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Old 27th January 2008, 08:12 PM   #1
mgm31 is offline mgm31  France
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Default Tube output stage for voltage DAC ?

Hi,

I got a CS4398 evaluation board. The XLR output sound great but I would try a tube output stage.

I did not found a lot of example :

Broskie cathode follower : http://www.tubecad.com/2006/08/blog0075.htm (no gain required)

Thorsten Loesch design (can't find the link, I got only a paper copy).

Does someone have experience in balanced voltage output dac with tubes ? What advice could you give ?

Thanks a lot
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Old 30th January 2008, 08:55 PM   #2
mgm31 is offline mgm31  France
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No idea ?

I will try Broskie's design and will see.....
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Old 2nd February 2008, 01:08 PM   #3
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Default Re: Tube output stage for voltage DAC ?

Quote:
Originally posted by mgm31
Hi,

I got a CS4398 evaluation board. The XLR output sound great but I would try a tube output stage.

I did not found a lot of example :

Broskie cathode follower : http://www.tubecad.com/2006/08/blog0075.htm (no gain required)

Thorsten Loesch design (can't find the link, I got only a paper copy).

Does someone have experience in balanced voltage output dac with tubes ? What advice could you give ?

Thanks a lot
Hi

Have a look at Lukasz Fikus's site at:

http://www.lampizator.eu

He has extensive experience with current & voltage out DACs & has on his site mods done to dozens of players. I have changed my Arcam 70.2 discrete output stage to a tube output stage as per the lampizator circuit, and the difference is huge. And this is considering that I already had various mods done including audiocom clock 4, BG NXs in powesupply, some NX hiQ caps for DAC decoupling, super regulators, disabling digital out etc etc.

He also has a step-by-step guide which is excellent. However, you need to make sure you feel safe with dealing with high tube voltages which can kill.

Regards

Fib
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Old 2nd February 2008, 03:01 PM   #4
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You want a tube output stage because you think tubes sound better than opamps but if that DAC is voltage out, it is already the poison inside.
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Old 2nd February 2008, 03:41 PM   #5
poynton is offline poynton  United Kingdom
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Default Re: Tube output stage for voltage DAC ?

Quote:
Originally posted by mgm31
...............

Thorsten Loesch design (can't find the link, I got only a paper copy).

............

http://www.fortunecity.com/rivendell...a/vasfda.html#


I tried a similar circuit, see the CD63/67 mods thread (http://www.diyaudio.com/forums/showt...ht=#post831469) around post 453

Andy
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Old 3rd February 2008, 04:51 PM   #6
mgm31 is offline mgm31  France
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Many thanks, especially for the lampizator link I didn't know

Yes, Opamp inside DAC are poison but at this time I got Opamp for filtering too. I can't throw my CS4398 eval board to the dust bin.....

The lampizator schematics seems not to deal with Vout+ AND Vout- but use only one output (Vout+ ?).

I'm searching a real differential schematic as explained in the tubecad journal.

The project is on my working table : I modified an aikido to this purpose. I'm waiting some parts for the power supply.
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Old 3rd February 2008, 10:13 PM   #7
JeroenR is offline JeroenR  Netherlands
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try cd enhancer II on http://ultranalog.com/
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Old 4th February 2008, 07:12 AM   #8
mgm31 is offline mgm31  France
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Yes.....

Not very cheap (sowter transfos, 110 ) but innovative.....
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Old 5th February 2008, 01:59 AM   #9
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You might already read this but just in case you miss it.

Aikido differential amp for DAC:

http://www.tubecad.com/2006/08/blog0077.htm

Or you could also try another design by member in this forum:

Building the ultimate NOS DAC using TDA1541A
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Old 5th February 2008, 08:22 AM   #10
poynton is offline poynton  United Kingdom
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Further to my post above :-

Here is one suggestion, originally from HiFi World magazine :-


http://www.diyaudio.com/forums/showt...ht=#post831469 post 504


and the one I went with, very simple and could be improved, based on Thorsten's work,


http://www.diyaudio.com/forums/showt...ht=#post831469 post 633

This last one, using Thorstens filter in differential mode, does work extremely well !!!

Andy
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