Transparent Interconnect Question....

I can't think of a single reason (in your situation, given your equipment) that you shouldn't choose balanced over single-ended; and not just for noise rejection (which shouldn't be that big a deal for just 1.5m anyway) but because you get so much more signal out of the balanced output of the preamp -- I think that would trump using a slightly less expensive (but good quality) balanced cable over a more expensive single-ended one.

OK, whose gonna take the first swing!?

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Actually, I was generalizing about "twice the signal". It does happen, but not always is it a factor of 2. And I already mentioned that noise cancellation is not the issue for 1.5m. What is really important is that (according to Eldartford) both the amp and preamp have truly balanced output and input circuit topology. Using them results in:

1.) Optimum signal transfer.
2.) No need to go through the unit's inversion circuits to convert to SE at the preamp and back to Bal at the amp. Thus eliminating two inversion steps for the signal.
3.) Better signal-to-noise ratio at the amplifier (since it doesn't have to work as hard to produce the same output.)

These (and there are other) reasons should be enough to produce audibly better results for the balanced hook-up, even if the cables themselves are one level down in quality from the single-ended ones.

N.

Herman,

If there were not a separate buffer circuit in the preamp to keep the SE output electrically separate from the balanced output, you could not use both outputs at the same time. With Krell, Levinson, ARC, and most other premium preamps, you can use the SE and the Bal at the same time because one (or both) are buffered. If the Krell is Bal circuit topology to begin with, then it's likely only the SE output is buffered.

Optimum signal transfer in Bal mode (compared to SE) occurs because the amp is receiving (from the preamp) a full strength push-pull signal around ground. A SE input (at the amp) must first go through an inverter circuit which takes the SE input signal, divides it into two SE signals, inverts the polarity of one of them, then recombines both parts as a balanced signal which the amp circuit has to see. But that "manufactured" balanced signal won't have either as low a noise floor or as high a signal strength as an actual balanced input signal coming straight from the preamp.

So with a (stronger) Bal signal at the input, the amp uses less (possibly half as much) gain to produce the same output voltage as when using a SE input. That results in greater headroom (less distortion at a given ouput to the speakers) than when using a SE input. So it's not just about less noise but better quality as well.

Checking the output specs for preamps that offer both types of outputs, you will notice the Bal outputs are usually rated at around twice the voltage as the SE outputs.

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rats, the situation you refer to is one where the Bal and SE jacks are internally wired together. A typical example are amplifiers that have both Bal and SE inputs, but to use the SE, you need to install a jumper clip into the XLR jack, usually between ground and the XLR's negative hot pin. This is because the RCA hot is connected internally to the plus hot of the XLR while the RCA neg is connected internally to the neg hot of the XLR. The jumper connects the RCA neg to circuit ground in order to make the SE input work. Only now, you are definitely driving only half of the amp's input circuitry with signal.

So you are right, in that you don't HAVE to have an inverter at the input, but then the relative benefits of using the Bal inputs just increase.