GSSL HELP THREAD!!!

[Afro]

Hey everyone,

plugged in my new-made GSSL today and got a little problem. When I turn the treshold pot all the way to the left without a signal, I get a little humming. But when I turn the treshold up, I get a loud noise.
I recorded a little sample:
http://picosong.com/FidR/

Turning the threshold up while having a signal, I get this delay-like effect:
http://picosong.com/FiTe/

As for the humming, I thought this could be the transformer (I'm using a toroidal transformer). But that shouldn't cause the loud noise or the delay... Is that right?

Any suggestions?

Thank you very much and greetings from germany,
Simon

 

[dirtyhanfri]

You can also inject an external sidechain at this point (into the capacitor, NOT into the opamp).

Jakob E.

I was planning to use 3 caps for different HPF values and a 5th position of a lorlin for a external (direct) signal, wouldn't it work? should I run that signal through a cap and filter it?

 

[gyraf]

external goes in directly to the connector (there is a 10uF cap after this point). For reference (ground/0V) for external in connector, use the 0V already present at XLR's pin1

EDIT: External sidechain input done like this will probably act somewhat different from the usual compression, being inserted after the sidechain VCA. But it apparantly works nonetheless (I'll verify on next chance I have with the unit).

Jakob E.

 

[timpanic]

Hello all you helpfull people! I need a little help. I´ve read this thread til page 100 but couldn´t find an answer.

I finished my gssl ( pcbgrinder component set, 2180b, 1mA Meter ). A lot works: bypass, led, passes clear audio, make up and all poti works BUT

the threshold seems very high. I only can do max 4 db GR and that only with highest ratio, fastest attack and threshold full.

Any suggestions where to look....thx a lot

Add: Solved the prob. Wrong mega ohm resistor near the meter trim point. Yuhu .. now it rocks !

 

[Majestic12]

Hello all you helpfull people! I need a little help. I´ve read this thread til page 100 but couldn´t find an answer.

I finished my gssl ( pcbgrinder component set, 2180b, 1mA Meter ). A lot works: bypass, led, passes clear audio, make up and all poti works BUT

the threshold seems very high. I only can do max 4 db GR and that only with highest ratio, fastest attack and threshold full.

Any suggestions where to look....thx a lot

I think we already solved this problem via email.
It simply was a wrong resistor value in the meter shunt.

 

[Afro]

plugged in my new-made GSSL today and got a little problem. When I turn the treshold pot all the way to the left without a signal, I get a little humming. But when I turn the treshold up, I get a loud noise.

Found the caue of the delay, I've had a tiny little cut in the ground-conduit. Fixed that with a cable.

But I still have that noise that starts when I turn Threshold and make-up a little to the right....
This is happening both left and right.

Anyone who could help me?

Thanks,
Simon

 

[frazzman]

Apologies for the seemingly dumb question... but should the unit pass a signal with the control PCB disconnected?

 

[gyraf]

Apologies for the seemingly dumb question... but should the unit pass a signal with the control PCB disconnected?

Try it and let us know?

Jakob E.

 

[MeToo2]

Apologies for the seemingly dumb question... but should the unit pass a signal with the control PCB disconnected?

Looking at the schematic, I think the answer is "yes," because all the points "a-f" where the control PCB connects have an alternative signal path (usually to ground via a high value resistor). So that means, no make up gain (= bypass), no compression, and no meter. I haven't tried it in practice though.

 

[Harpo]

Apologies for the seemingly dumb question... but should the unit pass a signal with the control PCB disconnected?

IMHO audio signal should pass close to unity gain, but don't try this for too long and only with decreased (up to 100mV signal level), else expect the TL074 to break/fry.
With control pcb disconnected, the TL074 will oscillate with pin14 only limited by the -12V voltage rail. Reason is the missing ratio circuit between "A" and "B" now without current injection into its inverting input pin13, only leaving the 1M feedback resistor in circuit instead of paralleling other resistors.

 

[Gertius]

Hey guys,
I have access to a homemade GSSL in the studio I work at.
The comp always exhibited quite loud 50Hz hum at -45dBFS, which basically rendered it useless.
Today I opened it for troubleshooting and I´ve noticed that the metal pin (screw) holding the toroidal transformer in place (on the bottom of the chassis) is touching the top lid of the (1RU) chassis. Isolating it from the top lid got rid of the hum completely.

Can someone please comment on this? I searched the whole thread, but didn´t find anything on the issue.
Is the pin supposed to touch the chassis at both ends? Other ressources on the web suggested just the opposite.
That´s why I went through with isolating the top part of the pin today, fixing the problem for now.
Could it be dangerous anyway? The pin is still firmly connected to the chassis on the bottom end, I measured 0 Ohms to safety ground.

