GSSL HELP THREAD!!!

[hipolitho]

Hello board!

I know you guys covered this already, but, I didn't get much info ato make it clear to me...

Assuming by what I've read... I am able use those DBX2001 on this clone. And, again, assuming that I can... is there any modification necessary from what is on the PCB outside the VCA area to make the thing work with the DBX2001?

I would appreciate very much any help. Thanks!

Chuck ???

 

[Harpo]

Assuming by what I've read... I am able use those DBX2001 on this clone. And, again, assuming that I can... is there any modification necessary from what is on the PCB outside the VCA area to make the thing work with the DBX2001?

Have a look at THAT design note DN127. On quick glance, differences are Rin and corresponding Rf in following opamp, and a to be shorted out divider resistor 1M, connecting to pin7 for symetry adjustment. Control voltage law 50mV/dB seems the same as DBX202C, so parts of the substitution circuit are not to be used. Are your DBX2001s known alife and working at all?

 

[hipolitho]

Thanks you very much Harpo!

The 2 ones I am willing to buy are in perfect shape, says the seller.

Could you be more simple Harpo? My technical knowing is very limited... I promess to read the THAT specs and try learn from it.

Should I leave the 1M resistors out or just replace it with a jumper? What about the trimpots? Is everything else the same on the board?

Thanks for taking the time!

Chuck

 

[Harpo]

The 2 ones I am willing to buy are in perfect shape, says the seller.

Do you want to look at or listen to it? Optical shape was never in question, what about its electrical behaviour?

Could you be more simple Harpo? My technical knowing is very limited... I promess to read the THAT specs and try learn from it.

Should I leave the 1M resistors out or just replace it with a jumper? What about the trimpots? Is everything else the same on the board?

Chuck, did you get your gssl from your post a month ago running correctly? You might have your supply voltages not working properly or wrong value parts fitted that would cause overdriving your converter. Changing your THAT2181 to an exotic DBX2001 would probably not fix this problem and may come up with other issues that might not be an easy fix. Redesigning this compressor for different essential parts would at least ask for a complete understanding of the circuit behind. This would no longer be paint by numbers.

If you are still comfortable with your plan, according to prementioned app note DN127, the 1M resistor between wiper of the symetry adjust trimmer and DBX2001-pin7 should be replaced by a wire link. Input resistor should be scaled down within parts limits to maybe 13k-15K and feedback resistor of following opamp for current to voltage conversion changed to half of this value for unity gain behaviour, as the following inverter makes up this -6dB loss. This resistor scale down would also call for an upscaling of the compensation cap across Rfb for a maybe 100kHz rolloff response.

 

[hipolitho]

Got your point... in fact, talking about my first post... after overdriving, the thing stopped passing any signal. I've read here in the forum the thing should pass audio even with no control board attached, so I assumed my main board was the problematic one.

I didn't find anything wrong by looking... so I simply decided to stuff new PCB from the start. This time looking for the mistakes I might have done on the first one. Only thing I am keeping from the first one is the 3 THAT2181LBs.

I thought about getting the fancy DBX for the new one thinking it would be "better", but, checking the forum I see there is no point for that. Only thing I am afraid of is that perhaps I have blown my THATs someway... Anyway... I have already ordered another PCB and all the components I already have, even with better quality this time. I have to be honest I was expecting to have problems with the first one and knew at some point, even with the first one running "ok", I would built another one "for real".

Maybe I will already order another 3 THATs in case I have mine bad... Everytime I order something in Brazil, it takes... 3 to 4 weeks to get here, it is a pain. I've quit about the DBX2001, talking to you helped me to decide that.

If anyone reading this would like to take this shot and getting those VCAs, here is the link for them:

http://cgi.ebay.ca/One-DBX-2001-Class-A-VCA_W0QQitemZ150398768970QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item230477174a#ht_2536wt_1009

At least they look cosmetic perfect.

Thanks again Harpo, I keep the board updated and look for help if necessary.

Cheers ya'll!

Chuck

 

[schrobbelbop]

Still struggeling with my turbo board.

Still waaaay too much compression when engaged.
Is it correct my gssl still compresses (only a bit less then GSSL mode) when switched to turbo?
or did i do something wrong with wiring?

Thanks for all of your help

 

[Harpo]

Still struggeling with my turbo board.

Still waaaay too much compression when engaged.
Is it correct my gssl still compresses (only a bit less then GSSL mode) when switched to turbo?
or did i do something wrong with wiring?

Thanks for all of your help

Feeding both inputs with the same mono source, both left and right outputs should read, sound and compress exactly the same, no matter if switched to gssl- or turbo mode. If feeding both inputs with same signal, but one side reversed in phase, turbo mode would still behave as before, but in gssl mode there would be no compression, because the summed signal would be canceled out.

