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Audio ADC and DAC kits - AD24QS, DA24QS and DA24DS

( Deutsche Version: Audio ADC und DAC Bausätze - AD24QS, DA24QS und DA24DS)

AD24QS - Audio Analog to Digital Converter 24 Bit / 192 kHz (4^th Generation)

unfortunately sold out, successor planned

AD-IOA - Microphone Preamplifier and more for the ADC

New and quite unique: DA2USB - Digital Audio to USB Interface

DA24QS - Audio Digital to Analog Converter 24 Bit / 192 kHz (3^rd Generation)

DA-IOP - Module for the DA24QS-B with Connectors for Balanced In- and Outputs ("Passive")

DA24DS - Audio Digital to Analog Converter 24 Bit / 96 kHz (Available again!)

DAC kits are available

Click here if you look for information about the obsolete 2ChPre

Click here for a Google search to read what DIY customers wrote in the WWW about the AD24QS and DA24QS kits

Here I introduce my Analog to Digital Converter AD24QS, the Digital to Analog Converter DA24QS ("QS" stands for "Quad Speed") and my DA2USB Digital Audio to USB Interface. The designs went through quite a couple of redesigns and I believe them to be really fine.

With a design like this, it cannot be and it never was my intention to beat the price of cheap devices commercially available. I can beat the quality only. If you need something cheap I can probably give you tips, too.

Click here (or on the photo) for an enlarged view of both devices. (On the left is the AD24QS, on the right the DA24QS.)

The new DA2USB is a driverless USB interface for transferring digital audio signals into a PC with up to 192 kHz / 24 bit. Thus it is a perfect completion for my ADCs. I designed it (admittedly by far not alone), because I often was asked for something like this and I didn't know any comparable solution.

Quick links to the articles, chapters and the most important design files:

Project "AD24QS - Audio Analog to Digital Converter 24 Bit / 192 kHz" unfortunately sold out, Successor planned
      and "AD-IOA - Balanced In- and Outputs and Microphone Preamplifier":

Project "DA2USB - Digital Audio to USB Interface"

Projects "DA24QS - Audio Digital to Analog Converter 24 Bit / 192 kHz" Successor planned
        and "DA24DS - Audio Digital to Analog Converter 24 Bit / 96 kHz":

How do they sound?

Every now and then I am asked about the sound of the converters or if I compared them to other devices by listening. My opinion concerning the quality of (not only my) converters is a very technical one and I must be a little careful because occasionally I might cause objections:

It is very well known what kind of deviations from the original signal a human ear is able to hear (e.g. distortion, frequency response, noise etc.) and also in which amount and under which circumstances this is the case. All these deviations from the original signal are measurable with a precision and sensitivity far, far superior to the human ear. I believe that any electronic system that is able to process audio signals in a way that they are falsified far less than what a human ear is able to recognize has no "sound", i.e., it can not be distinguished from other systems with a comparable quality. Given that, any audible difference is either imagination(!) or a deliberate or unintentional deviation from neutrality by design (and thus again measurable). This is why I do not believe in simple sound comparisons. Microphones and loudspeakers cannot and tube-amps shall not be neutral, for instance.

My conviction in other words: Would I hear the difference between a naked piece of wire and my converters I'd bet, there is something wrong with them. Or with the wire.

When trying to compare mine to other converters please also keep in mind: As far as I know, there are quite few pure analog / S/P-DIF converters like mine available in the world. Most equipment is PC-based, and to compare equipment designed for such different conditions of service would not be realistic - would it?

Some Unnecessary Words about the History (and Me)

The original intention for these designs had been my pure interest of designing such a pair of converters for myself. I aimed a very good technical quality, a couple of particular properties and it should look nice. When the first ADC design, the AD2496, finally satisfied me (after two redesigns), I decided to let other people know what I did and wrote about it on my website (the very first article).

The DAC, by the way, did not work as good as I aimed and it wasn't as elegant either. Any improvement wouldn't do. A completely new concept was required instead, but I had none. Thus I ceased this project.

However, I found it to be unsatisfactory that other DIYs weren't able to reproduce the ADC because they would at least need the PCB. So I started to offer and sell PCBs. Anyway - there were still a couple of components more or less impossible for DIYs to get. Even I had quite a lot of problems to get these odd parts for my sample devices. E.g., many of them are simply not available in small quantities.

Thanks to the people who bought the PCB anyway I saw there was enough interest for kits and I began to provide complete kits. Believe me, this is much more work than just to get hold of the missing components for a single device. E.g., you cannot buy exactly as much as you need - you have to buy packing units and of course from these packing units there will be parts left when the first parts that cannot be bought singly are sold out. Other sorrow was caused by delivery times, allocation, erroneous orders and so on. And, of course, the price for the DIYs should be fair. No, that was not easy.

When the first lot of kits was sold out (to be more precise: The first critical component was sold out), I originally didn't want to continue the kits. But it seemed to become a sad time without selling kits. Once again DIYs reading the article(s) and not being able to build it? And I had ideas how to improve the design, I had a couple of components left over... So I did not only start the redesign of the ADC but also the DAC, because I had a new concept. And I ordered components, once again. Because I prepared the dual channel preamplifier as a kit as well, this time I had to buy and stock 4 times as much components as before... In May 2009 I started one more round of kits, upgraded by the new DA24DS (meanwhile available on request only).

Up to now I made 7 revisions of the ADC-PCB (3 x AD2496, 4 x AD24QS), and another 3 revisions of the DAC-PCB (plus the ceased version). Both designs went through quite a lot of improvements. I am quite petty with details.

Anyhow, this project still remains a hobby for me. But of course, I hope, it is going to become a huge success. *Sigh*...