so the gain reduction remains the same while fading out?

Anybody would be tempted to get a closer look to this? I am toying with the idea of building a GSSL and the autofade would be a kool feature as I tend to use it a lot when needed on the real desk...

 

[AdoreaRecordingStudio]

Hello friends,

I've got what is otherwise a lovely GSSL sitting here.. However I am experiencing some high voltages across my rails (30.1 on +/- 15 rail and 20.2 on +/- 12 rail). I purchased this kit through the very pleasant Mr Rollins / micandmod.com and have not subbed any components.

I have spent hours confidently tracing my work and can't seem to figure out what is probably obvious for the brilliant collection of dudes in this site. Any ideas?