Custom Dual C84 Rack/PSU. Help please?

[pablobolche]

I have 5 SCA preamps racked on CH01 and they all work flawlessly ... and as I do a lot of live gigs I'm racking a C84 and a A12 on a separate rack with a PSU to move around.

I have a Rack and Mounted a PSU copied from JLM's PSU schematic on his web page... I am using a 220v to 12v/0v/12v 1A Transformer. My multimeter readings are ok and I have +30v / -30v / +48v / 0v. As I have it racked I get to have a CGND. Unfortunately I have no Earth at my work office, I now I have to address this issue, my bad.

Now I am rushing for the C84 and hook it up to my power supply and .... bang .... no sound.. , I thought I broke my C84 while making the change .. Then I re-racked it on the CH01 and .... its running flawlessly again.. So I think the problem might be my Ground Scheme cause I got to anxious and didn't pay attention to what I was hooking up ground wise.

I re-opened my C84 Schematic and researched the SCA Forum reagarding the ground configuration for these Mic pre's and found :
viewtopic.php?t=1558 ... It says to tie all three grounds from J1 to the PSU.

So again I'm rushing to my C84 and hook it up to my new rack with power supply , tie all earths together CGND to AGND to PGND to my PSU's 0v and now my mutimeter readings are all wacky..

As I am unversed in electronics but trying.... Please Advise

Might it be that I have no Earth connection at my office????

Might it be that as I am using JLM's PSU schematic with a 220v 12v-0v-12v tranformer in a 220v to 24v floating GND scheme????? is this right???
If so should I just get a 220v to 24v/0v/24v transformer and hook up 0v to my PGND to CGND to xxx to yyy ?

Or is my problem elswhere???


Thank You
pablobolche
Bolchevique Records
CHILE

[tpryan]

The C84 needs at least +/-27v and will not work with a single-ended supply or a floating ground.