[Heathkit] Chippewa!

[jeremy-ca]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at verizon.net>
To: <heathkit at mailman.qth.net>
Sent: Tuesday, November 06, 2007 3:08 PM
Subject: Re: [Heathkit] Chippewa!


> On 6 Nov 2007 at 14:54, rbethman wrote:
>
>> I do not know who made the other one - BUT - they do NOT have to
>> match!
>
> Exactly.
>
>>
>> Testing under power will tell you FAR more than the "look".
>>
>> Matching "tubes" is an audiophool phenomena.  An Amperex and an Eimac
>> side by side doesn't matter.  Output is where the rubber meets the
>> road!
>
> Again, absolutely correct. GG doesn't care at all if tubes are
> matched or not. Makes absolutely no difference, as long as both
> are in about the same condition.


In any design using parallel tubes they should be reasonably matched. Why 
you dont see it with many tubes is that the design and manufacturing 
tolerances are very close even between different brands. Credit Eimac and 
RCA for setting the standard that had to be followed by others in order to 
compete.

Heath used a pair of resistors in the SB-200 572B grids as an easy (cheap) 
way to force current sharing close enough to be acceptable as they are not a 
perfectly matched tube.

Chinese tubes can be all over the place but I have my doubts how much actual 
matching is done. I suspect it is a scam.

Carl
KM1H





>
> However, his tubes looked pretty hammerd-on to me: well used.
> They still may be OK. As you say, output power will tell.
>
> Ken W7EKB
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