Turbo Board issue on GSSL

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innercityman

Well-known member
Joined
May 12, 2016
Messages
442
Location
France
Hi everyone,

Hi everyone, as mentioned on the title, I would like to wire the turbo board and make it work permanently but as the kit I bought from Gustav have an HPF function switching on & off, I would like to retain this function. I can't find any thread talking about this.
So my first question is: is it possible ? and if yes, how to wire it ?

This is my first built and for now the GSSL works nicely.

Thanks for your advices !

UPDATE DECEMBER 27/2016

To explain the problem I got...I installed a turbo board on my GSSL and everything seemed to work fine until I realized that something was going wrong. My GSSL is inserted on the main mix buss of my analog console and it seems to work ok as I got a compressed signal on both my left and right monitors, but when muting right side of my stereo mix, left side signal is not compressed and the needle of the GSSL vu meter stays at 0. When muting left side, right side signal is compressed, so left side signal, the one that is sent to the turbo board seems to not go into the side chain, but as I said, I have both sides compressed when sending a stereo signal. Any advices???
 
innercityman said:
Hi everyone, as mentioned on the title, I would like to wire the turbo board and make it work permanently but as the kit I bought from Gustav have an HPF function switching on & off, I would like to retain this function. I can't find any thread talking about this.
So my first question is: is it possible ? and if yes, how to wire it ?

This is my first built and for now the GSSL works nicely.

Thanks for your advices !

I can't find a schematic for the turbo board, but I did find a picture, and I see the 22uF cap is populated on the board, so Im concluding that part of the side chain doubling is included.

I would gladly help you by drawing it onto a schematic or board layout picture, but I can't find any. You just need to switch the 100nF cap into the signal path before the 22uF cap on the turbo board, just like you're already doing in the side chain.

To elaborate

On the basic build, we are switching a cap in and out of the signal path just before the 22uF cap with a single pole switch to make the high pass. To do it on the turbo as well, you need a DPDT switch (one pole for what you are already doing, another pole to copy  the same with another 100nF cap to the turbo)

http://www.futurlec.com/Pictures/DPDT11.jpg

If you lift the + leg of the 22uF cap off the board on the turbo board, the pad you lifted the leg from, and the leg of the component will correspond to the two spots you are mounting the switch on the existing build.

I am not sure if I overcomplicated things for you. Let me know if it makes sense. I can do an ugly, but informative drawing, if all else fails :)

Gustav
 
Ok, thanks for your help Gustav. This seems clear. I will try that as soon as I'll got  a DPDT switch and I'll let you know. One last question... On the main board of the GSSL, there is 3 solder pads where the HPF wires are connected, but only 2 are wired to the single pole switch, so do I need to connect the free middle solder pad to the DPDT switch ?
 
innercityman said:
there is 3 solder pads where the HPF wires are connected, but only 2 are wired to the single pole switch, so do I need to connect the free middle solder pad to the DPDT switch ?

No, dont change anything on the existing set-up, just copy it to one side of the double switch, then do the same on the other side, drawing from the spots I described.

Gustav
 
Hey Gustav, just wanna thank you for the good advice... Just follow your instructions and the comp works perfectly with the turbo board and the hpf function is still working.
I must admit that with the turbo board installed, the need for the hpf is not so crucial and you still can here the difference between the signal with or without the hpf engaged but not so significantly. the thing is just that as the kit offers this function, I just wanted to retain it. So again, thanks for your help !
 
Just jumping in to confirm that the HPF function works on the sidechain the same way that it does on the original. -Anyone who wants to retain it with a turbo just do exactly as Gustav suggested.

That said; -as observed earlier- once the turbo is added,  there's less need to have the HPF as an option.

The GSSL ( as different from the SSL buss limiter design) had an over-sensitivity to large signals in the center of the stereo signal.... usual examples are kick drum, bass instruments etc. -As a result, the HPF was a "band-aid" idea to reduce the signal "pump" from  these sources, but -since it doesn't help with snare drums (which have less LF content) etc.- it's far from being a "correct" solution.

