Pre-amp for K4004B

The output of my K4004B is low when the signal input is low, like from an iPod. It does not drive my speakers at a high level. To increase the signal input strength, I tried two different small stereo amplifier kits to boost the input signal and act like a pre-amp (a 1W that uses the KA2209 IC and a 1 W that uses two LM386 ICs ).

The output signal from the K4004B was greatly boosted and drove my speakers quite adequately. However, unacceptable (and odd noise) was introduced. These pre-amps introduced “mains hum” on my speakers (unless run from a battery); and, most annoyingly, they even picked up RFI: if one adjusts the rheostat of the small pre-amp, you can actually tune to some FM stations and hear them through the output of the K4004B!

My question: is there a pre-amp that works with the K4004B that doesn’t introduce interference/noise?

Setting input sensitivity to 330 mV could be enough to drive power amplifier from such source. I tried driving an amp from a portable CD player, which even had no line output, so I had to use headphones output. With volume pot turned to max the output level was more than sufficient.
If you are not of a tighter budget, try K8021 preamp. With added functionality of switching inputs and changing gain it’s unbeatable for that price, and with a few gentle (not neccessary) modifications real giant-killer :slight_smile: