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Old 12th May 2003, 04:57 PM   #1
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Default voltage doubler for small Aleph?

Would it be alright to use a voltage doubler for a small Aleph amp?
I was thinking of using 2 12.5V transformers with a doubler and a pi filter to obtain 23V rails. DuncanAmps PSU designer says that I will get 23V with 1mV ripple, which is about what I want. I know that doubler circuits aren't thought very highly of, but why not use one?
Steve
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Old 12th May 2003, 05:48 PM   #2
joensd is offline joensd  Germany
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I think your transformer (2*12,5VAC!?) are good for a small aleph already.
Have a look here :
The Mini-A
Mini-A PCB's
The Mini-A lives!
Small Aleph?

Regards
Jens
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Old 12th May 2003, 06:17 PM   #3
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Default Re: voltage doubler for small Aleph?

Quote:
Originally posted by nobody special
I know that doubler circuits aren't thought very highly of, but why not use one?
Steve
No reason that a "doubler" or any other voltage multiplier should be thought <b> ill-of</b> -- as long as you realize that there is a trade-off between the multiplying and the number of joules you are periodically storing. In plain english, if the capacitors aren't big enough the output droops badly with increased current demand.
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Old 12th May 2003, 07:07 PM   #4
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Quote:
Originally posted by joensd
I think your transformer (2*12,5VAC!?) are good for a small aleph already.
Have a look here :
The Mini-A
Mini-A PCB's
The Mini-A lives!
Small Aleph?

Regards
Jens
Jens,
I was thinking of building some of those, but I really would like a little more power. Thanks for the suggestion.
Steve
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Old 12th May 2003, 07:11 PM   #5
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Quote:
No reason that a "doubler" or any other voltage multiplier should be thought ill-of -- as long as you realize that there is a trade-off between the multiplying and the number of joules you are periodically storing. In plain english, if the capacitors aren't big enough the output droops badly with increased current demand.
Do you have any guidelines for how to deteremine the capacitor ratings, etc?
I was using Duncanamps simulator, and used 6800F caps for the double caps, and a bank of 68000F for the first filter bank, a 2.5mH inductor, and then another 68000F for the second bank. The ripple was very low. The only thing that worries me is the doubler caps... I don't know what values are appropriate, and what kind of caps to use. The caps in the doubler seem like they have a lot of power continuously going through them. What does this do to their life?
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Old 12th May 2003, 10:13 PM   #6
moamps is offline moamps  Croatia
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Quote:
Originally posted by nobody special

but I really would like a little more power

Hi,

You have 4 transformer 12V/20A, 80 pcs 6800/25V caps, and you want to build some Aleph and get about 30W in class A. The best way to do this is building Aleph X; using 2 transformer for one monoblock, full bridge rectifier to get rails about +-16V and 20 caps 6800uF per rail (some inductor between maybe) and schematic with 8 output FET-s per channel. You will be maybe happy than with about 40 W pure class A.

Forget idea with voltage doublers, this principle can't work here OK (to much current). IMHO.

Regards
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Old 13th May 2003, 02:27 AM   #7
moe29 is offline moe29  United States
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I'd love to build an Aleph X, but i haven't been able to find
circuit art for a 1 sided PCB. (is it possible to do a 1 sided?)

Not all of us were here early enough to get it on the group PCB buy
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Old 13th May 2003, 12:26 PM   #8
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Quote:
Originally posted by moamps



Hi,

You have 4 transformer 12V/20A, 80 pcs 6800/25V caps, and you want to build some Aleph and get about 30W in class A. The best way to do this is building Aleph X; using 2 transformer for one monoblock, full bridge rectifier to get rails about +-16V and 20 caps 6800uF per rail (some inductor between maybe) and schematic with 8 output FET-s per channel. You will be maybe happy than with about 40 W pure class A.

Forget idea with voltage doublers, this principle can't work here OK (to much current). IMHO.

Regards

That's pretty much what I decided to do. Actually, that is why I bought these parts in the first place. I really don't like the idea of making an AlephX with just 12 volt rails, which is what they are going to load down to with the 7 amps of bias I will be running. I was thinking about making a stereo X and using 2 trannies per rail to get about 25 volts, but my heatsinking is not up to the task.
Thanks for the replies!
Steve
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