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If you're interested in ordering bare PCBs (printed circuit boards) for either project, just send me an e-mail ().

The forum site has moved to http://ezdiyaudio.informe.com!

The Google Group is no longer active, although the discussions are archived (for now).

Please read my DIY legal disclaimer! (I'm a DIY lawyer on the side .)

If you're interested where in the world people are building my boards, check out the world locator map!

Project 1: ezDual: AC-DC Dual Linear Regulated Power Supply (PSU) Skill Level: Top Background News Schematics Images Standard BOM Fancy BOM Please note that prices listed in BOM, and therefore total costs, may not be current, and may, in fact, be either higher or lower than what I have listed. If this bothers you enough, send me an e-mail, and I'll make changes. Obviously, I do not have time to update the BOM on a continual basis, so any errors are simply due to lack of effort, not just to bug the heck out of  you the casual DIY builder! Click on hyperlinks for data sheets. Please notify me of any out-of-date, missing, or dead links. Also, feel free to comment on my projects, or ask me questions, or tell me something I don't know. Background This is my first DIY audio (electronics) project. I consider it the first step on the way toward building my own Digital to Analog converter (DAC). What I wanted was a "pre-regulator" that could output +/- DC voltage that could then be input to another board. To do this, I looked for a simple design that could use a cheap AC wall wart - I did not want to use a transformer. At the diyaudio forums, I was alerted to a couple of designs that were just what I was looking for. These are (in no particular order): Richard Read (a.k.a. richie00boy): Quality Regulated PSU for Op-Amp Rod Elliot (Elliot Sound Products): Project 05A Preamplifier Power Supply These PSU's are based on the ubiquitous LM317/37 adjustable voltage regulators. There are no surface mount components, only through-hole parts, so it makes it easy for a first project (although some say SMT are easier to solder, but I'll save that judgement for a later date). The PCB and schematic were designed using the software from ExpressPCB, and the 3.8"x2.5" board is fabricated using the ExpressPCB double-sided standard board process. If you are interested in the thread that started it all, please go there for the nitty, gritty details. I think it will show how much I learned during this project. I will update this web page with pics and testing notes as the project moves along. Return to menu. News Update 11-07-06 (Election Day - Go Vote!): Well, I'll just assume you've voted today, before reading this update. So, I made some big changes to the PCB. First, I changed most of the ground pads to thermal pads, to make soldering easier. Second, I added a complete ground plane to the top layer. Basically, the reasons were 1) it can't hurt and 2) it's better for the environment. Update 11-01-06: Added a "Fancy" BOM for this project. Update 8/29/06: I realized that I never posted the BOM, so now I have. Update 8/22/06: Not really an update, but I updated the PCB drawings to achieve a more consistent style between project. I also renamed the project ezDual. Update 7/17/06: Over the weekend I got the three boards and populated (soldered) one of them. Lo and behold, it worked! I set it up for +/- 12.5V and used a 16VAC wall wart. It's hard for me to measure noise on my Tektronix scope, otherwise, I would put some pics of the scope traces.

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Schematic and PCB Drawings

Click on thumbnails to see larger versions.

Schematic	All Layers Dimensions: 3.8"L x 2.5"W
Pads	Top
Bottom

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Images

Top Quarter shown right	Bottom
Top (birdseye)	Top Labeled Link has digikey part #'s
4800uF supply!	New board design added 07/10/07

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Project 2: ezDAC: Asynchronous Upsampling 96kHz Digital-to-Analog Converter (DAC)

Skill Level:

• Top
• Background
• News
• Schematics
• Images
• Builders Gallery
• Technical Details
• Construction Guide
• BOM v.1.5
• Standard BOM (v.1.0)
• Fancy BOM (v.1.0)
• EuroBOM (v.1.0)

Announcement 10/19/07: Revised Design, New Boards On Their Way!

New ezDAC v.1.5 boards have been ordered! Please see news below...

As of September 2007, there are no v.1.0 ezDAC boards left. I would like to keep the project alive, which means ordering a new batch. I would like to get boards made with soldermask/silkscreen this time around, and a few other minor changes to make modding the board a little easier. I also don't want to increase the price of the board substantially. In order to keep cost down, however, I need to buy a relatively large number of boards (50 or more), which will cost me quite a bit up front. I am willing and would be quite happy to order more boards, but only if I know there is strong demand out there, and I won't be left with a hole in my wallet. So, if you - yes you - are interested in keeping the ezDAC project alive, please express your interest here: Interest Check Thread! If you really want to help out with the project, you can offer comments/suggestions on the revised board design (v.1.5) here: ezDAC v.1.5 PCB Design Thread. Thanks! And please keep reading...

