What do I need to modify to run Zenv4 off lesser voltage?

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Folks, because my DIYing runs pretty slowly (and I fried my original Zen revisited) I'm in a bit of a bind.

I have a lovely 500 watt C core tranny with twin 25vAC outputs, the rectifiers and a nice 30,000uF/3mH/30,000uF pi filter built plus some big *** heatsinks ready to go.

Problem is that Zen has come along way since the "revisited" and the Zv4 wants about 50 volts.

Is there any way to configure the cct so it runs off the same rails as the original? I've got alot of dollars tied up in this PSU and want to get this project finished and making sweet music (soon would be nice).

If I could just get the boards from Nelson, make a couple of component value changes and be done that'd be marvellous.

But is it possible?

All advice and help gratefully accepted

Umm, the plan was to use each output for a separate channel. 34 v for each side.

I'm just throwing away current capacity and channel separation if I use the rails in series.

Yes it'd work but is there a more elegant solution droppping the required voltage of the cct down a little?

Disabled Account
Joined 2002
I am fully with till.

If you however want ZV4, I would do as follows:

(a) Check if the unregulated voltage is around 34V per each channel.
(b) Change Z1-Z5 to get the total zener voltage of about 31V.
(c) You will see regulated voltage of about 27.
(d) Change R 13 with 2.7K.
(e) Adjust R4 to get 15V at the point between R5 and R14.

You will have ZV4 of a less output power.
What's the deal with inductance before the tranny? I want more volts from the PSU not less or else I want the cct to require less to run.

Unless, of course you're talking about using both sides in series again and not having channel separation in the psu. From preference I'd rather keep the 2 channel supply if possible.

Seems like the first post by jh6you gives me a method by which i can do this on the supplied cct boards.

Many thanks

till said:
2*25*1.4 makes about 70Volt. Why not use irfp140 or 240 instead of 044 and build a 70 Volts ZV4 .

Or just burn the Voltage you think is too much in the regulator Q5. Use a big heatsink for Q5 and vary the zehners for the desired voltage.

If i use 70Volt , i just change Q1, Q2 , Q5 to IRFP250 or IRFP150 is okey? no need to charge other ?

So you're broadly in agreement that the 5 step plan by jh6you to drop the supply to a regulated value of 27v is the best approach bearing in mind that it gives a drop in power?

I'm using horns with about 95dB/W so anything more than 10 watts ought to be fine.

Thanks for the input,
So are you saying that I ought to get rid of the zener stack totally and just use the 30,000uF, 3mH 30,000uF pi filter alone to give as much as I can to the output stage?

From memory the pi filter gave a pretty silent result.

My zen revisited sounded great for the first 60 seconds till the flames shot out of the mosfets :bigeyes:

Disabled Account
Joined 2002
Ref. to this (from the article on ZV4):

“Z1 through Z5 are 9.1 Volt Zener diodes which create a 45.5 Volt reference for the regulator Q5.You can adjust these to different voltages or bypass any of them if you find yourself using a different rail voltage. You can leave them out altogether, in which case the regulated supply will be about 4 volts less than the unregulated supply, but with the AC ripple removed. This works just fine in practice, and is usually referred to as a capacitance multiplier.”

I think Mr Nelson Pass always give us the best with his full effort. Meanwhile, he also leaves us a good possibility for the next best that are up to us, for instance as above.

If I modulate the rail voltage from 42 to 27, I could get about 20W (=30 x 27/42) of the output power. I believe this will work. The 27V could be accepted as the “every last voltage.”

Tho Mr Nelson Pass might make me of :Ouch: about 20 hours later from now…
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