AlanY

But you do need ASIO4ALL to get bit-perfect output, right? And iTunes won't work with ASIO, so I'm not sure this solves the OP's quest for a good transport.

The only question I'd have is whether or not it's possible to get bit-perfect audio out of iTunes on Windows XP. My impression was that it wasn't, apart from certain oddball hardware drivers. You might be forced to use Foobar as a music player.

I'm not sure I understand your reasoning for a flat target curve. Ideally your target curve should be the frequency response of a speaker with a flat on-axis response and a smooth power response, measured at the listener's position. Essentially IEC 60268-7.

The new impedance curve is super interesting. Apart from the OTL tube issue, it's also going to mean that conventional solid-state integrated speaker amps with headphone outs aren't going to be able to power the HD800 without a lot of bass bloat either. I guess it's a non-issue, since anyone willing to spend the money on these will want a dedicated headphone amp too.

There are only so many "little birds" who resist having photos of the internals of their amps posted online. In the tube amp realm, I can think of only one. It doesn't matter though, the 307A stands for itself, both in terms of construction quality and sound quality.

That might make sense given that the amp has selectable output impedance. Sowter is more known for those types of headphone OPTs.

It's a nice looking amp inside. I love the idea of creating a PCB just to be used as a template for assembly (terminal post locations pre-drilled) and copper ground plane. It makes every build repeatable and consistent, while not surrendering any of the point to point charm.

Just to be clear, the $1200 figure was just a guestimate on parts based on my DIY experience. I don't have any inside knowledge. This is much lower percentage markup than most high-end gear. The Bryston BDA-1 for instance, which I consider a good value, is only about $300 in parts including the chassis... about 7x markup. Most high end gear is 10x. The new Reimyo DAC is more than 15x. The 307A is only 5x, and that doesn't count labour, which is considerable, given that these are hand-assembled. BTW, if the iron used is at all above average, the parts cost will be higher. That is the biggest variable.

This wouldn't be unusual. Pete Millett is a fan of the Tent Labs current source boards. He even has a lower cost PCB design on his website that's meant to be interchangeable with the Tent Labs boards. The Tent Labs boards certainly aren't cheap parts... they're $117 Euros *each* (roughly $150 USD right now) and the amp needs two of them. The iron alone is another $300, assuming it's low end. Adding in the chassis and components and the parts cost in my mind is around $1200. Add in cost of labour and the profit margin on these amps is very reasonable for "high end" gear.

IMHO there isn't anything wrong with the look of the TTVJ/Millett amps. They have a certain made-by-an-engineer aesthetic. And the internal wiring of the 307A is very carefully done, almost paralleling the honesty of the outside. You don't get an enormous shiny polished chassis, but you also don't get wallwarts and a rats nest inside.

The manual for the DA11 is now posted on the Lavry site. No mention at all of CrystalLock so they've almost certainly abandoned the steerable clock concept, as they probably also did in later revisions of the DA10. Looks like it uses Philips TV remote codes, so you don't have to purchase a separate remote. They get positive points from me for this. I can't believe Bryston charges an extra $500 for the remote (not the remote circuit, just the remote handset) for their new BDA-1 DAC.

I think the verdict was that later revisions of the DA10 firmware always use the AD1896 and never use CrystalLock/Narrow modes regardless of how the switches are set. Though Lavry changed the manual to include something about a 50 second delay on mode switching, which might mean that the critics were measuring wrong (i.e. they were switching too frequently), but I kind of find that doubtful. Also, it looks like there's no mention of CrystalLock/Narrow in the DA11, and no interface for selecting them, which would seem to confirm that Lavry has settled on just using the AD1896 all the time. Not a bad choice overall in terms of sound quality.

The DA10 had the same spec. From the DA10 manual: "Use WIDE for non-standard frequencies between 30KHz and 200KHz."

But judging from the controls on the front, there's no way to select a completely different transfer function. It seems a lot simpler than what I'm contemplating (which can't be done in analog... the only DSP that can be done in analog is somewhat gimmicky in the sense that it's at best a first-order approximation of reality). How much is the optional remote? Is it included for that price?

Does "PiC" really appeal to anyone? I can understand the appeal of a more sophisticated system (e.g. a DSP-based convolution of the signal based on an average head or room transfer function), but just playing around with phase seems like a gimmick to me. If one was going to add anything, why not add basic bass/treble controls? Other than that, looks very nice. I'd prefer an analog input as well, but I'm not adverse to hanging an A->D analog stage off of my radio tuner just to use a fully-digital preamp, provided it sounds good enough.

The y1 looks sweet; thanks. It's so hard to keep up with the various DIY projects that are available. Do you know of any DIY DACs that use the Burr-Brown SRC4392 to reduce jitter? That's the part I'd really lust after.

It's hard to get rid of all hum beyond -85dB or so in DIY tube amps, especially those where the power supply and amp sections are in the same chassis. If you can't hear it above ambient noise, it may be in the -75 to -80dB range.

That's sweet. Thanks for the link. Maybe I'll build one with the BantamDAC for an office rig.

Is it still possible to get in on the order for the upcoming new PCB version? I confess I haven't been paying any attention to the DIY threads on HF (mostly I've been working on finishing a pair of speakers and thinking about what tube power amp to build).

I wouldn't call the original Millett with BUF634 bright; it's actually quite neutral (for an amp with relatively high distortion from a single-ended no feedback triode stage). The distortion profile of the amp is so strongly dominated by the tube stage that the buffers are comparatively insignificant. It is a fairly tubey sounding amp and by no means unenjoyable.

The BUF634 Millett was actually just called the "Millett" and not the "Millett Max". I have one that I built and really like it. I also bought two PCBs to build the original Millett Max but never got around to it, but I did hear it once at a meet and thought it was better sounding than the original at driving Grados. I know the BUF634 version sound quality depends somewhat on how good the output coupling caps are... I suspect this is probably true of the Max as well though I honestly can't remember the schematic.

Parts Express

Sorry to bump an old thread, but I wanted to ask what those blue grommets you use are called. Also, how do you determine whether to use the blue grommets or the traditional black grommets in a given location? BTW, your work is phenomenal.

Isn't the B22 really a small power amplifier? It stands to reason that it would have more noise, etc. than a small signal amplifier... which might not matter at all when driving a headphone load, but would make the B22 less optimal as a preamp.