Tube pre-amps: balanced a big deal?

“The trick is that the equipment has to support the balanced standard, otherwise known as AES file 48. Many 'high end audio' components do not, which means that you may not realize all the benefits of going balanced.”

Spot on as usual.

Kenny.

what is the AES standard, again? Which signal on which pins, etc? Thanks---Eric.

Pin 1 is ground, pin 2 non-inverted signal, pin 3 inverted (in Europe, pins 2 and 3 are reversed)

Ground is ignored (no signal current) for output **and** input; signal travels as a twisted pair within the shield, which is used for shielding only and no circuit return. This particular aspect of balanced operation is where most high end audio products simply don't get right; in a nutshell signal ground currents in the cable suddenly means that the cable becomes audible...

Overall the circuit will be low impedance. In older (studio) equipment, the input impedance was commonly 600 ohms (so the source has to be alright with driving 600 ohms with low distortion and no bandwidth reduction); newer equipment tends to be 1000-2000 ohms; semi-pro equipment (such as Tascam) tends to be variable and can be as high as 10K ohms.

Our balanced preamps support driving 600 ohms which very unusual for a tube preamp without an output transformer.

Note: the ability to drive 600 ohms is not the same as a '600 ohm output impedance'! This is kind of hard to do, which is my thinking about why so many high end audio manufacturers don't support the standard.

The only tube pre-amps I am aware of that can drive 600 ohms are Atma-Sphere’s and EAR’s. Atma-Sphere’s because Ralph Karsten is an unusually hip designer, EAR’s because Tim de Paravicini does most his work in pro recording studios (including Pink Floyd’s in London), where that ability is an absolute requirement. But Tim uses transformers to achieve his balanced outputs; to achieve the ability to drive 600 ohms from a tube pre-amp without transformers is the evidence of nothing less than pure brilliance!

You have to think in the long term, if the pre is to be a keeper. You may not need balanced output now, but what if you buy a new power amp like my Arc Ref 75 that only has a balanced input, your pretty much stuck without a balanced out on your pre.