A bespoke audiophile tube DAC: measurements and discussions. And politics season, a low point.

As per the title and image, this post will be a nebulous one because we're not looking at an easily-accessible mass produced product. 🤔

The reason is because we're looking at what appears to be a one-of-a-kind device that's not advertised, the company making it doesn't have any web presence with only a handful of posts I can find over the decades referencing the company/person who makes what appears to be typically tube-based products.

I came across this unit from an audiophile friend who commissioned this designer/maker for a good sounding DAC with tubes. This was what he got; the first iteration at least.

As you can see, it's a 2-box unit with identical metal chassis except for some cut-out differences for the volume control in the DAC section, a 6.35mm headphone jack (not pretty!), and digital input selector (coax, optical, USB). We can see the tubes sticking up from the DAC box. The box below is the (presumably linear) power supply with its own power button and a "dummy" knob that I guess is just part of the generic case.

I was told that the DAC chip inside is the ESS ES9038Q2M which we've explored previously like here and here.

The boxes are metal and of basically identical size: ~7.5" x 13" x 3". The DAC box is quite light, about 1.95kg, and the power supply weighs a bit more at 2.5kg.

AudioQuest DragonFly Copper: Review and Measurements. A classic dongle DAC returns. (And Rubber Soul - 2026 remix.)

Audiophiles following the news cycle know by now that after seven years, AudioQuest has released a new DragonFly USB DAC. The DragonFly Copper (US$250, CAD$345) was spoken of at High End Vienna 2026 and started shipping in September, replacing the Cobalt at the flagship. As usual with a new Dragonfly, the forums and review sites lit up within days of the announcement (see sites like this, or this). Recently, I even got E-mails from blog readers asking when I was going to review this device, so here it is by request. 😉

Over the years, I've measured these little USB DACs going back to the DragonFly v1.2 in 2014. More recently, I wrote the two-part series on the DragonFly Black in 2017 with a good chunk of that examining MQA "rendering", and then the three-way comparison of the Cobalt, Red, and v1.2 in 2019. In that last article, the Cobalt did not exactly manage glorious performance on the test bench, clipping at 100% volume with 0dBFS material, THD merely on par with the ancient v1.2, and higher idle current draw than the Red despite all the "low power" marketing. The Red, as I wrote back then, was the winner for lowest distortion among the Dragonflies.

So in my mind, the Copper arrives with something to prove at least to this "more objective" audiophile if it truly is to be a better device. In the company literature, AudioQuest claims to have made progress in 3 main areas: "twice the output power" as a headphone amp, "25% lower current draw", and the "high-conductivity copper-plated case" allows "for improved RF-noise drainage". We'll have a look.

I bought this DAC through consumer channels and this post is in no way company-sponsored.

FiiO K11 R2R DAC: Affordable R-2R desktop DAC & headphone amp. Let's talk about R-2R and euphonic preferences.

It has been more than a year since I last measured or reviewed a DAC!

To be honest, in 2026, DACs are IMO boring from the perspective of expecting any sonic progress when it comes to high-fidelity audio. They are very much a "solved problem" and will not pose any challenge for the audiophile who desires accuracy. Unless there's some new technology to evaluate or must-have features, digital-to-analogue conversion has clearly matured to allow extremely high resolution playback - perceptibly perfect even - within reach of basically everyone in the last decade.

[In the big cultural-level picture, I think we're at the phase now with less expensive products (eg. Chi-Fi) where more than adequate function has been achieved and we're going to be seeing an emphasis on "Design-Driven Innovation" where emotional, symbolic, and esthetic significance become more important with each generation for product differentiation. I think we're already seeing this with the FiiO line-up as I describe related products to this at the end of this post. In time, I suspect this will be an existential threat to many current High-End brands.]

Because of that lack of excitement around evaluating yet another DAC objectively, for more than 6 months now, this FiiO K11 R2R DAC (US$176, Canada link) has been sitting on my table for evaluation! 🙄 I bought this with the plan of using it in my office at the hospital for desktop speaker playback and headphone listening which I'll do after publishing this.

Make sure not to confuse this model with the slightly less expensive FiiO K11 non-R2R DAC (US$145) which uses the Cirrus Logic CS43198 chip. Feature-wise, I think they're very similar and look identical other than the stylized "R2R" stamped on the top of the case.

Okay, let's put this through its paces...