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In the Forum: Audio Discussions
In the Thread: Two-stages, hybrid, small, powerful class “A”?
Post Subject: One way to learn is to try...Posted by Romy the Cat on: 5/4/2006

 Chirag wrote:
Well..my first question would be regarding the application.  The big Melq tube is already doing the bass towers...is it not enough current? 

Chirag, I’m not planning to use this power amp in my system.  The Melq LF section does perfectly enough for my room. The Zarathustra prototype that I mentioned before:

http://www.goodsoundclub.com/TreeItem.aspx?postID=1029#1029

did something quite good but there were also the areas where it did not do good (driving high sensitivity for instance). I attribute it to the class AB operation. Also, we have some interest to see how it will perform if the very same amp will be biased class A and made with no cheating of any kind (unfortunately it means expansive). We really do not know how it will sound in comparing to the Melq LF section. I think the only one way to learn is to try. I assume that if everything will be done properly then it might be a very good full range amp, as I have seen how the class A amps (M1.1 for instance) do drive high sensitivity with good results. In the end I will hate if the amps will sound good, as I will have no use for it. Well, at least it will give me some self-confidence and reasons to call names the other guys who do SS amps.  :-)

 Chirag wrote:
In addition to the Aria guy, the tubecad.com guy has several circuits up using his "aikido" circuit as a driver and several mosfet and transistor outputs.  It looks on the surface like a complicated SRPP setup, but I am not capable of commenting on the design.  Most of his suggested amp diagrams focus on lower outputs of 10-20w, but using more current capable tubes, you may be able to drive a bank of solid state outputs to get you what you need.  I generally like his approaches and I'm not basing this on any experience with this particular design.

Thanks, I will look at his lately. Although we do not need any circuits, we have the one but rather some interesting packaging ideas, though I did not see any high-power-low-size class “A” design with bold objectives.  Well, over the last few days we have come up with a solution that do look attractive so far… will see…..

 Chirag wrote:
The other option I would suggest are the non-hybrid feedback based Pass Labs aleph amp circuits.  They remind me of the artificial sweetener Splenda...they taste kind of like sugar, but the overly sweet and chemical attitude does come through in the higher frequencies.  The Aleph 30 I tried for a few months did not screw up the midbass with my little Tannoys any more than my PP tube amps.  I am wondering how well his newer 30w "J" version could work on my 15" pro tannoys.

Thanks, Chirag, we all set with the topologies and circuit design. We are not in Kansas anymore and the whatever Mr. Pass does  Sonically is good only to be use as a ballast for ships…

 Chirag wrote:
I think the italian Pathos company has a products that might fit the bill.  From the smaller integrated amp I heard, it may not cut the musical muscle you require.  This amp has a lot of fluffly names around it, but they do claim tube driver and class A output.

Actually I did hear this amp in Belgium I believe. It was driving Danlavy V and it was very pleasant.  I do not think they were powerful though….

 Chirag wrote:
Regarding the Lamms, is it possible to cut away some of the odder opamp type middle stages and use a higher current tube to push the outputs?  The output setup and case is already there. 

Not really, I would like the Super Zarathustra be twice smaller then Lamm 1.1, twice or trice more powerful and be at least 10 time more advancely made and sound, not to mention way better engineered. If I remember correctly Lamm 1.1 had cheap consumer-type PSs, the first stage was around some kind of integral buffers, then it had SS stages, then tube-based SRPP, then another SS stage and then the MOSFED output. There is negative feedback around the stages and a lot of other things… The Zarathustra will be completely different amplifier with completely different design objectives, so even the box of the M1.1 will not be reusable.

 Chirag wrote:
If you're as intense as I believe, can your little 6E5P tube in the Melq configuration drive a bank of mosfets or transistors?

It will be very simple: no expansive and properly (sonically) made PS, super effective heat dissipation mechanism, Melquiades’ input stage in SRPP configuration driving the SS stage, no feedback, and the Dima’s own “kinky” output stage. I can hardly comment what is in the Dima’s output stage but Dima climes that it has some his own inventions that make it “different”. I prefer do not know what it is as I know absolutely nothing about SS.

Rgs,
The Cat

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