6SQ7 vs. 6SF5

[Rhodesplyr]

I've seen two Valco guitar amps recently (one of which is on my bench at the moment) that have 6SQ7s as the first gain stage.

I'm curious as to why an amp builder would use the triode + dual diode 6SQ7 rather than the simple single triode 6SF5. In both cases, the diodes were simply tied to ground.

The 6SQ7 has ~25k higher plate resistance, but that's about the only difference in specs.

David

[Rhodesplyr]

To answer my own question, I'm told that because the 6SQ7 was frequently used as a radio detector tube, they were produced in much greater quantities than the 6SF5 triode; thus, there was a more readily available supply of 6SQ7s.