Newsgroups: rec.audio

bower@pecan.cns.udel.edu (Ty Bower) writes:

>He often tends to use techno-babble and often seems to be making
>things up to make his equipment sound impressive.  More often
>than not, he will "spare" the listener the details of how and
>why he has achieved whatever engineering marvel he has achieved
>and give it a "cool name."  (Magnetic field power amps come to
>mind... what the hell is a magnetic field power amp, anyway?)

Indeed. A "magnetic field power amp" does not use magnetic field for
amplification in any way. All it is is an amplifier whose positive and
negative supply is increased during transient peaks. This allows the
amplifier to deliver a lot of power, but limits dissipation during
quieter passages. This allows Carver to use smaller (almost no)
heatsinks. In college, a friend of mine had that Carver cube amplifier.
Lots of power in no space and very light. It broke down all the time. It
was an excellent learning vehicle for a couple of EE students, though.

Carver's power supply is simply a transformer with many taps on the
secondary and more than one set of full-wave recitifiers. The taps are
switched according to the desired output amplitude. I think Carver also
runs the class AB output stage very close to class B for lower quiescent
power dissipation. I guess you could call the a "magnetic field amp"
because for large signals, a transistor is used to select how much
magnetic field gets switched to your output stage, but I really think
this is a marketing name.

At best, a power amp with switched power supplies and very lean bias can
sound as good as a comparable amp with single supplies and a rich bias.
At worst, Carver has added several hiccups in the open-loop transfer
function of the amplifier. Some would claim that the hiccups due to the
switched power supplies don't matter because distortion is not
noticeable when the music is cranked, but crossover distortion is most
noticeable in soft passages.

And then there's "Sonic Holography." In college this was considered the
ultimate piece of gear to have if you were going to take acid and play
Dark Side of the Moon past the clipping threshold of your amplifier. I
actually never heard sonic holography. Can anyone report on what it
really is? How does it actually work?

>So, although I myself can't condemn Carver equipment, I would
>never recommend it to anyone, much less purchase it myself.
>It's kinda like Bose -  either you love it or hate it.  
>Bob Carver and Amar Bose are almost the "religion & politics"
>of the audio world.  You just don't bring the subjects up
>at the dinner table....

Funny. The college I went to had an acoustics class given by Prof. Bose.
It was supposed to be an excellent class. I really regret not taking it.
Because we considered Bose "our dude," there were a lot of Bose speakers
around. I really disliked their sound and was considered a snob and an
asshole for saying so.

As for the Carver sound, I did listen to the cube a lot. My friend with
the Carver cube and I often had A/B sessions. We both agreed that my
Hafler 220 was better. We also agreed that my Hafler 110 preamp was
marginally better than his NAD. I forget what speakers he had. I think
they were some really tiny two-ways with a 4" woofer. They had much more
precise imaging than my Time Windows, but I was a bass freak. I really
think it made more difference which speakers were chosen than which amp,
though.

>A friend of mine does some DJ work, and a few summers ago he
>started using new Carver amps.  He has been surprised at how
>clean and powerful they were (much better than the old amps
>he was using.)  There are many other satisfied Carver owners
>out there.

A Carver amp would be an excellent choice for DJ work. DJ work rarely
requires great fidelity but the light weight of the Carver stuff sure
would be nice.

My friend with the Carver cube tried to lend it to the house for house
parties. He had all sorts of problems with thermal runaway and shutdown.
I had to run upstairs and get the Hafler which had no problem. Of course
we later found out that one of the speakers had a shorted midrange
driver. I don't remember whether the Carver was usable for parties on
speakers without shorted drivers, though.

Allan

P. S. -- Bliv, are you out there?