Re: OPT equalising circuit

In article <d_BSj.6957$ko5.2719@[EMAIL PROTECTED]
>,
 "Alex" <apogosso@[EMAIL PROTECTED]
> wrote:

> Thanks, Partick.
> 
> Your reply is constructive and informative, unlike the other one.
> 
> My case is not a Hi-Fi amplifier, but a radio with a single-ended stage.
OPT
> is quite lousy. It is designed for Rl=7.5K (for 6M5, EL80 or 6F6 tube at
> 250V). Its leakage inductance, referred to primary is as large as 165mH
--
> the windings are not interleaved.

There is an interesting variation on this capacitor thing that you will 
see in some old radios.  Rather than using a single capacitor which 
slowly rolls off the high frequency response, two capacitors are used, 
one across the primary, and another across the secondary of the output 
transformer.  The two capacitors, along with the leakage inductance of 
the transformer, form a third order low pass filter.  This provides a 
sharp cutoff to attenuate noise energy above the desired audio band 
while providing flatter frequency response below cutoff in the desired 
audio band, than a single capacitor can.


Regards,

John Byrns

-- 
Surf my web pages at,  http://fmamradios.com/