VP312DI MIC NOISE

[Piscolabis]

Hi,

I am testing the VP312DI out of the rack, and I have noise only with the mic input.
The DI goes perfectly with and without post transformer.

Its posible that is was a ground noise?
Cause I dont know how to conect the grounds from psu to module.
Im using a JLM audio Powerstation.

Any idea.
This is my first preamp build.

Thanks to all

 

[Walrus]

Aaaarrrggghhh!  :

What sort of noise!!

 

[Piscolabis]

Im testing with Sm57 without phantom.
Its not hum.

 

[Piscolabis]

Please Help!!!

I give you more information:

In the past I have a bad solder in the gar2520 that made it very hot.I fixed it. Does its posible that it was damaged?

The DI goes perfectly with a clean sound.

I hear the sound of the relays.

If I disconect the mic the noise disapears.
I checked the impedance between 2 and 3 pins in mic input and is 28 ohms.
Its normal?

I heve tested the mic and it woks fine in other pres.

I am checkiing without chasis, with the 38 pin connector directly to the xlrs and PSU, how should this be connected?
Should I make a starpoint for grounds. I dont use ground between the transformer and the main connection
I follow the attached 51x schematic only with +-16v.

Sorry for my english and I will apreciate any help
Nacho

 

[Walrus]

If the pre works in DI mode, then I would think the 2520 is OK.
It may be that the circuit is oscillating when you connect the mic.
For testing purposes, I would wire the mic cable screen to pin 5 and then join pins 1, 5, and 13 to the PSU 0 volts.



Edit: You may be better off posting in this thread.... http://www.groupdiy.com/index.php?topic=40821.0