Hello all,

My question is not directly 8051 related so I placed it on the chatboard.

For a guitarplayer I know I’m designing some small ‘gadgets’ like isolated buffers, switchable effectloops etc. These circuits process very low guitar signals (about 10mVac and higher).
The circuits are designed around OP247 opamps.
The usual supply for this kind of electronics is +9V which means I will have to use a virtual ground (input of the opamp on ½ VCC) and use input and output capacitors. This can influence the sound of the guitar. (not my opinion and certainly not my goal to discuss this…)

It so happened that I have a few NMA0515SC (http://www.cd4power.com/data/powe..._nmac.pdf) DC/DC converters. +5Vdc in, +/- 15Vdc out.
The switching frequency 110kHz. The +5V is available so no problem there.
The current needed will be around 15mA for both the +15Vdc and –15Vdc. Before I design the PCB there are a few things I’m worrying about.

I read in another thread (http://www.8052.com/forum/read.phtml?id=104410) on this forum that with good pi filters these converters can be used to power sensitive circuits like audio amplifiers / buffers. I have searched for example circuits of the converter / filter combination but I couldn’t find it.
I also thought about placing an 78L12 and 79L12 behind the DC/DC converter but I think that’s a little overdone.

Can anyone help me with an example of these filters and most of all : will these filters be sufficient enough to achieve a good working buffer?
I’m also a bit worried about the radiated emision (hope I’m using the correct term) of the DC/DC converter. Can this influence the signals?
The converter will sit aprox. 1.5 inch from the opamp.

Thanks in advance,

Peter