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[markorock37]

Building a solid state guitar amp, everything is ready to go except my rail power is too high. I'm running 52 volts and would like to get around 25-30 volts. I'm using a 36 volt power supply w center tap into a full wave rectifier and two 2200uf 50v caps. What's my best solution? Thanks

[Roly]

Please sketch, scan and post your current power supply arrangement.  I can think of at least a couple of quite different arrangements that would fit your description.

The most obvious first thought has to be buy/scrounge/swap a more suitable transformer.

[Enzo]

I think so too.   I have been cleaning out the shop, and scrapping some old dead stereo recievers and stuff.  I been saving their power transformers for just such projects.  A dead smallish stereo receiver ought to provide you a reasonable transformer.  For free.


One possibility.  Is your existing transformer by any chance a 120/240v primary one?  You could probably wire the primary up for 240v operation, but feed it the 120v from the wall, and that would drop your 52v to 26v.

[J M Fahey]

Agree that description is not clear.
Please draw your PS as-is including voltages, polarity and whether they are AC or DC.

[markorock37]

I did find another transformer with the right voltage I can use if neccessary. But 'Ill draw up the current configuration and try to get that up here this weekend.

[Roly]

There is a trick using SCR's that can be used to reduce the voltage of a transformer for a power supply (see attached).

The gate trigger voltage is obtained from a divider between the transformer peak voltage and the output voltage.  When the output voltage rises there is a point where the voltage on the gates doesn't rise high enough to trigger the SCR any more, thus limiting the output voltage.

It has a few "gotchas" however;

- at higher voltages the gates may need to be protected by diodes

- the output voltage is a function of the gate trigger voltage which is itself a function of the SCR temperature, so this simple circuit may show a high temperature sensitivity

- SCR's and audio generally don't make for good partners and there may be considerable, and objectionable, high frequency buzz in the output