I've designed a DAC somewhat similar to the gigawork DAC in this giant thread: http://www.diyaudio.com/forums/digital-line-level/137976-experience-diy-dac-78.html
It uses a CS8416 Receiver Chip, followed by a CS8421 Asynchronous Sample Rate Converter Chip which is clocked via a low jitter oscillator module with a finesse regulator circuit on the power line. This feeds a CS4398 DAC chip who's output drive a pair of Lundahl transformers. It has both analog and digital raw supplies fed from different power transformer windings and contains seven regulation stages with liberal decoupling at the chip pins.
It includes both TOSLink and Coax digital input, and headers for two additional off-board inputs.
The transformer output will accommodate both single ended and balanced output.
Some more information, photos, schematic, layout and parts lists are available here: Sheldon’s World Blog Archive Another Audio Digital-to-Analog (DAC) is Born
Pictures of the boards are shown below.
A blank board costs $40 including shipping within the USA. I'll also solder the three audio chips in place for you on a board for $85 including shipping within the USA. Foreign orders are welcome, but the shipping will cost an additional couple dollars.
If you are interested, I can be reached here, or at stokes(at)quadesl.com
Thanks,
Sheldon
It uses a CS8416 Receiver Chip, followed by a CS8421 Asynchronous Sample Rate Converter Chip which is clocked via a low jitter oscillator module with a finesse regulator circuit on the power line. This feeds a CS4398 DAC chip who's output drive a pair of Lundahl transformers. It has both analog and digital raw supplies fed from different power transformer windings and contains seven regulation stages with liberal decoupling at the chip pins.
It includes both TOSLink and Coax digital input, and headers for two additional off-board inputs.
The transformer output will accommodate both single ended and balanced output.
Some more information, photos, schematic, layout and parts lists are available here: Sheldon’s World Blog Archive Another Audio Digital-to-Analog (DAC) is Born
Pictures of the boards are shown below.
A blank board costs $40 including shipping within the USA. I'll also solder the three audio chips in place for you on a board for $85 including shipping within the USA. Foreign orders are welcome, but the shipping will cost an additional couple dollars.
If you are interested, I can be reached here, or at stokes(at)quadesl.com
Thanks,
Sheldon
Attachments
Yes, the square is for a PCB mount toroid transformer. IT's a 10 VA toroid with a pair of 7 volt secondaries.
If memory serves me right, the DAC consumes about 2.5 watts of power.
Sheldon
John-
Not currently, all sample rate materials are upsampled to 192KHz, so as far as the DAC is concerned, it's always playing at 192KHz.
The sample rate converter chip could be omitted and then the clock lines could be run from the receiver chip to the DAC chip, and then you would be able to change the DAC "speed" by fiddling with the resistors around the DAC. That's a big change to the design, and I'm not sure this board would be an ideal candidate.
Sheldon
Not currently, all sample rate materials are upsampled to 192KHz, so as far as the DAC is concerned, it's always playing at 192KHz.
The sample rate converter chip could be omitted and then the clock lines could be run from the receiver chip to the DAC chip, and then you would be able to change the DAC "speed" by fiddling with the resistors around the DAC. That's a big change to the design, and I'm not sure this board would be an ideal candidate.
Sheldon
Thanks for your reply Sheldon - I'll regretfully have to pass on this I think. I prefer to be able to select the correct speed for the sampling rate in question (i.e. after experimenting with the Gigaworks board I personally think 16-bit files sound best on the single-speed setting, etc). Many thanks,
- John
- John
Very nice design. I'm sorely tempted, even tho I don't really need one. 
Good choice on the CS4398. It seems to be particularly well suited to driving a transformer output. Not sure why, but it works well. I like the care (overkill) you've taken in the PSU.
Did you trim the output circuit parts to fit the Lundahl iron? Maybe you said, but I missed it. Just thinking that is another transformer were used, then those values might need some tweaking.
Good choice on the CS4398. It seems to be particularly well suited to driving a transformer output. Not sure why, but it works well. I like the care (overkill) you've taken in the PSU.
Did you trim the output circuit parts to fit the Lundahl iron? Maybe you said, but I missed it. Just thinking that is another transformer were used, then those values might need some tweaking.
Pano -
I have tuned the output slightly, but I'm not using most of the filter network capability that I added to the board on my prototype.
Thanks for noticing my over the top power supply and regulator work. If you are really into power supply overkill, the generic LM317 linear regulators can be swapped for higher performance LT1086 regulators.
Also the cost of the board is small potatoes compared to the cost of a pair of sweet lundahl transformers on the output.
Sheldon
I have tuned the output slightly, but I'm not using most of the filter network capability that I added to the board on my prototype.
Thanks for noticing my over the top power supply and regulator work. If you are really into power supply overkill, the generic LM317 linear regulators can be swapped for higher performance LT1086 regulators.
Also the cost of the board is small potatoes compared to the cost of a pair of sweet lundahl transformers on the output.
Sheldon
J-P. I don't see why you couldn't use other transformers, tho they would probably need to go off-board. The CS4398 is pretty tolerant of different loads. I've talked engineers at Cirrus looking for the "ideal load" but they won't go any further than saying it's spec'd for a 1K load. I've found it isn't too picky.
Of course this is possible but it would spoil the view on this beautifully designed board.
Seriously, I am fond of "one PCB" solutions with good supplies etc. More of this please ! Modular designs are very 2010 I really don't see the point of a few PCB's when everything can be on one board skipping the need for those dreaded cable harnesses etc. But I have a problem with ASRCs... everybody keeps telling me they're good but I would have to hear the first one sounding natural. Could be me of course.
Seriously, I am fond of "one PCB" solutions with good supplies etc. More of this please ! Modular designs are very 2010
I really don't see the point of a few PCB's when everything can be on one board skipping the need for those dreaded cable harnesses etc. But I have a problem with ASRCs... everybody keeps telling me they're good but I would have to hear the first one sounding natural. Could be me of course.
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J-P and Pano -
The board is designed for the Lundahl transformers, but before I finalized the design I looked around at all the various output transformers I'd want to use: Jensen, Onetics, Lundahl, etc. And none of them had the same footprint. I tried to drop lots of pads down and tried to make the board capable of different designs, but it got really messy. Plus there's lots of other good options like UTC that wouldn't be catered to with the layout. So I bailed on that, and just went with the Lundahls.
Sheldon
The board is designed for the Lundahl transformers, but before I finalized the design I looked around at all the various output transformers I'd want to use: Jensen, Onetics, Lundahl, etc. And none of them had the same footprint. I tried to drop lots of pads down and tried to make the board capable of different designs, but it got really messy. Plus there's lots of other good options like UTC that wouldn't be catered to with the layout. So I bailed on that, and just went with the Lundahls.
Sheldon
Hi Sheldon,
I like your board, nicely designed with a good PSU and great local decoupling.
How does the board handle 24/192 or 176.4 does the 8421 automatically bypass?
Also how easy would it be to add an additional AES input and SPDIF? The input selection can be handled by a rotarty type selector I suppose. Where do the Spare tracks for the cs8416 present on the board.
What type of transformer output are you using and where do I get hold of them?
Thanks in advance,
George.
I like your board, nicely designed with a good PSU and great local decoupling.
How does the board handle 24/192 or 176.4 does the 8421 automatically bypass?
Also how easy would it be to add an additional AES input and SPDIF? The input selection can be handled by a rotarty type selector I suppose. Where do the Spare tracks for the cs8416 present on the board.
What type of transformer output are you using and where do I get hold of them?
Thanks in advance,
George.
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