So you already pulled out the VCA from your turbo board -that once was powered with reversed supply voltages- and put it instead in a socket of your audio path VCA? Feeding both inputs with a mono source, switched to gssl-mode and varying the gain makeup value, you checked left and right output sound and/or measure the same, so this maybe broken VCA should have survived ?
You already checked, the turbo board receives signal from gssl mainboard thru the one side lifted 47K resistor ?
You already checked, the turbo board sends back control voltage to the correct side of the 100R resistor on gssl mainboard ?
Some close up pictures from your connections, mode-switch and turbo board might help.

 

[Autophase]

Just got an amazing deal on a meter for my GSSL, its 1ma Full scale, and its really big, 4"x3.5", its made by a company called "CLARE" its a spare for some test equipment completely unused, The scale says earth circuit ohms, but that is easilly replaceable with my own scale.
The best part is, it only cost me £ 7  ;D

 

[schrobbelbop]

Still struggeling with my turbo board.

Still waaaay too much compression when engaged.
Is it correct my gssl still compresses (only a bit less then GSSL mode) when switched to turbo?
or did i do something wrong with wiring?

Thanks for all of your help

Feeding both inputs with the same mono source, both left and right outputs should read, sound and compress exactly the same, no matter if switched to gssl- or turbo mode. If feeding both inputs with same signal, but one side reversed in phase, turbo mode would still behave as before, but in gssl mode there would be no compression, because the summed signal would be canceled out.

So you already pulled out the VCA from your turbo board -that once was powered with reversed supply voltages- and put it instead in a socket of your audio path VCA? Feeding both inputs with a mono source, switched to gssl-mode and varying the gain makeup value, you checked left and right output sound and/or measure the same, so this maybe broken VCA should have survived ?
You already checked, the turbo board receives signal from gssl mainboard thru the one side lifted 47K resistor ?
You already checked, the turbo board sends back control voltage to the correct side of the 100R resistor on gssl mainboard ?
Some close up pictures from your connections, mode-switch and turbo board might help.

Connections to Turbo board

Inside my gssl

Turbo switch

In my live rack

Yes i checked in audio path, seems ok!
No didnot measure any thing exept the psu on the board. wich is ok.

 

[schrobbelbop]

i'm 99% shure the switch is wired correctly. i see that the 47k's do the L/R summing for sidechain feed.
So it's right when i switch to turbo, with no board connect i have less compression. so is it not the problem
that the turbo is also sending a signal togheter with gssl sidechain to my vca's? i can image now both sidechain
signals are getting combined.... or am i wrong?

Is it possible to adjust my attack times. i found 10ms a bit to short and 30ms to long for my taste on drums.
is it possible do adjust?

also i would like to have gain bypassed when bypass is engaged but that's just wiring my gain pot to the double pole
bypass switch?

thanks!

 

[Harpo]

i'm 99% shure the switch is wired correctly.

Looks correct to me as well. Nice build.
The 9th pin of the audio-VCA socket should better be removed or soldered closed. YMMV. Also make sure, the transformer holding screw never gets in touch with the lid of your closed box.

Is it possible to adjust my attack times. i found 10ms a bit to short and 30ms to long for my taste on drums.
is it possible do adjust?

Replacing the 270K resistor connecting to attack switch CW position for 30ms by a 27K resistor in series with a 250K trimmer (or preferable 250K log pot) to make this full CW position a variable position for attack time varying between 1ms and 30ms seems the easiest way to do this with sourcable parts.

also i would like to have gain bypassed when bypass is engaged but that's just wiring my gain pot to the double pole
bypass switch?

Just leave out or remove the wire link between makeup pot wiper and "E" on control-pcb. The pot wiper then connects to the throw side of your DPDT switch, "E" connects to pole of this switch and the remaining throw side for bypass condition connects to 0V/"OFF". (this is differing from schematic)

 

[Jazzboms]

Hi
After solving some problems regarding the makeup(Some error with my bypass switch wireing.), there is something with my threshold that is not correct. I cant hear any compression, except with a oscillator tone, with max release, I can hear some changes in the overtone while turning the threshold. On drums I can hear any compression at all. I compare with my DBX 162 VU, and JoeMeek TwinQ. I have read that it should be transparent, but.....
What I have done.
- Measurred E and F. Correct V
- Also checked Pin 4 and 8 on Tl 072, and its correct V.

Measurring PIN 1 on tl 072 gives me 0.10 - 3.08. And pin 7 gives me 0.0 - 1.93. Is this correct
Any Ideas?

