Valve DAC from Linear Audio volume 13

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#531
Dubulup said:
HQ Player and others will Upsample to DSD (DoP).
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Just to clarify, DoP is a means to stream DSD data as PCM packets but this DAC won't know what to do with those PCM packets - its input needs to be supplied with a stream of native DSD data from something like HQ Player (other software solutions are available) or with a hardware resampler. My experience is with HQ Player only.
 
#532
agent.5 said:
I take one pcb.

Any chance that we may consider smd assembled from manufacturer and/or smd stencil?
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Good to have you on board (I just punned! 🙂 )

Whilst I'm happy to get the PCBs fabricated by our Chinese friends I would prefer to purchase the parts from a supplier of known quality - I provided a DigiKey basket for the SMD part BOM a few posts back.

Marcel thoughtfully designed the PCB so that the pads for the SMD parts are for hand soldering, so a little larger than the standard pads. I can include an SMD stencil when I place the PCB order and you guys will have to pass it around amongst yourselves, which would limit progress, or I can investigate multiple stencils as a costed extra for those who want one? An alternative for those who want to use a stencil with a hot air station or reflow oven would be to buy from JLCPCB - their stencil costs are very reasonable. Before someone asks, JLCPCB aren't an option for purchasing the boards, they would be cheaper than PCBWay but can't do the custom layer stack that is an intrinsic element of Marcel's design.

BTW, if you are thinking along the lines of using a stencil, the larger part of the smd soldering is on the bottom of the PCB.

I have a friend who did my smd hand-soldering and he offers that as a chargeable service - I have aked him for his price per board as I thought some subscribers may wish to take up that option. We did look at using a stencil and reflowing the board but it's too big for his oven.

I've atached some images below showing the sort of smd soldering required for this project, the first image shows all of the smd parts located on the top of the PCB and the other two are sections of the bottom - the larger 'hand solder' pads are clearly visible.

NfKgA5w.jpg


wIuSK08.jpg


x7nqGaB.jpg
 
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#534
Just a reminder that the project needs a reconstruction filter on it's output, post #182 referes;

https://www.diyaudio.com/forums/dig...-linear-audio-volume-13-a-19.html#post5868091

I used the third order filter and designed a simple PCB;

ggCcAGn.jpg


If there's any interest I can order a batch; 30 boards from JLC looks to be well under $1 per board before shipping.

My PCB is designed to fit into slots in my chassis but I can easily add some holes for conventional stand-offs.
 
#535
Actually you used the variant of post 215, with the Lundahl transformer:

https://www.diyaudio.com/forums/dig...-linear-audio-volume-13-a-22.html#post5872031

The design of the DSD-only version of the valve DAC can be found in posts 84 and 86:

https://www.diyaudio.com/forums/dig...c-linear-audio-volume-13-a-9.html#post5856267

https://www.diyaudio.com/forums/dig...c-linear-audio-volume-13-a-9.html#post5856542

Which of R48, R57, R58 and R59 have to be placed and which not depends on whether you want to use the Amanero-style interface at all and if so, whether you want to use the bit or the master clock.
 
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#537
Thanks Marcel. I guess it's a good feeling to see people picking up on your design at last?

I'll check out the stencil options and advise.

Marcel's comments about the resistor choices reminded me that, in case people haven't picked up on it, the PCB has the option of input via an Amanero format header or via ufl sockets.
 
#538
It looks like a stencil will cost around $25 each if I order with the PCBs (actually probably a bit less as I imagine the shipping cost for a combined order will be advantageous) - check out the screengrab below for info and please advise if any of the options I've selected are incorrect.

The stencil will be large so I imagine will will push up the shipping cost when I distribute the orders.
 

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#540
Raj1 said:
Thanks Marcel. For the output stage, can I use this?

http://itsonlyaudio.com/ultranalog/cdenhancer/cdenhancer2_3a5.pdf
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You could use this as a reconstruction filter, but because of the low filter order, you will have more ultrasonic noise coming through than with Ray's filter. Whether that is a problem depends on the rest of your equipment. You will need to add two 180 ohm resistors to ground at the inputs for current to voltage conversion.

nautibuoy said:
Thanks Marcel. I guess it's a good feeling to see people picking up on your design at last?
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Definitely! Thank you and Dan for taking the risk to build a variant that had never been built before.
 
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