GSSL add-on help thread

[mingus77]

Oooh! Thanks! Will try to cut nr. 4. Sounds pretty awesome allready, but maybe it can get even better! Love this huge forum!

 

[mingus77]

Is there any bom for super sc out there? Can’t find any.
Going for my next build with to SSC and turbo.

 

[Potato Cakes]

After pillaging parts from my poor neglected GSSL w/Cavendish and Turbo, I'm finally going to put it back together and put it to use. I'm am going to also use the VCA quad adapter boards from Ramshackles as I like the way the quad VCA performs in my Mixbuzz, but there really isn't much information regarding building and implementing in this circuit. If I'm using 2180 (pretrimmed) would I need to do anything different on the main board like you would for using gold cans (swapping resistors, etc). I've emailed them a while back and haven't heard any thing and they are on break from Christmas to New Years currently. If anyone has used these particular VCA adapters would you be as so kind to share here?

Thanks!

Paul

 

[Potato Cakes]

It seems that further desoldering on this board has caused some failure that then caused more different failures when trying to trouble shoot the initial problem. I'm pretty sure the PCB has reached it limit on how much abuse it can take, which has been a significant amount. So I broke down and ordered a new board. When it arrives and I get all of this stuff up and running I'll share the information that I've acquired regarding these mods. I've built other ones using these add on boards and they've all operated great, the issue here is this was one of my first forays into DIY and the evidence of errors is plentiful.

Thanks!

Paul

 

[Potato Cakes]

Alrighty.

I ordered another PCB from Gustav to start from scratch and replaced all of the power ICs as I fried one of them and I thought it would be safe to just replace all of them. I got everything back up and running and so I'm sharing some notes for all of the mods I did that seem to be very common and very worth it.

VCA adapters from Ramshackle:

There is no build manual for these on their site and I have been unable to receive a reply from them for any build information or component clarification, so I made some decisions based off of similar quad VCA adapters. For the boards, there are markings for all of the silkscreen items except the ones labeled "CB" (capacitor bypass) and I think for the VCA chips as well. I used .1uF ceramics for the bypass and the VCAs are either 2181 or 2180, whichever is preferred. I like the pre trimmed 2180 and I also used the A version, which gets expensive quickly when you need to order 8 of them. I used the same pins that are required for any of the DOA builds found on this site as I planned on installing sockets on the main board. On the GSSL PCB, all of the components in the silkscreen boxes labeled Left/Right VCA are to be omitted. For the resistors labeled 27K* on the end of both VCA silkscreen boxes need to be changed to 15k or a trimmer as this is where you will make adjustments for unity gain. The closest I had on hand was 16k2, but it was close enough as I was going to be using the trimmer on the Cavendish board for final adjustments. I have seen smart people say to change some of the resistors in the sidechain to compensate for the new VCA circuit, and other smart people say don't bother. I'm lazy and I chose not to bother. It seems to be fine leaving the values as is.

Cavendish:

This a wonderful modification for the GSSL and the instructions are pretty simple, but there are some items that were not directly addressed in the manual that may give a builder pause how to wire it. First is the output 5 pin header. This is meant to be wired exactly how it is on the GSSL output with the idea is if you add this to an existing working unit, you just move the cable mounted header to this board. Very clever on Expat's part. The other thing is which DIP8 connections are in and which ones are out. IC1 and 2 (NE5534) are input and 3 and 4 are output (NE5532). Don't mix these up as the pins for power are different. I made this mistake with DOAs installed and it made one of them so hot that it melted the solder holding one of the power transistors in place. I would also recommend using a multi turn trimmer to more easily make fine adjustments for the output trim. The instructions say to attach a cable from the ground point on the Cavendish board to a ground connection near the DIP8 I/O on the GSSL board. Any build that I do anymore I adhere to Ian Thompson's Grounding 101. I highly recommend searching for it on this site and reading it until it is fully understood. I applied these principles to this build where each PCB makes it's ground connection directly to the star ground point on the chassis, so I used the center header output pin to go to the star ground point. I did the same for the PSU, Turbo, and GSSL board. Also, be very careful when mounting the transformers. The copper trace carrying the audio signal to the transformer is near the screw mounting hole, making a potential short between that and the ground plane if the washer or nut being used breaks the surface of the solder mask. Also, the solder pads do not like to be subjected to correcting mistakes, so don't or you will be testing continuity between all of the points.

For the output section of the GSSL, the electrolytics (100uF) and the 47k resistors can be omitted. I was following a picture that SSL Tech has post of his build on the Cavendish build thread that just had the ceramic caps on the output section, but he was doing this to the older version board, which caused some head scratching when I wasn't getting any output. I consulted the GSSL schematic and started adding parts that looked like they needed to be there to let signal pass and then it did.

Also, don't forget to do that pin swap on IC 3 and 4 (output - NE5532).

Turbo:

I did mine permanently in circuit. After building a couple of these, I feel this is the best option for making something that is to resemble the 4000 console bus compressor. If you want one with all of the options, then I would recommend building a MixBuzz2 from DIY-Racked, which I have one in my FOH fly rack. It's a lot less headache and most everything is done on board. I installed this guy per the instructions except for the ground connection, which went straight to the star ground.


