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Old 18th September 2003, 09:39 PM   #1
AuroraB is offline AuroraB  Norway
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Default Amp dilemma

During the last 30 years, I have built quite a lot of audio stuff, both for personal use and semi commercial.
I am now about to embarque on a new power amp for myself, but cannot quite agree with myself in which direction to go...

In between various commercial amps, I have had several homebrewed amps going, - Hafler clones and and Borbelys being the most potent ones... I even gathered all the parts, made boards etc for the Alexander amp, which got very good words in a scandinaviam HiFi mag. Unfortunately time became scarse, and that project fell asleep... until this forum dabated it some time last year, and more or less deemed IGBTs to outer space..maybe a later version with IRFPs or ??
Since I work in the electronics field, I also get quite "saturated" from time to time, from playing with electronics in all sorts of forms...

However,- I now feel it's time to get back on the road...I need somewhere from 60-150W, class A or AB....but I need something that will work and give decent results without a lot of experiments and adaptions, which I don't have time for ,- just not yet...
I have staked out some options. At the moment my choices are the A75, maybe the KSA100, - but I somehow find the X topology, as presented in the X100 thread, mainly by Petter and also by Uli, quite intriguing..
Have any of you out there, except Petter and Uli, built the X-clone?? Any reports ???
Any suggestions for the other two alternatives, or all three for that matter, in terms of sonic qualities..???

Any other suggestions in the same league, anyone ???
( PS ... Aleph's is just not my cup of tea,-- at least not yet...
I need some decent horns first!!! )
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Old 18th September 2003, 10:16 PM   #2
Apogee is offline Apogee  United States
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I wouldn't underestimate the Aleph's if I were you...

I've heard several incarnations of this animal and I assure you that you won't find them lacking...

To give you an idea, I spend quite a bit of time listening to a Aleph 0s through a pair of Apogee Mini Grands. The Mini Grands are known for being extremely difficult to drive. A buddy and I had tried all sorts of amps including Krell, McCormack, Theta, Adcom, Sumo, and Coda just to name a few...

We hooked it up as sort of a joke (sorry Nelson) with the assumption that since it was "only" 40 watts that it wouldn't have a prayer driving the Apogees... We were very wrong! The little 40 watt Aleph 0s absolutely blew all the others away and not by a small margin...

As I stated, don't underestimate this design... We did and we were dumbfounded....

Just my thoughts...

Am slowly gathering parts for a pair of Alephs AND a pair of Aleph X's at this time... To say that I'm a Pass fan would be an understatement!

:-)
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Old 18th September 2003, 11:03 PM   #3
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I wouldn't bother with A75. I've built 3 of them and Alephs are better. If not Alephs, X series amps would be better than A75.

If, for any reason, you would decide on A75, I have complete front end boards and the original TO-3 output mosfets.
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Old 20th September 2003, 04:53 PM   #4
AuroraB is offline AuroraB  Norway
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Hmm.

Based on advice, it seems like my only choice is go and get Passified........

I wonder if Uli or Petter is around, to coment on any changes in their designs???
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Old 20th September 2003, 06:56 PM   #5
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hey aurora,

i haven't build an X yet but i am planning to. i have gathered most parts excluding the transistors already and simulated a number of iterations of the circuit.

I have tried Aleph and i found it worse than JLH. But i am sick of the intense heat these amps put out anyway. My speakers need only one watt or so to go very very loud (yes they are horns, real frontloaded ones) but i still want headroom so i never ever clip an amp here. That's why heavy biased class AB is perfect for me.

my version of the X will feature regulated PS rails +-20V, and i will bias it for 5W class A or something like that.

The only thing i am still developing is the current sources. Petter's version had six trimmers (one on each CCS) which i think is a little too much. Four should work, on each "bottom" CCS, and i think Pass uses four trimmers in the production version.

Right now I am using an overbiased AKSA. But i need more amps, i need balanced inputs, and i want to develope and try new designs.

regards,
keyne
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Old 22nd September 2003, 05:25 AM   #6
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Default Horns

With horn you should be sticking with tubes and a small transistor amp for the bass. A Tube amp would sure help the horn imaging.
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Old 22nd September 2003, 04:04 PM   #7
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jewilson,

i have had tubes and i will build tube amps again (one just needs to be rebuild because it gets too hot for my liking).
imaging or not imaging is not a question of tubes Vs. transistors. both can be implemented to give excellent results.
right now i'm more in the mood for transistors, that's it.

regards
k
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