I posted this in the Head Gear section, but I thought I'd add it here. I bought MorbidToaster's Calyx DAC out of curiosity and shameless consumerism and this is what I thought of it.
With the nuclear power stations across Japan almost all shut off, our electricity supplier threatened us with deliberate blackouts unless we could keep our usage down sufficiently. Japanese people, being determined, have been bearing the heat, my neighbours all with their aircon off and doors and windows propped open. Since my main listening rig consists mostly of Class A components with huge, room-heating power supplies, I thought it would be a good opportunity to see if it were possible to cut down the power I need to use when listening to a minimum, without a loss of sound quality.
The end result was unexpected -- something that requires another write-up altogether, but part of what ended up happening is that I spotted a Calyx DAC for sale and it caught my eye because it is USB-powered. Needing only 5V instead of 100-120V it would use considerably less power than my main DAC, the Audio-gd Reference 7.1, with its three transformers and heavy power regulation. In addition, Calyx has gained fame with their Femto DAC, which, along with the reputation for audio manufacturers in Korea made their standard offering too good to pass up*.
The Calyx DAC is an interesting piece of kit, consisting of a a heavy aluminium block containing, at the rear, a small circuit board with not much more than the minimum required to get balanced output of an 8-channel ES9018 using only USB power, via an XMOS DSP. Plunk it on a desk under a Mac Mini and you have a pretty resolving music system, especially if you use the volume control on the Mac, which works with the Calyx's USB input. The USB input is 32 bit, resulting in fine-grained attenuation down to -127dB, unlike my 24-bit Audiophilleo 1 USB to S/PDIF converter which only goes down to -72dB.
Not surprisingly, the sound quality improves using the separate power supply (looking akin to something pulled out of the back of a computer rather than a hi-fi component, with surprisingly cheap-looking DC cable) or something like the Vaunix lab-grade USB hub. Improving on the very good USB input required me using my Audiophilleo 1 + Pure Power with the coax input. With some back and forth with the Stax SR-009s, focussing on parts of individual tracks, such as the percussion in Waltz for Libby on David Chesky's Club De Sol, while I couldn't make out significantly greater detail, but music in general, typical of the effect of the AP1/PP combo with other DACs, sounded less flat, more 3-dimentional and real with it as the transport. What this amounts to is that it is possible to extract greater things from the DAC through the S/PDIF, but the USB input in the Calyx is the better choice unless you have a high-end converter or transport, such as I do.
One of my favourite albums that is very good for testing the performance of DACs is the classic Getz/Gilberto album (think "The Girl from Ipanema"). It both has a considerable degree of detail as well as having some of the most seductive saxophone playing I've ever heard. My benchmark experience of the album was with an Esoteric K-01, where I heard the most incredible micro detail. With the Calyx using the built-in USB for both power and data, there is, to my ears, something of a flatness to the sound, as if the detail is there but the musicality is lacking, not unlike my experience with the Apogee Duet II. Running from the Calyx power supply improved things somewhat, however switching to the AP1/PP as the transport I felt brought out the musicality and emotion of the music. More so, switching to the Vaunix hub as power instead of the Calyx PSU (which was also powering the AP1) there seemed to be yet more, which surprised me, as the Calyx PSU isn't cheap.
For use with the SR-009s I prefer using the Metrum Octave, which presents acoustic instruments in a way that sounds more real and less digital. However, with the above-mentioned ancillaries and at what would amount to a total cost double, or close to it, of the DAC itself, I'd extracted a euphoric level of musical expression and no longer felt a need to reconnect the Octave. Into the Phoenix, with both DACs using the AP1/PP in a daisy-chain configuration**, it was hard to tell it apart from the Reference 7.1. The Calyx sounded very slightly more forward, something akin to a description of how the Sabre DAC sounds in comparison to the old-school PCM1704UK Kingwa gave me, which was that the Sabre makes voices sound "younger". This impression is not one that shows up in quick back-and-forth comparisons, but was apparent listening to a whole track and then switching DACs.
While it doesn't have to drive headphones and is somewhat less critical, the output stage of the Calyx uses NE5532 OPAMPs. Those people whom either roll OPAMPs like some people roll tubes or whom are critical of anything without discrete components might thumb their noses at the use of such devices in a high-end DAC, but, at least with what I have, I didn't detect any untoward effects of their presence, unless my impressions of the effect of the Sabre DACs on the sound were actually due to the OPAMPs. However, I couldn't discern even the slighest effect of having both the single-ended outputs in use at the same time as the balanced ones, even if I plugged and unplugged while music was playing.
So, overall, though I didn't like it straight out of my computer, since the sound of instruments was rather flat stock, even if everything else about it was excellent. I do like it very with the addition of the Vaunix and AP1+PP. Annoyingly I found one on Audiogon going for only $995 -- a great price and quite a bit less than I paid. I'd say it'll be a great DAC for anyone like me who has gotten into tweaking their computer etc. as a digital source and will try, as I did, to get the most out of it, or someone who wants a "high-end" USB-powered DAC with a relatively small, if not light, form factor.
*It's a pity that it would take years to get back the cost of the DAC with power savings, but power being expensive here in Japan would make it more worth it to buy than the Reference 7.1, which, if left on continuously, would use something like $50/month of electricity.
**Input 2 of my Reference 7.1 has both BNC and RCA sockets connected together, so I can daisy-chain another DAC from the RCA, which is perfect for either the Metrum or Calyx, if slightly less than ideal due to RCA connections not being 75 Ohm until I can get around to replacing them with WBT jacks.
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