Tubular Technology

[David Maynard]

Here's a motherboard that will make you look twice. It incorporates a
*tube* audio amp.

http://www.infosatellite.com/news/2002/06/a050602aopen_tube.html

And just in case you think they're kidding...

http://english.aopen.com.tw/products/mb/ax4b-533tube.htm

http://club.aopen.com.tw/pss/largev...ts/ax4b-533tube-b.jpg&modelname=AX4B-533 Tube

Time to hit ebay for one of those antique tube testers.

 

[JAD]

hey Dave, I have had that Aopen board for about 3 years now....the sound
has "character.
I was pushing people here to take a look at it then, they balked at the
idea.

 

[David Maynard]

hey Dave, I have had that Aopen board for about 3 years now....the sound
has "character.
I was pushing people here to take a look at it then, they balked at the
idea.

Interesting. I hadn't heard of it before and ran across it when I was doing
a search on tube testers because I'm interested in antique radios, TVs, and
tube audio equipment (not necessarily 'old' in the audio context).

Dern near passed out when I saw the bucks a 7591 pulls in these days. Ain't
a trivial issue when you see on ebay a 'great deal' for an amp with 4 empty
sockets.

 

[Matt]

hey Dave, I have had that Aopen board for about 3 years now....the sound
has "character.
I was pushing people here to take a look at it then, they balked at the
idea.

Okay, I gotta ask ... when you power up and boot XP, does the tube warm
up in time for you to hear the little XP greeting tune?

 

[Conor Turton]

Interesting. I hadn't heard of it before and ran across it when I was doing
a search on tube testers because I'm interested in antique radios, TVs, and
tube audio equipment (not necessarily 'old' in the audio context).

Was in PC Format magazine ages ago. AFAIR fromt he review they said
that you got a far fuller sound with better bass out of it.

 

[David Maynard]

Was in PC Format magazine ages ago.

My not being a reader of that mag probably explains why I didn't see it

AFAIR fromt he review they said
that you got a far fuller sound with better bass out of it.

Yes, the ages old "tubes sound better than transistors' debate. And, among
those who think so, why?

Many who've done waveform analysis tend to think it isn't because tubes are
'cleaner' than transistors but that they distort, in a manner pleasing to
the ear. In particular, even 2'nd order harmonics. And then there is the
argument that tubes overload more gracefully. Which might seem to only
matter if you're driving the things 'loud' but it also relates to the wide
dynamic range of audio that can have overdriven components even when it
seems like you're at low volumes.

And then there's the debate about triode vs pentode mode, super triode,
super linear, single ended, push pull, class A, AB, etc. circuit
configurations; and the really contentious debate about heretical negative
feedback, ARG!.

 

[Doug Warner]

And then there's the debate about triode vs pentode mode, super triode,
super linear, single ended, push pull, class A, AB, etc. circuit
configurations; and the really contentious debate about heretical negative
feedback, ARG!.

Hmm. in school (when tubes ruled, and transistors were new kid on the
block (very low power), negative feedback was accepted as the normal
method of limiting the distortion inherent in tube amplifiers.
Was it not readily accpeted when first proposed?
(This probably belongs in some electronics group, but, given the silly
appearance of tubes on some motherboards, it's not totally O.T.)

To reply, please remove one letter from each side of "@"
Spammers are VERMIN. Please kill them all.

 

[David Maynard]

Hmm. in school (when tubes ruled, and transistors were new kid on the
block (very low power), negative feedback was accepted as the normal
method of limiting the distortion inherent in tube amplifiers.
Was it not readily accpeted when first proposed?

It's always been there, negative feedback I mean, so the 'debate' is really
a misnomer. What they're arguing about is really an overall amp feedback
rather than in individual stages and it's manly among 'purists' (pure of
what I'm not sure as overall feedback was (and is) common staple in many
commercial tube amps.

Negative feedback, especially whole amp, is more problematic in tube amps,
however, because of capacitor and transformer coupling adding poles and it
'masks' the 'triode' characteristics, as well as altering overload
characteristics (since feedback will attempt to compensate till it 'snap'
fails), that some purists maintain is the 'tube sound'.

There is potentially some merit to the point as distortion analysis
indicates that overall amp feedback introduces less pleasing 3'rd order
harmonics.

Its even more common, essentially mandatory, in transistor designs because
they almost exclusively operate class AB with forward Vbe cross-over
distortion that usually needs heavy feedback to reduce.