api 325 conversion

[zmorrow]

Hi all just picked up some 325 cards.

i have some utc a24's i'm gonna use backwards....
Does any one know what value or how to calculate the value of c5 and r1 zobel network for this tranny?

also does any one have recommendations for coverting these to 312?

I'm gonna do the following:

cr1&2 to 1n4007
C1&C2 to 220uf@50
C6 t0 120pf
Remove C4 and r4 replace with jumper.
C3 to 1000uf@16
100Ohm resistor from pin 4 to pin 3

Any experts wanna help me out with my first time.

[emrr]

RCA used A-24's backwards on their API 2520 based preamp, with a 45K resistance across the 15K winding, input tapped to the 600 ohm winding. I've never ever seen a zobel used on a UTC transformer. Also, not sure why you'd want to use those, when you can get the Ed Anderson API clone input transformers much more cheaply, and the A-24's are wanted by pretty much everyone for LA-2A builds. You generally see the carcass of the RCA/API preamps that have been robbed of their A-24's.

[zmorrow]

Doug thanks for your reply.

Well we are using the a-24 because we have alot of them laying around here.
I was aware of the rca trick and i thought we would give it a shot.

[dude24man]

here's a thread that mite help. arty


API 325 to 312...help please.

[ulysses]

Sell your pile of UTCs and use the money to buy some nice new Jensens, with money left over for hookers and blow. Or keep them for when you decide to build your own LA-2A clone.

[emrr]

A potentially critical part of the RCA A-24 usage is the inclusion of the A-33 shield, since the A-24 is not designed for input use. You may or may not find more susceptibility to induced noise without the shield.

[foldback]

Originally Posted by ulysses

Sell your pile of UTCs and use the money to buy some nice new Jensens, with money left over for hookers and blow. Or keep them for when you decide to build your own LA-2A clone.

LMAO

Seriously, look at this place for ideas

Classic Audio Products of Illinois