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 reins 18th February 2012 02:33 PM

reducing voltage

Hi,

I would like to reuse a broken amp as 1 Channel as E-Bass amp. I plan to built the pre-amp also in the housing. Now my question:
I have a regulated voltage of +-21V. Op-amps work only with max. 18V. Is there an easy way to reduce the voltage by 3V? Would a Zener work?

Thanx
Stephan

 pdul 18th February 2012 02:54 PM

LM317 Current Calculator - Electric Circuit

Try to look at this link.:)

 rcbuck 18th February 2012 03:10 PM

I would use a 78L15 and a 79L15. That should be sufficient to run the op-amps. If you need +/- 18V you will have to use the LM317 series as already suggested.

 RJM1 18th February 2012 03:19 PM

There are a lot or op amps that work up to +-22V.
LME49860, MC34072, LT1078MH, MC33171DG
For example.

 reins 18th February 2012 03:20 PM

I hoped fpr a somehow simpler solution ;-)

But it's ok then.

Stephan

 boyofwax 18th February 2012 03:46 PM

The easiest way is to put 5 diodes is series with the supply. If you have a symetrical ps you put 5 on the + and 5 on the -. Pls observe polarity.

Use silicium diodes only as they have a drop of 0.6V each (0.6V x 5 = 3V). 1N4xxx series will do and are common.

This is the most simple, though I'd prefer the 78xx and 79xx series. They are also available in 18V version.

 FRANK BRAUN 28th February 2012 02:56 AM

try using LM 7818 from NS (max. out current == 1 amp.) if you used LM 317, 1.5 amp max.

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