Thanks.

 

[regularjohn]

- Measurred E and F. Correct V
- Also checked Pin 4 and 8 on Tl 072, and its correct V.

Measurring PIN 1 on tl 072 gives me 0.10 - 3.08. And pin 7 gives me 0.0 - 1.93. Is this correct
Any Ideas?

Measuring voltages on any opamp pins other than the voltage rails is kind of pointless because you're just measuring the in and out signals to the opamp which will change depending on the level of the signal.
The voltages of E and F will both vary depending on where the make up gain and threshold pots are set.  E is the wiper for the make up gain pot which has +12VDC on one side and 0V on the other.  And F is the wiper for the threshold pot which has -12VDC on one side and a reduced (by the 47K) +12VDC on the other.
Problems like you describe are caused by shorts, bad soldering, incorrect wiring, or incorrect component values.  Take the schematic and trace through the circuit.  Use a continuity meter to verify that the connections are correct.  When you find the problem yourself, you'll feel sooooo much better, kinda like you accomplished something!  

 

[audiophreak]

I hope this is O.K. to repost it was posted by Lukas’ SSL roadmap for debugging and surgery (livingnote)

http://picasaweb.google.com/audiophreeek/LucasSRoadMap?feat=directlink

the  original PDF's were too big to post here , so here is a link to JPG's, if you want the PDF - PM me.

  Hope this helps,
                          Chip

 

[johnmellor]

Thanks for your reply regularjohn. I have made the resistor changes described to accommodate the 2180LB.
So I have got the 5k trimmer like you said, how do you connect it, it's got three pins right?
Also since my last post I've got Sifam 34A(http://www.canford.co.uk/Products/21375/58-354_SIFAM-34A-PPM-METER) meter with alice driver board, will it be necessary to still have a trim? (looks like its  going to be a 2u box haha)

cheers

 

[Jazzboms]

Thanks John And Audiophreak.
Im starting the checking.

 

[regularjohn]

Thanks for your reply regularjohn. I have made the resistor changes described to accommodate the 2180LB.
So I have got the 5k trimmer like you said, how do you connect it, it's got three pins right?
Also since my last post I've got Sifam 34A(http://www.canford.co.uk/Products/21375/58-354_SIFAM-34A-PPM-METER) meter with alice driver board, will it be necessary to still have a trim? (looks like its  going to be a 2u box haha)

cheers

Solder the middle leg on the trimmer to either of the outer legs, it doesn't matter which one.  The two outer legs go where the resistor legs go.  Some trimmers aren't the same size as the resistor footprint.  If that's the case, just take two extra component legs that have been discarded (like the ones you used for the many jumpers on the pcb), and use those as "stilts" so to speak.

 

[Autophase]

Hey guys, just noticed some odd behavior from my gssl, if i feed just the one channel, left or right into the gssl I get audio coming from both outputs.  although the output from the corresponding input is about twice as loud as the output with its corresponding input unplugged.
Do this indicate a short on one of my I/O's?

 

[Phil]

Hey guys,

i got my GSSL ready and working - Thx for the help and for the info everbody posted on this board.
I still got 4 questions left cuz i'm not sure if everything is working correct.

1. Regulating my Behringer BE-47 Meter was only possible by using a 100K pot (I guess i'm using about 40-50K of it) - Can that be? Why doesn't the recommended 5k pot work? What could be wrong here?

2. I'm using a 900k resistor instead of a 750k resistor on the control PCB - it's right to the release switch. Can somebody tell me if the difference is hearable? and what it really changes?

3. If the 50k trimpots on the main pcb are for the THD and can only be set correctly with measuring hardware, to what positions should i turn them and what exactly is the purpose of it all if i'm not even able to hear the difference when changing them?

4. And last question for a possible mod:

What is the Supersidechain board for? Same for the Turbo-Board?

Thx again for everything

Phil

 

[Bonke]

Hi all!
I finished my first GSSL some years ago and now I´m building three more. My first of the "new" ones is working like a charm but my second has a problem.
It passes audio and the makeup gain is working but there is no compression and the meter is dead. I have tried searching this forum but can not find an answer. It has probably been answered in this thread but it is 200-something pages.... :-\

Can anybody help me in the right direction?
I have swapped all IC´s. Out-ruled the controlboard. (works with the other unit). Searched for solderbridges around sidechain and TL074.

The compressors are built with That 2180´s. The first (working) one has panasonic FM caps and the second one Nichicons. The 3,9K´s resistors besides the VCA´s are changed to slightly different values on the two compressors, 4,8 - 5,0K. Other than that they "should" be identical.

Anyone who has that simple explanation? 

Henrik