GSSL HELP THREAD!!!

[senor_roboto]

as the GSSL's onboard power supply provides +/-15V and +12V, wouldn't it make more sense to run it off the +/-15V rather than +30V unregulated?

that way you can you skip the AC conversion & 7915/7815 section on the board, and just have the 7812 to provide the +12V

seems simpler solution to me? no current worries then...unless DBX requires more than 1.5A (no idea, but if it does then obv the studer power supply isn't going to work anyway...)

right, totally could save a few parts that way but the rest of the board runs off those +/- 15v rails and as far as i can tell the 30v dc unregulated isn't connected at all. I guess I'll try it the simple way first and just measure how much it's drawing. thanks!

 

[miszt]

here is the answer I got from Gustav regarding the fuse type for the GSSL... (THAT, not DBX)

I guess for 110V, I would try a 500mA slow blo (usually marked T for träg), go up or down in size if needed.

 

[Gustav]

here is the answer I got from Gustav regarding the fuse type for the GSSL... (THAT, not DBX)

I guess for 110V, I would try a 500mA slow blo (usually marked T for träg), go up or down in size if needed.

Jakob calls for a 315mA here, but I told you to try with a 500mA, and go up or down if needed, since I dont know what you need for 110V.

What I wrote to qualify it  was.

A fuse is a protection device, you’ll want to end up with a rating that doesnt blow at random times, but protect the circuit in case of current overdraw.

meaning, you should figure it out, but a 500mA will get you started to check your unit.

Even then, your fuse rating does not equal the current draw of the operating circuit. Fuse rating needs to be higher.  You dont want to blow it on start up, where you're drawing more current than in operation.

In essense, you can't simply quote my answer to give him the current draw on the circuit. Also, he will probably omit portions of the circuit (in and output balancing for one) as well. It also depends on the build of his PSU....

Gustav

 

[miszt]

the quote was intended simply to show that the device doesn't draw more than 500mA if operating normally - i was not suggesting that the circuit draws 500mA; I made it clear I have no idea what the current draw is on the circuit quite a few times


do you know what the current draw is on the circuit? and the diff with DBX? that's what senor_roboto wanted to know..

 

[Harpo]

GSSL current draw with DBX 202c gold can VCAs:

hey guys! long time lurker, first time poster here. I've built a couple GSSL's successfully so I'm familiar with the circuit and how the power supply works etc. does anybody know what the overall current draw from a GSSL with DBX 202c VCAs is?

Welcome.
Are the DBX 202c VCAs known working at all ?
Compared to your already built couple GSSL's with maybe THAT2180 audio-VCAs and NE5534s for the 50mV/dB-to-6.1mV/dB conversion, about ignoreable 2mA DC power less in the same build. Without context of planned implementation and addition of any -especially optical- gimmicks (a single illuminated switch might draw more power than the complete GSSL without this blinky power hog...), this is nearly impossible to answer.

I have a studer 369 console with two 1.915.100 power supplies and I was wondering if it's possible to install a GSSL off the power rails of the studer. there's a couple of empty spaces in the frame and i thought it would be cool to build in a better mix bus compressor.

the various rails coming off those supplies are
1.  +/-15v 1.5a max
2.  unregulated DC 30v 0.5a max
3. 48v phantom 200ma max

seems like the 30v dc unregulated could work right?

'a better mix bus compressor' compared to what ?
1.5A max doesn't say what power is still availiable under load (1.5A - current drawn by your mixer in operating condition). Else connecting the GSSL is probably easiest done at the +/-15VDC rails if the studer supply is capable of the additional load (maybe 100mA into a predictable load inside your console and without additional shiny disastergenerators). Leave out the 7815, 7915 and parts in front of these vregs. Inject your studer psu's +15VDC and -15VDC at the vregs output (watch  vregs different pin layout) and link the 0V reference voltage. The additional required +/-12VDC rails are regulated on GSSL mainboard by the 78L12/79L12 vregs. Only fit the 7812 and surrounding parts for the aux.+12VDC rail, if needed at all.
DC power consumption of the GSSL doesn't have much to do with the AC mains fuse rating  and fusing characteristic (depending of type and VA-rating of the mains transformer and whatever the local mains voltage might be). Your semiconductors will blow much faster than the fuse could melt its internal wire. The fuse is there to protect your house from catching fire in the event of failure.

