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Buffalo 24 -> pulling the output to current mode
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Hi, Greetings!. I am just a beginner in electronics, so help would be much appreciated... here is my question: how do I pull the output to current mode in my Buffalo24? (I read somewhere that loading the output with a resistor...). I would love to connect both polarities (plus and minus) in each channel to a tube buffer output stage ... but have no idea on how to convert the output to current, and in that case, will I have the 1.65Vdc offset as well ? best regards ! Pepe Edited by user Monday, September 21, 2009 1:54:22 AM(UTC)
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The Buffalo24 will act like a current-out DAC when driving a low impedance, and a Voltage-out DAC when driving a high impedance. All you need is a tube I/V stage with a low input impedance (less than a few ohms).
Try to find a differential-input I/V stage if you can, as you lose a lot without it.
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@fokko:
Thank you for the link, I am precisely following Lukasz's scheme but he does not tell how to set up the DAC in current mode
@Brian
I appreciate your comments Brian, could you be more specific about the load ? (how many ohms are "less than a few"?)
Best regards
Pepe
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Ideally, a current source wants to see zero-ohms, so as close to that as you can get. The IVY, for example, has an input impedance in the mOhm (< 1-ohm) range. There is no mode to select for current output, it is just what kind of load you present.
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Brian, thanks a lot for answering. I have heard somewhere that "voltage" dacs (the output is voltage instead of current) do use in fact op. amps for this conversion (just right inside the chip), so I thought that pulling current would actually get better results in sonic terms. My tube output is just 1 tube working in anode follower (stereo), so I will connect buffalo outputs for each channel to the tube grid and the cathode, respectively. (+ polarity and - polarity, to be more precise). The question of pulling current from the buffalo, as you pointed out, presumes that I should load the output then with let's say a 20 ohms resistor from grid to ground, and no capacitor between the output and the grid. In voltage mode, nevertheless, I would use a capacitor in order to get rid of the 1.6Vdc bias that buffalo sets. Do I make any sense ? best regards, Pepe Edited by user Wednesday, September 23, 2009 12:40:27 AM(UTC)
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Lindamar, te he puesto un privado. Dime si lo recibiste.
Saludos
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lindamar wrote:Brian, thanks a lot for answering.
I have heard somewhere that "voltage" dacs (the output is voltage instead of current) do use in fact op. amps for this conversion (just right inside the chip), so I thought that pulling current would actually get better results in sonic terms.
This is actually completely untrue. Most voltage output DACs do not use internal opamps for current-to-voltage conversion. It is a different internal architecture. I do not consider myself qualified to advise on implementing a tube output. Others here or on DIYAudio will be able to better assist you there.
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thank you Brian, your comments are welcomed and appreciated.
I'll try to find out in DIYaudio as you say,
best regards
Pepe
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@Amaro : indeed !!, take a look to your inbox please.
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Buffalo 24 -> pulling the output to current mode
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