Yet Another Color Preamp
This is a great circuit! I played around with the power supply and designed a PCB, mostly as an experiment. Did a quick plate build. Call it a proof of concept as I want to tweak case work and plate. Maybe even add remote with an R2R arduino volume control. Possibly try a tube rectified/regulated (glow tube) supply.
Anyways the color pre sounds amazing. It takes a slight edge off my KT88 push pull monoblocks. I run an EAR 834 clone through the color preamp as well. Maybe redundant in some sense, but it doesnt hurt. The meters actually helped with cartridge alignment and 1 khz test record. Tons of gain....
The pots on input are a good idea, especially with the inherent drive of the 834 clone. The real win with the preamp is streaming.
Happy to share the PCB files. The layout isnt perfect, but the results work well for me. YMMV as to my ideas on power supply. That said, I built a board out for the basement, no choke and 12V 4A laptop power supply feeding boost converter for HV.
The preamp can take any line level. Too much signal, believe it will clip (check video).
Another idea might be to try zkit4 schematic from decware. Single tube color gain stage. I use this sometimes… one tube.
The pcb I made is roughly 4x7 inches.
I understand the concern regarding frequency response, impedances and so on. So long as the output stage of the phono “sees” correct resistance, it’s just a voltage divider imo.
Have fun!