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GSSL compressor Help

Verfasst: Fr Sep 26, 2008 5:26 pm
von stereokillah
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

Verfasst: Sa Sep 27, 2008 2:27 am
von stereokillah
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/viewto ... light=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 ...

Verfasst: Sa Sep 27, 2008 1:52 pm
von kubi
What kind of noise do you suffer from? High pitch noise? 100Hz (120Hz) hum? 50Hz (60Hz) hum? Noise across the whole audio band?

Verfasst: Sa Sep 27, 2008 3:32 pm
von stereokillah
HI
the high noise is about 60hz

Verfasst: Sa Sep 27, 2008 6:45 pm
von stereokillah
i do a printscreen of frequency when the make is at +20
Bild

Verfasst: Sa Sep 27, 2008 6:51 pm
von kubi
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?

Verfasst: Sa Sep 27, 2008 7:45 pm
von stereokillah
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

Verfasst: Sa Sep 27, 2008 7:56 pm
von stereokillah
I have one unit with a transformer 5va and with the 100nf and the resistor 10r there no more hum

Verfasst: Sa Sep 27, 2008 8:11 pm
von kubi
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.

Verfasst: Sa Sep 27, 2008 9:01 pm
von stereokillah
thanks
but i 've tried to move the wires and after move the transformer but nothing.

Verfasst: Sa Sep 27, 2008 9:22 pm
von nrgrecording
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.

Verfasst: Sa Sep 27, 2008 10:04 pm
von stereokillah
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.

Verfasst: Sa Sep 27, 2008 11:11 pm
von nrgrecording
5VA? Maybe thats the problem. Even the small "onboard" transformer for the pcb is rated with 10VA. I think I've used 20VA.

Frank.

Verfasst: Sa Sep 27, 2008 11:17 pm
von stereokillah
NO

the 5va work fine on my unit

the others, 15va have this hum noise.

Verfasst: Sa Sep 27, 2008 11:20 pm
von nrgrecording
Interesting! :D
Ok, don't keep us in suspense... rip out the transformer from the other unit and let us know. :wink: