voltage doubler for small Aleph?

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nobody special

nobody special

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Joined 2002
#1
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
 
#2
#3
nobody special said:
I know that doubler circuits aren't thought very highly of, but why not use one?
Steve
Click to expand...

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.
 
#4
joensd said:
I think your transformer (2*12,5VAC!?) are good for a small aleph already.
Have a look here :
http://www.diyaudio.com/forums/showthread.php?threadid=2001&highlight=minia
http://www.diyaudio.com/forums/showthread.php?threadid=6970&highlight=mini+aleph
http://www.diyaudio.com/forums/showthread.php?threadid=7287&highlight=mini+aleph
http://www.diyaudio.com/forums/showthread.php?threadid=1224&highlight=mini+aleph

Regards
Jens
Click to expand...

Jens,
I was thinking of building some of those, but I really would like a little more power. Thanks for the suggestion.
Steve
 
#5
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.
Click to expand...

Do you have any guidelines for how to deteremine the capacitor ratings, etc?
I was using Duncanamps simulator, and used 6800µF caps for the double caps, and a bank of 68000µF for the first filter bank, a 2.5mH inductor, and then another 68000µF 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?
 
#6
nobody special said:

but I really would like a little more power
Click to expand...


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.:nod:

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

Regards
 
#8
moamps said:



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.:nod:

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

Regards
Click to expand...


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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