Please note that prices listed in BOM, and therefore total costs, may not be current, and may, in fact, be either higher or lower than what I have listed. If this bothers you enough, send me an e-mail, and I'll make changes. Obviously, I do not have time to update the BOM on a continual basis, so any errors are simply due to lack of effort, not just to bug the heck out of you, the casual DIY builder!

Click on hyperlinks for data sheets. Please notify me of any out-of-date, missing, or dead links. Also, feel free to comment on my projects, or ask me questions, or tell me something I don't know.

News

Update 11/13/07

First, let me say "Happy Birthday" to my mom. I love you. Next, I wanted to let you all know that it has now been confirmed that ezDAC v.1.5 has been successfully built by confessit on the SM forum! Here's a link to the thread.

Update 10/29/07

I have added the v.1.5 BOM and construction guide (pdf format) for the new boards. The first set of boards have been shipped out today!

Update 10/19/07

I have ordered a new batch of boards for ezDAC v.1.5! The new PCB drawings are in the schematics section. Changes to the board include shorter, more direct traces where possible, addition of (optional) current regulating diodes (CRD) in the output section, option to use very low jitter surface mount oscillator, more decoupling caps at the IC's, jumperable power rails which will allow for easier mods to the regulator section, and last but certainly not least, the addition of soldermask/silkscreen layers! Thanks, to all those who provided such valuable input on the design of the new board.

Update 8/21/07

Ray from the Netherlands is almost finished with his super-modded ezDAC, and has sent me some pics for the gallery.

Update 7/13/07

Ted S. from Virginia has contributed pics of his recent build of the ezDAC.

Update 6/11/07:

Rich from the UK has kindly created a EuroBOM using Farnell and Rapid as suppliers. Thanks, Rich! By the way, if anyone is interested where in the world ezDAC/ezDual builders are located, check out the new world locator map!

Update 6/08/07:

Another builder, Hao-Wu from Taiwan, has finished the ezDAC! He did it quickly, too, only a couple of days after receiving the board. Hao-Wu has made some measurements.

Update 5/24/07:

With my time being more precious these days, I've decided to look into the art of toaster oven soldering of smt components. I bought the Oster convection toaster oven, and will try to make this work over the summer. What does this mean? Well, I may eventually be able to sell "half-kits", or boards with most of the difficult smt parts pre-soldered (but probably not through-hole). I've had inquiries about selling assembled boards, but it takes me several hours to build a single board. At this point in my life, I simply don't really have the time to do this, unless I could charge hundreds of dollars. However, if I could figure out how to utilize the toaster oven approach, maybe the process of building would be much faster. Keep your fingers crossed for me.

Update 4/12/07:

BOMs now set for standard output. More...

Update 4/11/07:

I made a SPICE simulation for the I/V (current-to-voltage) section of the ezDAC using TINA-TI (which you can freely download from their website). It's called ezDACIV.TSC. Click here for more info...

Update 4/06/07:

JR (aka cyclebrain on ezDAC Builders Group) posted some measurements he performed for the ezDAC.

Update 3/24/07:

I added some new pics to the Builders Gallery. JR from Arizona built the DAC utilizing a transformer-powered ezDual as a PSU, instead of an external AC wall wart. Nice job, JR! I think I will do it this way on my next build.

Update 2/26/07:

ExpressPCB has now switched from lead-free to tin/lead process for their mini-board service. What does this mean? Well, the new boards are shinier, and they should store better. Here's a note on storage from the website:

Storage note: PCBs plated with a tin/lead solder finish can be stored almost indefinitely before they are assembled. Our lead-free boards also store well, but we recommend keeping them wrapped in plastic if they will be stored for more than one month prior to being assembled.

Update 2/15/07:

Leo K. (a.k.a. multibit16 on head-fi) has completed a working version of the ezDAC using mostly the fancy BOM (see the pic in the new Builder's gallery below).

Update 1/16/07:

Finally, someone other than me has built a working ezDAC (v.0.99)!

Update 12/22/06 (v.1.0):

I changed the 10uF decoupling caps to 1206 all around, because I thought the 0805 variety were one of the more annoying components to solder on the board. They are just too bulky in that package. As you can tell by the version number, this will be the final minor revision of the ezDAC. Future versions will focus on "better" regulation and output stages, but that will come at a price. The board will probably be bigger and definitely become more complex.