 

[senor_roboto]

hey harpo. thanks for this,
the studer has built in limiters on the group masters and stereo buss masters. i think these are more intended for broadcast so they don't have much / desirable character like the gssl.

ok so first i need to determine what the actual draw is on my +-15v rails. then, see how close it is to the 3 amp max provided by the  2 supplies.

then I need to determine the current draw of GSSL, stripped down to bare minimum .  as i see it this would look like:
78L12 and 79L12 vregs only, VCAs and sidechain circuit.
i can omit the 7812 for lamps, and remove the GSSL in/out balancing stages

ok I think I'm on the right track. thanks guys!

 

[Harpo]

...then I need to determine the current draw of GSSL, ...

see above, about 100mA into nowadays load impedances and without eyecandy...

... and remove the GSSL in/out balancing stages...

you want a DC-offset free, predictable impedance source, capable of driving the paralleled resistors (audio-VCAs and sidechain-VCAs, each into a virtual ground node) in front of the VCAs, so maybe keep the 5534s debalancing stages. Half of each NE5532 output stage is a current-to-voltage converter (these VCAs are current-in/current-out devices, not voltage-i/o) and I doubt the 5532s will still operate when you dremel half of the chip away ;D. IOW better keep them if you don't want to layout your own I/V-converters. As always YMMV.

 

[senor_roboto]

ok! noted. thanks harpo. you guys are amazing! will post pics when it's done

 

[tylergarcia]

Somehow I'm getting 36v when measuring the AC at the inlet on the board. I may be measuring incorrectly, because I'm getting 12v at the meter. The linked picture is hopefully enough to get an idea as to what's going on. I'm measuring set to AC with the black probe on ground and the red probe on one of the 15v inlets. 

http://imgur.com/a/xrfnc

 

[Murdock]

Hey,
after some time playing with my G-SSL I couldn't be happier!
I really want to thank all the people who made this project possible!
But there is a small thing that worries me. Everytime I switch it off, the meter needle  jumps (hits the other side) as if it would get a short overload...
Is this normal? Nothing to worry about?

 

[Gustav]

Somehow I'm getting 36v when measuring the AC at the inlet on the board. I may be measuring incorrectly, because I'm getting 12v at the meter. The linked picture is hopefully enough to get an idea as to what's going on. I'm measuring set to AC with the black probe on ground and the red probe on one of the 15v inlets. 

http://imgur.com/a/xrfnc

If you are getting 36V from the centre tap to a side, you may be on 220/230V main with the primary wired in parallel, when it should be wired in series.

Even so, 36V still seems higher than I would expect, so maybe measuring error, maybe 240 mains.

...but check the primary side wiring first.

(Adding your location to your profile would have given us a clue about your mains voltage).

Gustav

 

[Gustav]

Everytime I switch it off, the meter needle  jumps (hits the other side) as if it would get a short overload... Nothing to worry about?

Nothing to worry about.

Gustav

 

[Murdock]

Everytime I switch it off, the meter needle  jumps (hits the other side) as if it would get a short overload... Nothing to worry about?

Nothing to worry about.

Gustav

OK, that's good, thanks!
Would you care to explain why this happens? Just out of curiosity...

 

[Gustav]

Everytime I switch it off, the meter needle  jumps (hits the other side) as if it would get a short overload... Nothing to worry about?

Nothing to worry about.

Gustav

OK, that's good, thanks!
Would you care to explain why this happens? Just out of curiosity...

I honestly dont know the exact reason in this case.

Maybe the blocking cap leading up to draining into the meter circuit. maybe supplies not turning off symmetrically causing offset in the opamp can kick some DC into the meter. Maybe both, Maybe something third. Someone smarter than me will know the correct answer

Did you notice the meter also kicks when you power the unit on?

Gustav

 

[Murdock]

Thanks Gustav.
Yeah, it also happens when turning it on.
It jumps less when turning off while the bypass switch is in
and doesn't jump at all when turning on while the bypass switch is in. 
But there is allways some "sound" when turning the unit off.

 

[tylergarcia]

Gustav, thanks for the info. I added my location. I'm on USA power, and as far as I can tell the primary wiring is correct. I'll admit, I don't understand it enough to say so myself but I purchased a transformer that was used in some build guides where the color codes matched up and assembled it that way. I'm concerned that I'm possibly measuring incorrectly. Could I possibly get a solid answer on exactly where i'd put my probes to measure the voltage coming out of the secondary? I appreciate it. I can't seem to find an answer by searching the thread. Thanks so much.

