timwhit said:
They add distortion in a way that no integrated amp can.
Says it all, really.
As for PW's vinyl analogy: Vinyl always sucked, it's just that the cover notes were bigger and better.
I'll grant you that an A to D converter with an indifferent quality low-pass filter also sucked. I personally listened to several different CD players before settling on an 8-times oversampling player that didn't muddy the sound.
But then I freely admit to being an audio freak, although after the lifestyle changes that a family enforces, I'm somewhat more pragmatic. :-?
The irrefutable fact is that 'tube' amps colour sound, although some of the better ones are extremely subtle about this, only impacting if you drive the amp to clip (which is exceedingly stupid). On the other hand, old or cheap transistor amps introduce an annoyingly harsh type of distortion, and when overdriven they are intolerable (and will most likely destroy your speakers).
But a lot of this is ancient history. Class B amplifiers based on bipolar transistors are highly efficient and bloody awful when it comes to distortion. I'm well out of the loop, so I don't know if they're still used in PA work, or superceded by Class D. Maybe Stereodude would know?
Any reasonable amplifier will use Class A-B, but great sins were committed in the past in the name of marketing. In particular, THD (Total Harmonic Distortion) figures were widely quoted as the be all and end all, with numbers as low as 0.001% or better all too common.
Compare this with up to 10% for speaker drivers. :roll:
The trick is that it's easy to achieve low THD with liberal application of negative feedback, but that can either ignore other faults, or introduce a bunch of its own. Intermodulation distortion springs to mind as a metric that's hard to quantify but may be just as significant as THD.
Some years ago now, people started to use MOSFET (Metal Oxide Semiconductor Field Effect Transistor) as an alternative to bipolar transistor designs. Although not as efficient, they have
headroom, that is they clip less sharply than conventional bipolar transistors, although they're still not as forgiving as valves.
It's called having your cake and eating it too. Better clipping behaviour without the coloration of most tube designs. I'd expect most HiFi nuts to go MOSFET, although a good bipolar design is just as good for most purposes.
Only hard cases would lay out their own money for a tube solution, and I haven't even begun to itemize the other drawbacks.
Despite their method of providing the high voltages for the tube, I wonder if they will be able to get it past safety certifications? After all, the inside of a PC is user-accessible.
