GSSL HELP THREAD!!!

[mfdu]

just got my boards from CHef @ audiokitchen. very tidy. i'll be getting into part stuffing this weekend.
dont have the VCA's (THAT Corp haven't felt like returning my emails yet) but i also have to finish my fault finding on my pair of 1176's, so i'll be busy enough i think.

cheers.

chris.

 

[tree]

Thanks Much Chris...

Yes, those are the points i used for referencing the DC and since my meter showed 0 on the - 15 side, i suspected and replaced reg. 7915.

NOW, with no socketted bits mounted on the card, the -15 rail reads between -15.30 and -15.32.
On the +15 rail i get between +14.98 and +15.00.

How close to identical should these rails be???

Real glad just to see anything on the -15 side.

 

[chrissugar]

Those voltages are OK, you don't have to have exactly 15V.
OK so now you have the good voltages. next logical step is to put one by one the 5532 and 5534 opamps and measure the voltages at the coresponding pins. Add one chip at a time, measure, if OK add next chip, and so on and so on till you find the chip that kills the -15V.
If everything is OK you can add the VCAs and measure the voltages on their pins.
BE CAREFUL! Avoid to make shorts between pins while you measure because in some situations it can be fatal to some chips.

chrissugar

 

[tree]

Great. Thanks Chris.
Was just about to plug everything and switch it on to "see" what happens :green:
but appreciate the need for patience to save little disasters.

 

[chrissugar]

That is the way to do it with the least amount of dammage. :grin:

chrissugar

 

[gyraf]

(Good work here, Christian :thumb: - Thanks!)

 

[chrissugar]

Thank you Jakob for the apreciation, but it is nothing compared to what you do for our comunity. You are the man. :thumb:

chrissugar

 

[tree]

Sorry to keep bothering....for a minute there bet, you thought you'd seen the last of my particular greenness, but noooooooo

Been pouring over meta on this, haven't seen anything specifically like it....though there are some threads indicating tlo72 might have something to do with it???

Symptom;
Does not sound as if compressing.
Even with ratio set at 10:1 and threshhld almost full counter clockwise, unit does not SOund as if compressing.

-Meter works.
-Output gain works.
-Bypass works.
-Threshold seems to work - reads hotter on meter when turning counter clockwise - though reduces apparent output volume more extremely than i would expect.

Does this sound like similar issue as meta thread,
http://www.groupdiy.com/index.php?topic=5324???

Very Very Thankful for All your help.

 

[chrissugar]

[quote author="tree"]
Even with ratio set at 10:1 and threshhld almost full counter clockwise, unit does not SOund as if compressing.

-Meter works.
-Output gain works.
-Bypass works.
-Threshold seems to work - reads hotter on meter when turning counter clockwise - though reduces apparent output volume more extremely than i would expect.
[/quote]

If the threshold works, the meter show activity and the gain is reduced it is compressing. That is how compression works. You should compensate with makeup gain.

Although it is possible you have a ratio problem. If you use for example 2180 you should change the 100K resistor from pin8 of TL074 to pin2 of TL072 (ON SCHEMATIC!!! There is a difference between the schematic and PCB, the pins of the two opamps in TL072 are swaped on the PCB) to 120K.
That will make the ratios to work correctly.

chrissugar

 

[tree]

Hmmm.
Sorry, Christian, still doesn't sound like compression to my ear,... Threshold control seems to be acting more like a counter volume control, if you know what i mean - when set fully counter clockwise and with gain m.u. fully cranked clockwise (regardless of ratio, attck or release settings) almost no signal is present. Also, for instance it doesn't seem to pull UP drum room ambience much at all compared to my other compressors (smart C1, tubetech laca2b, 1176, etc... i am also a little familiar with original ssl bus comp from mixing on e series desks).
[/quote]
"If you use for example 2180 you should change the 100K resistor from pin8 of TL074 to pin2 of TL072 (ON SCHEMATIC!!! There is a difference between the schematic and PCB, the pins of the two opamps in TL072 are swaped on the PCB) to 120K.
That will make the ratios to work correctly"

Sorry again, i'm very new at this - getting a bit dizzy....
I am using 2180LA s thruout Gustav's board.
If looking at pcb component side, - with 3 vcas accross the bottom- am i right that the 100k on TLO74 pin 8 you are talking about is located directly below TLO74 as the topmost of 4 resistors; 100k, 620k,100k and 220K??
And do you mean i should just take that 100k out and replace it with 120k??
(Its trace doesn't seem to go to pin 2 of TLO72 on Gustav's pcb or am i wrong)

Pin 2 of TLO72 on the pcb seems to go to 100p, 56k and 100R etc., no?

