GSSL HELP THREAD!!!

[dave293]

Since my last post I swapped out the VCA in the turbo sidechain and now the unit has developed a problem where it seems to turn itself off after being turned on for a second or so.

Your problem was not sidechain related (else the left side audio would have been affected as well).
Look out for shorts and correct orientation of your VCA at the Turbo board.

Have not found and shorts as of yet, I will have another pass through and check. But I tried firing up the unit without the turbo board connected and the power problem still occurs so I am thinking I have two separate issues.

With the power problem, after powering up the unit for a second or so the brightness dims completely, but adjusting the threshold knob changes the brightness of the led. Turning the threshold counter clockwise (or all the way down) the LED returns to full brightness. Which has me scratching my head.

 

[Harpo]

With the power problem, after powering up the unit for a second or so the brightness dims completely, but adjusting the threshold knob changes the brightness of the led. Turning the threshold counter clockwise (or all the way down) the LED returns to full brightness. Which has me scratching my head.

Look out for a short between 'F' and '+12V' (probably at either side of the connection between main-pcb and control-pcb). A magnifying glas might be useful to spot and remove the short (solder blob, piece of stranded wire, ...).

 

[tabuckner]

Hi All,

I've resolved my previous voltage deficiencies by replacing the transformer but I've come across a new error.
-The Unit passes audio in bypass with no error.
-The Unit will also pass a signal that can be affected by the make-up gain.
    -When compression is engaged the Unit will exhibit some characteristics of compression, however, there does not appear to be a true monitoring of the input signals.

By that what I mean to say is; the compression can be altered by changing any of the temporal or ratio parameters (attack, release, ratio). The compression is also drastically altered by raising or lowering the threshold. But there does not appear to be any sort of control voltage telling the compressor what to listen to.

Has this error occurred with anyone else?

Does anyone have any information or tips to lend?

What components could be causing the apparent lack of signal following?

Thanks,
Taylor A.

 

[tabuckner]

Just a quick addendum:

I have checked the wiring to my bypass switch several times and have concluded that the issue does not lay in that aspect of the circuit.

 

[monkey8911]

Hey Guys, I´m new to the forum and was wondering if you could help me with a problem that I can´t find a reason for.
I´m building the New GSSL, I have it all completed but ran into two little problems.

1. The bigger one:
When I switch on the power on the compressor the first time of plugging in, the gain reduction meter starts to show about 8-12 dB of reduction without any audio going into it. The LEDs in the meter do not light up and the compressor does not work.

BUT, and this is a big but, when I switch it off, the LED will flash after about one second (when the meter falls back to zero), and when I turn the compressor on again, it works just fine.

I find this very strange. The compressor will do this every 2nd time I turn the power on - which means that I have to turn it on and off once before I can turn it on and make it work.

Do you guys have an idea what could cause this problem?

Thanks a lot for your help in advance!!!

Martin

 

[ilfungo]

Hi
I've ended another GSSL+Turbo + carnhill output transformer
he sound great but I've a strange problem,
all work well but the make up gain have a strange behavior
When i turn  the make up,  L-R level go a bit off
when the pot is at minimum the channel are perfectly
matched...
Ideas?
Thanks


Ps . Hi monkey8911
search in the forum, it is widely discussed
It's a latchup problem
http://groupdiy.com/index.php?topic=47.6020

 

[Harpo]

Hi
I've ended another GSSL+Turbo + carnhill output transformer
he sound great but I've a strange problem,
all work well but the make up gain have a strange behavior
When i turn  the make up,  L-R level go a bit off
when the pot is at minimum the channel are perfectly
matched...

With same signal feeding both inputs, switch GSSL to bypass and measure both outputs to adjust/tweak unity gain level.
Should read the same as input voltage, else substitute the 27K* Audio-VCA input resistors (located left side of the Audio-VCA-module outline) with a 50K trimmer/rheostat, trimmers initial value about centered for 30K, and adjust for exactly same output voltage as input voltage.

