GSSL HELP THREAD!!!

[synthetic]

I just read all 90 pages. Woof.

I've read that powering up without ICs is a bad idea. However, I want to test the without converting my endangered DBX202s to puffs of smoke. So would it be alright to switch it on for a while and measure the voltage before plugging in the ICs? I realise that the voltage will be out of whack, but I just want to check for shorts to keep from killing chips.

So, should I just plug in a few op amps to give the regulators a little bit of a load?

 

[gyraf]

Just leave the 202's out for initial testing - the load of the other opamps is plenty to get regulation right.

Jakob E.

 

[Ilya]

Hi everyone!
Just finished my first GSSL. It's working perfectly, but there's a small issue. It hums (but with really low volume) and the volume of the hum changes with makeup, it also hums in bypass. While checking with a probe (a wire with cap/resistor) I found that the hum originates somwhere in the sidechain circuit. Another strange thing: my lythics have metal lids and when I touch them with the probe some of them hum too, 3 of them are in the PSU in +12/+15 filter section and the loudest hum is from the lid of the cap right after 074 (after vca). I feel that both positive Vregs are hotter than negative.
I just can't locate the source of the hum. My unit isn't racked yet and hum doesn't change if I move my transformer. Maybe a bad cap somwhere? Any ideas?

 

[gyraf]

Are your PSU voltages correct?

Does it still hum when you short the inputs to ground (this is the right way of testing)?

Touching the metal on the 'lytics will introduce hum, as they're often connected to one side of the component, and thus to the signal path.

It's hard to judge hum before the unit is boxed in a metal case - I never had any hum problems with this construction when boxed, so maybe you shouldn't worry prematurely..

Jakob E.

 

[Ilya]

My PSU voltages are ok.
With 'lythics I mean that the hum is directly there - I hear it when I touch them with the probe (and I'm listening to the output of the probe amplifier, not the compressor. And to me it seems strange that only positive half of the PSU hums...
I know that you've never had any hum issues, that's why I'm asking.
And yes, I'm measuring with inputs shorted.

 

[gyraf]

Build and box the unit, and then take it from there..

Jakob E.

 

[khstudio]

Need Help!

For some reason 1 of my SSL's doesn't seem right

I'll explain, I've got 2 unit's. I built them raw with no mods, then slowly did the mods while checking in between to make sure all was well to keep confussion down. Anyway, 1 unit has 2180's & the other 2151's, they both worked great until I installed the sidchain filter board. Now only the 2151 works correctly.

What it's doing:
1 - it does work but lost a little too much punch, with or without the SCFB.
2 - The Threshold is where I notice the bigest problem - I have to crank it WAY past the point I used to - both units used to give me 20db of compression before the halfway point but now this one needs to go to 9:00 or 75% CCW to do it no mods were done here.
3 - I totaly removed the SCFB (side chain filter board) & it's the same
4 - checked for solder problems... non to be found.

This unit was actually my favorite. I'm not sure what to check anymore. I didn't change too much & was very careful. Right now the SCFB is totaly removed & it's still f**d-up.

Any Idea's ????

Anyone with 2180's & NO threshold mod's - Where is your threshold knob sitting for 20db of compression

One more thing, The only odd thing I've done in the past few days was hook up an LED to a short pair of wires so I could move it around the meter to see where it lit it up the best... this was off the LED pads. now when I was moving it around the wire came unsoldered a few time & I don't know if they touched together. Even though the unit almost works right, could I have shorted something? & what should I check?

 

[khstudio]

Greg,
the SCFB works great on my one unit... very cool on the drum buss, straight or paralell, especially when the bass is added in too. I was concerned about the reduced summing resistors from 47k to 20k & how they might affect the "AUDIO PATH" or ruining what I already liked... but all is well, with that unit at least.

Thanks again for the boards.

Kevin

 

[Greg]

Not really sure what to tell you. If you install the sidechain high pass at less than unity gain, then it makes sense that you'd have to turn the threshold more to acheive the same compression ratio. However, I have no idea why it would behave the same way if the sidechain was removed.

[quote author="khstudio"]Greg, the SCFB works great on my one unit... very cool on the drum buss, straight or paralell, especially when the bass is added in too.[/quote]
Just so there is no confusion, the high pass filter isn't adding any low end, it's actually removing low frequencies from the sidechain. Just wanted to make sure you knew what the filter was doing. :guinness:

 

[khstudio]

Yea, I know what it's doing :wink:
I meant Bass Guitar.


About the levels & threshold - The unit that's working right has the board installed & the levels are fine + the threashold works like it did before the SCFB. This sucks & I can't figure it out.

 

[khstudio]

OK, The voltages @ the wiper/threashold pot are off :!:

The unit thats right:
-10db = .5 volt (2 o'clock)
-20db = 7.3 volt (1 o'clock)

The unit thats wrong:
-10db = (neg) - 1.1 volt (12 o'clock)
-20db = 5.3 volt (9 o'clock)


Somethings not right.

