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Old 15th April 2005, 05:02 PM   #1
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Default Where do you draw the line between tube and sand?

I should explain the cryptic title: do all you die hard tube fans go tube all the way through the chain, e.g. tube RIAA or tube DAC all the way to OPT? Or is there a point where, just as many concede that silicon is better for power supplies or CCS's that the front end/low level stuff is "better" left to silicon (I know "better"is no absolute). I have read many opinions on the former issue but none on the latter.

And I ask this for practical reasons for myself. I am building myself a full audio chain and love the idea of it being balanced throughout and tube throughout, but the complexity of tackling a balanced tube RIAA preamp and a balanced tube DAC frighten me. I'm pretty sure I must choose to build either an SE tube preamp or a balanced SS preamp, and similarly for the DAC. What do you recommend or what do you have preference for?
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Old 15th April 2005, 05:39 PM   #2
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RIAA is easy. For balanced, just make two identical networks and run diff amps fore and aft.

Hmm, if the signals are 180 out of phase, the phase shifts in the network should just rotate around the circle and not cause any unusual common-mode cancellation, no?

As for a DAC, someone look at the digital standard (SPID/F? or whatever it is) and see how hard it would be to decode.

Depending on how many logic chips you want to use, I doubt it'll end up much worse than that all-tube clock.

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Old 15th April 2005, 05:48 PM   #3
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Quote:
Originally posted by Sch3mat1c
RIAA is easy. For balanced, just make two identical networks and run diff amps fore and aft.

As for a DAC, someone look at the digital standard (SPID/F? or whatever it is) and see how hard it would be to decode.
So you are in the "go tube AND balanced" camp I see

I dunno about balanced RIAA, Morgan Jones' schematic looks BIG to me.

Tube balanced DAC is easier, the KISS way is to just invert the data stream and have 1 DAC chip do the + phase and the other chip do the - phase.
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Old 15th April 2005, 05:50 PM   #4
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It's difficult to deny that silicon is always going to be superior for constant voltages and costant currents. The laws of physics are on its side.

Personally, I'll use silicon for signal handling in a limited set of circumstances, mostly source followers. See the SYclotron, for example.
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Old 15th April 2005, 06:16 PM   #5
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Quote:
low level stuff is "better" left to silicon
GIven a forced choice i would rather leave the hi level 'stuff' to silicon, somehow i find the silicon signature more objectionable at the millivolt/microvolt levels. It is all, of course, very relative - i have a reasonably musical all-SS system which doesn't , surprisingly, annoy the hell out of me. Otoh, even a little silicon in my all-tube system has the ability to stick like a sore thumb. The final result is very much a question of mix and match. And not an easy mix to match right.
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Old 15th April 2005, 07:05 PM   #6
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A sensible man would keep silent, - but - here goes (my opinion only). You can get perfectly good results with either vacuum or sand in audio. Sand is more difficult to design well, and the construction is different. I like tubes because a) I understand them, b) they are rugged enough not to need special care in handling, and c) the glow of their filaments transports me to a simpler time, and soothes my soul. Regards, Bill.
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Old 15th April 2005, 07:12 PM   #7
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Bill, you're a sensible man. There's no room for that in audio!
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Old 15th April 2005, 07:23 PM   #8
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What about mV level with SS (JFET or bipolar) input and tube cascode with resistive load?
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Old 15th April 2005, 07:43 PM   #9
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My opinion is: Anything you can build/maintain yourself, go with all tubes, with the possible exception of the use of power rectifiers. With a format that's likely to be obsoleted in a few years or is CD quality or worse, making the final effort to do it in tubes may not be worthwhile.
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Old 15th April 2005, 11:45 PM   #10
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Quote:
Originally posted by leadbelly


So you are in the "go tube AND balanced" camp I see
Well I was just suggesting a solution for you... but now that you've dragged me into it, I KISS.

I don't really care, so I listen to 128k MP3's on my computer (and am proud of *enjoying* what you would be led to believe is the worst media ever!) and send that through my tube preamp and monoblocks (Frankenhouse and Hept'AU7).

Balanced specifically has no purpose in a home system, maybe for a generally large system like a club, church or PA system in general.

It does make PP easier, but then again, you have all those extra stages that *could* be rolled together into just one or two stages. And you get into trouble when you have someone who prefers SE output.....

Quote:
I dunno about balanced RIAA, Morgan Jones' schematic looks BIG to me.
I don't have his book, but balanced, like stereo, can easily get unweildy very quickly. Come to think of it, if you're going to do stereo RIAA, you need essentially four channels!

Quote:
Tube balanced DAC is easier, the KISS way is to just invert the data stream and have 1 DAC chip do the + phase and the other chip do the - phase. [/B]
If you just want balanced for transmission, the KISS way would be to use one DAC and split it at the output, but...

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