Hope you forgive the green ramble. I must repeat, i really appreciate your help. I'm hoping maybe the unit is compressing but at very low/light ratio or something that i can't quite recognize as compression?

:?

 

[chrissugar]

[quote author="tree"]
If looking at pcb component side, - with 3 vcas accross the bottom- am i right that the 100k on TLO74 pin 8 you are talking about is located directly below TLO74 as the topmost of 4 resistors; 100k, 620k,100k and 220K??
And do you mean i should just take that 100k out and replace it with 120k??
[/quote]

Exactly. Change that 100K resistor to 120K (yes, the topmost from that group of four)
I especially specified that I mentioned ON SCHEMATIC because there is a little error between the schematic and PCB (opamp1 of TL072 on schematic is opamp 2 on PCB, and opamp2 on schematic is opamp1 on PCB).

[quote author="tree"]
Hope you forgive the green ramble. I must repeat, i really appreciate your help. I'm hoping maybe the unit is compressing but at very low/light ratio or something that i can't quite recognize as compression?
[/quote]

No problem, we are here to help each other. :thumb:
It looks like you have a ratio problem so if you change that 100K to 120K it will work OK.
Do it, and report back to see if your problem is gone.

chrissugar

 

[chrissugar]

Here is a thread dedicated to the ratio problem:
http://www.groupdiy.com/index.php?topic=944&start=0

A quote from that thread:
[quote author="Steffen"]
without the mod the 2:1 ratio was something like 3.5:1 and 10:1 was inverse!!! 10 dB input level boost was resulting in 0.5dB level drop on the output! (ratio = 10: -0.5 ???)
[/quote]

I have the feeling that you have that "inverse" problem. I had it with my first SSL comp and after the mod the ratios were correct. Read my posts in that thread, I made a comparison between the two kind of ratio corrections and had a verdict.

 

[drpat]

...

 

[tree]

Great. Thanks, Chris. Thanks drpat.
I'll report back after re examining threads and testing.
:thumb:

 

[tree]

after much thread reading again... changed the following...

-100k to 120k between 074 and 072
-the noted 15k to 27ks for unity gain mod
-put 47k in series onto positive leg of threshold (series = one leg of res to pot + post, other leg to + wire, correct?)

FINALLY got to do some testing today and am quite sure that although i can at least hear some compression artifacts going on now, something is still WAY off somewhere. Try as i might, i cannot come close to getting the sound of say,the kik& snare to "pump" in the slightest, if you know what i mean.
RATIO, ATTACK and RELEASE seem to act only very very subtley when A/B'd to identical settings and program material thru my alan smart C1. I'm sure that the two should by no means be identical sounding but shouldn't the effect of pumping (16db @ 4:1 on kik and sn, for instance)be audible on GSSL? My GSSL currently seems to almost do nothing in this case except decrease volume via threshold.

The THRESHOLD is acting more like a volume control - when fully counter CW almost all signal is gone and can not be made up for by GAIN pot (even when GAIN cranked fully CW).

Have gone over and gone over the main board - cleaning and resoldering any iffy looking joints etc.
Is there some area i should zero in on as far as rechecking resistor values goes?

Feel like i have about 20db gain reduction on my brain that i'd really rather use on a kik and snare.

thanks for any help or direction you might have.

 

[drpat]

...

 

[tree]

thanks drpat.
do you mean front panel "control boards"?

Meant to mention also that the 120k (that i put in place of the 100k as suggested)
looked to be about 117k on my meter before i put it in....it was the only one i had. Make a dif?

 

[tree]

Have gone over the control board many times redoing any suspicious looking soldering, checking rechecking wiring of knobs and all resistor values (by colour code)everything seems good there, but still no go.

Voltages seem good too, but the only things that seem to be truly doing what they should are volume and bypass. Threshold acting only as a kind of volume control that reduces gain to almost null when cranked fully counter c.w.- even when gain make up is cranked fully c.w.

So i guess it's time to start pulling stuff out of the main board and checking voltages? Or?

Considering these odd symptoms, does anyone have any suggestions as to where to start this process or how - bearing in mind my cursed green nature...???

Frustrated but willing. Thanks any and all.
:?

 

[gyraf]

Tree,

Try tracing the sidechain signal all way through to DC control voltage at the vca's..

Jakob E.

 

[tree]

Hi Jakob;
i see. will do.

s.