DAC suggestion to pair with MC275 & Usher Spk

I also have an MC275 and a sub. Rel Storm III in my case. Speakers are B&W 804S. Sounds great to me.

Lately I've been focusing on improving my digital front end, but one aspect I have toyed for a while is relieving the MC275 from reproducing low frequencies. Even if your speakers can't get that low, your amp is still bending head over backwards to reproduce the low end, which is consuming significant power and where tube amps are not best. So, introducing a crossover between the pre and amp and allowing the MC275 only to amplify say 100 Hz and up, while letting the sub amplify from 100 Hz and down looks interesting on paper. This is called biamplification and some people swear by it. I haven't tried it (yet), but thought I should bring this to your attention considering the options you are considering. Please note not all subs can reproduce 90-100 Hz well - my REL for example is not good above 60-65 Hz. Even though it's capable of doing higher fdrequencies, it doesn't sound good.

I hope this is useful.

Certainly 2 MC275 are a good solution. However, think about the heat and the expense of buying/rolling/replacing that many tubes. Might not be an issue for you.

With 2 identical amps you could:
1. Operate each as monoblock and have them reproduce the full bandwidth to each speaker.
2. Have both amps operate as 2-channels, and have amp A feed mids/trebble from channel 1 and bass from channel 2. Same for other amp. Dividing the frequencies prior to the amps would still need to be dealt with.
3. Have both amps operate as 2-channel, but now have amp A drive hi/mids of left and right speakers and amp B drive bass on both speakers.

Keeep in mind the 501 are monoblocks, so they couldn't drive both speakers.

I'm personally inclined for tubes for hi/mids and SS for bass, provided a crosssover sits in front of them. Maybe a 501 is too much (power and expense). Maybe a 252 would do - depends on your speakers and budget, of course. This would be like my option 3, but with SS for bass. I don't know what advantage is there to have with ttubes for bass.

Rbw,

I understand Lenehan is a boutique shop out of Australia, with very limited distribution. Do you know if they distribute elsewhere? There was a forum member whose userid escapes me now, who has a PDX and kept speaking highly of it, but also mentioned the PDX was more like a work in progress than a finished product, so being close to the manufacturer was a big benefit (he was down the road from Lenehan).

BTW, I wasn't aware the PDX was meant to directly drive an amp.