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Help...+- 70volt to +- 15volt needed

Started by Tassieviking, April 21, 2023, 12:32:42 PM

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G'day all.
I am thinking of trying out  some of the high power "D" amp modules that are everywhere.
Silicon Chip magazine had a story on some modules they tried out, a 1000 watt amp and 1000 watt power supply that they called a 500 watt amp put together.
I might try this out with a Bass preamp I am making.

The problem is that the power supply has only got +- 70v rails, and a single +15v output also.
I guess the easy option would be to convert the +15v to -15v with a LT1054 or similar but it would be a bit less then -15v at the output.

Since I would be dropping from 70 volts to 15 volts at an unknown current I don't really want to use a dropping resistor, not even going into a 7815 regulator.

The 7815 and 7915 can go up to 35 volts max so they are out.

This would be a common problem with any design requiring more then +-35 volts going to the power amplifier PCB, most pre-amps will want a nice +-15 volt supply.

Does anyone have a good solution ?
Maybe a Zener diode with a low loss mosfet or transistor to do the dropping ?
I would love to hear what methods others have used in the past.

There are no stupid questions.
There are only stupid mistakes.


Might be a bit of an uncommon amp module?
Most of the guitar amp manufacturers using those kind of modules have a split +/- aux. supply to run the preamps.
For example, the ICE power modules often have +/-25V aux output.


Silicon Chip magazine tested several cheap modules and felt that the two they picked would actually pass Australian safety standards, and the components ratings were up for the job.
They did recommend that the speakers should be 4ohm or above which de-rates the setup to approximately 500 watts @ 4ohms and not the advertised 1000 watts @ 2 ohms.

Here are the links to the amp and power supply provided by the magazine:


They stuck them in a metal case 304mm wide (12") x 279mm deep (11") and 88mm high (3.5") along with an 80mm quiet fan.

I thought it would make for a nice Bass amp for home, I would just make a pre-amp PCB that sits against the front panel, pots mounted on the PCB.

Maybe a Lab Series L4 or a Sunn Beta Bass, there are lots of bass amps that are solid state.

I think it would fit nicely in a Hammond 1444-12103 aluminium case (12x10x3)
or a Hammond 1444-12123 case (12x12x3)

I don't need it but it would be fun making it anyway, my daughter could use a louder Bass amp for home.

There are no stupid questions.
There are only stupid mistakes.


Honestly I would just build up a cheap PSU for the 15v rails.
Life is what you make it.
Still rockin' the Dean Markley K-20X