Tube amp top plate phenolic boards

[seti]

Has anyone here used phenolic boards as top plates instead of metal? I'm going to order a few samples but was hoping someone else has been there done that....?

 

[gadget73]

As the chassis to mount the sockets in? Radio makers did that in the 1920s sometime, but got away from it due to "hand effect". Basically they didn't shield the guts underneath so moving near the thing would affect it. Phenolic also tends to be kind of brittle, so if its not well supported you're liable to drive the sockets right through if not careful.

 

[BillWojo]

GPO-3 fiberglass sheet would be interesting, red in color, extremely strong and stiff and not to pricey for something a little exotic looking. I used 1/8" thick for the crossovers in my avatar.
Maybe an aluminum foil ground plain could be glued on the back side for shielding.

BillWojo

 

[seti]

Yes to mount sockets to instead of metal top plate like. You can get them pretty thick as well so not worried about brittle..

I will look up "hand effect".

Thanks for the info.

 

[gadget73]

If you foil back them it'll do fine. The lack of enclosure may not affect it, but it will probably be more prone to hum pickup. The hand effect thing is more picky with radio circuits just because they are very sensitive to extremely slight changes in operating parameters. The old tube tuners would usually drift as they heated up because the parts would change value ever so slightly. Later / better ones had auto frequency control to compensate but stuff from the 20s and 30s you just had to tweak from time to time.