GSSL compressor Help

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GSSL compressor Help

Postby stereokillah » Fri Sep 26, 2008 3:26 pm

Hi and thanks for all your help thread and web site about diy.
I'm beginner in diy and i've build 5 gssl 1 with dbx 202c one with 202x and the other with 2180Lb.
The transformer are 2x115v to 2x15v 15va ( i use it on 220v)
the pcb come to audiokicthen (revesion7)
i added the turbo board all work fine
but i have a hum sound about -60db on 0 make up and -40db on +20 make up.

I ve try search and read ssl help thread night after night.( i'm registred on prodigiydiy but i'm waiting for log)

The earth is connecting to a screw on back panel and after to the pin earth of iec connector

If someone have a idea Thanx
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Postby stereokillah » Sat Sep 27, 2008 12:27 am

OK
i find some solutions but i don't have the time to do


the fisrt one

-IEC Earth is mounted to the Star Ground
-Seperate wires from Input XLR's Pin 1's to Star Ground.
-OV from the Main PCB to Star Ground
-OV from PSU to Star Ground

The second

solder a capacitors 100nf and resistor 10 Ohm 5Watts between the Star Ground and the wire ground pcb

http://sound.westhost.com/earthing.htm


the third
make a pcb psu with 470µF@35V -> 10Ω -> 470µF@35V -> 10Ω -> 470µF@35V

http://www.prodigy-pro.com/forum/viewtopic.php?t=27700&highlight=gssl

the fourth

-buy a Adjustable Voltage Regulator psu by Nmats

http://www.geocities.com/m_natsume/psu.html

- buy a JLM psu pcb

http://www.geocities.com/m_natsume/psu.html

The last

cut and wired the ground on pcb but i don't know where



I will do this solutions one by one tomorow when i have time and i will give the solutions for my units.

Good luck ...
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Postby kubi » Sat Sep 27, 2008 11:52 am

What kind of noise do you suffer from? High pitch noise? 100Hz (120Hz) hum? 50Hz (60Hz) hum? Noise across the whole audio band?
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Postby stereokillah » Sat Sep 27, 2008 1:32 pm

HI
the high noise is about 60hz
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Postby stereokillah » Sat Sep 27, 2008 4:45 pm

i do a printscreen of frequency when the make is at +20
Image
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Postby kubi » Sat Sep 27, 2008 4:51 pm

60Hz means this is hum that occurs before the rectifier.
Your mains transformer is most likely introducing the hum if your grounding is alright.
Could you please provide us with a photo of your compressor's inner guts so that we can see the grounding scheme used?
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Postby stereokillah » Sat Sep 27, 2008 5:45 pm

thanks Kubi for your help


the pin 1 of xlr input are conncet to the screw's ground

the transformer ground wired to to screw with a 100nf and 10r parallel

and the screw to iec
Last edited by stereokillah on Mon Sep 29, 2008 10:26 pm, edited 1 time in total.
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Postby stereokillah » Sat Sep 27, 2008 5:56 pm

I have one unit with a transformer 5va and with the 100nf and the resistor 10r there no more hum
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Postby kubi » Sat Sep 27, 2008 6:11 pm

I bet it's the wires from the transformer's secondary winding (brown, red, blue). These wires are running in parallel to your signal wires (black) and introduce noise.
Try to lift/move the transformer's wires while the unit is on and you will instantly notice a change in noise level.
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Postby stereokillah » Sat Sep 27, 2008 7:01 pm

thanks
but i 've tried to move the wires and after move the transformer but nothing.
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Postby nrgrecording » Sat Sep 27, 2008 7:22 pm

If you have a dual DC power supply you could check if it comes from the transformer and the AC wiring.

Try to remove the connection between Pin 1 and the chassis connector of the XLRs. Remove the ground wires to see if it gets better (just for testing) :wink:

I had Problems with one SSL when using metal-stand-offs - but you're using plastic so thats fine.

Did you removed the powder coating completely at the starground? Otherwise its possible that there is NO connection to the chassis. I like to use self-locking-nuts or chopper discs here. I use an angel-grinder to remove the powder coating. Normally it is done by putting a label on the surface of the case before the powder coating process. We have to do it afterwards.

Frank.
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Postby stereokillah » Sat Sep 27, 2008 8:04 pm

Thanks nrgrecording

I've tryed to disconnect the the pin 1 xlr to the chassis and remove the ground wire and the noise stay no change.

Yes i have removed all the powder coating under the startground.

I really think thats the transormer because i have exactly the same unit with another transformer (5va) and i don't have moise on it.
It's build with the same compenents.
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Postby nrgrecording » Sat Sep 27, 2008 9:11 pm

5VA? Maybe thats the problem. Even the small "onboard" transformer for the pcb is rated with 10VA. I think I've used 20VA.

Frank.
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Postby stereokillah » Sat Sep 27, 2008 9:17 pm

NO

the 5va work fine on my unit

the others, 15va have this hum noise.
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Postby nrgrecording » Sat Sep 27, 2008 9:20 pm

Interesting! :D
Ok, don't keep us in suspense... rip out the transformer from the other unit and let us know. :wink:
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