[Spidey9534]

Hi,

I'm looking for a replacement amplifier for my main system and have been doing quite a bit of research over the last few months. I don't pretend to be an electrical engineer, but I do get the basics of SS and tube equipment differences. (that statement could be a death sentence in here) lol.

The AVA Fet Valve hybrid amps look very interesting to me as well as the Blue Circle BC24/28 hybrids, which leads me to my questions.

Can someone please explain the major differences in the design? I have read about some of the differences, but my feeble understanding of electrical designs leaves me more confused than informed.

1) I've read that the amps use different tubes. Can someone explain in a basic way why? Pros/Cons?

2) It 'appears' to me (keep that in mind) that the BC equipment seems to be heavily biased to A Class? I can't figure out if the AVA amps are. Is this significant? Magic first watt and all that.

3) The relative wattage output seems to be significantly different in the amplifiers, yet the costs are 'fairly' close? Significant?

Lastly has anyone compared these units and have an opinion about their merits, sonic qualities, etc?

My System if it's of any consequence:

Ah! 4000 CD
Audible Illusions 3
CJ MF2100
B&W Matrix 3E

Thank you,
Matt

[rockadanny]

An oldie but I am interested. Anyone?
I am mostly interested in your opinion on sound differences.
(Don't know whatever Spidey ended up with.)

[IronLion]

Damn, digging in the crates on this thread. 

[rockadanny]

Yeah. I got the bends just typing my reply. 

[avahifi]

I tried to dig up some info on the Blue Circle amps mentioned above, but their web site says they are discontinued now and there is nothing there I could find aside from some reviews. I have not heard their products aside from trade show conditions, where making good comparisons is really tough.

I did notice that the 120 watt per channel model 28 had a list price of almost $4000, about double the cost of a nearly 300 watt per channel Fet Valve Ultra 550 amp.

Regarding design ideas, because small signal vacuum tubes have very limited current drive capability and a relatively high output impedance, we have always noticed that this is a poor choice (in our opinion) for trying to directly drive the rather high input capacitance of a solid state output stage.  Thus we have designed and use our patented Transcendence transimpedance amplifier circuit for this task.  This consists of a triode tube in a special loop combined with a power mos-fet device.  The triode provides high input overload immunity and all the voltage gain, while the loop combined with the mos-fet provides high output current drive and a very low output impedance, ideal for the job it must do.  From the reviews I have seen, it appears that Blue Circle, as do others, assigns just a vacuum tube to this job.

Now of course any circuit can be executed anywhere from very well to pretty awful, so just the circuit design goals will not give you the complete story or a sure fire prediction of the sonic quality obtained. There are still lots of unknown variables out there too, otherwise all amps would sound the same, essentially perfect.  We have not got that far yet.

I do hope you will consider one of our amplifiers and hope this has answered some of your questions.

Regards, and Merry Christmas

Frank Van Alstine

P.S. Our amplifier are biased into about 20 watts of Class A operation.

[Spidey9534]

Hi All,

I'm actually still alive....

To answer your question or interest in what I ended up with. I was lucky enough to audition a used Kora Mercury integrated tube amp from a local shop and I've never looked back.

Good luck in your search.