ECP Audio/Beezar Walnut X.3 DAC

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by TomB, May 20, 2021.

  1. TomB

    TomB MOT: Beezar

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    Interest has developed lately for the ECP Audio/Beezar Walnut X DAC. My intent, if you will all allow, is to start this as a detailed build thread, similar to what I did with the T4 Headphone Amplifier. Posts with photos and detailed descriptions will be posted almost daily, once the actual build begins.

    Of course, I've sold all of my remaining stock - including one that I had intended to keep as my personal DAC. So, I was sort of forced into building more if I wanted to have one ... and I definitely do. So, I received further inquiries about more Walnut X DACs and asked the interested parties if they'd be willing to help with the initial investment by pre-ordering at 50% of the sales price. They did, so here we are.

    I'll be building 5 DACs, counting the personal one for me.

    Of course, the first thing I did was contact Doug Savitsky, the DAC's designer. Maybe some of you have heard of the DSHA-3F or T4? (Tongue in cheek, of course) Those of you who've invested in those amplifiers are well aware of Doug's achievement as probably one of the most pre-eminent headphone amplifier designers in our headphone culture. I personally think he's the best, but I'm obviously biased. ;)

    Anyway, I contacted Doug because I needed more PCBs. Of course, the first thing Doug asked was whether I needed any changes. I said yes, because the RCA jacks were a tad too far back on the PCB, but that was it. Needless to say, I was very surprised to find out Doug included pads on the PCB for not only the sterling Lundahl line-level output transformers used before, but he also included pads for the top-of-the-line Lundahl, amorphous core transformers. So, prospective customers can choose either option. Remember, however, the amorphous core Lundahls are very much more expensive than the regular Lundahls, by over 3 times. Multiplied twice for stereo, that's quite a bit more money, or $1375 vs $1000 standard.

    I'll go into a bit more detail on the basics of the Walnut DAC as things go along, but suffice to say it incorporates an excellent Wolfson balanced DAC chip, asynchronous USB at 24-bit, 192kHz, beginning with a genuine Amanero USB board, and outputs through Doug's proprietary DSHA-like, fully differential amplification section, to the Lundahl line-level output transformers. The DAC itself is single-ended on the output, mainly because it was designed as the perfect complement to the T4. However, we understand that some have used it with the 3F with excellent results. Of course, it's perfectly suited for almost any other headphone amplifier or music source in a component stereo system.

    Here's some pics of the Walnut X.1 DAC:
    [​IMG]
    [​IMG]

    Details on the innards are as follows:
    [​IMG]

    The pic shows an Amanero clone board with which I had a dubious flirtation. We only use genuine Amanero boards anymore.

    More to come!
     
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  2. TomB

    TomB MOT: Beezar

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    There's an awful lot to do to bring a product to market at the point of sales. Besides a lengthy prototyping, there's the process of lining up all the suppliers, contacting them, getting quotes, making final checks that the items and their dimensions will work, etc., etc.

    As mentioned, it all begins with the PCBs. So after contacting Doug and receiving a new PCB design, the first thing to do is order the PCBs. Those represent an investment of several hundreds of dollars and up to two weeks before delivery. So, after receiving a couple of pre-orders, I got that going, first.

    Here's an image of the new PCB design:
    [​IMG]

    Nothing really different from the old one, except the RCA jacks appear to hang of the back of the PCB. That's because there's a 2mm gap between the PCB and the back plate. Before, the jacks lined up with the edge of the PCB and it resulted in the jacks being slightly recessed in the back plate. Nothing functionally was affected this way, but still - not perfect.

    The other thing to notice is double the number of pins on the transformer pads. That's to allow for the amorphous core Lundahl option.

    One thing Doug and I did that in retrospect, may have been a bad decision, was to make the Walnut X DAC as small as possible without resorting to SMD caps and transistors in the power supply. All of those big electrolytics and TO-220 transistor pads are for the fully linear-regulated power supply. So, it's as small as we can make it.

    That small size is counter to marketing practice with a lot of headphone amplifiers and DACs. One headphone amplifier manufacturer in particular, who shall go nameless, uses very simple amplifier circuitry combined with almost foot-long traces on the PCB. The result is a very large case that is then machined and anodized to perfection. They go for very high prices, including a similarly cased power supply.

