[ionburn]

I remember I did use an old valve radio back in schooldays. I don't remember any issues but I would now worry a bit about safety. The guitar I used then had low output pickups so it was quiet, if I remember rightly.

Guitar pickups ar a bit variable as (although probably more a relative thing) some are designed for lower impedance hence less prone to hum. Some are much higher output too. In general terms they are low impedance as compared to valve inputs.

I have a Vox practice amp which I have had for some years. It's circuitry is IC based (TBA810S according to the diagram I have) with input transistor. Extremely simple, but I think it's good sound is due to the well constructed cabinet and perhaps the speaker used (it looks a bit like a miniature AC30 - traditional Vox).

My point here is that a radio can be used but for more serious use in the longer term a well designed unit for the job is better. I do wonder how well a valve radio (specifically speaker) would cope with a heavily overdriven input via various pedals?