DIY Factory

Project 2
A project brought to you by Kev.
Updated 31 December 2005

General Description
An open ended project based around the API 312/325 pre-amp/driver card.

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API-312 Microphone preamplifier card

Typical for it's vintage, the above amplifier card uses PCB tracks as an edge connector. It carries three main components, input transformer , main gain block and the output transformer. The unit pictured has an API2520 as the main gain/driver block. It is not the purpose of this page to look into the 2520 and only to acknowledge that it and many other gain blocks are available to a project like this. Apart from that there is very little more that makes up an API312/325 card.

Looking at the schematic above we can see diode protection on the power supply rails for the opamp in CR1 and CR2 and some local supply smoothing via C1 and C2. R4 and C5 make a zeobel network to control ringing of the input trafo.

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yes it is a Jensen input transformer

Parts List
if there is one

Downloads

Tamas has provided a ZIP file with some schematics and picture
BloakDocs.zip

if there are any

Pics

none yet

ERRATA

So far so good.  Check back for any updates in this area.

Contact :

this page is still under development
and more will be added

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www.diyfactory.com