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In Reply to: Interesting page about CD with tubes posted by ZiBi on December 30, 2006 at 16:09:29:
I have an MF X10d, whose effect makes me happier than the unbuffered CD output, exactly at advertized and reviewed (by those who like it). I have none of the downsides predicted by my audio purist friends, who denigrate any additional circuitry anywhere.My state of knowledge isn't sufficient to effectively determine if what he's doing is essentially any different, except for cutting out the existing crappy circuitry sooner.
Can you enlighten me?
He clearly likes what he's doing. Reading his site, I can only agree with some of his conclusions. YMMV.
Follow Ups:
There are better and worse op-amps, just as there are better and worse vacuum tubes. There are also better and worse ways to use these components.Most tube buffers are cathode-followers, which have less than unity gain but have low output impedance. Plate-loaded tubes have higher output impedance but higher than unity gain (which depends on the circuit). It is possible to use a big-ass tube to get both voltage gain and sufficiently low output impedance to sort-of work as a replacement for the typical mid-fi heap o' op-amps CD player output circuit, but it makes the sound critically dependent upon the interconnect cable. It may also invert polarity.
"Cutting out the crappy circuitry" is exactly the difference--and some (not MusFi) think it's a big difference. I haven't tried to do it, but on theoretical grounds I'd have to agree with the site. If the analogue integrated chip circuitry that the actual chip feeds into degrades the sound (because it's cheap crap) then the tube buffer added at the end of that chain (like the external buffer you have) can't 'fix' it. But if the tube circuitry REPLACES the 'crappy' circuitry and performs the function that the old circuitry performed, then, if tubes really do do a better job (let's say they do), you have gotten a double hit of improvement. That's the story.
Seems a lot of the tweaking of digital sources eventually gets into replacing or displacing some of the output circuitry. Some of the CDP and the DAC makers/builders deliberately use tube output circuits.When I now use my MF tube buffer, it's not directly hooked up after the CDP output, since I have an outboard DAC hooked in between with a digital IC. So at least some of the CDP's output circuitry is bypassed, though I know it's replaced in the DAC to some degree, before it enters the MF unit. Not ideal, but sounds damn good anyway.
I've often fantasized about bypassing all that stuff and wiring in the useful parts of the MF tube buffer as the sole output circuitry altogether. However, I've also fantasized building flying machines, though the pigs just aren't cooperating! Seriously, had I the electronic and soldering skill I'd do the same DIY this guy did or something pretty similar.
Right.. I would too. Whether it's in the cdp or the dac, the hit is against all the other ic chips etc that follow the dig-to-analogue chip if I understand this right. Scott Nixon does similar stuff. DACs don't seem to come with schematics and even if they did, I doubt if I could read one right. Best I can do myself is have a tube preamp following the dac.
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