anyone know what a "balanced" tube is?

[TwofacePimp]

I was talking to one of my friends about ordering a new set of JJ tubes for my mesa, and he said to make sure that one of the 12ax7 preamp tubes is "balanced" for the phase inverter (V5 position). When I asked him what it meant, he said he didn't really know, but that's what he's been told in the past. So, if anyone knows what this means and if it's necessary, it would be good to hear from you. Thanks!

 

[TwilightOdyssey]

Re: anyone know what a "balanced" tube is?

"Balanced" usually refers to circuit topology, not to individual components, unless it's an input or output jack. I work in audio, and I have never heard of a 'balanced' tube before. This is not to say that such a thing doesn't exist, just that I don't think it matters.

As you know, different tube types are used for different purposes. Some tube amps are able to be configured so that they use both sides of the tube at once (push pull), instead of one tube handling + phase or signal and another handling - phase or signal (single ended). You can swap some tube types for others in some places of the amp, but in others, you MUST use the tube prescribed for that purpose, like the phase inverter, rectifier, etc. Perhaps this is what your friend was referring to, or heard from someone?

 

[Lewguitar]

Re: anyone know what a "balanced" tube is?

Small bottle 12ax7 and 12at7, etc. type tubes can be thought of as being two somplete tubes in one bottle. Probably your friend is referring to each 1/2 of the tube being matched in terms of gain. I just use really good tubes! I've never measured each half for gain or anything. Lew

 

[Curly]

Re: anyone know what a "balanced" tube is?

see this article:
matched phase inverter

 

[lastwinj]

Re: anyone know what a "balanced" tube is?

"Balanced" usually refers to circuit topology, not to individual components, unless it's an input or output jack. I work in audio, and I have never heard of a 'balanced' tube before. This is not to say that such a thing doesn't exist, just that I don't think it matters.

As you know, different tube types are used for different purposes. Some tube amps are able to be configured so that they use both sides of the tube at once (push pull), instead of one tube handling + phase or signal and another handling - phase or signal (single ended). You can swap some tube types for others in some places of the amp, but in others, you MUST use the tube prescribed for that purpose, like the phase inverter, rectifier, etc. Perhaps this is what your friend was referring to, or heard from someone?

pretty close. preamp tubes (12a?7 types) are run single ended. output stages are either single ended or push pull.

germ

 

[TwofacePimp]

Re: anyone know what a "balanced" tube is?

see this article:
matched phase inverter

Thanks Curly! That article makes a lot of sense. Ordered my JJ's, can't wait for them to come in. :32: