Solid State Guitar Amp Forum | DIY Guitar Amplifiers

So I have an old Kenwood KA-3500 stereo amp that I'm thinking of converting for guitar use. I'll be modifying a lot of stuff in it to simplify operation. I've done this before on other amps that were less featured then this one.

I plan to use the stereo output to drive two seperate 12" speakers (it puts out about 40 watts rms per channel), but the input will be mono to both channels. I'm sure that folks here understand that.

My question here is: This amp has multiple different imputs including two tape inputs, phono, tuner, and Aux. I am assuming that the tape, tuner, and aux imputs are all designed to accept a 1 volt peak-to-peak signal, while the phono takes a low strength signal (like a mic or pickup). I'm trying to figure out which input to tap for the guitar (direct pickup input).

I'm guessing that the phono input would be best, but any other ideas?

None of them will work well, I'm afraid.

Phono input indeed has lower sensitivity but it also features a so-called "RIAA compensation" filter (Google it), with akward response of 20 dB bass boost and rolled down high frequencies.

More than that, all those inputs are definitely too low in impedance.

Your best chance is a DI box that can output line level signal or an entire preamp / multieffect capable of doing that. Otherwise you most likely have to build something similar on board.

Agree with Teemu's thoughts :-[

Though you can use the Aux inputs if you use a preamp first.

If you just want a clean guitar interface then my PhAbbTone would make an ideal starter project.
http://www.ssguitar.com/index.php?topic=2013.0
The output of that will interface with no worries and you may even be able to tap the DC supply from the Kenwood if batteries are a problem but the unit will last a very long time on a single battery.
Phil.