GSSL HELP THREAD!!!

[Harpo]

@Dave, something like this hookup drawing might help you for your transformer.

@ptron, trimmers should fit, if so required (IE THAT2180 is pretrimmed). Trimmer for meter adjustment isn't needed if you know what fixed resistor to use instead, but might come handy. When using trimmers, watch out for initial setting about centered.

@alessio, beautiful cases (just hope the sawtoothwasher police doesn't look twice ;D). Your problem might be heat related, so look out for cold solder junctions. Resistors across the release throw positions might help popping, but the timing will be all over the place with each R/C string in parallel to a more or lesser degree.

 

[mitsos]

Hey all, there is probably a very simple answer to this, but I can't find it.. How do I set up a mono ext sidechain input for a GSSL with turbo? 

thanks!


@alessio, nice cases! Are those little locking pots for adjusting meter, unity and makeup gain?

 

[Harpo]

Hey all, there is probably a very simple answer to this, but I can't find it.. How do I set up a mono ext sidechain input for a GSSL with turbo?

maybe this way

 

[Alessio]

@Harpo thanks for your answer but I dont understand what this means: "but the timing will be all over the place with each R/C string in parallel to a more or lesser degree".
And for the solder junctions... All over the compressor?   I probably need a scope to follow the signal and see where the distortion starts...

@Mitsos yes they are little multi turn trimpots

 

[mitsos]

alessio, very nice!

Harpo!!! I vote to change this thread to Harpo's GSSL Help thread!!  Thanks once again sir!!!

 

[Harpo]

@Harpo thanks for your answer but I dont understand what this means: "but the timing will be all over the place with each R/C string in parallel to a more or lesser degree".

Each release time is set by a cap with resistor in parallel, all separated for each switch step. When you link these steps with a resistor between each step position, these are no longer separated. The lower these linking resistor values are, the less jumpy/popping will be the switching between steps, but the paralleled values from neighbouring steps will even more change the selected release time. Pick your poison or get used to the standard behaviour.

And for the solder junctions... All over the compressor?   I probably need a scope to follow the signal and see where the distortion starts...

If both L+R are affected, the fault most probably will be located in a common to both part of the circuit - psu, sidechainfilter or sidechain. By swapping VCAs you might check/exclude, a maybe faulty sidechain VCA is causing this problem. As you have 2 units, it might be easiest to compare between these two. It might be a single bad solder connection.

 

[wordave]

i THINK is like this but someone tell me if im wrong please

http://www.sendspace.com/file/dyzdvl

Yes thank you, After a while of working out my idea seems to match yours. Can someone confirm this?

All my parts arrived today, Had a technician make a the PCBs at work. Just need to drill the holes myself!

Cheers
Dave

 

[Alessio]

Thanks harpo the problem is that the distortion is on both units and is getting worst and worst... Is not heat related because today was immediately audible.
???What is happening?

 

[Alessio]

and with no compression the units are fine...
The faster is the attack the worst is the distortion with or without the sidechain filter...
If I disconnect the turbo board the distortion is the same...

So I would say main PCB or control PCB!
I've tried to swap VCAs and TL074 nothing change!

Could be some brocken OPamps 5532 or 5534?

 

[mitsos]

Dave: Harpo posted a link for you a few 8-9 posts up...


Harpo, about the mono ext sidechain...

I looked at it a bit more now... I just send the incoming signal to one sidechain (ie, turbo) and not the other? The other sidechain gets disconnected?  

Is that a cap to the left of the 33K? DC blocking? How big would that have to be? I am guessing not too big since it looks nonpolar?

thanks!

 

[wordave]

Harpo posted regarding my power transformer question (Cheers mate much appreciated).

I was referring to the comment that I quoted, any takers?

 

[Harpo]

I looked at it a bit more now... I just send the incoming signal to one sidechain (ie, turbo) and not the other? The other sidechain gets disconnected?  

as you like, turbo or gssl, dice it out, doesn't matter. Your sidechain should only receive signal from the external source, so the sidechain feed from both debalancing line receivers get disconnected.

