SDS-PAGE wrote:Eric, I tried pluggin in 12AX7 in liew of 12AU7 and there is a marginal increase in volume. I guess 100x amp factor of 12AX7 is needed in my case.
So what happened to the EF86? That ought to have plenty of gain unless it's inside a feedback loop (which, BTW, you could disconnect, or try fiddling with the feedback resistor... note that'll affect the bass damping ie tone as well).
Some bass amps have input resistors as high as 5 megs.
You do need a relatively high efficiency speaker to get decent output with only 10 watts for bass, and (a) many home speakers aren't very efficient (look for 95 dB/W/M and up efficiency), and
crossovers tend to be power soaks (thus the
piezo tweets seen on some bass cabs, they don't need crossovers).
The guitar pickups I've measured generally put out in the 100 mv range, about 1/10th typical input sensitivity for a tube
power amp, with a 12AX7 preamp tube you should have plenty of gain unless you've got a
really lossy tone control.
Last week I saw an itinerant (if you're British, read:
buskers ) 3 piece Mexican
ranchero band where the bass player (solid-body) was playing through a battery powered Peavey that couldn't have had more than an 8 inch speaker in it, and he was keeping up with the lead (and loud enough for a couple dozen patrons) , but the lead was playing an acoustic. So, yes, even a small bass amp can be useful. BTW, they collected about $100 (at $10 per song) in less than an hour, then moved onto another bar. Probably pays better than the average rock gig, I'd guess...