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Old 22nd November 2001, 02:42 PM   #11
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Smile a mini Aleph?

Grey,
after that interesting thread on a SOz with current sources I'm anxious to see the mini Aleph you'll be dishing out soon? Keep the community posted.....
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Old 22nd November 2001, 04:30 PM   #12
Fuling is offline Fuling  Sweden
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Wow!
Biamped speakers internally powerer by Aleph 3s... sound like a winning concept to me!!

Is there anyone who knows what swing loss I can expect in the current source? I believe I can get about 15 watts with +-16V rails, but if the current source "steals" too much swing i guess the power would be significantly lower.
Also, do you think 1A bias would be enough, or should I go higher?

Cheers!
/Daniel
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Old 22nd November 2001, 07:28 PM   #13
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Default What a wonderful idea.

After I build Aleph 3, I left some MOSFET here. This idea gives me a hint here. I think I will build an Aleph with one pair of IRFP240. Every thing will be easier then original Aleph. For my small surround speaker, 15W should be enough.

Thank you Fuling
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Old 22nd November 2001, 08:11 PM   #14
paulb is offline paulb  Canada
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Default Me too

I'm now working on the amp that will eventually drive my woofers in a biamping setup, but I think the small Aleph would be a great idea for the tweeters. Keep us posted, Grey!

[edit} I have a 36V, 288VA transformer that I will be using. Transformers are way too expensive to not use the ones you have lying around.

Are there sources for PCBs around? I've never looked.

Paul

[Edited by paulb on 11-22-2001 at 03:50 PM]
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Old 22nd November 2001, 09:27 PM   #15
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Aiming for 15 watt in 8 ohm (nominal), means 1,36 amps for class A operation using a constant current source. Since the ALEPH uses sort of a "modulated current source" you can get by with aprox. 0,75 times this value i.e 0.75x1,36 = 1.02 amps.
However if the load you use (your speaker) is not amp friendly (impedance dips) 1 amp is probably a bit skimpy.
I used a single IRF ALEPH current source in a ZEN biased at aprox. 1 amp and liked the results better than the original ZEN. Tested this thing on 3 different speakers and it works perfectly.

So I would say, go for it
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Old 22nd November 2001, 10:12 PM   #16
Fuling is offline Fuling  Sweden
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Thats just what I tought!
I believe I can get away with 1A, since the amp IŽm using now is biased at about 1,5A (constant, not dynamic) and that one drives my speakers to any level I wish without problems.
The speaker sensitivity is about 88dB/w, by the way.

Zen with aleph current source sounds interesting, I wouldŽnt mind testing that concept some day. But one of the criterias for this project is to get rid of the output caps, which I believe is quite difficult with the Zen (to say the least)

Thanx everyone, let me know if you get any more great ideas!!

/Daniel
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Old 23rd November 2001, 12:27 AM   #17
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Daniel,
All you have to do to get rid of the output caps is build a pair of Zens (carefully match the parts in each pair). Then you can run them as a differential, like the SOZ. There will be DC at the output, but it'll be matched on both sides of the speaker so the net result will be 0V across the coil. You'll still need the input caps, though.

Grey
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Old 23rd November 2001, 10:51 AM   #18
Fuling is offline Fuling  Sweden
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GRollins

That is one option, yes. Not a bad idea at all, but I think it would be both cheaper and easier to build a downscaled aleph, and I guess it would be more efficient too.

By the way, yesterday I came up with an idea about an amp with some kind of "signal tracking current source" (completely different from the CS in the Alephs)
I will give it a try as soon as I get som time. IŽll let you guys know if i works!

/Daniel
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Old 23rd November 2001, 08:36 PM   #19
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You can build an easy signal tracking bias circuit
by using the output voltage instead of current.
Referring to the Aleph 3 schematic, you eliminate
R114, C103, and R124-127. Then simply attach a
resistor from the base of Q105 to ground say
47K or so, and adjust to taste
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Old 23rd November 2001, 11:34 PM   #20
Fuling is offline Fuling  Sweden
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Thanks for the input, mr Pass (and everyone else, of course!!!)

IŽll try that idea a.s.a.p., but as usual IŽm short on money and time...=(
Right now IŽll better go get some sleep, itŽs half past midnight and IŽve had too many beers...=) Tomorrow afternoon seems like a waaay better time to read schematics and stuff like that...=)

Cheers!
/Daniel
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