Is that a cap to the left of the 33K? DC blocking? How big would that have to be? I am guessing not too big since it looks nonpolar?

yupp. Assuming low impedance feed. Its a DC blocking hpf, cutoff at 1/(2*PI()*R*C), a 1uF would have this -3dB cutoff at 4.8Hz. A little smaller=higher cutoff will do and its only for sidechain.

 

[Harpo]

I was referring to the comment that I quoted, any takers?

sorry, me again. bypass DPDT toggle switch wiring

*credits go to Keith

 

[mitsos]

Wordave: this is how I wired mine:
http://www.groupdiy.com/index.php?topic=34219.0
hope that helps!


Hi Harpo, I'd like the turbo to be on full-time and use a DPDT switch to switch the ext sidechain, so my confusion is if the incoming (mono) signal has to be split to both sidechains? If so, how?

Thanks for the cap clarification. Got tons of 1uF's around!

cheers!

 

[Alessio]

I'm checking with the oscilloscope... really interesting!
Clean signal on the input side opamp 5534 pins 2,3 and 5,6
When I'm compressing I have almost a square wave on pins 1 and 14 of the TL074 but a nice sinewave on pin 7 both L and R channels.
But I have no signal on any 2180A...

When I'm not compressing I have a nice waveform on pin 7 and squarewave on 1.
And on the That 2180A nothing... I'm I becoming crazy?

The signals on the 5532 of the SSC boards are clean sinewave!

On the output side of the unit I have clean sinewave on Pins 1 and 7 of the 5532...

Is like all the vcas... are dead... no signal...

 

[wordave]

Thank You Harpo and Mistos!

Work begins on Friday, Wish me luck!

 

[Harpo]

Hi Harpo, I'd like the turbo to be on full-time and use a DPDT switch to switch the ext sidechain, so my confusion is if the incoming (mono) signal has to be split to both sidechains? If so, how?

In normal operation your full-time on turbo is connected to one side of the audio feed and the gssl-sidechain to the other, so both side audio is controlled, no matter what polarity the incoming audio signal is in relation to the other. If you don't disconnect both of these audio feeds from both sidechains, but keep one side connected, the sidechain will get triggered by this remaining audio signal as usual that might override your external mono feed, connected to the other sidechain. If you just want this overriding, use 2 other 47k summing resistors, resistors one side to each sidechain-in, both resistors other side to your external mono signal with DC blocking cap in front. Otherwise (usually) your external mono signal feeds the sidechain exclusivly. One side, the other or both doesn't matter, as the feed is mono and after rectification+ratio (there is no higher of two from mono) both sidechain paths recombine for attack/release and control both audio-VCAs with the same single control voltage.

 

[mitsos]

a! I think I see! So I only need one since it's a mono signal, it will work just like the (single sidechain) GSSL works. Guess I overthunk it. oops! Thanks for the explanation once more! Man do I owe you some beers! 

 

[Harpo]

But I have no signal on any 2180A...
Is like all the vcas... are dead... no signal...

All alife, else you'd be missing signal at gssl-out. VCAs are current-in/current-out devices.
Did you already check the +/-12V rails when this distortion happens.

 

[Alessio]

Actually you are right I still have signal on the output...  ???
So why this happens:
All the voltages going to the VCAs are correct like all the voltages going to the Op Amps... +12 -12 +15 -15... I've checked them multiple times.
With the oscilloscope (without the 2180A in the socket) I can see a clear sinewave on pin 1 (of the socket). When I insert the VCA I can't see anymore signal on pin 1 and I see square waves on the pins of the TL074.
So I think that somehow the VCA is doing something wrong... It makes sense?
I dont know what to do... The very first unit I've built without the SSC was working. The only thing I've changed is the power transformer.
I use this: http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=te62073&x=0&y=0
Instead of this: http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=te62063&x=0&y=0

Thanks very much Harpo you are the best!  ;D


Alessio