DIY passive preamplifier questions

[winters860]

Sorry if this has been covered, but I was wondering if somebody could answer a couple of questions for me or point me toward information that could let me figure it out myself.

Suddenly, I've got my power amp back from my tech, but lack an appropriate preamp. It's a solid state Marantz 510M with an input impedance of 30K ohms.

I've got a lot of the parts on hand (sans resistors and hookup wire) to go ahead and build a passive preamp like Redboy's recent one, but with the addition of an input selector. First off, might one work well in this application? Second, would the Alps 100K potentiometer I already have on hand be okay? Third, what value of resistors should I use?

Thanks for any and all help.

 

[bricktop]

you might be able to get away with a 100K LINEAR potentiometer (which the alps is not). See http://sound.westhost.com/pots.htm for explanation of how to change the law of a potentiometer. I suggest this because that shunt resistance of 30K will alter the the response of the 100k log (audio) pot to something i'm not quite sure of..probably an awkward attenuation vs rotation curve... Rod suggests a 22K across the wiper of a 100K linear ..which is close enough to your 30K across a 100K linear that would give log response. So you might have to get a different potentiometer, but the linear ones ares on the cheap, which is good. You can save that alps for something else. good luck