Cheers!
Christian

 

[Harpo]

Hey guys,
I have access to a homemade GSSL in the studio I work at.
The comp always exhibited quite loud 50Hz hum at -45dBFS, which basically rendered it useless.
Today I opened it for troubleshooting and I´ve noticed that the metal pin (screw) holding the toroidal transformer in place (on the bottom of the chassis) is touching the top lid of the (1RU) chassis. Isolating it from the top lid got rid of the hum completely.

Can someone please comment on this? I searched the whole thread, but didn´t find anything on the issue.

This ?

The probably poorer shielding of your 19"case from not removing the paint/coating where bottom/sides/top of your case connect might just have kept resistance high enough to keep your transformer alife.

 

[Gertius]

*gulp* yeah that´s exactly how it was. thanks for commenting, Harpo!

I didn´t build that compressor and am happy that I found the error through the hum that was generated.

Anyway, now the comp works fine and I´m really happy that the issue is sorted.

Cheers!
Christian

 

[main repairman]

Cau guys.
Why do we need in the PSU (rev. 11) resistors 10R and 22R?
Thank you

 

[neilbaldwin]

Finished my GSSL build today and I'm struggling to power the LEDs in the 8027-B 1mA VU meter.

The VU meter itself works fine but as soon as I apply power to the LEDs the needle quickly shoots to the bottom (left) and stops responding. Remove the power to the LEDs and it works again.

I've tried taking power from +15V and also the +12V at the control board connection point (both going via limiting resistors) but still can't get it working. I even tried removing the LED from the control board and patching in there but same effect. I know it's going to be something obvious but I have to ask before it drives me mental 

Thanks

 

[Harpo]

Finished my GSSL build today and I'm struggling to power the LEDs in the 8027-B 1mA VU meter.

... sure there are LEDs inside ? This model is coming with either an incandescent lamp or (IIRC two series connected) LEDs at whatever colour for illumination.

The VU meter itself works fine but as soon as I apply power to the LEDs the needle quickly shoots to the bottom (left) and stops responding. Remove the power to the LEDs and it works again.
I've tried taking power from +15V and also the +12V at the control board connection point (both going via limiting resistors) but still can't get it working. I even tried removing the LED from the control board and patching in there but same effect. I know it's going to be something obvious but I have to ask before it drives me mental

Could be voltage regulator(s) hanging on startup or wrong value resistor to limit current for LEDs/drop voltage for a lightbulb to keep it within its allowed/wanted range. Don't connect to the +/-12V rails.

 

[neilbaldwin]

Thanks Harpo.

Yes, it's the version with two white LEDs in series.

I should've made it clearer that in fact I can get the LEDs to light up it's just that when they are lit up it stops the actual VU meter from operating - the needle is 'locked' to the bottom/left. With the power removed from the LEDs the VU meter operates normally.

 

[neilbaldwin]

I gave up with the LEDs in the VU meter. Opened up the meter, desoldered the tiny LEDs and replaced them with two white 3mm 'normal' ones. Works fine now taking the power from the two pads for the Power On LED on the control board.

*shrugs*

Maybe there was a fault on one of the original LEDs or maybe a short in there somewhere. Very odd.

 

[dangerousben]

Guys, I have a funny problem on a recent GSSL: Its a build equipped with a turbo board, a crc board and a custom HPF for the side chain. Turbo and HPF are switchable. The switches are backlit with LEDs and the meter is equipped with a LED aswell. I take the power for these LEDS from the +12V rail.

Here comes the funny part: When I'm in bypass mode and turn the make-up pot all the way up all lights go off. this happens even if only the normal power LED is connected as usual.
When I enter compression mode all is fine.

So what's the deal here? I don't think any of the voltage regulators is broken since all is fine as long as i don't turn the makeup-gain all the way up in bypass mode.

 

[MeToo2]

*gulp* yeah that´s exactly how it was. thanks for commenting, Harpo!

I didn´t build that compressor and am happy that I found the error through the hum that was generated.

Anyway, now the comp works fine and I´m really happy that the issue is sorted.

Cheers!
Christian

That situation could have been potentially seriously dangerous. Humbly suggest that you also check the continuity between PSU 0V/ chassis/ XLR pin 1 and the IEC earth on the mains plug, and also check the other mains wiring, fuses, switching etc. and that you are happy with the construction quality e.g. how thick the earth cables are, is the chassis bonding OK between all panels, how the earthing stud is attached to the chassis, what size fuses are fitted, sleeving on cables etc. I would probably have expected such a fault to trigger some safety mechanism somewhere (like an ELCB trip or blow a fuse).