GSSL HELP THREAD!!!

[darkus]

If you are using both turbo and super sidechain boards you have to add a second sc board for the turbo board as well.

So you need two ssc boards with the turbo mod.

 

[tzman]

Well that depends...

If you'd like to be able to switch between "normal" GSSL board with SSC and "turbo" mode without SSC, then you only need 1 SSC board.
If you like to be able to use the SSC function with "turbo" enabled, you would need 2 SSC boards. A bit overkill, because with the "turbo" mode you don' really need the SSC as well...

But yeah, depending on how you would like your unit to function and how you've got it wired up right now, that could be your problem (ie. SSC only working on the left channel).

 

[Harpo]

...but right channel is a few db lower than the left channel! (around 4 db ish) this happens with compression on or off..
i got ..
vca boards (serpent)x2

Double check for same resistor (and cap, if difference would be frequency dependant) values at both sides of the audio path.
Swap right side with left side VCA boards. If level difference with GSSL set for bypass follows the swap, difference most likely is caused by the components on VCA boards (you didn't mention your component values, depending on how many 1,2,3 or 4 VCAs are fitted per VCA board). If 'around 4dB ish' would be 6dB difference, more likely look out for shorts especially at the last inverting stages. Following signal flow with updated schematic for the curent pcb revision might help. The '.1' silkscreen error (should read 100pF) between the two 1K placeholders at both DBX202C substitution circuits isn't relevant for your VCA module build.
Good luck

 

[tzman]

Quick question I haven't found the answer to:
If using 2181 VCA's, is it normal that after trimming for least THD, the trimmers positions end up at different places between the left and right channel? One is almost fully CCW and the other almost dead center...

 

[Harpo]

Quick question I haven't found the answer to:
If using 2181 VCA's, is it normal that after trimming for least THD, the trimmers positions end up at different places between the left and right channel? One is almost fully CCW and the other almost dead center...

Doesn't mean much and shows a trimmer to be usefull. Depending on type of THAT2181 (A, B or C grade), the value of the resistor between +/-15V-SymAdj.trimmer and VCA-pin4 will be different to allow injecting a tiny offset correction voltage (+/-0.55mV for A grade VCA with 680K Rsym up to +/-2.88mV for C grade VCA with 130K Rsym) and making use of the complete trimmers range.
For min.THD adjustment you set the audio-VCAs Ec- port (more exactly the differential between Ec+ and Ec- ports) to 0V for the VCAs current-in=current-out bypass condition with a moderate (maybe 0dBV) 1kHz sine test tone running thru your unit. This 0V at the Ec- port is maybe easiest done by temporarily shorting out the 120R shunt arm resistors at the 1K/120R voltage dividers in front of the NE5534s in the DBX202C substitution circuit.

 

[ptron]

thanks a lot harpo!! i believe component placement is right since the other 2 compressors are working great!! i will check around last inverting stages i think i know what that might be hehe
it is vca 4x 2181b , the other 4 were fine tho. problem is my sketchy soldering most likely

all the best from mexico!!

 

[ptron]

ok so. lets be more specific! sorry for the bad explanation.
the right channel is 2.5 db louder than the left channel. and the vca trimmer (mounted on main gssl board) wont work on this vca.
maybe has something to do with the issue?!
the other vca is behaving normally..
i couldnt find any shorts or anything aroudn I/O section or near vca`s... ill try to swap them ( should i swap the whole vca board or just the vca chips and opamp?)

voltages are right on all the 5532 and 5534, TL074 and all vca`s voltage is right...  the other 2 units work properly. makes me think its not placement issue but im a bit doubtful now.

just to know if i am wrong, the last inverting stage would be around the 100uF and 100nF on output?

all the best!

 

[tzman]

Quick question I haven't found the answer to:
If using 2181 VCA's, is it normal that after trimming for least THD, the trimmers positions end up at different places between the left and right channel? One is almost fully CCW and the other almost dead center...