Socket installation on the GSSL board:

Use the Harwin sockets as the larger Mil-Max ones require a hole to be drilled that is larger than the solder pad. Make a note of which solder pads in the VCA section near a socket point are actually supposed to be connected and which ones are not. There is at least one pad per VCA socket connection that are very close but are not to be connected. This will be less apparent then you do actually drill the hole and enlarge the solder pad. Use a drill bit that will be just big enough to push the sockets in place and drill from the bottom (solder side) to the top (component side) and use a slow RPM speed. After you solder the sockets in place double check with a multimeter to ensure there is continuity where there should be. If not, you'll need to jump the copper traces that need to be connected.


I've attached a photo of the mess once I brought this sadly wired build to the end of it's long very painful journey. But now that I've installed a new faceplate that isn't full of random holes drilled by hand, I'm going to put it in my studio rack and actually get some use out of it. Oh, one last thing, put heatsinks on your PSU regulators, anytime you can actually fit on on there. I've had some builds that I would be fine without them but eventually the regulators got hot and the power sagged below usable operating power for the circuit. Since you'll be adding more demand than what was intended for this circuit, adding heatsinks will make consistent power one less thing to think about.

Thanks!

Paul

 

[Potato Cakes]

One more pic.

 

[Gustav]

https://www.pcbgrinder.com/blog/gssl-sc-turbo

Just did this, which may be useful to some

Gustav

 

[salomonander]

hey guys,
how would i balance the external sidechain input on the ssc board? it seems the signal gets routed directly (via a coupling cap) into the sidechain.
could i just pop a 1:1 transformer in between? if so, is a 600:600 ohm fine or would i need a 10k:10k? cheers

 

[Gustav]

hey guys,
how would i balance the external sidechain input on the ssc board? it seems the signal gets routed directly (via a coupling cap) into the sidechain.
could i just pop a 1:1 transformer in between? if so, is a 600:600 ohm fine or would i need a 10k:10k? cheers

You could use an opamp.

But why?

Gustav

 

[Potato Cakes]

You could use an opamp.

But why?

Gustav

I second. Why?

The external side chain is changing the signal that makes compression happen, but it doesn't feed into the audio path. So there isn't any need to balance it other than you've run out of things to do.

Thanks!

Paul

 

[salomonander]

thanks guys,
too late i already put them in
now, maybe you can help me with an issue im having since installing the sidechain board. im not getting unity gain anymore. i changed nothing about the rest of the wiring (except briging the all bypass connections on the switch pcb). does anyone have an idea whats wrong? cheers

ps: do i need to change the two 20k resistors on the ssc board to 10k ones?

 

[Potato Cakes]

The side chain board I have has trimmers on it for setting unity gain.

Thanks!

Paul

Corrected Below

 

[salomonander]

The side chain board I have has trimmers on it for setting unity gain.

Thanks!

Paul

hey Paul,
thanks. so trimmers instead of the 20k resistors? which parts determine unity gain`?

 

[Potato Cakes]

I'm looking at my board and I was mistaken. The trimmers are for setting the TM and TL side chain settings. The Crush 'n' Blend had the trimmers for setting unity.

You should be getting unity as you can see that the 47k resistors on the main board you are removing to make the connection to the SSC are not in the audio path. All you're doing is picking off signal before the DBX202 or emulator circuit to the side chain, but you aren't interrupting it. If you are getting a decrease in output then that means some noise or electrical signal is triggering the THAT 2180/1 which is then sending signal to the VCA's CV input which is gain reducing the audio signal. You've got something with the SSC board that isn't quite happy.

Thanks!

Paul

 

[salomonander]

thanks mate it works. was just a stupid mistake (took a resistor out of the wrong bag). still, those 10k instead of 20k are correct? i think i see the same on your board in the black market but i might be wrong. cheers

ps: anyone know if pins need to be swapped on cavendish PG1.1?

 

[Potato Cakes]

Mine are 20k as per the silkscreening. The red looks a little on the brown side in the photo, but it is 20k.

THanks!

Paul

 

[salomonander]

hey,
maybe you guys can help with another issue. i built a relay bypass board for the gssl. very simple with 4 relays. i did use flyback diodes but got clicks whenever engaging and disengaging. i just did some research and added a 200ohm resistor in series with the diode and a 20nf cap across the relay. but its still clicky. doesnt matter if i switch the 12v or ground. im taking the aux 12v off the main board. any ideas? cheers

 

[gyraf]

Does it still click when you switch with shorted inputs? Otherwise your clicks are not from the relay coils, but from switching in audio or DC signal, and in that case you can't avoid the clicks.

Jakob E.

 

[salomonander]

Does it still click when you switch with shorted inputs? Otherwise your clicks are not from the relay coils, but from switching in audio or DC signal, and in that case you can't avoid the clicks.

Jakob E.

thanks Jakob,
yes it does. i attached a schematic of my bypass board. im a bit of a noob so maybe i messed something up. i only drew 2 relais. the other two are connected just the same. in case you spot an error please let me know. im taking the voltage off the main pcb. same with the ground. i tried using a seperate ground connection to star ground but that did not work. i assune the 12v rail has its own earth..... cheers!

 

[salomonander]

anyone have an idea what might be wrong? also, when engaging my relays (they are bypassing with no voltage) my power led and my vu led slightly dim. maybe the psu isnt strong enough (i run main board, turbo, 2x ssc, crc plus 4x 12v relays)?
i do still have my rectifier soldered in on the main board although using crc....