It's a DAC Explosion! (V-DAC -> V-DAC II or rDAC?)
Good grief! I bought my V-DAC soon after it was released, and there weren't too many alternatives (at a similar price point) at that time. I haven't been following the tech or the market since then, but I recently started wondering about upgrading the DAC (love it though I do!). When I looked, the upgrade choices were almost mind-boggling! Admittedly, I don't have a whole lot of money to spend on an upgrade, but even the budget+ end of the market seems to have some choice now.
So, my first thought was to upgrade to the V-DAC II (asynchronous USB is probably my main concern). The Arcam rDAC is currently sitting second on my list, but it's ~£100 more than the V-DAC II. I'm going to do some more research, but, if anyone feels the will to impart any wisdom, I'd be all ears. 
I'll report back if/when I made a decision, make the upgrade, etc!
Cheers,
Simon
P.S. Is there a sale forum on this site? If/when I do upgrade, my trusty V-DAC will be surplus to requirements.
I have to ask - Are you only looking at UK companies? If you don't mind buying American then there is the HRT Music Streamer II + which is about the same money as the rDAC. I have a CEntrance DACport which is very nice, about £280 but it's a headphone amp/pre amp as well although extremely portable (great for laptop use). If the included HP amp doesn't bother you either how about something from HK like the Matrix Mini-i or Yulong D100 mkII.
I just ordered the D100 mkII which should be here next week. I will be reporting back soon after with my findings so watch this space.
I have the V-DAC II, and I really like what am hearing. My next upgrade would be an M1. 
Thanks for the comments so far! One thing I hadn't previously considered was HDCD support. I don't have *very* many HDCDs, but I have some. It seems that DACs with built-in HDCD support are quite few and far between...?
Obviously, I want to listed to my HDCDs *as* HDCDs (i.e., 20-bit rather than 16-bit). If my DAC doesn't support HDCD decoding, then my only alternative is to manually re-encode the 16-bit source data as 24-bit. Which is possible, but inconvenient.
What I'm saying is, I'd be happy to pay a little bit extra for a DAC with in-built HDCD support. Does anyone know of any, preferably not much more than the £300 mark? :)
That's an interesting request. If they do support 20bit direct it's not something that many seem to advertise much. Of course it's possible that if detected they will upsample 24bit fixing your problem without the need to convert yourself. How will you do that btw? Do you have a PC that supports 20bit?
I think your best option here is to email the companies for the products you are interested in and ask them. Reading Arcam's specification for the rDAC it seems to suggest that 20bit is not supported without conversion. My DAC seems to suggest the same thing in the spec but it tells you what it's inputing on the screen so I will try to source a 20bit file and see what happens. I'll get back to you on that one.
Thanks for the comments so far! One thing I hadn't previously considered was HDCD support. I don't have *very* many HDCDs, but I have some. It seems that DACs with built-in HDCD support are quite few and far between...?
Obviously, I want to listed to my HDCDs *as* HDCDs (i.e., 20-bit rather than 16-bit). If my DAC doesn't support HDCD decoding, then my only alternative is to manually re-encode the 16-bit source data as 24-bit. Which is possible, but inconvenient.
What I'm saying is, I'd be happy to pay a little bit extra for a DAC with in-built HDCD support. Does anyone know of any, preferably not much more than the £300 mark? :)
Encoding a 16-bit source to 24 bit might not achieve anything. That said most HDCDs I have, Roxy Music e.g. sound superb in normal mode.
I thought about the HDCD thing a bit more last night, and, while there are a few DACs supporting HDCD decoding (the (discontinued?) MF X-DAC is one I saw), I can understand why it's not a commonly found feature.
Really, I think that HDCD decoding belongs right near the beginning of the chain, before any other form of processing (e.g., volume control) gets involved (almost certainly making the conversion to 20-bit impossible).
WMP performs HDCD decoding. (Unsurprising, as Microsoft owns HDCD these days.) However, I left WMP a long time ago, and I can't see myself bothering to fire it up, configure it, etc. to listen to a small subset of my CDs.
I do believe that other media players should implement HDCD decoding (during playback). I use MediaMonkey -- no sign of support there, so far. 
But, yes, there is a workaround: just Google "hdcd.exe". The process I'm planning on using (temporarily?) is:
1. Rip to FLAC
2. "flac -d track1.flac", to get the equivalent WAV
3. "hdcd.exe < track1.wav > track1_hdcd.wav"
4. "flac -e track1_hdcd.wav", to get the HDCD decode into FLAC format
5. Import the HDCD version of the file into my library, marking the album as [HDCD]
Steps 1 & 2 could be combined into "rip to WAV", but I'm hoping to be able to dispose of the HDCD version at some point, when it can be decoded on the fly. Other people's preference may be to not bother keeping the 16-bit original, just the HDCD decode; but I'd prefer to keep an exact rip of the CD, just in case (i) something happens to my CD or (ii) I later discover the HDCD decode isn't perfect.
Cheers,
Simon
I have an rDac and am very happy with it - it sits between a Mac Mini and my Ayre AX7e amp, which drives Harbeth 7/2 speakers. So ostensibly the weak link in the system but it doesn't sound like it. It definitely betters my old Meridian 508/20 that preceded it, itself no slouch. I can't comment on the difference with the VDAC's, it should however last you quite a while if you upgrade the rest of your system, so perhaps worth the £100 extra for that.
One tip - if you get it then buy the Maplins VN10L power supply. Improving the power supply is a recognised route to get more out of the rDac, but most of the options cost the same again, so it's a completely different cost equation. The VN10L is £19.99 though (see link below), which is negligible in the scheme of things. And it does make a difference, taking all that is good about the rDac one step further, and tightening up the bass a smidge. Just remember to set it to 6V before you try it though!
http://www.maplin.co.uk/low-power-multi-voltage-desktop-power-supply-32754