voltage dac valve output stage..what have you done?
Oct 22, 2008 at 8:40 PM Thread Starter Post #1 of 6

adamus

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I am considering adding a valve output stage to my dac (voltage out).

this circuit looks fairly simple....

balanced_dac_and_broskie_cathode_follower_filtered.png


what have people here tried?
 
Oct 23, 2008 at 4:19 AM Post #2 of 6

nikongod

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Most tube circuits are fairly simple. you can build a fairly nice tube-output for a V-out Dac with very little money in the actual audio section.

Sounds somewhat cagey, right? you may think im leaving something out. you are correct!

you have to build the power supply too. A tube circuit with a cheap power supply sounds cheap.

you should plan to spend about 1/4 of your budget on the actual amp section and 7/8 on the power supply. If you get REALLY creative in your efforts to save money on parts for the audio stage spend a little more on the power supply then my equation would lead you to believe.

Be safe.
 
Oct 23, 2008 at 6:18 AM Post #3 of 6

adamus

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completely agree, when i said simple circuit i wasnt including the power supply.

Power supply: i will probably go solid state (not enough room for a tube rectifiier), no chokes (again space) and some good quality lytics. for the circuit above, using something like 6n1p, or 6992, i reckon i will need a B+ of around 250 - 300v.
 
Oct 23, 2008 at 9:25 PM Post #4 of 6

Ciu

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Hello !

That's what I 've done :
http://img206.imageshack.us/img206/3...cfecc86rt8.png
I 've redrawn an original schematic published by JR Broskie in Tubecad.com
This is a buffer with no gain, and filtered input, with low voltage tube ECC86/6GM8
The B+ is 24v, simple LM317, with a slow turn-on , about 30s
The heater,6.3v, 600mA, is also a simple lm317, with a slow turn-on , about 10s
Works perfectly for a symetrical voltage DAC...
Other tubes than 6GM8, characteristics in Tubecad's blogs
R.C.
 

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