Yes, planning on going the stencil / toaster oven with PID microcontroller / leaded solder paste route. In terms of board houses, I've heard some bad things and have a friend who's had bad experiences with JLCPCB, what are the preferred fabs around here? Unfortunately lost a couple of hours of progress on the design due to me forgetting to save, but am working to have this design done soon.
OSH Park are made in the US and good quality if you don't mind their turn time and constraints. I have used many other houses like Advanced Circuits, Sunstone, Royal Circuits, Imagineering, etc. at work and they are all more than acceptable for the type of boards you would be ordering (but also far more expensive).
I've used JLC for fabrication of quite a few PCBs and never had a problem - they've made exactly what the gerber files have told them to make. The last batch had small smd parts and they soldered up nicely in a friend's reflow oven.
I've also had excellent service from PCBway, including the fabrication of a 4 layer board, with a custom layer stack, for my valve DAC build.
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I was looking at Advanced Circuits and Sunstone, I might go with one of these two for the final products, but I honestly might go with JLC or PCBway, or whatever the cheapest on PCBShopper is for prototypes. If we eventually get a group buy going, this would be a good way to get very high quality boards for a good price. I will be traveling most of the day today but will be continuing on the design later tonight. -- Here is a link once again to the most recent version of the PDF:
AK_DAC.pdf - Google Drive
AK_DAC.pdf - Google Drive
damn i wish i have nerves to learn kicad so i could just use your schematic files. is there a reliable way of converting eagle<=>kicad projects?
doesnt matter, i would continue with pcb maybe tonight.. also i should use 4layers where needed, and convert old parts also to 4 layer where needed
also could you please be specific about clock source part number and footprint i should use on SRC part?
just to clarify what should be located on "main" board; serial isolation , src, xlrout, preregs?
thanks! happy holidays to all.
doesnt matter, i would continue with pcb maybe tonight.. also i should use 4layers where needed, and convert old parts also to 4 layer where needed
also could you please be specific about clock source part number and footprint i should use on SRC part?
just to clarify what should be located on "main" board; serial isolation , src, xlrout, preregs?
thanks! happy holidays to all.
tonitonitoni -- AFAIK, there's no easy way to go from KiCad to EAGLE. KiCad is really not that hard to use though, especially having used another EDA tool in the past. There are a couple of weird steps in the workflow, which I would be glad to guide you though if you're having any confusion about, but the schematic capture and PCB layout tools are fairly close to eagle, if not slightly more usable. I would like to get the full schematic done before beginning to ask which modules will go on the "main" board, which I plan on calling / being a backplane, but I plan on having as few things as possible on it, likely just the power supply for the 8V utility bus, maybe a power switch, and sockets for each of the submodules. I've been going back and forth on the idea of moving the I/V stage away from the DAC board, slightly increasing the length of the feedback loop, but gaining more modularity. I think the way Im leaning is to design a DAC module with I/V onboard, and then move it offboard later if there's a perceived need.
I think this could be a mistake. Think about it, AKM wouldn't have implemented
I-V current 'sense' inputs if it wasn't necessary. This is indicating (to me at
least) the current 'path' is very important to reach chips capability.
I would suggest if you do move I-V stage away that it is very close, probably
directly underneath and the ground will be important.
TCD
If you are referring to the I/V opamps as shown on page 12 of your last schematic, they look correct pretty much for as much as is shown. Not sure where you are putting the voltage dividers for the non-inverting opamp inputs. That is one area where you may want to depart a little from the eval board schematic. I used some pots across the lower divider resistors to adjust down the divider output voltage from approximately 2.5v to approximately 1.9v so as to bring the I/V opamps outputs quiescently down to ground.
Departing like that to 1.9v also causes output current to get asymmetric according to this japanese warrior (google translate helps);
http://www.easyaudiokit.com/bekkan2019/NewDevice/NewDevice.html
I have not yet verified it myself.
BTW, standard Wire library for stm32duino has a I2C scanner example it turns out. So thanks for pointing that such utilities exist.
http://www.easyaudiokit.com/bekkan2019/NewDevice/NewDevice.html
I have not yet verified it myself.
BTW, standard Wire library for stm32duino has a I2C scanner example it turns out. So thanks for pointing that such utilities exist.
I have stumbled on this:
https://www.stereo.net.au/forums/up...1502.jpg.4995f0ce6d62873ca758340d355e16b4.jpg
Looks okay to me. You can find it here;
AKM new Verita AK4499EQ dac - Page 3 - Digital Sources, DACs & Music Streaming - StereoNET
And some more material here;
First start on AK4499EQ - Digital Sources, DACs & Music Streaming - StereoNET
True, but no harm it seems. Sound doesn't get worse to my ears and there is less common mode offset in the differential summing stage which seems to like it better. Remember, we are trying to minimize very small amounts of objectionable distortion that might be noticeable by what Martin Mallinson dubbed 'a very perceptive listener.'
In this case we might be trading off some asymmetry in dac output current for slightly less common mode offset in a subsequent differential summing and filtering circuit.
Personally I prefer 1.9v, but I would suggest a trimpot should be fine to include for offsetting the voltage divider if people want to experiment.