    When we went very small with the Walnut X DAC, passing glances from many seem to dismiss the DAC as puny and lightweight, contradicting the ingenuity of the circuitry and layout inside. We're sticking with it, though, and some are beginning to find out the Walnut X DAC punches well above its size. :)

    The second supplier is the transformer mfr. Lundahl is sourced from Sweden. There is a US distributor, but if their stock is limited, the lead times can be significant. I ordered three sets of transformers to start (two pre-orders and my own) and can add more if the DAC sells. Transformers are the last item to be soldered into the PCBs, so I can add them later while still building the 5 DACs total.

    Luckily, I still had 5 sets of machined casework left from SwiftAtlanta. Hence, why I'm building 5 for now.

    I did not have any wood left, though, so also confirmed with Doug that he can supply the DAC's sides. Doug works best with a fully assembled casework piece, though, so I spent yesterday assembling an empty case. I will be shipping that to Doug this morning.
    [​IMG]

    Lastly, I'll be ordering parts from Mouser later today or tomorrow. That takes a while, because I have to compare what I need with what I already have on hand and make a detailed shopping list. Luckily, none of the parts (I hope) are long-lead items. Plus, Mouser can get things to my house in 3 days just using normal shipping.
     
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  3. YMO

    YMO Friend

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    I hate to ask....but why USB only?
     
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  4. Armaegis

    Armaegis Friend

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    A wolfson? Time for a head-to-head vs the gamma3 :D

    Since we have transformers on the end, could this not have also been built with XLR outputs?
     
  5. TomB

    TomB MOT: Beezar

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    Several reasons, all good ones:

    1. ECP Audio/Beezar Audio focuses on minimalist designs with absolute quality as the focus. Multiple inputs and a smorgasbord of connectivity and options is absolutely counter to that design philosophy.
    2. USB is still the most prevalently used connection method with DACs, period.
    3. With asynchronous conversion of the USB stream, via the TI SRC4190 chip, asynchronous USB is arguably the superior method of connection, period. Here's a link you may find interesting that explains a lot about it:
    https://www.naimaudio.com/sites/def...files/dac-v1_asynchronous-usb_mwp_jan13_0.pdf
     
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  6. YMO

    YMO Friend

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    There are others here who are like after hearing so many good USB solutions, nothing beats SPDIF standard.
     
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  7. TomB

    TomB MOT: Beezar

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    I doubt that head-to-head will result unfavorably for the Walnut. Even though I've never met him, however, AMB (Ti Kan) is a friend in the business and I'd rather not throw shade in his direction. ;)

    As for the XLR, see the post above about minimalist design. Also, the Walnut X was originally designed as a complement for the T4, which does not have balanced connections.

    The other item to remember - and maybe I'll post about it in more detail sometime - is that cost is a huge issue. People (not saying you're one) who look at an amp or DAC, state that the parts cost is just a couple of hundred and that there must be massive markup, are totally clueless. XLR inputs would have made more expensive casework, more expensive PCBs, more expensive almost everything.
     
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  8. TomB

    TomB MOT: Beezar

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    I should also add that prototyping a new design is sometimes difficult and expensive. The first time Doug presented me with the PCBs, I built one. To put it bluntly, it didn't work. Nothing I tried seemed to help. I ordered several different AC walwarts with varying voltages - nothing worked. Doug and I started trading e-mails back and forth for days and weeks.

    I scoped it, to no avail. We couldn't determine anything from this:
    [​IMG]
    You can see my stupid fingers and t-shirt while I photograph my old B&K analog scope to share with Doug. Imagine trying to trouble-shoot an unworking prototype, long-distance. This was taking days and that scope image was meaningless (mV of power supply noise).

    Eventually, through detailed metering of the voltages inside the DAC, we determined that the voltages were not sufficient at many points on the board. The linear-regulated power supply was not working correctly in developing the desired voltages. Doug got to work and came up with several diode and resistor changes around the regulators/transistors in the power supply and I ordered the new parts from Mouser. Again ... days of waiting in shipment, then installing the parts, etc.

    We finally determined all the correct ratios around the regulators and the DAC started working beautifully! It hasn't missed a beat, since.
     
