Bottlehead Forum
Other Gear => Digital => Topic started by: Doc B. on September 11, 2012, 06:20:19 AM
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I got some good news this morning that John Swenson has made significant headway on a central part of the DAC that he was struggling with this summer, the interface with the EEPROM that will allow the DAC to incorporate future firmware upgrades. If things continue to go well for him we may have a new prototype to work with soon that is much advanced over the one we have been demoing for the past year or so. I'm still not offering release dates or quoting prices as there is work left to be done that can't be started until we complete this stage. But I do want to share the most recent progress in the design development.
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Great! So it's not being abandoned, then. That is great news!
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Tuned in for any updates...
Glad there is progress!
-- Jim
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2nd that - any info would be great!
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"..., the interface with the EEPROM that will allow the DAC to incorporate future firmware upgrades."
That sounds interesting. Do you plan on using FPGA's in your DAC?
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Yes
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There is an FPGA that is the heart and soul of this DAC, it pretty much does everything. It does the S/PDIF decoding, the USB decoding, all the work for the very low jitter adjustable clock that follows the S/PDIF data rate, output encoding, display drive, and pretty much everything else.
About 95% of this project has been coding the FPGA. Because the FPGA does pretty much everything I'm not stuck doing things the way a particular chip does things, BUT it means it does take time to program the FPGA to get it to do exactly what I want and sound the best.
Because it IS based on an FPGA, pretty much any part of it can be changed out in the field. The simplest way to add upgrades is to plug in a memory chip whose contents gets copied over into the FPGA configuration store. Making that work is what I have been working on all summer. The manufacturers of these chips seem to do everything in their power to make them complicated. I finally got it all up and running this week. I can now send DOC firmware upgrades on a little memory chip rather having him send it back to me for reprogramming. This will be a feature on all the production DACs so as we make improvements they can be incorporated in your DAC by just installing a new little memory chip.
I thought hard about using USB to download firmware files, but that means we have to write software that runs on Windows, Macs, Linux and every version of these under the sun, and keep them maintained forever. Mailing out a little chip is just WAY easier! And since this is a kit, the users should not be afraid to open the lib and put in a new chip.
Now I have to build a version of this to send to DOC. I had two boards made, but I had to make a bunch of changes to the board to get this chip to FPGA copy thing to work. (it's amazing how much information is left off data sheets)
Anyway it definitely is NOT dead. I am working furiously try to get this done as soon as possible. This version I'm sending to DOC is very similar to what the final will be like. I it DOES sound amazing!
John S.
John S.
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Great to hear. I was worried a while back, that the DAC had lost momentum and would be shelved.
I am still looking forward to it...John
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Doc or JS - what will the final footprint be? Will it be akin to your other products or a totally different form factor?
Wormwood
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This is very exciting! Are we looking at so something for as soon as early next year?
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Is the dac going to use tube output, or will it be driven by chips, Jfets, opamps?
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I can pretty much guarantee that there will be a tube output stage of some sort. That's one of the things still under development.
As far as I know its going to look similar to other Bottlehead products, with the wood base and metal top plate with everything connected to the top plate. The current thinking is that the board I am designing (which has all the chips etc) will hang down underneath the top plate with its own aluminum housing for shielding purposes. (primarily to keep the digital noise out of the tube circuits!) All the digital input jacks are mounted on the board and stick up through the top plate. There is an edge connector on the board and a slot in the top plate for inserting a display baord which will have some form of sample rate display and lock detect etc. This makes it very easy to add other display options such as my favorite, a Nixie tube display!
This edge connector is also an interface for attaching additional input options and connections as time goes along.
The rest of the box will contain the tube circuit and the power supplies similar to existing Bottlehead products I presume.
As to schedule, thats a toughy, there is still a lot of work to do, I can guarantee at least one more prototype will be needed (I'm working on that already).
Then once we get a prototype working Doc and company have to make it into a kit, THAT part I don't have any insight into.
I know you want a date, but as of right now I can't give that.
John S
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JS,
Thanks for the overview. The Nixie tube display I have seen but never really chased before but to think with that on the plate it would look awesome... and looks do count!
Wormwood
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I love Nixie Tubes, growing up in the early sixties my dad used to design all kinds of equipment with Nixie Tube displays, I would get hooked just staring at these things for a long time. About 8 years ago I built a Nixie clock, I have it on my mantle in the listening room and love to watch the thing count when I have the lights down dim listening to good music.
John S.
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Would you be able to point me in a how-to-build a Nixie Clock site.
Sorry for going OT.
