[Hallicrafters] SX-32 audio amp question.

[Richard Knoppow]

     Unless the tubes are very different they do not need to be 
matched.  The amp in the SX-32 runs AB1, very nearly Class A.  Also, the 
cathode resistor is unbypassed so there is a little feedback which tends 
to compensate for any distortion from unbalance.  Its worth checking the 
values of the resistors in the audio circuit to make sure they are close 
to the right values.  If you want to be fussy you can check the tubes 
for similar mu on a tube checker but exact match is not necessary.

On 11/8/2015 9:38 AM, Karel J wrote:
> Hi, writing this on my phone from the ladies clothing store. Please forgive
> crappy formatting.
>
> I moved fairly recently and have been working to get my hamshack up and
> running.
>
> My sx-32 needed some minor repairs and alignment. No problem, but I noticed
> one of the 6V6 tubes was not lit.
>
> The other was quite hot, and audio sounded OK. I slapped in a replacement,
> and the radio is again happy.
>
> Since these are two 6V6 in push-pull, do I need to worry about matched
> tubes? They were the same brand, which leads me to think they may have been
> a matched pair.
>
> Getting on fleabay shows me a few options for tubes. Normally, I buy NOS or
> good tested tubes from hamfests or a place in Vancouver. Anyway, I am
> seeing these *new* tung-sol branded tubes.
>
> Back from a few years ago, you could still get Svetlana 12ax7s (the winged
> c logo, I think) and they were great quality.
>
> So, should I bother worrying about matched tubes? If so, new or verified
> used? Or NOS?
>
> Thanks everyone.
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL