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Old 25th June 2008, 01:38 PM   #1
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Default 2 * Aleph 30 = an Aleph "60"?

I saw a post re scalability of the Alephs, a light bulb went off, I came across locally & bought two of BrianGTs original Aleph 30 “kits” (pcbs, parts and matched output devices).

I’d like to use the 2 kits to make an Aleph “60”. For my 84 dB, 3.1 ohm speakers, the target load is 3 ohms, power into that load min 60 watts, 100 would be a little better.

They will preferably be monoblocks, other than that, I’m open. I guess I could make two Aleph 30 amps, and “parallel” them, which would allow future flexibility, but require 2 more cases . .

As the speakers drop to 3.1 ohms, and it should sound better, I want to bias them as high as possible. It helps a little that I’m in the same city as Conrad.

I searched on aleph 30 bias, but got 1430 hits . .

Has anyone done something like this?
How are the rail voltages, transformers and current calculated?

Thank you
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Old 25th June 2008, 02:35 PM   #2
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Otto-man,

do a search for the Volks(wagen)-60.

25Vac transformers and biased to 2-1/4 amp, calculate the dissipation/ch yourself to size the trannie.
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Old 25th June 2008, 02:36 PM   #3
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hi,

as i have build it. so i know little bit about it.

pls check the attachment here already stated to changing the watts and how much current do you require.

i hope you can find here.

i am using 10 ampire 29-0-29v..amp output is 30w for now as i am still learning about it. heat sink need to be very big. mine gets alst cound on high volume 46c, amban is 30c. i think the temp is ok....not really bad after 7hers of operating.

best regards
michael
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Old 26th June 2008, 08:16 AM   #4
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Jacco

I searched on Volks 60 and didn't see much, finding more searching on the Aleph 60 . .
I saw that Grey has said that "the Volksamp 60 is basically an Aleph 2 running at lower bias". Not that bias is the main criteria of good sound, but it should help with that, with the low ohms. But it seems the Aleph 60 should be my "model".

> 25 Vac transformers and biased to 2-1/4 amp

What % current gain did you assume to arrive at those values?



space2000

Your schematic says its for the Aleph 3; I may be wrong but at a quick glance it appears more complex than BrianGT's Aleph 30?


To make a 60 from the 30, apart from doubling the output devices and heatsinks (or more if current gain is increased to say 65%), and larger transformers - what component values need to change?

Thanks
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Old 26th June 2008, 09:26 AM   #5
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Here's one in my lingo with a main numbers list of the various Aleph models, 1st one that pops up when i do a Goggle dive.
You'll find identical lists at several home pages of English speaking Aleph builders.
(whenever i really need to find something at Gurgle i run through a dozen different language versions)

Numbers

The Aleph2 has both different rail voltage levels and is biased higher.
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Old 26th June 2008, 01:25 PM   #6
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Jacco

Thanks for that link, I thought you'd suggested searching just here at diyaudio . .
Btw, I saw you have esl 63s ~ I have Apogee hybrid ribbons . .


To keep the rail voltages around 2*25, but bias the 60 to the level of the Aleph 2, what is the formula for amps bias and the traffo's VA?

Can anyone say if/ which component values in BrianGT's Aleph 30 would need to change?

Thanks
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Old 26th June 2008, 01:46 PM   #7
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Old 26th June 2008, 02:32 PM   #8
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Thanks ZM!

{The resistor that affects Ac current gain (R21 in the Aleph 2); on BrianGT's Aleph 30 BoM - doesn't appear to be flagged, I'll have to track it down . . }


In Aleph-Power.xls, puzzled that doubling the number of fets makes *no difference to power at any ohms
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Old 26th June 2008, 02:48 PM   #9
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Quote:
Originally posted by otto88
Thanks ZM!

{The resistor that affects Ac current gain (R21 in the Aleph 2); on BrianGT's Aleph 30 BoM - doesn't appear to be flagged, I'll have to track it down . . }

....
that's resistor in series with 220uF - connected from output rail to base of upper ZTX




Quote:
Originally posted by otto88
.........

In Aleph-Power.xls, puzzled that doubling the number of fets makes *no difference to power at any ohms
overall current and PSU voltage is what's count ;

number of outputs will have influence on damping factor , open loop gain and - naturally - on exact dissipation per device
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Old 27th June 2008, 01:14 AM   #10
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Thanks Zen Mod


the terms in Williams spreadsheet?
eg Transformer wattage - factor 2/ 3 /4

I *think the explanation of factor 2 is
"because the 50% current gain means that the current source delivers 50% of the peak current at idle"

If Ac current gain is 65%, what is the factor: 3 /4?
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