Doesn't mean much and shows a trimmer to be usefull. Depending on type of THAT2181 (A, B or C grade), the value of the resistor between +/-15V-SymAdj.trimmer and VCA-pin4 will be different to allow injecting a tiny offset correction voltage (+/-0.55mV for A grade VCA with 680K Rsym up to +/-2.88mV for C grade VCA with 130K Rsym) and making use of the complete trimmers range.
For min.THD adjustment you set the audio-VCAs Ec- port (more exactly the differential between Ec+ and Ec- ports) to 0V for the VCAs current-in=current-out bypass condition with a moderate (maybe 0dBV) 1kHz sine test tone running thru your unit. This 0V at the Ec- port is maybe easiest done by temporarily shorting out the 120R shunt arm resistors at the 1K/120R voltage dividers in front of the NE5534s in the DBX202C substitution circuit.

Thanks!
That's some great info!

 

[Harpo]

the right channel is 2.5 db louder than the left channel. and the vca trimmer (mounted on main gssl board) wont work on this vca.

The trimmer is for min.THD adjustment and has nothing to do with level. The *1M parts value on GSSL is for a DBX202C. With 4 paralleled THAT2181B, this *1M would decrease to 56K as the next standard parts value to allow for a +/-1.7mV correction voltage (keeping the 1M instead would only allow for +/-0.094mV).
Assuming all VCAs on both modules are alife, swapping L/R modules will show the location of the probably wrong resistor value.
- If this 2.5dB increase follows the swap, double check resistor values at VCA inputs (20K) on module and the current setting 5K1 resistors to VCAs pin5.
- If this 2.5dB increase is still on right channel, tweak the feedback resistor value at the VCA-following I2V converter stage (15K from GSSL schematic) to half of the paralleled 4*VCA input resistor values =0.5*1/(4/20000), giving 2K5. The compensation cap in parallel to this 2K5 feedback resistor will increase from 100pF to 330pF...470pF. 

i couldnt find any shorts or anything aroudn I/O section or near vca`s...

A short at the last inverting stage wouldn't cause a 2.5dB but 6dB level difference (and distorted signal because opamps don't like to drive a zero ohm load).

just to know if i am wrong, the last inverting stage would be around the 100uF and 100nF on output?

around NE5532-pins1,2,3 from updated schematic, further going to XLR output-pin3. 

 

[weiss]

hello !! eeeh so ... hehe i got a bit of a problem... all is fine but right channel is a few db lower than the left channel! (around 4 db ish) this happens with compression on or off.. turbo or single sidechain :/
thanks a lot!!

had this problem as well. check your IC sockets and insert the IC's of the VCA again..
that was how i solved it.

can anyone help me with the bypass switch?  I had to change on and off state of the bybass button because it is reversed. But when i switch cables of the button to change on/off connectors, it is in bybass mode all the time, what did i do wrong?

 

[Harpo]

the bypass switch

Be a lot more specific. Looking at only the mouser catalogue, they are selling 130364 different type of switches.

I had to change on and off state of the bybass button because it is reversed.

So your switch is maybe a pushbutton switch, leaving only 19740 different type of switches from this catalogue ...
For the standard GSSL bypass switching function you want a DPDT switch (double pole double throw position switch).

But when i switch cables of the button to change on/off connectors, it is in bybass mode all the time

Do you have a multimeter? Ohm out your switch in order to sort the conducting pins for the switch status 'pushbutton activated' and 'pushbutton released' (or look up this parts datasheet for a definitive answer and get maybe useful additional information). Have a look at the GSSL schematic in order to match these sorted out pins with the switch symbols from schematic.
Was your circuit ever operating correctly before (from your pics some posts ago, the HPF jumper was missing, but fixing this issue was already answered) ?

what did i do wrong?

Without knowing what you have done, no idea what you might have done wrong.

 

[darkus]

Hi guys. So i have my GSSL with Turbo and CRC boards up and running, everything sounds sweet. Alot better than i ever expected this unit to sound.

