Spatial M3 Triode Master Preamp/amp choices

@jplunkettj   You might want to contact Clayton and ask him what sort of output impedance he expects with amps that drive his speakers. All the installations I've seen have used amps with a fairly high output impedance.


While I've heard class D amps sound very smooth and detailed, they tend to have the lowest output impedance of any amps. Clayton's speakers may not be designed for that (as seen by his use of amp with higher output impedance). The way you would design a crossover for a speaker meant for an amp of high output impedance tends to be different for a speaker meant for one with a low output impedance. For more on this topic see:
http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html

I know our amps work very nicely on that speaker according to Clayton. I would expect the ARC to be a bit dry on that speaker. The Purifi amp with a tube preamp is worth exploration- depending greatly on who did the implementation of the Purify module. You might also look at Berning as he has some very musical amplifiers that should work nicely with the Spatials.

You'll want a bit of power- 50-60 watts is nice; you'll have trouble clipping an amp with that kind of power. My speakers are 98dB and I find that about half that- 30 watts- is about right in my room of similar size. Owing to the fact that your speakers are 3dB less efficient, you'll need twice as much power to get the same volume levels.


Of course I don't listen at super high levels all the time; most of it is likely less than 1 watt! For this reason I would be careful about the amp you get- you want bandwidth and low distortion, but an important property of the amplifier is also that as you decrease power, the distortion goes down with it to unmeasurable. This is something that SETs do very well, but getting enough power is tricky with SETs (if you run them past about 20% of full power, the distortion that starts to show up causes the amp to sound 'dynamic' because the ear uses the harmonics generated as cues to how loud its playing) since the large the SET, the less bandwidth you get.

So you'll need a push-pull amp. Finding one that has that distortion property I mentioned above is a trick but I can tell you that to do that with push-pull, the amp needs to be fully balanced and differential from input to output. This causes its primary distortion component to the the 3rd harmonic with succeeding harmonics at a much lower level. If the amp does not run feedback then its distortion will be linearly decreasing as the power is decreased. This is desirable because that first watt is so important to getting the system to behave and sound like music.

Other things that will help an amp of this sort- class A operation, and if you can find it, triode output tubes (as they are more linear). If the amp runs pentodes, it will need feedback to sound right, as pentodes are not that linear.