Author Topic: DIY project for the year - DAC with valve output stage  (Read 1338 times)

Offline El Sid

DIY project for the year - DAC with valve output stage
« on: January 11, 2017, 04:00:50 PM »
After almost a year of getting back into audio after a long layoff, I've started getting a sense of things and what I like/want. I bought a Maverick TubeMagic D1 DAC to get a feel for the (new to me) world of  Dacs, and have been very pleased with it and learnt a lot. But it is very entry level, and has shortcomings, eg USB is 16 bit max.

I quite enjoy DIY and, as a no-longer-practising elec eng, am fairly capable.  So i have decided to build a DAC, and because I like the sound of valves, one with a valve output stage.

This isn't much more than an idea at the moment, but here are some random thoughts on where i'm headed:

  • I think i'll base it on the Soekris DAM R2R DAC - seems to be well-regarded, and there's a wealth of info out there on using it.
  • It already has line-level SS outputs, but I want to learn about valves, so i want to add a valve output stage. More of a buffer than an amp i suppose. i could make a switch so you could use either the valve or the on-board SS output.  Valves only got a passing mention when i studied elec eng, so i don't know much about them other than general principles, never designed around them. For me this is the most daunting part of the exercise.
  • I will build it up modularly, starting with the Soekris board with the bare minimum of support circuits, and add more functionality from there. Ultimately i'd like it to be fully remote controlled, take any data stream the Soekris can, and maybe have a detailed display.
  • I would like it to look really good, so for the aesthetics will rope in my bro who is a set/display/furniture designer and has a really good eye. He studied civil eng for a year designs very practically too

Any advice/comments/suggestions/criticism welcome - i'm sure i'll often come to the DIY section for help. Sensible advice such as "rather just buy a DAC" will of course be ignored.

Besides, I put all that effort into building my workbench, so need to use it....



(right half is wife's jewelry work station)




Offline chrisc

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Re: DIY project for the year - DAC with valve output stage
« Reply #1 on: January 11, 2017, 04:06:04 PM »
What is the tall blue device?
Music is the shorthand of emotion

Offline gavinbirss

Re: DIY project for the year - DAC with valve output stage
« Reply #2 on: January 11, 2017, 04:07:30 PM »
What is the tall blue device?

oscilloscope


Offline Jaco

Re: DIY project for the year - DAC with valve output stage
« Reply #3 on: January 11, 2017, 04:07:40 PM »
^ Oscilloscope?

Offline gavinbirss

Re: DIY project for the year - DAC with valve output stage
« Reply #4 on: January 11, 2017, 04:11:48 PM »
El Sid,

Worry about the output stage for Soekris later. It is has selectable filters and allows for custom filters.

Soekris can have a 10K volume pot to control volume...

Regarding remote control, if you use a LMS (Squeezebox/MPD) music server you would most likely use a Apple/Android/web interface to control it.

A ladder based DAC does not require a I/V stage so you will really only be adding a buffer which may not be needed if you are using the RAW outputs.

If you do need a tube buffer look at Glass-ware.com, there is even Akidio based (improvement on SRPP) boards. Perhaps a tube preamp should be the more universal solution?

http://glass-ware.stores.yahoo.net/newhardware.html

Look forward to see what you come up with.
 :dop:


 
« Last Edit: January 11, 2017, 04:19:34 PM by gavinbirss »

Offline El Sid

Re: DIY project for the year - DAC with valve output stage
« Reply #5 on: January 11, 2017, 04:20:34 PM »
What is the tall blue device?

As other posters said - it's an old school analog Tektronix scope, standing on its back with the front pointing to the ceiling. Modern digital ones look similar from the front, but are about a quarter of the depth and a tenth of the weight  ;D

Offline chrisc

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Re: DIY project for the year - DAC with valve output stage
« Reply #6 on: January 11, 2017, 04:24:39 PM »
It'll get dusty like that
Music is the shorthand of emotion

Offline El Sid

Re: DIY project for the year - DAC with valve output stage
« Reply #7 on: January 11, 2017, 04:36:22 PM »
El Sid,

Worry about the output stage for Soekris later. It is has selectable filters and allows for custom filters.

Soekris can have a 10K volume pot to control volume...

Regarding remote control, if you use a LMS (Squeezebox/MPD) music server you would most likely use a Apple/Android/web interface to control it.

A ladder based DAC does not require a I/V stage so you will really only be adding a buffer which may not be needed if you are using the RAW outputs.

If you do need a tube buffer look at Glass-ware.com, there is even Akidio based (improvement on SRPP) boards. Perhaps a tube preamp should be the more universal solution?

http://glass-ware.stores.yahoo.net/newhardware.html

Look forward to see what you come up with.
 :dop:

Thanks Gavin - the idea is to make a "valve" sound out of a Soekris. It's just something i want to do - not necessarily a sensible thing!

Thanks for the links to the buffers - will check them out. But i may want to get more hands on and build from scratch.

I have an Exclame, so effectively have a valve pre anyway.