Amp preamp impedance matching...can anyone explain?

@dpop 

It is an interesting topic - but it seems likely that studio gear with 600 ohm loading requirements (apparently to damp ringing?) is operating with very different needs (power, bandwidth?) than a high-end 2ch home audio preamp. Here we need only efficient voltage transfer; no power. Ringing apparently not an issue with good line-level output transformers into any power amp load. Again, the VAC Renaissance V is not prescribing a specific load impedance. 

I do remember that a few headphone models present 600 ohm loads, usually from Beyerdynamic or AKG, which are brands that seem a bit more concerned with studio use than other headphone makers. Most dedicated headphone amps (which are typically OTL and "high current" designs) have very low output impedance, and have no problem driving those or any other headphones. I haven't seen a 600 ohm load specified or required for any other piece of home audio gear in many, many years.

@mulveling 

You might find this article interesting:

THE 600 OHM AUDIO STANDARD, WHERE DID IT GO?

@dpop 

Right near the start of that article: "600 Ohms in order to achieve maximum power transfer to the receiving equipment". Power transfer is not a requirement in this application. It's an interesting article and I'll read it, but I also think this is all confusing the main topic here, which concerns impedance matching a preamp to power amp for efficient voltage transfer, not power transfer - all meaningful power is supplied by the power amp reacting to the input voltage.

@mulveling 

Yeah, I guess I drove it off the rails a bit, but no one else seemed to be paying any attention to the original part of the discussion, so I figured no big deal.