Why tube amps don't have balanced inputs

If you haven't noticed, most tube amplifiers do not have a balanced input. Paul helps us understand why.

[genez]

I found (and still find) that balanced XLR offers an exactness and clarity that unbalanced can not match. But, if you seek a mellower than real life sound? Something more homogenized in effect? Balanced may not be what you seek.

[Michael-bjsz]

Primaluna makes tube amps with balanced inputs. I’ve seen McIntosh tube amps with balanced inputs and these are just 2 among many.

[johnlebeau]

A 12AX7 is indeed a dual tube, as are most if not all of the 9 pin miniatures. I am dubious about the advantage of balanced circuitry unless you are running 50' cables. Since I have never heard, and am sure I never will, otherwise identical electronics in balanced and single ended mode, I cannot say for sure.

[stevekirby]

Except that most tube amps with single ended inputs have another tube for a phase inverter, typically just before the output section (on each channel). So if you had a true differential input, you wouldn't need that tube and you could now use both sides of a (hopefully gain balanced) 12AX7 or similar for your balanced input. Actually saving the 2nd PI tube. Only problem there is that you wouldn't be able to handle the option of a single ended input. Which severely limits who could buy the amp. So it's better from a marketing standpoint to have a single ended input to accommodate the most users, and convert to differential (push/pull) after the initial gain stages. As you say, transistors being cheap and simple enough to apply, it's easier to design something that will handle either input.

[spacemissing]

Try to design one and you will soon understand why.

[acitizen]

Audio Research has been making balanced tube amplifiers for decades.

[RushFan]

Love your videos Paul. Just a heads up, next to American beer, EVERYONE else makes really strong beer. :P

[shanestephenson]

Hi Paul it's Shane from Australia I'm a big fan mate love your work and "l Do Subscribe" 😁👍🎧

[tomasw]

I'm working on a Audio Research Reference 300 mkii. I'm looking for an adapter to test it. It ONLY has a balanced input.

[dhpbear]

For a single-ended input stereo amp. you'd have 1 tube for the 1st preamp stages, another for the 2nd preamp stages, and one for the phase-inverters.

For a balanced-input stereo amp, You'd have 2 extra tubes for the 1st and 2nd preamp stages, but you'd *eliminate* the phase inverters! That would be a net increase of only one tube!

[arthurott]

I've owned several BAT tube amps that only had balanced inputs.

[samgates]

You could use Transformer inputs an outputs but good transformers are very expensive.

[hugobloemers]

I am not sure why if you have a balanced input do you need to have an amplifier that is balanced all the way. The advantages of balanced is to have noise cancelled out in the interconnects. Once you are inside an amplifier this can be mitigated very well with a single ended circuit. You could even have a balanced input transformer based attenuator and have the secondary coil unbalanced out.

[brianyoung]

Paul just some tube trivia, 12ax7= 12.6 volt heater, ax has to do with internal construction, 7 useful elements.

[kirmussaudio]

To say tube amps do not have balanced circuitry does not reflect on all tube manufacturers. Majority of higher end tube manufacturers offer both RCA and balanced connections.

[gryphongryph]

If a product sound better balanced than single ended, then it is bad design, balanced need 2 of everything, making everything double expensive, why not use the money for better parts, also home audio, not much need for balanced, and I own balanced and single ended equipment.

[stephensr]

Most valve amps with XLR inputs are not actually balanced. On the inside you will find that only one of the + pins is connected.

They add a resistor to reduce the higher balanced signal voltage to match the RCA. In practice this means that you get the convenience of being able to use a balanced cable however you don't get any of the advantages balanced offers.

[mikelm]

Also the user of tube amps often enjoy the high 2nd Harmonic Distortion that tube amps often create. Balanced working would tend cancel the 2nd HD.

[AnimusInvidious]

Please don't stoop to groveling for subscribes. Not classy.

[cryptoclyps]

listening this through balanced Loxjie P20