Update 11/14/06 (v.0.99):

An error in the board was brought to my attention over the weekend. I had added a pad to the mini-plane on the 3.3V reg (U8) just to the right of F1. It was shorted to ground, and of course, that would be bad. Anyway, it's now fixed.

Update 10/17/06 (v.0.98):

I've made a few tweaks to the board since the prototype, but nothing functional has changed.

Update 10/09/06 (it's alive...):

Big freakin update!!! I built the prototype this weekend, and it works (to my amazement, sort of). The only snafu is that the negative rail didn't power up, but since one of the tester's told me he had the negative rail working, I assume I toasted the regulator. Well, it didn't set me back, I just hooked up a spare -12V supply downstream of the regulator (see the pic below with two psu's!), and the DAC is singing nicely. I'm quite pleased so far with the sound, and this is with two power supplies and not the greatest soldering job on the input/output connectors. Also, I used SRC4192, PCM1798, and AD8065 for the ASRC, DAC, and op amps, respectively. I think the next iteration - the reference build - will be quite nice. For this, I will try the higher end AD1896, PCM1794 and AD8610 for the op amps. Also, I may use the Vishay PTF's in the regulator section, where it is possible. Have a look at the pretty new pictures. Also, I've added a (skimpy) little section on technical details. I'm not pretending that I know everything here, but I do know quite a bit about what I've done, and how I did it. I hope this may help someone.

Update 10/04/06:

I started to build the prototype over the weekend. I got most of the smt components done (only screwed up once), but was missing two 0805 resistors that go in series with the XO clock output to the DAC and ASRC. So, I placed an order on Saturday, and should get those any day now. I've posted a pic of the board as it is now. I will try to finish the board this weekend, if not sooner, and start testing it. It turns out surface mount soldering is really not as difficult as I had imagined. In fact, I think I do prefer it to through-hole. Once you get the hang of it, that is. Even the SSOP chips are not so bad to solder (just use a lot of flux!).

Update 9/26/06:

Not an update, really, but I haven't done anything to write about in the past week or so. However, I did practice my surface mount soldering skills last night on an old video card that I had lying around. It's actually easier than I though, and I am now eager to build the PCB. I needed to order a few more things, in the meantime. Well, hopefully, I'll have a good update in a couple of weeks, for anyone who is keeping track of my progress. Also, the second tester got the board this week, and he said he will attempt a build in the next few weeks or so.

Update 9/20/06:

The prototype is currently being built by two testers, who have generously volunteered their efforts. I will hopefully have some time after Oct. 1 to build it myself, but until then I have to write a grant proposal (you know, so I can earn a living and stuff doing science). Some problems have been encountered with the power section, but those appear to have been due mostly to shorts (i.e. solder bridges). We are now sorting out an issue with the oscillator. I've posted a picture of the board (partially built)  given to me by one of the testers who is working very hard on this (goes by the screen name TEDRO on head-fi). Thanks!

Update 9/18/06:

The BOM had a major mistake, which was that the adjustment resistors were all reversed with the fixed value resistors at the voltage regulators. The BOM should now be correct. Also, the schematic for the negative rail (-12V) had the caps polarized in the wrong direction, and that is now corrected.

Update 9/11/06:

I know, I know, not a great date to post this update...I couldn't wait, though, the boards are in! See pics below. I am sending out boards to two testers. Please, keep your fingers crossed for us.

Update 9/04/06 (prototype!):

Finally got up the courage to order the boards today! Woo hoo!!! They should be here by Friday. The pics below are of the prototype version of the board which has a few extra holes for monitoring various signals. The bypass pin on the ASRC has a jumper, so it can be bypassed (duh). If the prototype works, these additions will be removed, as they make the board quite ugly IMO. As for other changes, the only major one is that I re-routed some of the traces on the I/V stage. None of the electrical connections were modified, though.

Update 8/27/06 (v0.95!):

Did some more cleanup. Added some more ground fill on the top side, and also added pads to the inputs for larger bypass caps, along with additional vias to the ground plane. I think at this stage, everything is pretty much set. I'll do one more round of inspection for misconnections or shorts, and will put an order in for the board (hopefully) sometime this week.

Update 8/26/06:

Cleaned up some traces, ground fills, etc. The design phase is very close to being finished (I hope). I also made the PCB drawing higher rez (360 dpi), which will enable photo quality prints.

Update 8/25/06 (v0.9):

Added series 0805 resistors (R35,36) to the MCK lines. Update the BOM.

Update 8/22/06:

We are now in the prototyping and testing stage. This will take several weeks, perhaps, a month or two. Remember, patience is a virtue best served cold.

