Atom D525 mini-PC project, looking for tips

I would not suggest an Atom CPU for Pianoteq, at all. Any of them.

I have just bought the fanless Shuttle XS35GTV2 with Intel Atom D525 CPU and I am just testing Pianoteq on it. I managed to get polyphony of 48-64 at 44.1kHz sample rate nearly(!) without overloads with a buffer of 128 samples. I am just testing the integrated sound card, no external USB, and direct access through Linux ALSA, no JACK yet.

Lowering the sampling rate allows for higher polyphony without any overloading problems at all. Setting the buffer up to 256 samples also allows for a polyphony of up to 96-128 with only minor possibility of overload (with this and the previous "nearly" I mean that you really have to push down sustain pedal and drive across the keyboard wildly up and down to get a few short red overloads on the graph - when turning off the overload protection, I seldom hear a problem in the sound-fuss anyway).

I can report more after testing my external USB master keyboard with built-in sound-card of better quality, and eventually JACK as well.

Well, I was a bit too optimistic when believing that I won't get x-runs (overload glitches) in real life. But just playing the non-dramatic demo song "K1 Blues" makes a few glitches with those settings. So lowering the parameters further will be necessary if you really want to get a perfect clean sound. The sample frequency is the best help, but that is exactly what I wanted to keep at 44.1kHz.

Another complaint goes to the Shuttle. It is fanless, but you really have to let it stand vertically in open air flow on all sides - you cannot just "hide" it somewhere nor even put lying down on a shelf or table. It already heats at almost 70°C (inside temp., not outside!) even when idle and standing. So, maybe, another solution with a small and quiet but active cooler would be more practical. E.g. the Mac Mini is actually even more compact(!), the fan is told to be completely quiet, it only needs to "breath" some air on the backside, and it has a full Intel iCore processor (full power!) and in the basic setup it isn't so much more expensive either.

Hi again. I do not think an external sound card would make much difference. Ok, it could take a bit of the CPU power for managing the USB port, possibly...

Anyway, today, I have done some experiments with an Intel Atom D2800 (BTW: the Intel DN2800MT board is really a nice piece of hardware!) and an external USB-to-SPDIF converter (Musical Fidelity V-Link 192). It seems to be significantly better than D525 (D2800 is dual core, at least). But when really making the effort (beating all the lowest bass keys like crazy, with a sustain pedal pushed), I can still get the CPU overloaded even with the default rate of 29400 and relatively low polyphony. (Well, concerning "such effort": I have never actually made "such effort" with any powerful computer yet, so maybe... ;-))

I think it would need some skillful player to try it with some *real* (though complex) music. Considering any normal usage, I think it actually may be very well usable even at 44100 and some reasonable polyphony.

One more note: I actually tried the same "bass-beating" test on an MacBook Pro 2010 (Core i5 M540 @ 2.53GHz) and the result was not any better: overloaded within a second :-) So, I guess the Atom D2xxx is not bad at all.

(Well, ok, the polyphony was set at 256 ;-))