A curious question, but I have a few spare EF732, miniature pentode valves as used in the Telefunken AK47 microphone. I'd like to use them on a preamp and run it with a 'warmer' sound, - so some controllable harmonic generation. Can anybody advise on the best way to do this. I'l be running at 24V rail. I thought of straddling the supply with a divider chain having a pot in the middle to bias the grid. Would this work? Is there a better way? Thanks for help in advance.