Wormwood
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Not genuine "Nixie", EF based, but a complete kit ....http://www.adafruit.com/products/194 (http://www.adafruit.com/products/194)
These are just a few of the Nixie clock sites out there .... (Lots of Russian tubes on eBay) ....
http://www.electricstuff.co.uk/nixclock.html (http://www.electricstuff.co.uk/nixclock.html)
http://www.nixieneon.com/perl/nxSchematics.pl (http://www.nixieneon.com/perl/nxSchematics.pl)
http://hackaday.com/2012/10/11/nixie-clock-without-a-pcb/ (http://hackaday.com/2012/10/11/nixie-clock-without-a-pcb/)
http://oldheadphones.com/crystal/info/nixie.html (http://oldheadphones.com/crystal/info/nixie.html)
http://lupinesystems.com/nixie/ (http://lupinesystems.com/nixie/)
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I had a tektron 2a3 amp that used a nixie tube for a channel selector display. Of course it didn
't do anything for me, but guests always remarked how cool it was.
John, aren't you worried about noise from the hv needed for the nixie tubes?
-- Jim
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John / Doc,
I just wanted to confess to eagerly "lurking" on this topic & say thanks for all the work to date. When this is ready, I'm all in!
Cheers,
Bill
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Any progress updates? Any chance it would be ready for next Xmas? Depending on the price, I might be able to commit for that.
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RME has been using FPGA's in their studio gear for more than a decade now. They have the interfaces and the upgrading down to a science. I am very fond of their products and I am glad that you decided in favor of this approach.
Best of luck. It must be a ton of work.
There is an FPGA that is the heart and soul of this DAC, it pretty much does everything. It does the S/PDIF decoding, the USB decoding, all the work for the very low jitter adjustable clock that follows the S/PDIF data rate, output encoding, display drive, and pretty much everything else.
...
John S.
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Woo hoo! The new boards arrived today! John and will be talking over the next few weeks and getting this new prototype up and running in the system.
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Woo hoo! The new boards arrived today! John and will be talking over the next few weeks and getting this new prototype up and running in the system.
Sweet, good things come to those who wait.
.
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Doc,
It's going to be portable, right?
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fmistermort.typepad.com%2F.a%2F6a010535d07789970c0120a5a72c3b970b-800wi&hash=9599384ed40393d38084b872ce551c4683c22180)
Looking forward to seeing how it all shakes down.
Stephen
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Are there any progress images of the DAC in it's current iteration? I saw/heard an early prototype at last years bay area meet but wasn't able to see the internals.
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At this point, we ordered the iron for the new power supply for the new PCB's. We are just about wrapped up and ready to ship Bee Pres, and once we are over that hill, it will be all hands on deck to wrap up the remaining work to be done on the DAC (though we can't do much without the power supply at this point).
-PB
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"Are there any progress images of the DAC in it's current iteration?" Uhh, I think Wormwood provided the photo of the Dac.... Doc was so thorough in the design that he even included the kitchen pan.... He tried the "kitchen sink" , but found it would dramatically increase the shipping charges so chose to go with the pan....... And the "included" blanket is due to the fact you will be so much in love with the sound, you are provided with the option to be able to sleep with it....... I believe anyway......
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I was thinking a nice future upgrade for the DAC would be network connectivity. That would be quite useful for those running their music off severs in a different location from their music system. The Raspberry Pi would make a nice and affordable Linux computer which could be built into the DAC. Just a thought.
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Just a quick update - power supply components are on hand and the design team is working on the physical layput of the DAC today.
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The Raspberry Pi would make a nice and affordable Linux computer which could be built into the DAC. Just a thought.
I'm using a Raspberry PI with Raspian (Debian Linux) as a NFS file sharing computer and a PC Engines ALIX computer as an MPD client. The Raspberry Pi is an amazing little computer for $35.
http://cheap-silent-usb-linux-music-server.blogspot.com/ (http://cheap-silent-usb-linux-music-server.blogspot.com/)
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Doc, Glad to hear things are moving again on this project!
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This is truly exciting, from different perspectives. DAC's are a 'white hot' audiophile item these days. If Bottlehead can get peoples attention in this arena it would be a HUGE move. Not an easy task with the Schiit, Audio-gd, Halide, Metrum, Empirical Audio, M2Tech, Wadia, April Music, Wyred, CEntrance, Audiophilio, Peachtree, Mhdt, MYTEK, Sotm, Hiface, JK, Twisted Pair, Burson, Eastern Electric, Lamizator, Pacific Valve, DAC Magic, JDS .... well, you get the idea. No pressure!
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I have a good chassis layout drawn electronically, but one datasheet for a physical part that has not arrived has some anomalies, so we'll be hanging on for a day or two until that pops in before ordering the next prototype plate.
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Paul, any chance I can get a copy of the chassis layout? I'm interested in making a custom enclosure out of milled Aluminum and a parts layout would be helpful for me. PM me if you can help, thanks.
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That's always up to Doc B., and I'd expect a few tweaks to happen between this prototype and the production prototype, especially with the jack field.
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No, sorry, we are not ready to share any files for this product. We don't even know for sure if it will work they way we hope it will.