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Old 29th January 2006, 12:24 PM   #1
Bakmeel is offline Bakmeel  Netherlands
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Default Aleph 2 - Or not?

Fellow enthusiasts,

About a year ago I set off to construct an Aleph 2 amplifier. Having read lots of discussions on the web, taking in advice of Mr. Pass himself, and studying the service manuals of several Aleph versions, it seemed the right choice to build an Aleph 2.

But as the gathering of components goes on, there grew some doubts... and the doubt becomes stronger. For what I read in some discussions on Aleph 2, it seems that this amp may not be working very well with low impedance speakers. And for it's concept, I think I must agree.

My speakers (Piega P5 LTD) have a rated impedance of 4 Ohms, but following its characteristic curve, its more like 3 Ohms for the greater part of its curve. I know they are current-hungry and they seem to work best on high-power amplifiers (hence the first choice for an Aleph 2). They also have a tendency to sound kindof harsh when connected to class B amps, really showing the meaning of a tranSISSStor amplifier... FWIW they are rated around 200W per channel.

The tricky thing is: I already have most of the power supply gathered now, and all of the mosfets matched and ready. So with 50 IRF240 fets and a monstrous power supply with 1kVA 2x42V tranny, 2 3mH air coils and around 400.000uF caps (all per channel), this limits the choice of amplifiers left to build.

Should I stick to the Aleph 2, beef it up with more bias current and/or more parallel devices? Try to build an Aleph 1.2 or maybe an Aleph X? what about an A75 or Norman Thagard's A40M?

I'm a bit lost in the woods, so any help or advice is welcome..
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Old 29th January 2006, 01:04 PM   #2
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Default Re: Aleph 2 - Or not?

Quote:
Originally posted by Bakmeel
Norman Thagard's A40M?
Eeeeh, which one is that ?

Pump up the Bias !
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Old 29th January 2006, 03:20 PM   #3
Bakmeel is offline Bakmeel  Netherlands
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Default Re: Re: Aleph 2 - Or not?

Quote:
Originally posted by jacco vermeulen

Eeeeh, which one is that ?
Its actually Nelson's A40, but in Audio Electronics, edition 1999/6 through 2000/4 Norman Thagard gives it a complete explanation and gives it a Mosfet output stage...
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Old 29th January 2006, 03:34 PM   #4
AuroraB is online now AuroraB  Norway
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Has this revision been on the net??

I have a set of parts just about suitable for this, -but the trafos are 300 VA, -slightly under the limit for the KSA50
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Old 29th January 2006, 03:57 PM   #5
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Default Re: Re: Aleph 2 - Or not?

Quote:
Originally posted by jacco vermeulen


Eeeeh, which one is that ?

Jacco,

I am sure you have read about Norm Thagard, the astronaut, engineer, medical doctor, audiophile, audio diyer and most famous of all NP collaborator on the A75. He's a cool cat as oppose to your gato caliente
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Old 29th January 2006, 04:40 PM   #6
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Hi Bakmeel,

I think the Aleph 2 will work fine. What you could do is lower the power supply voltage a bit and up the bias accordingly for the same dissipation and a bit more power into lower impedances.

This would probably mean new transformers wich would bring us to alternative B:

Build an Aleph-X, performance is a lot better at lower frequencies (more control, less boomy). It´s also better at higher frequencies but this could be a matter of taste.

I don´t know your speakers but if they go quite low (<30Hz) the difference will be welcome. If your speakers stop at higher frequencies the Aleph will have a bit more bass (like a higher Q-factor)

William
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Old 29th January 2006, 08:08 PM   #7
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Quote:
Originally posted by Blues
He's a cool cat
Dear Allan,

i know his designs, built his designs, even know what the guy looks like.
I did not ask for the man but the design, i missed his Mosfet version of the 40.(probably at the time i was in the waste bin)
Nope, you won't see me in space. Pigs don't fly, me neither.
Just found the article in 5 ZIP parts overhere, thanks.
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Old 29th January 2006, 08:47 PM   #8
Blues is offline Blues  United States
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Quote:
Originally posted by jacco vermeulen


(probably at the time i was in the waste bin)



Sorry, Jacco. Don't set the waste bin on fire...
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Old 29th January 2006, 09:10 PM   #9
Bakmeel is offline Bakmeel  Netherlands
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Hi WuffWaff,

New trannies are no option for obvious reasons, but beefing up an aleph 2 would be... I just would have to take the extra dissipation for granted, but if my calculations are right, I'd might handle around 100W extra in the heatsinks Í have planned.

The Piega's are specced to 40 Hz, but below that they give a natural roll-off to wherever the units can take it. But that is exactly the region where they really need control, so after all maybe an Aleph X is the way to go...

How "boomy" would you expect an Aleph 2 to be?

Jacco,
There's 6 articles total for the entire amp. Would you like a photocopy of the magazines?
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Old 29th January 2006, 10:37 PM   #10
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Quote:
Originally posted by Bakmeel
Would you like a photocopy of the magazines?
That would be great.

WWWilliam,
i'm waiting for the X boards from the CaronDimonio GB to arrive.
Mind telling which loudspeakers you had on the A-X ?
(pssst, and what's the latest Ingolstadt drooler ?)
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