"Do you have balanced headphones? If so, which ones?"
-Yes. HiFiMan HE-6.
"If not, are you looking at balanced headphones or a balanced amp in the future?"
-I am looking for a balanced amp.
"For balanced headphone output, how important is it to have dual three-pin XLRs as well as a 4-pin XLR?"
-Well, the Eddie Current Balancing Act and Woo Audio WA22 both have dual three-pin XLR as well as a 4-pin XLR (and single-ended output). I feel that if implementation isn't a nightmare, and you don't have to compromise on sound quality to achieve this, it simply gives the amp more utility and diversity in outputs.
"For a balanced amp, how important is it to also have single-ended outputs?"
-Once again, if implementation isn't too hard and doesn't affect sound quality, it's an excellent feature to have, and I feel it boosts the value of the amplifier via sheer utility.
"If single-ended is important, is the quality of the single-ended outputs as important as the balanced outputs, or is this more of a “utility” thing so you can use all kinds of different headphones?"
-Quality is always the utmost concern. I'm willing to accept sacrifice of optional outputs if the sacrifice is made in the name of sound quality. However, the ideal amp, to me, is highly versatile in the different types of headphones it can drive. I'd be much happier with one amplifier that can drive a cadre of headphones. So it's definitely a utility thing.
Other thoughts on the ideal balanced amplifier:
-Overengineered. Over is better than under.
-Versatility. Make one amp that can drive every flagship well, and you have a winner on your hands. This is obviously difficult, given different impedances and sensitivities, but the more headphones the amp can support, the better the general versatility of the product. After all, different people like different things, and the more headphones your amp can be used with, the larger your potential userbase.
-Tubes. Tubes are wonderful. From what I understand, it's hard to drive inefficient headphones with solid state amps, so I guess we're probably looking at tubes. *Moar* tubes. Power, driver, rectifier, whatever you can throw at us.
-Balanced and single ended inputs, to support more DACs. I would imagine the top-end DAC in your lineup will be balanced, so I would imagine we can put a checkmark in this box.
-Dual single-ended outputs.
-Speaker taps. Posts on the back would be a welcome addition. Once again, if it hurts sound quality, forget it. But if it can be done while preserving SQ, it's a solid option.
-Separate power supply chassis. Worth a thought.
-Crossfeed. Some people like this, others don't care. At least warrants consideration. Once again, not at the expense of SQ.
-Spike feet! Cheap way to improve aesthetics and improve heat dissipation.
-Cost should not be an object if compromising SQ is involved. If this is a flagship product, then no compromises should be made.
Thoughts unrelated to balanced amplifiers:
-If your balanced amp ends up being solid state, a tube buffer might be a nice addition to the product line. That way, people who want tubes don't need to compromise. That'd also once again open up your product line to a wider audience, as people with non-Schiit solid state amps might be interested in just such a product.
@ Jason Stoddard & Mike Moffat: Keep up the good work, guys. All of us are looking forward to seeing what you have in store for us.