Valve DAC from Linear Audio volume 13

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nautibuoy

nautibuoy

Member
Joined 2010
nautibuoy

nautibuoy

Member
Joined 2010
I've just been talking to my solder-slinging friend. He's just bought himself his first house so with all the associated expense he's keen to take on the smd soldering for anyone who wants it done, even for a batch of 15 boards.

I have a spare PCB and a full set of smd parts here so I'm going to take them to him tomorrow to hand solder it and from that he'll work out a per PCB price for smd assembly using a stencil and hot-air work station.

My feeling is that this service will cost around $50 a board - don't hold me to it - so not that much more than everyone buying their own stencil and doing their own soldering.

More info when he's had a look at my spare board.

Would this service be of interest?
 
R

Raj1

Member
Joined 2003
nautibuoy said:
I've just been talking to my solder-slinging friend. He's just bought himself his first house so with all the associated expense he's keen to take on the smd soldering for anyone who wants it done, even for a batch of 15 boards.

I have a spare PCB and a full set of smd parts here so I'm going to take them to him tomorrow to hand solder it and from that he'll work out a per PCB price for smd assembly using a stencil and hot-air work station.

My feeling is that this service will cost around $50 a board - don't hold me to it - so not that much more than everyone buying their own stencil and doing their own soldering.

More info when he's had a look at my spare board.

Would this service be of interest?
Click to expand...

I might take him up on it, yes.
 
D

Dubulup

Member
Joined 2016
thuanth43 said:
I'm tempted to get one board but my library is only PCM :-/

Also, I suppose there's only single-ended output?
Click to expand...

nautibuoy said:
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;



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.
Click to expand...

I'm interested in a pair of these w/ standoffs.

Ray - you may have opened Pandora's box...looking back through your pictures I'm sure I'll have plenty of questions. But these boards should be the hard(er) bits together.
 
nautibuoy

nautibuoy

Member
Joined 2010
I'm currently rebuilding my Audio Server, starting with a clean install of AudioLinux (V4.5). The server is more powerful than the Windows 10 PC I've been using for testing the Valve DAC.

I've got The installation done and have AudioLinux running in RAM, just updating the HQPlayer library now so I'll be able to see if DSD512 is viable, both on the server and with the Valve DAC, quite soon.
 
M

MarcelvdG

Member
Joined 2003
MarcelvdG said:
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.
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I forgot one thing: you will also have to do something to get the right bias currents through that extra valve stage. Either use 180 ohm resistors to a positive voltage of a few volts rather than ground, or connect the tail resistors of the extra valves to a negative voltage of a few volts.
 
R

Raj1

Member
Joined 2003
MarcelvdG said:
I forgot one thing: you will also have to do something to get the right bias currents through that extra valve stage. Either use 180 ohm resistors to a positive voltage of a few volts rather than ground, or connect the tail resistors of the extra valves to a negative voltage of a few volts.
Click to expand...

Thanks for taking the time to have a look, Marcel. It is highly appreciated.

There is a slight difference in how I’m using the circuit. It is currently biased through Rod Coleman’s DHT heater supplies. The source is an AK4497 DAC (in direct DSD mode) feeding the 3a5 output stage, which then drives a pair of Audeze LCD-3 cans. If the changes are going to be complex, it may be better for me to stick with the current reconstruction filter and then use the circuit as is after. Of course, keeping the circuit simple does have merits, so I may end up going that way eventually. Thoughts?
 
nautibuoy

nautibuoy

Member
Joined 2010
So, this has been moving quite quickly and just thinking things through, I hope you'll understand if I don't want to get bogged down with a plethora of different options so I'm thinking I'll offer just these;

  1. Bare DAC PCBs
  2. DAC PCBs with the smd parts soldered
  3. Reconstruction filter PCBs

If you just want bare PCBs It'll be down to you to solder them however you wish, by hand or you can buy your own stencil(s).

Providing a suitable DSD imput to the DAC board will be down to you though I'm obviously happy to help based on my own experience.

As soon as I get the cost of the soldering option I'll post so you can make your choices knowing the financial commitment you'll be making. I'm not looking to make anything out of this - my reward is being able to help others enjoy the fruits of Marcel's endeavours - so everything will be just to cover the outlay I'll need to make. Being slightly cautious, based on previous GB experience, I will ask you to commit money up front. I'll aim to include the price of onward shipment to you guys in the costs. I'll leave the GB open until I'm ready with the costs.

I hope that's all OK with everyone.
 
nautibuoy

nautibuoy

Member
Joined 2010
Here's where we are;

diyAchim - 1 PCB
Raj!1 - 1 PCB (UK)
dubulup - 2 PCB (USA)
ericoto -1 PCB
HenSch - 2 PCB (Germany)
mterbekke - 2 PCB (Netherlands)
rfbrw - 1 PCB
Pistollero - 1 PCB (Portugal)
luchoh - 1 PCB (USA)
pgour - 1 PCB
agent.5 - 1 PCB (USA)

Total = 14

There's no hurry but if you could add/verify your country to give me a headstart on the onward shipping costs.
 
M

MarcelvdG

Member
Joined 2003
Raj1 said:
Thanks for taking the time to have a look, Marcel. It is highly appreciated.

There is a slight difference in how I’m using the circuit. It is currently biased through Rod Coleman’s DHT heater supplies. The source is an AK4497 DAC (in direct DSD mode) feeding the 3a5 output stage, which then drives a pair of Audeze LCD-3 cans. If the changes are going to be complex, it may be better for me to stick with the current reconstruction filter and then use the circuit as is after. Of course, keeping the circuit simple does have merits, so I may end up going that way eventually. Thoughts?
Click to expand...

I was seeing problems that aren't there. I just looked up the 3A5 datasheet ( http://www.r-type.org/pdfs/3a5.pdf ) and apparently the CD enhancer II circuit is designed for a 0 V input common-mode voltage. Apart from adding those 180 ohm resistors to ground, you don't need to do anything special to interface the valve DAC main board with the CD enhancer II circuit.

(For the record, using termination resistors to a positive supply at the DAC output would have been impossible anyway because of the way the mute circuit is designed.)
 
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