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Re: [Amps] tetrode push-pull amp schematics

To: "Vic Rosenthal" <>, <>
Subject: Re: [Amps] tetrode push-pull amp schematics
From: "Jeff AC0C" <>
Date: Thu, 18 Jun 2015 01:52:15 -0500
List-post: <">>
I'm not sure the gentlemen's value assessment on the amps various attributes (other than the focus on clean) - but there is definitely merit to having done something uncommon - just for the sake of doing it. "I've got a home brew push-pull pair here" makes a very nice discussion topic in a rag chew.


-----Original Message----- From: Vic Rosenthal
Sent: Thursday, June 18, 2015 1:45 AM
To: <>
Subject: Re: [Amps] tetrode push-pull amp schematics

The 4CX1500b is designed to be exceptionally clean in class AB1. I don't know if anything significant is to be gained by operating class A as a previous poster suggested. Unless you need a shack heater!
I also don't understand why push-pull is so attractive.
The easiest way to get an unbalanced output is to use link coupling as shown in the old handbooks. You can use a fixed link with a series capacitor as a loading control.


On Jun 18, 2015, at 4:26 AM, Charlie <> wrote:

Brad et al-

Thanks for the replies. Lessons learned:
1) A Startpage search is not a Google search!!!
2) This book link is a goldmine:
3) I still am vague on converting the balanced output shown on the "older"
schematics to unbalanced 50 ohm contemporary design.

Any further ideas along these lines? I too am thinking of a push/pull
4cx1500 amp, Brad. I am looking for exceptional linearity.

Charlie N6CFH

-----Original Message-----
From: Brad Osburn []
Sent: Wednesday, June 17, 2015 3:21 PM
To: Charlie;
Subject: Re: [Amps] tetrode push-pull amp schematics

Under the heading of For What it's Worth

I too am building a push-pull amp (4CX1500B). Basically I'm using Rich's
single ended broadband input (4:1 balun xfmr terminated in 200 ohms, 100
either side).  Which I have completed and according to my impedance meter,
looks good.  I don't care about power just want a clean signal, so I'm
thinking of running class A.  I'm down to the tank circuit and I think I'm
going to have a balanced output into my horizontal loop antenna, (600 ohm
ladder line input)  thru a 4:1 balun. For a screen supply I'm again using
Rich's zener string off of the plate supply.  Generates a whole bunch of
heat thru the dropping resistor, but I think it should prove to be pretty
full proof.
May incorporate the 4:1 balun in my tank circuit by going to a 200 ohm
output, as I said I'm still designing. Found quite a few designs in the 1949

Handbook. I built Rich's balanced tuner and it works well, may incorporate
that in my output as well.

This is my first amp I've designed so I'm just trying for 160-80-40. Using a 2400 volt control transformer (5kva) for my supply and I took 5VDC linear
supplies and redid the control board to give me the 6V+- out I need for
filaments and so I have a regulated filament supply.  Limit inrush to less
than 2X.

For the record Rich said don't do it (band switching). But I've wanted to do

this since HS.


-----Original Message----- From: Charlie
Sent: Wednesday, June 17, 2015 12:41 PM
Subject: [Amps] tetrode push-pull amp schematics

I am looking for a schematic of a push pull tetrode amp. Any ideas?


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