NAD - '63 Fender Showman

[JSett]

Vibrolux Reverb would be optical trem like all blackfaces.

My 65 blackface VibroChamp is bias trem. I thought the early Blackface Princeton Reverbs were too.

*Edit: just checked my book for the AA1164 Princeton Reverb schematic... Bias wiggle trem.

[blacktiger]

Vibrolux Reverb would be optical trem like all blackfaces.

My 65 blackface VibroChamp is bias trem. I thought the early Blackface Princeton Reverbs were too.

You are probably right. I was thinking that the small BFs might be the exception.

[JSett]

I think I understand why they didn't use it for the larger ones, larger tubes probably don't like the bias being 'wiggled' in such a way. It's a much bigger voltage swing.

[Veitchy]

I think I understand why they didn't use it for the larger ones, larger tubes probably don't like the bias being 'wiggled' in such a way. It's a much bigger voltage swing.

That was my understanding, as well as it getting a bit noisy in the bigger amps.