Somehow I'm getting 36v when measuring the AC at the inlet on the board. I may be measuring incorrectly, because I'm getting 12v at the meter. The linked picture is hopefully enough to get an idea as to what's going on. I'm measuring set to AC with the black probe on ground and the red probe on one of the 15v inlets. 

http://imgur.com/a/xrfnc

If you are getting 36V from the centre tap to a side, you may be on 220/230V main with the primary wired in parallel, when it should be wired in series.

Even so, 36V still seems higher than I would expect, so maybe measuring error, maybe 240 mains.

...but check the primary side wiring first.

(Adding your location to your profile would have given us a clue about your mains voltage).

Gustav

 

[Gustav]

where i'd put my probes to measure the voltage coming out of the secondary? I appreciate it

Measuring from the center tap to one of the sides, like you describe below,  should give you about 15VAC

I'm measuring set to AC with the black probe on ground and the red probe on one of the 15v inlets. 

I dont understand your reference to 12V on the meter...

Gustav

 

[tylergarcia]

Thanks, Gustav. I should have specified the 12v was from the meter light wires. After re-measuring I may have the correct amount of Ac coming in but noticed that one of my 22R are burned up. Am I correct in thinking that if my 12v rails are okay but my 15v rails are reading 40v+ that there could also be a regulator issue?

where i'd put my probes to measure the voltage coming out of the secondary? I appreciate it

Measuring from the center tap to one of the sides, like you describe below,  should give you about 15VAC

I'm measuring set to AC with the black probe on ground and the red probe on one of the 15v inlets. 

I dont understand your reference to 12V on the meter...

Gustav

 

[Gustav]

Thanks, Gustav. I should have specified the 12v was from the meter light wires. After re-measuring I may have the correct amount of Ac coming in but noticed that one of my 22R are burned up. Am I correct in thinking that if my 12v rails are okay but my 15v rails are reading 40v+ that there could also be a regulator issue?

For the sake of easier trouble shooting, make sure to specify when you are referring to the transformer AC output (going to the board), and the rectified DC (after the bridge/in the circuit).

A burned 22R would suggest a short somewhere, a misplaced IC, too much voltage on he trafo secondaries, or faulty wiring.

If you did not place your ICs before trying to power the circuit (recommended), I would boil the first suspects down to a short, faulty wiring or too much voltage on the trafo secondaries.


The 12V rails are tapped off of the 15V rails, so if you are getting 40V on the 15V rail, I would suspect the 12V regulator would shut down, or at least get enormously hot, if you are actually getting 12V off of it.

Step 1. Disconnect the trafo from the circuit, check that the secondaries are 2 x 15V.  If they are higher, come back and let us know.

Step 2. Measure the center tap to the sides without connecting the trafo to the circuit to verify its wired up correctly. Should be about 15V on each side (It varies with a load on the trafo, but you can get a ballpark figure).


Gustav

 

[tylergarcia]

Black probe on center tap and red probe on one of the sides yields ~18v with the transformer unattached.

Thanks, Gustav. I should have specified the 12v was from the meter light wires. After re-measuring I may have the correct amount of Ac coming in but noticed that one of my 22R are burned up. Am I correct in thinking that if my 12v rails are okay but my 15v rails are reading 40v+ that there could also be a regulator issue?

For the sake of easier trouble shooting, make sure to specify when you are referring to the transformer AC output (going to the board), and the rectified DC (after the bridge/in the circuit).

A burned 22R would suggest a short somewhere, a misplaced IC, too much voltage on he trafo secondaries, or faulty wiring.

If you did not place your ICs before trying to power the circuit (recommended), I would boil the first suspects down to a short, faulty wiring or too much voltage on the trafo secondaries.


The 12V rails are tapped off of the 15V rails, so if you are getting 40V on the 15V rail, I would suspect the 12V regulator would shut down, or at least get enormously hot, if you are actually getting 12V off of it.

Step 1. Disconnect the trafo from the circuit, check that the secondaries are 2 x 15V.  If they are higher, come back and let us know.

Step 2. Measure the center tap to the sides without connecting the trafo to the circuit to verify its wired up correctly. Should be about 15V on each side (It varies with a load on the trafo, but you can get a ballpark figure).


Gustav