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SideA 3rd April 2003 08:44 PM

Having trouble building a power supply for a phono preamp
Hello everyone!

I am building a phono preamp which requires a +/-15V power supply. I found a schematic for a +/-35V power supply and was told by a friend that the transformer can be replaced with another one and produce a voltage of +/-15V. Is this true? If so, what would be a suitable transformer to use, or else would I need to look for another schematic?

Another question I have is in respect to the fact that the power supply is dual channel. If I am building a Minimized GainKlone, would there be a way to power both the preamp as well as the GainKlone with the schematic I have listed above?

Thanks for your time,

vbd 4th April 2003 07:34 AM

Hi, SideA
Yes, you can change the transformer secondary voltage to get 15V, around 11VAC, but then you have only unregulated voltage... Have a look at:
This site is really a compilation of EVERY basic thing you need to know ! :)
You could power the regulators from the power amp supply BUT take care of their max voltage input of 35V, it is probably wiser to add a "preregulator" with a zener diode, a resistor and a transistor (a simple series resistor could do the job )...
You may power both preamp channels with only one +/- 15V regulator, as the currents should be low.
You also may use better regulators such as LM317/337 with a few extra resistors...
Hope this helps

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