 

[khstudio]

I think I'm getting closer -

At the 15k resistor feeding the "audio VCA's" & at the summing resistors I'm getting a positive voltage of aprox. 8mv, give or take...

on the bad unit I'm getting NEGative voltage :shock: :shock: :shock:
of aprox. -1 to -3 @ the same spots - voltage varies a little depending on the resistor & wether it's before or after it but you get the idea... it's always negative.

I measured the main voltages @ the important pins & all seems ok
I changed the input IC's & no change
Checked for solder bridges & found nothing

I'm STUCK


HELP

 

[khstudio]

Please :sad:

I just left my friends shop after 3 hours of him checking it out & he could find what was causing the problem either & he's no dumb dude. We changed all VCA's & most IC's, check PS, all diodes, you name it. I put it back to stock & still can't get it to respond like it used to. :? I swear, the units were perfect & ready to rack up & use.

Hopfully one of you guys can help me narrow this thing down?
I am trully lost on this one.

If anyone has a voltage chart or a way of measuring specific areas to narrow it down would be MUCH appreciated.

 

[fenderfred]

Hi!
i'm going to start a GssL and i get some of the parts needed.
I received a W08(800v) in stead of W04(400v).
Will it work correctly?or not?
Thanks

 

[mathflan]

Hi fenderfred

I'm french too from saint etienne, if you want, I can Give you one W04.
I don't know if the W08 will works...

 

[Ilya]

Hi, fenderfred
W08 will do just fine. It's rated for 800V which is 2 times more than 400V...

 

[Greg]

hi khstudio:
I got one of my SSLs back the other day, and it has 2180LBs in it, so let me know what voltages would be helpful to you and I can measure them for you soon.

 

[mathflan]

I have just finished my SSL :grin:

It' huge!

I have two questions :

- I'd like to remove the big "tick" noise when I power Off the SSL, any idea?

- How can I Verify if my high pass sidechain from greg works?
Just put an CD for example in the KEy input?

thanks

 

[dax]

This is my First SSL build and i have been trouble shooting / reading this long thread for about a week. My comp is passing audio but only the makeup gain works (threshold affects some volatages but not the audio)
no compression, meter etc...
i have treid swapping out all VCA's and IC's and am positive they are oreinted correctly. I have also treid replacing the bridge rectifier and the regulators and some cas around them
My continuity meter tell me the -15v rail is shorted to gorund but i cant find where??? here are my voltage readings....(with audio passing)

5534s
1. 12.05
2. -0.00
3. -0.00
4. -15.00
5. 0.60
6. 0.00
7. 14.65
8. 12.05

5532s
1. -0
2. 0
3. 0
4. -15.00
5. 0
6. -0
7. 0
8. 14.66

TL074
1. 0.04
2. -0.00
3. 0.00
4. 12.21
5. 0.00
6. 0.00
7. -0.84 vari to 0.00 with threshold
8. 0.00*seems wrong
9. 0.00
10. 0.00
11. -12.18
12. 0.00
13. -0.00
14. 0.63

Tl072
1. -3.08 vari to 3.08 with thresh
2. -0.00
3. 0.00
4. -12.16
5. 0.00
6. -0.00* seems wrong
7. -0.00 vari to 1.96 with makeup
8. 12.22

VCA Section
5534s
1. 12.03
2. -0.00 vari to -0.09 with makeup
3. -0.00 vari to -0.09 with makeup
4. -15.00
5. -0.70 vari to -0.60 with makeup
6. -0.00 vari to -0.09 with makeup
7. 14.66
8. 12.03

that 2181s
1. -0.00
2. 0.00
3. 0.00 vari to -0.09 with makeup
4. 0.00
5. -2.69* seems wrong
6. 0.00
7. 14.68
8. 0.00

SC 2181
1. 0.00
2. 0.00
3. 0.00
4. 0.00
5. -2.69
6. 0.00
7. 12.22
8. 0.00

Connectors to controls
c. 0.00
b. -2.90 vari to -10.20 with threshold
a. 3.70 vari to 0.00 with threshold
0. 0.00
-. -12.18
d. 0.00
g. 0.00
e. 12.21 vari to 0.00 with makeup
f. 12.21 vari to -12.18 with threshold

...any help is greatly appreciated thanks in advance
daniel mc

+. 12.21

 

[mathflan]

Hi,

My SSL comp works fine but

I have a little noise problem when I activate the SSL compressor,

I recorded an MP3, with the make up gain at maximum.

http://sounddiy.free.fr/images/montage/SSL/SSL%20NOISE.mp3

The noise doesn't come from PC monitors or other parasite objects, I powered off ALL, check all.

It's maybe a ground loops?

- the chassis of the XLR inputs and outputs are connnected to the RACK chassis by XLR screw.

- I connected the PCB ground input on only input XLR.

- I disconnected the PCB ground Output.

- The EARTH is connected to the rack chassis by the screw of the Europa connectic.

- I use a RELAY Board. I connected the Ground of The PCB to the Ground of the relay board.

My toroid transformer is far from PCB but close to Outputs XLR, some Centimeters...

any idea?