THE ZDAC-1 Design Notes

Steve Deckert
FEB 2010


The ZDAC-1 circuit board is a straight forward implementation of the Cirrus Logic's CS4398 DAC chip, CS8421 up-sampler, and CS8416 receiver per the Cirrus data sheets.  The dac chip was chosen over the CS4397, CD43122 and Burr Brown's PCM1793 which can all be used in the circuit with little modification.  My original test models were centered around the PCM1793 and DIR9001 receiver combination, but in the end there was a musical synergy in keeping everything Cirrus. 

With surface mount chips it became practical to have the boards OEM'd to our specification from a manufacturer in China and then complete them here. When they arrive, we inspect them to be sure the parts are per our specification and no substitutions were made.  Then we resolder the entire board by hand using a solder with high penitration and containing silver. Then we do a 48 hour test to insure everything is working to spec. At this point we install the analog stages with matched components and continue to test.

The next step is to install the finished board into the chassis using a special process that eliminates 90% of the vibration or resonance of the board itself.  Yes, tube dampers make tubes sound better and the same principles are true for solid state components.  This technique also eliminates micro-cracks caused from excessive G-forces that occur during rough handling during transport and ensures that fatigue cracks from vibration in the solder joints never develop over time .

To enhance the reliability even further, a high temp oil and gas resistant coating is applied to the finished board. This does two things; locks the part bodies to the board eliminating individual resonances of those parts and insulates the leads and all solder making the board nearly waterproof. The pin spacing on surface mount chips is not much wider than a human hair, so it only takes a piece of metal dust to land between them to create a short and render your DAC useless. This coating virtually eliminates this possibility and makes the DAC immune to sound changing humidity as well.

We make the chassis to match our ZBOX tube output stage so that the two products could be used hand in hand.  It consists of heavy gauge steel with a thick baked on powder coat finish that is almost impossible to scratch.  The finish is on the inside as well, including the holes, ensuring that rust will never plague the appearance. Like all Decware products, the jacks are top grade Gold/Teflon RCA outputs, and the best most expensive IEC connector made.  Switches are high grade toggles with silver contacts.  China can make a decent circuit board.  The parts on the board, ie., caps, resistors, chips, etc., are not made in China.  However, when it comes to RCA jacks, IEC connectors, chassis, and just about everything else... Chinese parts are complete junk.

NOTE TO D.I.Y. guys:

The company we use in China to produce the boards for our DAC is also producing their own version of it and selling it on eBay.  Admittedly this gave me great pause for obvious reasons... but it IS a great opportunity for someone wanting to build their own DAC and install it into their own chassis.  Of course the DAC on eBay is not going to sound anything like our ZDAC-1, but if a guy wanted to buy one and figure out which board version he has, where the errors are on the schematics, what mods to do and so on, you should be able to get a pretty decent sounding DAC out of the deal for a reasonable cost. 

Here is a 130 page thread on the eBay dac:

Decware will not be offering the ZDAC-1 in kit form and will not offer any support or advise to those who purchase the eBay dac.


As everyone knows, tube amplifiers are our main forte and everything we build here is by hand one piece at a time.   I was very reluctant to use a Chinese contractor to manufacture our boards for this project.  I've got many dac boards spanning back over the past 5 years that we built and stuffed here that could be used for this project... and had I used them it would have avoided the need to write this paper entirely.  To build this DAC board in limited quantities here would have cost me an additional $300.00 per board.  That would have translated into a much higher price ZDAC-1 or a watered down version of it that doesn't make the grade sonically.  My goal was to create the very best sound quality possible for under a grand and to make sure that it was well above the overwhelming number of sub one thousand dollar dacs already being sold by other manufacturers.

The way I see it, despite having the board stuffed in China, the parts on it are not Chinese. We do all the QC and final assembly and soldering by hand making the ZDAC-1 a FAR CRY from the typical practice of purchasing a finished product designed and built in China and then re-branding it as so many manufacturers do. 

Steve Deckert




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