Update 8/16/06 (v0.8):

Added a decoupling cap to the Vcc pin on PCM1794 (U3). To accommodate this, I had to move R22 to the underside of the board. The BOM has been updated as well.

Update 8/15/06:

Added pads for additional decoupling caps on PCM1794 (U3). I also put in a digi-key order, so I can check all the component footprints.

Update 8/14/06 (v0.7):

I added a transformer (T1) to the SPDIF input. The purpose of the transformer is to provide galvanic (electric) isolation, which should reduce common-mode noise. Additional changes include moving the power inputs (VIN+/-) closer to the regs, and adding some more vias for bulk capacitors on the power supplies to the op-amps. Both the PCB and schematic have been updated accordingly.

Update 8/10/06:

I created a preliminary bill of materials (BOM).

Update 8/09/06:

First, I made some changes to the schematic to bring it up-to-date with the PCB. I've been working mostly on the PCB, and the schematic was getting left behind, so to speak. On the PCB, I corrected the bypass pin on AD1896, which was previously set to high (active). It should be set to low. Otherwise, the data just goes right through without getting processed, and we wouldn't want that. I also put a ferrite in series with VA on CS8416 (F1) and on the power rail on the underside of the board (F2) closer to the clock. The other (input) ferrites were removed. Finally, I re-routed some of the traces near the clock to make them a little neater.

Update 8/07/06 (v0.6):

At this point, it's really a matter of incremental change and small fixes. Getting closer to v1.0...

Update 8/05/06:

Cleaned up some traces, fixed some minor connection mistakes. Added a little bit more ground. Also, you may notice I changed the logo!

Update 8/04/06 (v0.5):

O.k. Now we're really cooking. I added more ground plane to the top half connected by vias to the bottom ground. I am now right at the mini-board maximum for holes on the board (350). This was a suggestion given by amplifierguru on the diyhifi forum. It is supposed to reduce impedance, which is a good thing (or so I'm told). I also connected C26,27 directly to the trace from pin 23 on U3 (this change was prompted by a post from Chris Jennings on the diyaudio forum).

Update 8/03/06 (v0.4):

The lost update. Watch for the DVD coming soon...

Update 8/03/06 (v0.3):

Caps C25,26 were originally connected to ground, because I thought they were for decoupling. After looking at the schematic and data sheet for PCM1794 more carefully, I realized these caps should be connected to the 5V supply. I'm not sure exactly what this is for, but I think it sets a reference voltage for the DAC. I'll have to check this out to be sure. Anyway, I re-routed the caps and made them through-hole, as I will use tantalums here. In addition, I changed all decoupling caps from 1206 to 0805 after reading that smaller smt caps are better for this purpose due to decreased lead impedance. Now the board has 1206 resistors and 0805 caps all around (obviously, excluding through-hole components). Well...one step closer to mini-board production! At this point, I will probably spend some time making sure all the connections are correct according to the data sheets and will start putting together a BOM (bill of materials).

Update 8/02/06 (v0.2):

Added some ferrites on the power rails, re-routed a few traces, and added some extra ground vias.

Update 7/31/06 (v0.1):

Over the weekend I finally got around to working up an initial design for the double-sided PCB. The schematic was also updated. Component values have been left out for now.

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Schematics and PCB Drawings

Click on thumbnails to see larger versions.

Schematic (v.1.5)	All Layers (v.1.5) Dimensions: 4.0"L x 2.5"W
Top Layer (v.1.5)	Bottom Layer (v.1.5)

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Images

Top (v.1.5) New!	Bottom (v.1.5)
Top (v.1.0) Quarter shown right	Bottom (v.1.0)
Labeled Prototype Italics are on bottom layer	DAC + PSU(s)

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ezDAC Builders Gallery

• Leo K. (UK)
• JR (AZ)
• Hao-Wu (Taiwan)
• Ted S. (VA)
• Ray (Netherlands)
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Leo K. (UK)

Leo is using a Burson Buffer on the output of the DAC, and PFM Flea regulators on the 5V and +/-12V outputs.

added 2/15/07	added 2/19/07
added 4/11/07	added 4/18/07

JR (AZ)

added 3/24/07	added 3/24/07
added 3/24/07	added 3/24/07

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Hao-Wu (Taiwan)

Hao-Wu is using PCM1794 and AD8610. He's made two versions of the ezDAC.

added 6/08/07	added 6/14/07
added 6/14/07	added 6/14/07
added 7/23/07	added 7/23/07
added 7/23/07	added 7/23/07
added 7/23/07	added 7/23/07

