Solid State Pultec question
« on: November 24, 2004, 09:12:34 PM »
Hi all,

I'm finishing up a Pultec with a Jensen input transformer and Sowter inductor. I want to try using an API 325 card for the amp. My question is this: I have a regular 325 card and a variant with a Jensen JE-11P-1 1:1 input transformer. Would there be any particular advantages or disadvantages with either version of the 325?

Here's the 325 schematic

Thanks
Seth

The definition of insanity: "Hey, this thing could be really cool - if I had the money to fix it up, which I don't, but if I did it could be really cool - if I had the time, which I don't, but


Solid State Pultec question
« Reply #1 on: November 25, 2004, 05:56:30 AM »
Hey Seth.

I have to say that in the grand scheme of things I know very little.  But I'll say that I'm working on a similar project with a Quad Eight line amp.  The line amp doesn't have an input transformer.  As far as I know the filter section's output is unbalanced.  So why use an input transfomer you may be able to use someplace else.  

Perhaps that Jensen may impart some sonic characteristic though?  

I get my panels back from engraving for my Pultecs in a matter of days.  I'm working a mount for my Triad inputs.  Then it all gets thrown in a case.  Perhaps we'll both have pics before the new year.

rafafredd

Solid State Pultec question
« Reply #2 on: November 25, 2004, 08:53:36 AM »
Pultec used interstage transformers between the EQ section and the gain makeup amp to macth impedances/noise, so a 1:! won´t be of much effect in here.

Use the 1:1 at the input, before the EQ section, then just shunt the input of the 325 card with a resistor of the desired filter impedance. (This resistor can change the way the EQ section works, so be carefull about this value).

Solid State Pultec question
« Reply #3 on: November 25, 2004, 11:28:20 AM »
Thanks guys. Rafa, could you explain a bit more about the resistor?

Thanks.
Seth

The definition of insanity: "Hey, this thing could be really cool - if I had the money to fix it up, which I don't, but if I did it could be really cool - if I had the time, which I don't, but


 

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