The Turbo adds the second sidechain, and returns the unit to the original SSL design, which doesn't have the same center-sensitivity issues, so can be left full-bandwidth.

Since the HPF reduces the sensitivity to LF content, it helps "hide" the center sensitivity, but it also  stops the unit from compressing bass instruments 'correctly' compared to the original ("turbo"-ed) SSL design... for this reason, I have never added the HPF function, and -as observed earlier- it's not really "needed"

It's an easy thing to add though, as described by Gustav. If your front panel already has it, just do the "small capacitor" trick using a second pole on the switch.

-If you want to make the unit Turbo-Switchable however, the switch may be a candidate for 'repurposing' to be a "GSSL/Turbo" mode switch... this may prove to be more of an interesting option in the long run, in my experience.

Hoep that helps!
Keef
 
Hi Gustav,

If you lift the + leg of the 22uF cap off the board on the turbo board, the pad you lifted the leg from, and the leg of the component will correspond to the two spots you are mounting the switch on the existing build.

So what I did is that I took the signal coming from the turbo board, from the free hole where the + leg of the 22uf cap was soldered, and wired it to the middle pin  (pole) of the switch, and sent back the filtered or non filtered signal (depending on the switch position) to the + lifted leg of the 22uf cap. Is it correct ?
 
Regarding the GSSL schematic, I've noticed that the signal is coming to the + side off the 22uf cap, so what Gustav advised me to do seems to be correct (sorry for my poor knowledges, I'm learning everyday). So what I did should work, sending the signal arriving on + pole of the cap to the switch and returning it with or without the 100nf HPF cap to the lifted leg of the 22uf cap is what needs to be done. I will try as soon as I can to restore back the connection of the lifted leg of the cap and the turbo pcb to see if the issue remains. I precise that the issue I got is that left side signal seems to not go into the turbo board sidechain, and left side signal isn't compressed, but when sending a stereo signal into the GSSL, both sides are compressed.
 
Hi,

I must admit that I'm a bit disappointed by the poor interest of my thread, anyway I don't give up so... I've been able to do a test today, just to see if the problem came from the switch wiring or not, so I bypassed the HPF switch and turned back the connection between the + leg of the 22u cap and the turbo board, and the issue remains. So it's not a wiring problem with the HPF switch... I double checked the wiring of the turbo board and everything is ok. I checked my resistors values, it's ok... I'm getting mad! Could it be the VCA that is "dead" or the TL074...? Don't know how to test them.
 
innercityman said:
Hi,

I must admit that I'm a bit disappointed by the poor interest of my thread, anyway I don't give up so...

First, check the "basic" build, with no mods, then add the turbo, make sure everything works, then - do the alternative switch layout.

At the moment, there are too many variables to make a real contribution to solving the problem. I am sure its not a lack of interest in helping in general :)

Gustav
 
First, check the "basic" build, with no mods, then add the turbo, make sure everything works, then - do the alternative switch layout.

Hey Gustav, thanks for the reply.

In fact, I made few tests... First of all, I switched the turbo board and came back to the original GSSL design and everything is fine. My GSSL "unmoded" works just as it should, whatever one side signal is muted or not, . And I also bypassed the switch by reconnecting the 22uf cap of the turbo board where it should be originally, and the problem remains the same. So after these tests, what I can say is that the problem doesn't come from the HPF wiring, not either from the GSSL itself but surely from the turbo mod. I'm pretty sure that if I solder back the lifted leg of the 47k resistor on the GSSL board, and I lift the leg of the other 47k resistor just beside to solder my SC input wire for turbo board, I will get the same weird behavior but on right side. In the same time, this is not such a big deal as the unit seems to work properly when sending a stereo signal on it, but I'm pretty sure there's a problem unless someone tells me that it is normal. What I don't understand is why the left side signal is uncompressed when muting right side or turning the master channel pan knob all the way to left side, but  both sides are compressed when sending a stereo signal to the unit. That would be nice to have the turbo board layout or schematic, but it seems that a lot of people around already tried to get it without any success.
 

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