Justblairs Audio and Electronic's Pages

The World Wide Web has made the sharing of information easier, more convenient and more rapid than ever before.  It’s not without it’s flaws though the main one being just the huge wealth of sites to peruse, remember and revisit.  It makes it easy for a product to go astray and last week I discovered such a product.

I was updating my links pages recently, and I realised that I had omitted Peter Daniel’s excellent Audiosector site.  I suspect that Peter requires little introduction, but in case you have only been recently bitten by the diy audio bug (in which case congratulations, its a brilliant and rewarding hobby) I had best tell you a little about him.

Peter Daniel’s Audiosector site was one of the first sites I came upon when building my first Gain Clone amplifier.  He supplies both kits, forum support and inspiration to many many builders out there.  His National Semiconductor Lm3875 based amp modules have been built by so many people.  Perhaps the attraction is the simplicity of the designs that beginners love?  Perhaps it is the constant praise from satisfied customers…

The kits are not all Peter does, he has exotically manufactured pre build amplifiers as well.  A quick search on Audiosector reviews shows it’s not just the DIY builders that rate his designs.  HiFi Choice, 6Moons and HiFi+ to name just a few have raved about his designs.

Here is where that dastardly internet plays it’s dastardly games.  I knew already that Peter did DACs already.  I had heard of his NOS (Non Over Sampling) DACs on other sites in fact a couple of years ago. When I built my own NOS DAC from the DDDAC 1543Mkii kit, I had looked at Peter’s site.  His NOS DAC was very well reckoned for instance on this review.  However I had rejected it at the time because I was looking for a native USB solution.  I suppose that when I had settled on the DDDAC 1543Mkii route, I stopped looking so hard at USB DACs.

So imagine my surprise when I touched base with Peter last week and he pointed out he was doing a USB version.  It was like spotting an elephant in the room!

NOS DACs for those that don’t know, are devices that fly against the commercial trends in digital processing.  Normally in a DAC, the signal is up-sampled then filtered, this process is described as oversampling.  It removes measured noise from the signal.  This noise can be created by various nasties such with in-penetrable names like jitter and loss.  By upsampling, the nasties are pushed beyond the audio frequency band, where they can be filtered without affecting the audio signal.  This makes the DACs measure better and designed correctly should have no negative effect on the audio experience.

However there is a huge fan base for Non Over Sampling (NOS) DACs.  Devices that by nature measure less favourably are being loved and adored by their owners.  This is remarkable.  Their proponents maintain that NOS DACs sound better despite poor technical measurements.  I certainly love the timing of my DDDAC 1543Mkii, I can hear what they mean.

Peter’s hidden (at least to me) DAC uses the same circuit essentially as his original SPIDIF DAC.  Comparing the two circuit boards (the USB version is the blue circuit board in the images), you have to look to the inputs to spot obvious differences from a distance.

Getting close up and the differences are more obvious.  What is shared however between the DACs is the filtered power supply design and the output chips.  These are TDA1543, a favourite for NOS DACs, particularly as they are current output devices, meaning they can, with a couple of resistors, output directly to the RCA plugs.  Removing the need for output op-amps simplifies the signal path, reducing parts count and reducing colouration of the signal.  This is a popular arrangement for NOS DAC designs…  Peter has gone for a very simple design here, a theme seen in many of his amplifier kits also.  You can see in the right hand image, the TDA1543 output uses only a Riken resistor and capacitor per channel.

Differences then between the SPIDIF and USB versions of the boards come down effectively to the input chips.  On the SPIDIF DAC a CS8412 receiver is pressed into action to convert the incoming SPIDIF signal to I2S, on the USB version, the conversion is done by the PCM2706/7 USB DAC performs this duty.

Peter has taken care to use identical separate power supplies for digital and analogue signals to avoid digital noise being output in the signal.  This I guess is synonymous with the design of the DAC.  The designs are again simple.  From the transformer, the power is rectified by 4 MSR860 diodes and then smoothed by a large cap and a couple of chokes.  It is then regulated by fixed voltage Panasonic 80xx series regulators before feeding the circuit.  Simple if you read the reviews works in this design.

One great advantage of working with low component counts is that you can really take care over the component choice.  High quality items can be used in the design without the costs soaring beyond sensible.  Peter Daniel claims

“The component choices have been optimized over the period of one year before I released the DACs and the parts are carefully chosen for their sonic signature in specific sections of the circuit: eletrolytics are Black Gates and resistors are Caddocks and Rikens.”

This sheds some light on why this DAC managed to creep below my Radar.  DIY people like to tweak designs, swapping components in and out in an attempt to reach perfection.  It is the rabid arguments over the merits of a carbon film vs. a Russian mil spec metalized resistor that grab my attention in forums.  Peter is clearly one of us, enjoying the tweaking process and squeezing each ounce of quality from a design.  Somewhat selfishly, he has negated the need (and the rewards) of tweaking.  I am sure that some troll will argue that his dedication to optimising component choice has reduced the DIY fun!  Depends what you are after I suppose..

So how much does this elegant design cost?  Latest prices according to Peter are:

SPDIF DAC kit is $280, transformer additional $30 and Cardas dual RCA $20.

USB DAC kit is $250, transformer and RCA extra.

Both DACs are also available as assembled and tested circuits, mounted on

wooden board, at $80 more.

Compare this to commercial DACs and you can see these compare favourably to mid-fi commercial products.  A big plus for the DIY builder is the simplicity of Peter’s designs.  Even with SMT soldering to be done (trust me it’s not that hard) these are the probably within the capabilities of all but the most ham fisted of builders.

However for those that choose to purchase pre-built, all that’s left to do is find a beautifully simple case for your DAC.

At this point I guess I am supposed to wax lyrical about the exquisite musical sound that these little units produce?  Well sorry I am going to have to disappoint you on this one.  I haven’t heard the DAC itself.  As I said at the start of the article, when I was choosing my USB DAC, the Audiosector DAC was only available as a SPIDIF design.  I wanted to go USB, a decision I have never regretted.  The DDDAC 1543Mkii won my vote at the time.  Would  have chosen differently had Peter’s design been available?  Well I don’t know, my decision was definitely a little easier without this DAC in the mix.  My curiosity is burning over this DAC, I would love to hear it against my DDDAC 1543Mkii.

If anyone out there is a proud owner of Peter’s design and wishes to give their impressions, there is a space here at Justblair’s for your article.  If you are thinking about a SPIDIF or USB DAC, the pedigree of this unit alone must make it worthy of consideration!

Peter can be contacted directly through his website, or alternatively he would appear to be Omni-present on many DIY forums to answer your questions about life, love but mostly  audio design.

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