Before anything else, have you given it a good clean/dose of Deoxit?
Is it a P22? If so, and you like the sound, why not keep an eye out for a good P22/30/50/80 or any other from the Aiwa mini compo series?
They pop up from time to time on
eBay, often as a pair with the power amp and sometimes with the tuner and/or the tape deck. There’s an SA-C80 preamp on
eBay at the moment for a starting price of £100 that would match. I’d be inclined to make a cheeky offer In your shoes, OP.
I have the 30 series pair and they are respectable enough for desk/kitchen background duties.
Out of idle curiosity and because it was the only amplification easily to hand , I’ve test run a Lumin, a Matrix X Sabre, a Krell AV processor, a seventies SS Japanese kit preamp, a Quad 44 and a Lexicon Dolby processor into the Aiwa power amp with Tannoy 15” MGs at the other end.
Although they all clear up the sound, it is the power amp that is the binding factor in the combo IMO and it does not, at least to my ears, benefit enough from a better or more costly preamp to justify spending too much on pairing with it.
The other option might be to find an ifi, Beresford or SMSL preamp/DAC to sit on top of it?