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azira 9th January 2004 11:54 PM

+24V rail, Zen or DoZ or ???
I found a brand new complete PS for cheap so I decided buy it now project later. It's output is 24V, 10Amp unregulated. It only has a 4700uF cap in it for filtering so I think I will probably parallel it with at least that amount.
I want to turn it into a pretty simple amp project. At 2-channels with ~5amps/channel and 8-ohms, I could get up to just under 10-watts with a Class-A something or other per channel.
Simple like Zen, or DoZ... What would be good for this PS?

GRollins 10th January 2004 02:04 AM

The question becomes whether that 10A is available continuously. It'd be a shame to roast the power supply if it can't keep it up 24/7; a class A amp is a brutal load.
Zens take, what, 3A or so per channel? I don't remember offhand, and it's been quite some time since I looked at the DOZ schematic. At any rate, 6A (for two channels) would hopefully be doable for a 10A supply. If you feel that the 10A is a trustworthy rating, then you could boost the bias.
Yes, I'd consider increasing the capacitance on the power supply, but don't put on so much that the inrush pops something in the supply. You'll have to look over the supply and see how well it's built. With luck, it'll take a couple of Farads and laugh...


azira 10th January 2004 04:04 AM

It's heavy :)

It's an Acopian U24Y1000, it's listed at $135 on their website and I got it for $25. Pristine condition...

The website says at full load, the expected output voltage can be down by 10%. I think it'll handle the 6A, I don't think I'll bias it up any. I'd still have to adjust some of the Zen components to set the bias right.

GRollins 10th January 2004 02:13 PM

Sounds like a plan. Give it a shot. At worst, you can always reduce the bias if the supply looks as though it's collapsing.


EDIT: Might not hurt to do a Pi filter on the power supply, as in:
Power supply->cap->inductor->cap
The ripple in the specs looks a bit on the heavy side and that will help tame it.

Kashmire 11th January 2004 12:02 AM

Note that there is a thread specially discussing an amplifier design using low voltage power supplies. A +24 volt power supply would be perfect!

Nelson Pass 11th January 2004 06:25 PM

Arrrr, a small matter to build both power amps, simple they be
sez I, and report back to your mates.


azira 15th January 2004 11:32 PM

Ok. So I'll start with the Zen.

What kinds of considerations will I need to take into account for running a Zen at a lower rail?

I was thinking that I will need to adjust some parts to maintain the bias, but since I won't be able to output as much power, maybe I won't need to maintain the bias current.

There is a variable resistor to adjust the base voltage so I don't think I'll need to adjust that area too much.

Perhaps I just get the parts and ... build it ...

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