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Stephen, we all know our output tubes in push-pull circuits need to be balanced. But in shopping for preamp tubes for the TC-15, the question of whether it is necessary or helpful to balance triodes or match any of the 12AX7s arises.

I'm assuming it is a good idea to do this for the phase inverter part of the circuit, and perhaps elsewhere. But I'm still too new at grasping the various aspects of tube circuits to be able to figure this out myself. Others could probably benefit from this knowledge as well.

So, what do you advise - balanced, or matched, and at which positions? Most of the tube vendors provide these services at reasonable cost.

Regards,
Jim

Sorry to butt in, but there is a great article here on the subject of the importance of matching the phase inverter.

http://www.guitaramplifierblueprinting. ... verter.pdf

I hope this is helpful.

Joe G

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Some assembly required,
Brain sold separately...

Good article so wont add to it.

Power Tubes:

Some amps are designed to require power tubes that have the same cathode current. Sometimes severely mismatched tubes will cause a hum and even some from the same manufacturer really need to be matched. It doesnt hurt to have them matched.

Re: pre-amp tubes, to quote another source, TheTubeStore

Circuits that actually require matched pre-amp tubes are so uncommon that we only offer this service on an order by order basis. The price for pre-amp tube matching is $5 per tube and not refundable. Power tubes require matching because the way they amplify sound waves can create exceptionally bad sound if they are poorly matched, but pre-amp tubes generally aren't used this way and so matching them is unnecessary.

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Stephen
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