GSSL HELP THREAD!!!

[BladeSG]

The pictures from Kev's Group DIY page have what looks like a 100nF MKT cap there. I used 100nF caps in both of my GSSL's (still need to be racked) with 2180LA and 2180LB VCA's and there's no apparent problem I know of either.

http://recording.org/users/kev/G_SSLclone.htm

 

[daArry]

I wish these cap issues got sorted out once n for all lol...

Seems to come up every few months where then a few more discrepancies between the schem and whats marked on the PCB legends come to light...

If you look at the cap in question on the other VCA ckt you can see it's marked as .1 and the one by the side of the 5534 is 100p...

 

[RemcoV]

if i look at the schamatic i see (in the 202-emulation part) 2 100pf caps and 1 100n cap. So when there were some weird things going on in my comp so i looked at that, and also did some other things (removing the trimpot and 1M resistor. So i could very well be that not the caps but the trimmers were causing my troubles.. (if so, i'm sorry for the confusion)
I uses 2180LC vca's in my version.

Greetz
Remco

 

[Rogy]

Gentlemen, the cap question is already discussed and clearly answered before in this thread:

http://www.groupdiy.com/index.php?topic=2566

Jacob stated:

"The feedback cap in the emulation circuit is an experiment. It started out as a 100p stabilisation cap (at rather high frequency, admitted), but the 100nF with it's slight integration turned out to make the circuit work in a (subjectively) nicer way. Yes, you could argue that this wouldn't affect the "real" 202 if you use that one, but these will behave a bit different anyway."

So he suggests 100nF although 100p will also work.


As for the usage of That 2181 VCA's (which are NOT pre-trimmed), this document should be read:
http://www.thatcorp.com/desnotes.html#DN133

Changes I made to the SSL schematic for usage of 2181A are:

On the main VCA emulation circuit, omit the 68R resistor from pin 4 to GND.

On the main VCA emulation circuit, replace the 10K resistor from pin 4 to the "Distortion Trim" pin by a piece of wire (= short).

On the main VCA original circuit, replace the 1M resistor from the THD leg of the 202 to the 50K trim pot with a 680K resistor. The trim pot value remains the same (50K).

This is how I built mine; to be tested within a few days when I find the time.

Above values are for That 2181A; different values for 2181 B and C can be found in the That document I linked to above.

Just removing the 68R, 10K, 1M and 50K trim resistors totally defeats the distortion trim, which is not good for 2181 VCA's. This only works for PRE-TRIMMED 2180 VCA's.


Hope this helps!


Regards,

Rogy

 

[radiance]

Thanks Rogy!

 

[dukasound]

Hi
I exchange resistors after Rogy's sugestions and after reading That's explanations about substitute 2150 to 2181 (Rogy, thank you) :thumb:
Is schematic now right for use THAT 2181LA?

Just to know :roll:
Need exchanging parts if we use 2181 instead 2150 in sidechain?
Why VCA in sidechain is feeding with 12V?
THAT suggest 5K1 on pin5 (V-) and we use 3K9?
We stoped disscusing about 1K, 1M, 1N4148 and point "A" connections who is difference than original circuit?
Duka

 

[kryckmeister]

Any ideas??? I've been messing around with my SSL for a couple of days now, and it seems to be working, but no audio signal runs through it. I used a voltmeter (anyone?) and everything seems to be fine when checking the XLR connectors. I'm really out of ideas now.
Please help.

 

[radiance]

@ Viitalahde: I know this sounds obvious but do a thorough search for shorts / solder bridges in the side chain area. Also meassure if al the IC's voltages are correct.
I had a short once that made me crazy for a couple off day's. Only after meassuring all pins off the TL 074 and the TL 072 I found out where it was.
The pcb layout is very tight at some places...

 

[cipo]

Hi, i'm new in this forum. Maybe I mistaked to open a new topic (testing ssl). i think this is the right place.
Just finished my ssl clone with 2180 vca's. It seems to work well but i still have problems on low frequencies compression. If I send a 60 or 80 or 100 Hz sine signal to input and let it compress even just 4 db the result is distorted at fast attack and release. This happen until 400 Hz about. Could somebody help me?
Thank you and best compliments to everybody for the great cooperation.

 

[gyraf]

Cipo,

I believe this will happen with just about any compressor you try this with, at similar settings.

Low-frequency content and fast timing dosen't work out neither in theory nor in practice.

Jakob E.

 

[cipo]

ok, thank you Jackob.
One more question:about the threshold. Is it normal that in this project if I turn all the threshold up it respond with infinite compression and I can't hear any signal in output? ...or there is something i mistake?
thanks

 

[gyraf]

[quote author="cipo"]about the threshold. Is it normal that in this project if I turn all the threshold up it respond with infinite compression and I can't hear any signal in output? ...or there is something i mistake?[/quote]

Shouldn't do so. Check for shorts and component values around there, as always.

Jakob E.

 

[radiance]

Yes, solder bridges are a P.I.T.A.

 

[Rogy]

Answers to Duka's questions:

Is schematic now right for use THAT 2181LA?

Yes, it's correct.

Need exchanging parts if we use 2181 instead 2150 in sidechain?

Good question. It works witk the actual component values but maybe some things could be improved. I'll have to take a closer look at that later.

Why VCA in sidechain is feeding with 12V?

Because the VCA needs a very stable supply voltage. If the supply voltage fluctuates, the control voltage will also fluctuate and the gain reduction as well (VCA = current in/out device).

Even if the +/-15V fluctuates, the +/-12V will likely remain stable and the gain reduction as well.

THAT suggest 5K1 on pin5 (V-) and we use 3K9?

This resistor determines the current available to the device. Smaller resistor than recommended is not a problem because the VCA only uses the current it needs. If more is available, that's fine but doesn't change a thing. So 5K1 is fine, 3K9 also.

We stoped disscusing about 1K, 1M, 1N4148 and point "A" connections who is difference than original circuit?

The point A connection is same as the original on the PCB but is indicated wrong in the schematic.

Greetz,

Rogy

 

[gyraf]

Thanks, Rogy!

Jakob E.

 

[Greg]

On my next two SSLs, I plan to use a toggle switch for my bypass and power instead of the rotary. For the bypass, a DPDT switch is needed, right? And I just want to make sure that the switching needs to be ON-NONE-ON, correct? I think this means there will only be two selectable positions... I've seen the ON-OFF-ON, which I think will have three, and I don't think I want that.

And for power I just need one pole.

I just wanted to make sure because the toggles I'm looking at are kind of expensive.

 

[gyraf]

Yes, a double-pole on-on switch. One will have to disconnect sidechain, the other to disconnect makeup gain

 

[dukasound]

Anyone knows part number of SSL knobs from Sifam?

Thanks
Duka

 

[bubba_b]

Well, I just wrapped up my second SSL, plugged it in and flipped it on....wa-la! Nice bright blue lights!.....

......and no sound.

I have no idea what's wrong and don't know where to begin looking. It passes absolutely no signal, but gets power all the way through to the control board (otherwise there'd be no power light, right?). Here's what I know:

When I opened it up and compared it to my other one that works stellar, I noticed the (+) and (-) leads from the trafo to the IEC were backwards. So I swapped 'em and tried again....same result. Also, there's a pop when I connect or disconnect a cable from the left input, but not from the right or either output.

Help! Where do I start?

 

[radiance]

@Duka: knobs are S151.006 grey
caps are C151 blue

You will not get the same blue as a standard color. It's more greenish blue but it looks ok. I used them on my clone as well.