With same signal feeding both inputs, disengage bypass switch (GSSL now is in compressor mode) and measure both outputs.
Both output voltages should read the same, no matter what amount of makeup gain dialed in, else substitute (both or only one of) the 1K Audio-VCA control voltage input resistors (located right side of the Audio-VCA-module outline) with a 2K trimmer/rheostat, trimmers initial value centered for 1K, and adjust for exactly the same output voltage as the other output level to trim out resistor and VCA ec- tolerances.
If you don't have a DBX202C VCA-module fitted, but use the DBX202C substitution circuit with buffered 1K/120R attenuator and a THAT218x, this will work as well. (with substitution circuit you always jumper the 1K resistor located next to THAT218x pin1, else you have a (1K+1K)/120R attenuator and the GSSL operates at only half of its usual compression).

 

[ilfungo]

Thanks Harpo!!!
Problem solved, bad tl072....
Thanks!

 

[ilfungo]

Hi Harpo
last question ( I hope)
I used  Carnhill 2281 on output, changing the output resistance from 100r to 22r...
I do not know how to calculate zobel network, for now I used as on Neve1290 preamp  0 .01 uf +1 k5 resistor.
you think might go well?
Thanks!

 

[Harpo]

I used  Carnhill 2281 on output, changing the output resistance from 100r to 22r...
I do not know how to calculate zobel network, for now I used as on Neve1290 preamp  0 .01 uf +1 k5 resistor.

...if needed at all. I'd try without a zobel first and fit the HF damping parts only if doubtfully needed at all.
Carnhill 2281 both primary and secondary windings connected in series for 600R:600R 1:1 ratio (pin 2+4 joined and pin 6+7 joined) ?

Your 'bad TL072' is not the source of a L/R level mismatch. TL072-pin1 controls both L/R sidechain VCAs and TL072-pin7 controls both L/R audio-VCAs by the same generated control voltage, so a mismatch will most likely be caused by parts tolerances after the TL072 outputs, so downstream the split to the left side and to the right side.

 

[ilfungo]

I'm using 2281 in 1:2 configuration ...

 

[Harpo]

I'm using 2281 in 1:2 configuration ...

.. so both NE5532s have to (and will have a hard time to) drive 150R instead of 600R and GSSL bypassed give out a +6dB boosted signal from your 1:2 stepup ratio.

 

[ilfungo]

I Know, but +6 db is for resolve one problem on my console...
"so both NE5532s have to (and will have a hard time to) drive 150R instead of 600R "
Do you think that can be a problem?

 

[Harpo]

I Know, but +6 db is for resolve one problem on my console...
"so both NE5532s have to (and will have a hard time to) drive 150R instead of 600R "
Do you think that can be a problem?

Yes. Easier to fix with a same feedback resistor value as input resistor value in front of the audio-VCAs, IE replace the 15K feedback Rs with 27K resistors.

 

[tabuckner]

Just a quick addendum:

I have checked the wiring to my bypass switch several times and have concluded that the issue does not lay in that aspect of the circuit.

Hi All,

I've resolved my previous voltage deficiencies by replacing the transformer but I've come across a new error.
-The Unit passes audio in bypass with no error.
-The Unit will also pass a signal that can be affected by the make-up gain.
    -When compression is engaged the Unit will exhibit some characteristics of compression, however, there does not appear to be a true monitoring of the input signals.

By that what I mean to say is; the compression can be altered by changing any of the temporal or ratio parameters (attack, release, ratio). The compression is also drastically altered by raising or lowering the threshold. But there does not appear to be any sort of control voltage telling the compressor what to listen to.

Has this error occurred with anyone else?

Does anyone have any information or tips to lend?

What components could be causing the apparent lack of signal following?

Thanks,
Taylor A.

 

[Harpo]

What components could be causing the apparent lack of signal following?

The amount of signal level not reaching/exceeding threshold level, else the unit seems to be operating as it should from your wording without giving a single number.

 

[museic]

Now that the sifam ppm 14 is no longer made what are people using for meters? Just did a search of ebay but none of them fit a 1u case. I like the side to side ones like gyraf used on his. Anyone know a us supplier?

 

[gyraf]

I think maybe the good people at PCBGrinder has found something like that: Look under "Hard Candy"..

Jakob E.

 

[museic]

Sweet! Just what I was looking for.

 

[thomasdf]

I was wondering: is it easy to add the autofade function just like the original SSL comp (switch + rate) to that kit?
From time to time it's a pretty useful feature..
Thomas