Why Single-Ended?

Thanks Almarg

if you google around you will find debate on whether a cartridge is balanced, as I see it that really doesn't matter. The important thing is how you deal with it. if you transformer couple it with a center tapped secondary then that would definitely be balanced. Of course you could take any SE source and do the same thing.

Thanks for the spell check. My point is that when the air compressions and rarefactions hit the microphone it is equivalent to a single ended source. The diaphragm vibrates back and forth. There is no equivalent diaphragm moving forth and back. Same for a speaker, the cone moves back and forth driven by a balanced or SE amp. At the end of the day does any of that matter? probably not. 

As I see it any "advantages" of balanced are outweighed in the home environment by the simplicity and linearity of an SET amplifier. At least that's what my ears tell me. 

 I will admit the only extended listing I've done to OTL amps were Atmasphere at some dealer I believe in San Jose years ago. Can't remember the name or anything else about the system except they were playing vinyl and it did sound excellent, so I get it that many would prefer it. I do remember the guy had a lot of vinyl for sale, they all smoked cigars so the place smelled foul, and the owner was an arrogant jerk, at least he was to me.

So Ralph, you have come over to the dark side with an SE preamp. There is some hope :>)

Full disclosure; my preamp is the Atma-sphere UV-1, single-ended. I decided to buy this unit based on it's sonics and simple design. To me, it does everything right; wide and deep soundstaging, realistic imaging, deep bass extension. It presents a clear, yet classic sound using 6SN7 tubes.
  My CDP and DAC are a balanced design, thus the reason I posted my question. If this preamp or a CJ or Coincident offered a balanced input thru a transformer, it might introduce artifacts thru the circuit.

The way balanced line eliminates cable artifacts is twofold. First, ground is ignored, so the shield is not part of the sound (nor the is noise to which its exposed; in a single-ended system the shield is part of the signal path).

You cannot eliminate capacitance between wires.  Low output impedance helps to lower effect of it, but it so does with single ended design.  It will be difficult to get rid of shield to wire capacitance since many preamps have balanced output referenced to ground.  It will be pretty much any transformerless output stage including my Benchmark DAC1.

I get that it does not make sense for you. But that does not mean it does not make sense. The idea here is to remove distortion sources (now this is strictly my opinion). If you can't use feedback to get rid of distortion, how do you get rid of it? Eliminate distortion sources! A common complaint about tubes: 2nd harmonic (ask any solid state guy). OK- fully balanced differential design gets rid of the even orders. Now we are left with the odd orders. To reduce them, we set bias points in the voltage amplifier such that it cancels the odd orders. Then design the circuit to use as few stages of gain as possible (in our amps there is only one stage of gain, making them a simpler signal path than an SET). Use triodes throughout. Get rid of the output transformer (which may or may not add distortion). Take care to avoid obvious diode issues (proper metallurgy) in component selection. Stuff like that.

You forgot that we are discussing Fully balanced topology and not design of particular amp in general.  Setting bias point, as you described, can be done to single ended amp and has nothing to do with issue that we're discussing.  Please tell me how Fully balanced amp topology reduces third harmonic better than single ended amp.

So Ralph, you have come over to the dark side with an SE preamp. There is some hope :>)

Ha! We've been making some variant of that since the company was founded. Not sure that 'come over' is the right phrase...

if you transformer couple it with a center tapped secondary then that would definitely be balanced.

I very much doubt that there even is such a thing as a center-tapped SUT for the reasons I outlined earlier. We have made up SUT boxes that were entirely balanced using Jensen SUTs. All transformers (including SUTs) are capable of operating single-ended or balanced; no center tap required- works better without it.