OK I have explained this before, but I will explain it again:
1. The DAC is an incredibly noisy device and produces a lot of digital noise which pollutes the power supplies within the DAC
2. The DAC will in most cases use the same power supply for the processing D to A data as powering the output buffer in the DAC, assuming it has one. It should do if it is a good design.
3. The output buffer stage in the DAC has zero gain, as most modern DACs output 2 volts straight out of the D2A chip(s). These output buffers are feedback devices, which is not good for great audio sound. Yes, you get a low impedance output but the audio performance is heavily compromised, as in compressed soundstage width and depth.
4. There should be seperate analogue power supplies, one for the DAC processing and one for the analogue output buffer. This is rarely done due to the cost involved.
5. A good preamplifier will provide superior dynamic range, better deeper bass and a wider and deeper soundstage.
6. Probably one of the biggest draw backs of a DAC/preamp and using it as a preamplifier is its digital volume control. This has been done to death on here so I am not going to bother to cover it.
Very interesting thread and good points in this post. I'm currently in the same process with my ATC SCM50ASL's. I recently changed my DAC from Holo Spring 3 to T+A DAC200. I also have Holo Serene preamp in my setup, which was obviously originally bought to be used with Holo Spring 3. Now I'm trying to decide if I'll keep the Serene in the mix or use DAC200 directly to the ATC's.
At first I owned Holo Spring 3 with the integrated analog preamp module and then upgraded to Holo Serene. I wanted to try what a separate preamp would bring to the mix and even though I ended up keeping the Serene, the difference was small in this case. It added little bit of grunt/authority/punch to the sound though, which is usually the most obvious difference between a separate preamp vs DAC with volume control.
T+A DAC200 has a high quality integrated analog preamp with discreet Class A design and relay controlled volume. The digital and analog sides of the DAC have separate power supplies. Higher end T+A dac/preamps even have own power connectors for the digital and analog sides. I've now had the DAC200 for about a month and currently I'm leaning towards driving the ATC's directly from DAC200 outputs. DAC200 has "0...5,0 Veff / 22 Ohm variable" XLR-outputs while Serene has 40ohm XLR-outputs with Max amplitude of 17Vrms.
The differences I've noticed:
- With direct connection, the soundstage is clearly more open, deep and spacious. It's easier to place the instruments in the soundstage. You even get a feeling of enveloping soundstage with some material, it's an impressive effect. There's better clarity to the sound but the sound never gets sterile/clinical/tiring. Resolution is just extremely good. Low end actually hits deeper with a better texture and nuances. Overall the music just fills the room better this way and everything sounds so right.
-With Holo Serene, the soundstage is in front of you and more flat and even. Overall sound is slightly smoother and more relaxed, yet at the same time it's more immediate and tighter/controlled. But you clearly lose some information on the tracks. It's definitely and easier listen than direct connection. Bass quality is interesting since with Serene, the mid to upper bass acutally hits slightly harder and you get a feeling of little bit more authority and punch, BUT the bass never hits as deep as with direct connection and you lose low end information and nuances. There's less sparkle in the top end of the spectrum.
Few points: I drive my T+A DAC200 with Holo Red streamer to Intona Premium USB cable and I upsample everything to DSD256 with HQPlayer. In DAC200's case, this makes a HUGE difference compared to bitperfect signal to the DAC. DAC200 is actually two dacs in one case since the PCM and DSD sides are completely different designs.
Also all ATC users, remember that you can change the input sensitivity of your ATC's from the default 1V to 2V and anything inbetween if you can calibrate the levels. But 2V can be done without calibration since you just adjust the pot from the default position to the other end. I've played with both and 2V gives you an easier listen but obviously takes away some of the immediacy/authority/grip since with this setting the poweramps are more difficult to drive. But maybe if you use a preamp with very hot outputs, 2V can be useful.
I've also tried Rothwell -20dB XLR attenuators back when I used Linn Akurate DSM/3 in fron of my ATC's. I can't recommend this since they clearly worsened the sound quality. My idea to this experiment was to add the attenuators so that I wouldn't have to attenuate the signal so much in digital domain. But trust me, it's better to just use the Linn's own digital volume control and forget the Rothwell's.
But yeah I tend to agree that if the volume control on the DAC is digital... try a separate preamp. If your dac has a proper preamp built in (analog and preferablt with relay controlled volume) then it's not that simple.
EDIT: I forgot to mention that you can completely bypass the DAC200 integrated preamp section. This is what I've done when used in combination with Holo Serene.
www.passivepreamp.com
