A couple of days ago I took my DAM and headed out to a good friend of mine to do some listening tests.
My DAM at the moment is powered by a Salas BiB at 12VDC. It has a DIYINHK XMOS based USB to I2S interface powered by a Salas Reflektor-D at 3.3VDC. The same power supply powers the isolated side of the DAM.
The first objective was to assess the importance of a good DC power supply instead of a plain transformer. In order to do that I took with me an extra 50VA toroidal with 2 x 7V windings.
My friend’s system consists of Magnepan speakers, a DIY fet-based preamp and DIY power amp (solid state, 60KG monster). It is widely regarded as a very revealing and non-forgiving system. Any change in any of its components (or a component withing the components) is clearly heard.
The DAM was connected to the preamp through its unbuffered outputs.
We gave the system some time to warm up (it was probably a couple of hours) and then sat down to listen. We started with the DAM as it was, with the Salas BiB. We then unplugged the Salas and hooked up the plain transformer.
The change was immediately obvious. The sound thinned, it became more harsh in the high end. It also lost resolution and detail. Going back to the BiB made all the good qualities come back.
Thus, I can definitely recommend a proper DC power supply for the DAM. I cannot say whether it was the Salas that did the work or that any DC power supply would do the same, but the improvement was definitely there. Note that I have the BoM for the Salas BiB I built in the Soekris’ page.
The second objective was to assess the difference that could be made by using a “proper” output stage after the unbuffered outputs.
So I built a pair of AMB alpha20 line amplifiers. I set their gain to 2 and powered them temporarily by the same Salas BiB that powers the Soekris.
Note that my DAM outputs roughly 1V RMS at its output @ 0db since I’m using a filter that includes attenuation at FIR2 (I can’t really remember which one it is though..). This meant that the alpha20 brought its output to a nice 2V RMS.
Going back and forth between using the alpha20 and just the unbuffered outputs, the conclusion was that the alpha20 removed a small amount of the “magic” of the DAM while not really helping in anything besides output volume. I was hoping that it would help improve the dynamics of the DAM – its Achilles’ heel IMHO. In my friend’s system the DAM sounds “flat” compared to his other sources (a heavily modified Sony 50ES cdp, a Buffalo 3 DAC, and an Aune S16). However, this “flatness” is not particularly obvious in other more forgiving systems.
So, my assessment of the DAM so far is as such: It has great detail, exceptional mid-range, proper bass, it is a little soft on the highs, but its main problem is the dynamics. It can sound a bit “flat”, with this “quality” either accentuated or minimized, depending on the rest on the system.
If there was a way to improve its dynamics, to make it more “aggressive”, it would be a stellar performer (with a proper DC power supply of course). As is, it is just great VFM.