Need help with tubed output for PCM1793 DAC - Page 2

kenpeter · 30th January 2009, 03:53 PM

I think I've presented about the ultimate circuit for exactly that.
But I have no proof other than the LTSpice simulation as shown.

However, I lack the skill to explain it adequately. A lot of what
it seems to excel at came as an unexpected bonus surprise.
I have never built one, and as far as I know, nobody ever has.

I've written Broskie to see if he wants to tackle an analysis,
and potentially debunk this idea before it wastes anyone's
time on something that won't actually work.

I am too busy at work to bench this right now. My boss would
tear my head off if I was playing with tubes before my regular
work was completed.

I don't have a DAC like yours, but I have an Tek AFG3252 dual
channel function generator on my desk that can fake it.

Koifarm · 30th January 2009, 04:17 PM

Look here:

http://www.lampizator.eu/LAMPIZATOR/...Lampizator.doc

Build the alternative setup.( Cathode follower ).

Here his site.

http://www.lampizator.eu/

Steel left signal from pin 18 and right signal from pin 12 of the PCM1793.

revintage · 30th January 2009, 04:40 PM

The outputs from the DAC are at +1,4V DC so this must be handled if you want to directcouple to a tube. The circuit in my post above was adjusted to that specific DAC that where at over +2V DC. It can be fixed.

The Lampizor does not work with diff outputs.

kenpeter · 30th January 2009, 05:11 PM

Mine is shown (simulated) handling 10VPP common mode ripple.
Which implies that it can easily handle 5V offset in either direction.
Though it was designed around 2.5V offset. Whatever...

Its clear that this is a much hated circuit, though no-one has
ever built one or rationally debunked it. Lets keep it that way.

kkillebrew · 30th January 2009, 05:13 PM

Quote:

Originally posted by revintage
The outputs from the DAC are at +1,4V DC so this must be handled if you want to directcouple to a tube. The circuit in my post above was adjusted to that specific DAC that where at over +2V DC. It can be fixed.

The Lampizor does not work with diff outputs.

I would like to use a 6dj8 tube to build this. What adjustments need to be made for the 1.4 v 1793 DAC?

revintage · 30th January 2009, 07:31 PM

This should do it. Signal out will only be 0,4Vrms, THD below.05% with falling overtonespectra.

It looks great when simmed but as kenpeters I have never built it.

Contact sunrise to hear if it it worked like he wanted.

kkillebrew · 30th January 2009, 07:54 PM

Quote:

Originally posted by revintage
This should do it. Signal out will only be 0,4Vrms, THD below.05% with falling overtonespectra.

It looks great when simmed but as kenpeters I have never built it.

Contact sunrise to hear if it it worked like he wanted.

Nice! Thanks. Any kind of spec on that LED? or Just a regular instrumentation red type? I will check with Sunrise.

alevans51 · 30th May 2011, 03:36 AM

Consider using the Burson audio buffer instead of an electron tube.

30th January 2009, 04:40 PM	#13
revintage diyAudio Member Join Date: May 2007 Location: Eskilstuna, Sweden	The outputs from the DAC are at +1,4V DC so this must be handled if you want to directcouple to a tube. The circuit in my post above was adjusted to that specific DAC that where at over +2V DC. It can be fixed. The Lampizor does not work with diff outputs. __________________ Brgds Lars

30th May 2011, 03:36 AM	#18
alevans51 diyAudio Member Join Date: Aug 2006 Location: New Orleans	BURSON AUDIO BUFFER Consider using the Burson audio buffer instead of an electron tube.

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30th January 2009, 03:53 PM	#11
kenpeter diyAudio Member Join Date: Nov 2007 Location: Dallas	I think I've presented about the ultimate circuit for exactly that. But I have no proof other than the LTSpice simulation as shown. However, I lack the skill to explain it adequately. A lot of what it seems to excel at came as an unexpected bonus surprise. I have never built one, and as far as I know, nobody ever has. I've written Broskie to see if he wants to tackle an analysis, and potentially debunk this idea before it wastes anyone's time on something that won't actually work. I am too busy at work to bench this right now. My boss would tear my head off if I was playing with tubes before my regular work was completed. I don't have a DAC like yours, but I have an Tek AFG3252 dual channel function generator on my desk that can fake it.

30th January 2009, 04:17 PM	#12
Koifarm diyAudio Member Join Date: Aug 2005	Look here: http://www.lampizator.eu/LAMPIZATOR/...Lampizator.doc Build the alternative setup.( Cathode follower ). Here his site. http://www.lampizator.eu/ Steel left signal from pin 18 and right signal from pin 12 of the PCM1793.

30th January 2009, 05:11 PM	#14
kenpeter diyAudio Member Join Date: Nov 2007 Location: Dallas	Mine is shown (simulated) handling 10VPP common mode ripple. Which implies that it can easily handle 5V offset in either direction. Though it was designed around 2.5V offset. Whatever... Its clear that this is a much hated circuit, though no-one has ever built one or rationally debunked it. Lets keep it that way.

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