[Amps] 572Bs

[Carl]

Thats the first Ive ever heard of that, better tell the old BC engineers who 
just used what came in the door.

OTOH, in parallel you are dealing with a single bias supply or lack therof 
for zero bias. Matching became important since sweep tubes were all over the 
place as were also RCA's 8122 disaster. With varying bias requirements for 
the same idle current matching was needed to keep one tube from running away 
to quick destruction.

Good transmitting tubes are built to repeatable tolerances that dont require 
matching. Ive yet to find a need for matched 572B's from China even in a 4 
tube amp. The quickest way to destruction is to keep using the old parasitic 
suppressors, its simple to build much better ones and with no voodoo science 
involved....get the parts from Mouser for a few bucks.

With 3-500Z's its the same, they dont need matching. Any uneven color is 
usually uneven cooling, especially in a Heathkit. A slight real difference 
is unimportant,tantalum plate 3-500Z's should be run with a little color 
anyway for longevity.

Carl
KM1H



----- Original Message ----- 
From: "Al Kozakiewicz" <akozak at hourglass.com>
To: <amps at contesting.com>
Sent: Wednesday, January 19, 2011 10:26 AM
Subject: Re: [Amps] 572Bs


> In any realistic parallel application. matching is not important.  You 
> match tubes for gain in a push-pull configuration to ensure linearity as 
> each tube only conducts for half a cycle.
>
> Al
> AB2ZY
>
> ________________________________________
> From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf 
> Of Paul Manuel [k4pdm at yahoo.com]
> Sent: Wednesday, January 19, 2011 8:26 AM
> To: amps at contesting.com
> Subject: Re: [Amps] 572Bs
>
> --- On Wed, 1/19/11, Randall, Randy <Randy.Randall at uchealth.com> wrote:
>> Got mine from RF parts.  Matched
>> quad for a Ameritron 811A.  Working no issues.
>
> Thanks, Randy. That brings up another question, is matching important in 
> grounded grid operation (a Clipperton L?) I read somewhere that it is not.
>
> 73, Paul K4PDM
>
>
>
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