    Last edited: May 20, 2021
  9. TomB

    TomB MOT: Beezar

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    That left casework.

    Doug did not actually design the casework for the Walnut X DAC. I did, with his design and methods he used in the T4. As mentioned a couple of times already, the Walnut X was supposed to be a complement to the T4.

    Casework for Doug's designs are intricate, complicated, and very precise. I had already made the initial leap with the hardware, however, resulting in several parts boxes of all sorts of specialized and undercut screws and socket-heads, etc. - all designed with the minimalist theme of appearing if not perfectly flush, as inconspicuous as possible.

    Once again, I utilized the resources of Swift Atlanta. They possessed the correct mixture of aluminum sheet metal processing and services. This included high-precision laser cutters, brush sanders, and finishing techniques. It doesn't happen automatically, though. You can't just sit down with a metals processor/finisher, describe what you want, and wait for them to come up with something.

    Drawings are required - in great detail. Once again, you're talking about investments of several thousand dollars. The only way to make this economical at all, is to order in volume. That means things have to be perfect. Otherwise, you end up with a unusable mess and wasted money - in volume!

    So, drawings were needed for the base plate, the top plate, the sides, the back plate, the front plate (both of them), etc., etc. This all had to fit perfectly with a 2mm clearance around the PCB. Needless to say, more time and effort. The actual process also included several iterations as I would send revisions after noticing some mistakes. I think, in total, I transmitted drawing revisions to them on 5 different occasions.

    Here's some of that work:
    Top-
    [​IMG]

    Front-
    [​IMG]

    Overall Layout (from top) -
    [​IMG]

    Laser-etching -
    [​IMG]

    Anodizing Masking -
    [​IMG]

    As you can see, even drawings for laser-etching and anodizing masking are necessary. The ground runs throughout the casework, but it only works if some of the anodizing is masked at the screw holes for each part. The anodizer has to know this. Similarly, the laser-etcher needs picture-perfect artwork to provide the laser-etching.

    In total, I produced nine different drawings for the casework. I drew them up in AutoCAD, plotted them to PDF, then combined them all into a single PDF packaged file. This was then e-mailed to Swift Atlanta for their quotes and questions. It took about 5 tries before we decided it was good to go. Even then, Swift Atlanta was careful to let me inspect the parts work as things were going along, especially the finish work of anodizing and laser-etching. We rejected quite a few parts along the way on the T4. This one went more smoothly. :)

    P.S. Just in case someone has a mind to copy, these drawings are not complete, nor do they show some of the final changes! ;)
     
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    Last edited: May 20, 2021
  10. Beefy

    Beefy Almost "Made"

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    Gorgeous work, TomB. Always loved the technical and aesthetic design that you and Doug come up with!
     
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  11. MichaeLeroy

    MichaeLeroy Facebook Friend

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    I'm certainly looking forward to following this build.

    I have a Walnut X.1 and am quite happy with it. Giving it a proper review would take more skill that I have. As a casual comparison between the Bifrost and Walnut using the T4 and ZMF VCs, I'd characterize the Walnut as more laid back and open sounding. The Bifrost sounds a touch bombastic and in your face next to the Walnut. (Hard to say on detail retrieval without proper level-matched A/B switching.) The Bifrost is my metal DAC, and the Walnut is my Jazz DAC. I'm happy to have both for their different flavors. Of course, your listening experience may vary with equipment, source material, and musical taste.
     
  12. TomB

    TomB MOT: Beezar

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    The first shipment of Lundahl amorphous core transformers arrived yesterday:
    [​IMG]

    The PCBs have also shipped from Imagineering and the Amanero USB Boards have shipped from Italy (that will take a while). I've also shipped the empty case to Doug for purposes of fabricating the wood. It'll be interesting to see what Doug comes up with. For the T4 and the earlier Walnut DACs, he used Sapele Mahogany. However, he usually comes up with a surprise of some sort whenever he does wood. Whatever it is, I'm sure it'll be gorgeous. :)

    I'll be working on the Mouser order this weekend. As mentioned before, that will take some effort, because I have to go through the entire BOM and compare what I need with what I have in stock.
     
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  13. purr1n

    purr1n Super Friend

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    Ahh, the old Wolfson chip and Doug to be the whisperer? This has got to be guud!
     
