Old Rickenbacker steel guitar amps?

[Steve A.]

There are a few on the Rickenbacker site of the M and B series from the 50's and 60's but I was wondering about the older ones.

I was just looking at the M8 and M8E schematics and either one of them should work great in a Valve Junior chassis. (The M8 uses a 6AV6 preamp tube, the M8E uses a 12AX7.)

BTW the 6AV6 has a single stage while the 12AX7 of course has two. So how does the gain of the 6AV6 compare to one stage of the 12AX7? I can look up the parameters but I am looking for a more subjective comparison of the two. (The circuits- attached below in PDF format- are quite different.)

Thanks!

Steve Ahola

[Enzo]

Look up 12AX7 in the RCA manual, it says right there, for characteristics and curves, use 6AV6. The 6AV6 should work exactly as half a 12AX7. The small differences in electrode capacitance - like less than a pf - would have very little effect. The 12AX7 has larger plate dissipation, but that is rarely an issue.