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Ted S. (Virginia)

Here are some pics from Ted's build. As you can see, he made some custom mods to the design. For example, he uses a surface mount XO (connected by wire leads), instead of the Abracon XO. Also, Ted made a switch so he can have two digital inputs (from a SqueezeBox and DVD player). For the digital connection, Ted even made his own BNC cables!

added 7/13/07	added 7/13/07
added 7/13/07	added 7/13/07
added 7/13/07	added 7/13/07
added 7/13/07	added 7/13/07

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Ray (Netherlands)

Ray has done some nifty mods for his project, which you can learn more about at his website for the ezDAC. He has also contributed his version of the BOM. In his words,

"Here's some pictures of my EzDAC project, as promised. It's nearly finished now, the empty space in the case is for a Flea board i'm waiting for to arrive. The thin white wire that runs from under the DAC board is the miniature coax the Flea is going to be hooked up to. I use two small toroidals to feed three regulator boards that provide +9V and +/-15V to the DAC board. The other supply (with the black tranny) is for The Flea."

added 8/21/07	added 8/21/07
added 8/21/07	added 8/21/07
added 8/21/07	added 8/21/07
added 8/21/07	added 8/21/07
added 8/21/07	added 8/21/07

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Technical Details

Function	Description
Digital Input - SPDIF	Cirrus Logic CS8416 Digital Audio Interface Receiver - capable of receiving up to 192 kHz PCM signals, although I have not tested this, and the ezDAC is designed to upsample any incoming signal to 96 kHz - even if the input is at a higher bitrate.
Digital Pulse Transformer	Newava S22083 - provides some galvanic isolation from noise leaking through on the SPDIF input signal, and creates a balanced SPDIF signal.
Voltage Regulation	The board is designed to accept +/- rails and ground from an external supply. There are four onboard (linear) regulators (3 LM317 for +3.3V, +5.0V, +12; 1 LM337 for -12V) which step down the voltage to feed the various digital and analog sections. Nothing fancy here, but the LM317/337 seemed appropriate for the "ez" theme of my DAC. Also, at least for the op amp section, I like the adjustability aspect. There is quite a bit of latitude here, in terms of choosing input voltages. Appropriate heatsinking (warm-to-the-touch) should definitely be used, especially for the 3.3V regulator.
Power Input	Powering the ezDAC can be done in practically any way that is desired, but typically, one would use a supply in the range of +/- 12-15 VDC (do not use AC), depending on the voltage that is chosen for the op amps in the analog output stage. My own ezDual power supply was made for this purpose. Furthermore, the onboard regulators can be bypassed with superior individual regulators, such as the Jung regulator.
Clock	The aynchronous master clock (MCLK) for the ASRC and DAC is generated by a 4-pin (half-size) Abracon 24.576 MHz (low-jitter) crystal oscillator powered by the 3.3V regulator. The clock recovered by the CS8416 receiver is bypassed.
Upsampling	Upsampling to 96 kHz (fixed setting) is performed by the ASRC (asynchronous sample rate converter), which can be either AD1896 or SRC4192. These two chips are pin compatible.
D/A conversion	Digital-to-Analog conversion is performed by Burr-Brown PCM1794 or PCM1798, which are widely considered to be very high quality DAC chips. The PCM1794 has higher output current and slightly better S/N and distortion specs. It is also more expensive, of course. I have also chosen the (less harsh) slow rolloff mode for the onboard digital filter.
I/V (Current-to-Voltage conversion)	The I/V stage is passive and uses a single low value (25-50R) resistor for each differential signal.
Differential-to-Single Ended Conversion + Gain Stage	The differential signal from the I/V stage is converted to a single-ended signal and gain is applied using a very simple ("textbook") single dual supply op amp per channel. The analog filtering is minimal, only using one high quality silver mica capacitor in the signal path.
PCB Construction	The PCB is double-sided, with a continuous ground plane on the bottom layer that is "stitched" to ground on the top side by numerous small vias arranged in a gridded pattern. To save cost, there is no solder mask or silkscreen. The board uses a mixture of surface mount (smt) and through-hole components. The smallest passive components are 0805, which are really easy after you've done a few. The reset generator is SOT-23, which is small, but also not a problem. CS8416 is SOIC-28, which can (probably should) be soldered one pin at a time. The resampler and DAC are SSOP-28, which are more difficult, but can be hand soldered as well. Every other component should be easy. There are plenty of places on the web to get soldering advice, and I can tell you exactly my technique that I used for this build.

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