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  14. purr1n

    purr1n Super Friend

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  15. TomB

    TomB MOT: Beezar

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    Thanks for that - and the promotion to article, too!

    Well, everything has now been ordered. I just finished making the orders to Mouser and DigiKey. Yes, as usual, neither one had everything, so I had to split the orders between the two.

    Here's what it looked like, just a little while ago:
    [​IMG]

    Ordinarily, I split the work between the far desk at the window for all the soldering and minor assembly and the closer desk for testing. Although, the closer desk serves a multitude of purposes, depending on what I have going on, as evidenced in this photo.

    So, I have a couple of tubs of leftover parts toward the window. The monitor screen at left is connected to a laptop/docking station on the wire shelf, mostly out of the picture to the left. I can rotate the monitor and squish it against the wall above the laptop and wire shelf when not in use. Beneath the desktop are several tube testers, DMMs, and a couple of scopes. None of it is very fancy, just used stuff from ebay or generous hand-me-downs from Doug. ;)

    Right now, I have the PCB layout on the screen from Eagle, with a browser and tabs open to Mouser, DigiKey, and Newark (didn't have to use Newark, thank goodness). I have the BOM printed out in the middle where I cross off the parts once I've checked the tubs, decided how many I need, checked to see if Mouser/DigiKey has them in stock, and then added to my shopping carts. I also cross off the parts on the printed out layout by the keyboard, too - sort of a "measure twice, cut once" sort of thing. This helps if the BOM list isn't exactly complete; I can hopefully pick it up on the layout.

    The parts are very tiny and tightly packed on the PCB layouts, so at my age, I need both the printed version and a blown-up version on the screen to find all the parts labels. It's like sorting and labeling nothing but giblets for several hours. There are at least 154 parts listed on three pages of the printed out BOM, not counting hardware fasteners for the casework, etc. It all took quite a while.

    I'm happy to report, however, that nothing was shorted and everything was in stock at least at one or the other, Mouser vs. Digikey - and it's all on order for the five Walnut X.3 DACs. That's not to say I didn't make a mistake somewhere and find something missing. I always forget something when making one of these orders, but I feel good about this one (or two, counting DigiKey). :)
     
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  16. TomB

    TomB MOT: Beezar

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    I've got shipping notices so far from Imagineering and DigiKey. Mouser will probably send one tomorrow; it takes awhile because the order was so complicated. I'm pretty sure the Amanero USB boards have shipped, too, but I've asked for a confirmation/tracking number on that, too.
     
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  17. pengers

    pengers Rando

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    Curious, was there ever an X.2?
     
  18. TomB

    TomB MOT: Beezar

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    Technically speaking, yes. However, the tiny difference was insignificant with respect to the performance of the DAC. It came in the middle of the first run, so it went un-noticed and un-mentioned. The difference was that Doug added pads for the on/off switch, where before it was simply mounted on the back plate.

    The X.3 is similar, in that Doug re-positioned the RCA jacks at my request. This distinction would've again gone un-mentioned by me, probably. However, the addition of the pads for the amorphous core Lundahls is significant with regard to the capability of the DAC, so I'm actively noting the difference and option potential. ;)

    On a parts shipment update subject, it figures Mouser would send me a shipping announcement within an hour after I posted the update above. Domenico at Amanero USB Boards has also confirmed that the boards have left Italy. That means they will still take a while to get here, but plugging in the USB boards is the last step in building the PCBs, so there's time. :)
     
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  19. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Are the transformers step up transformers for I/V or are they 1:1 to remove the DC bias?

    And with the popularity of the Pi2AES and other Pi solutions that use S/PIF, AES, and some even straight I2S out, will there be and option for something other than USB?
     
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  20. TomB

    TomB MOT: Beezar

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    1. There is a fully developed, ECP Audio DSHA differential I/V included in the circuit. So, no - the transformers are 1:1 for line-level. However, there's a lot more going on than just saying it removes the DC bias. The resulting impedances are absolutely perfect for line level sources. You'd have to ask Doug for specific details.

    2. Sorry, no. Amanero Asynchronous USB at 24-bit, 192 kHz is it (or lower), as stated earlier in this thread. :)
     
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