I only have a small minor problem with my unit. The first powering on attempt always fails. I press the switch and nothing happens. I press it to "Off" and i see the power on LED to blink quick. When i press the switch immediately after that, i get the unit to power on.
I already replaced the 1000uF elcos in the PSU section, no difference. I had this problem before installing Turbo and CRC mods.

Im using the NRG pushbuttons from Frank Röllen. If im correct, user Weiss had a similar problem to mine with the power on switch.

Any help?

 

[Harpo]

The first powering on attempt always fails. I press the switch and nothing happens. I press it to "Off" and i see the power on LED to blink quick. When i press the switch immediately after that, i get the unit to power on.

Voltage regulator(s) latching on start up. (must have been answered on about every single of the last 50 pages of this thread...)

I already replaced the 1000uF elcos in the PSU section

nothing to do with it.

Im using the NRG pushbuttons from Frank Röllen.

Frank does a lot of things, but to the best of my knowledge he never started a business in switch manufacturing.
The manufacturer (might be EAO, NKK or RAFI, just for the more common used pushbutton switch types) and part number most likely will be stamped on the switch body. The switch body, switch cap and maybe switch illumination or switch socket will be different part numbers for these for usual modular switches. The supply current and voltage requirements for different types of illumination are more than factor 20 apart, so if your switch has a provision for illumination, knowing these parameters is essential. (The EAO short reference catalogue for this is 188 pages, hence my request to be a lot more specific.)

 

[weiss]

Be a lot more specific. Looking at only the mouser catalogue, they are selling 130364 different type of switches.

NRG pushbuttons from Frank

So your switch is maybe a pushbutton switch, leaving only 19740 different type of switches from this catalogue ...
For the standard GSSL bypass switching function you want a DPDT switch (double pole double throw position switch).

http://micandmod.com/en/parts/168-vintage-british-console-pushbutton-yellow.html

Do you have a multimeter?

yes.

Was your circuit ever operating correctly before (from your pics some posts ago, the HPF jumper was missing, but fixing this issue was already answered) ?

yes.

Without knowing what you have done, no idea what you might have done wrong.

just inverted on and off buttons, as the compress button does bypass and not enable the compression.

Ohm out your switch in order to sort the conducting pins for the switch status 'pushbutton activated' and 'pushbutton released' (or look up this parts datasheet for a definitive answer and get maybe useful additional information). Have a look at the GSSL schematic in order to match these sorted out pins with the switch symbols from schematic.

i have not found any datasheet. ohm out is a good option. thanks for that.

 

[darkus]

Sorry Harpo for me being a dumb ass.... =)

So i should replace the voltage regulators, or is there something else to do?

 

[Harpo]

i have not found any datasheet. ohm out is a good option. thanks for that.

Might be NKK series UB http://www.nkkswitches.com/pdf/UBIlluminated.pdf
The switch labeling should confirm this (or not...)

 

[Greg S.]

I only have a small minor problem with my unit. The first powering on attempt always fails. I press the switch and nothing happens. I press it to "Off" and i see the power on LED to blink quick. When i press the switch immediately after that, i get the unit to power on.

Check the +-15V, I use 7815 and 7915 from ST Microelectronics, they work
Segor.de

 

[Majestic12]

I only have a small minor problem with my unit. The first powering on attempt always fails. I press the switch and nothing happens. I press it to "Off" and i see the power on LED to blink quick. When i press the switch immediately after that, i get the unit to power on.

Check the +-15V, I use 7815 and 7915 from ST Microelectronics, they work
Segor.de

I only got the unit to work with everything else than ST Microelectronics regulators.....

 

[ptron]

Thanks a LOT! Harpo!! i think i have to let this one sit for the time being! going for some gigs in the summer later tonight, had to finish some music with the working gear hehe
thanks really for all the help! ill get back to the bench when i am back!
safe happy soldering to everyone!

 

[Bowie]

I'll back this up and add that I recall the SB4k BOM says specifically NOT to use SD Micro for this so some people have definitely had issues with them not working.