Suggest a bass amp circuit for this power xfmr - please

[mlp-mx6]

475V bridge rectified, 550ma.

2 6.3V taps, 1.5A and 12A (!) (these actually measure now at 6.8V each)

The tranny is a Stancor 9002.

I think I'd like to build a bass amp with this HEAVY thing. Can I get good tone out of 6550's or KT88s at 475V?

[CaseyJones]

Whoa! You could build an arc welder with that thing...

6x 6550 will draw 9 amps on the filament, so far, so good. Your filament will likely drop down to 6.3v under load.

I'd like to see just a little more from the high voltage for 6x believe it or not.

Four 6550s are more than enough to piss the neighbors off. The cool thing about four is that you have more OT choices available. Go 6x and you'll pretty much have to buy an SVT clone OT. Just about any "100 watt" Marshall clone OT will work with four tubes.

Ampeg preamp, Marshall power amp. Why not?

[mlp-mx6]

The HT secondary is about 335V. Another power supply option would be to do a voltage doubler (like a Music Man). Would that make it a better fit for 6550/KT88?

[dano-rator]

Doesn't doubling the voltage halve the current?
I don't think 275ma is gonna work for 4 tube output.

I've no experience w/ 6550/kt88 at 475v, weather they'd stay clean and hit hard I'm not sure???

Dan

[CaseyJones]

The HT secondary is about 335V. Another power supply option would be to do a voltage doubler (like a Music Man). Would that make it a better fit for 6550/KT88?

OH. I thought you have 475v B+ after the rectifier.

[mlp-mx6]

OH. I thought you have 475v B+ after the rectifier.

That is correct - rectifying with a bridge gives me 475V rectified DC. I'm wondering if that is a high enough plate voltage for 6550s/KT88s. Perhaps 6 6L6s would be a better match?

Sorry if I was confusing.

[KT66]

Hey mlp, I think using a voltage doubler would result in 2.7 X 335 = about 900 volts, which seems kind of high for most of the normal tubes used in guitar amps. The data sheets say that 2 X 6550 @ 450V on the plates puts out 70W, that seems like plenty to me. If it were me I would make a B-15 clone W 2 X 6550, SS recto & beefed up filtering. I think I read somewhere that Ken Fischer's personal B-15 was that way. I have been wanting to make an amp like that for myself and I came across this website : http://www.billfitzmaurice.com/ and thought that building a tuned bass cab for it would be a good idea.

Bob-I posted an interesting thread about a bass amp he made recently that makes me want to put a piezo pickup in my P-Bass : http://ampgarage.com/forum/viewtopic.php?t=9644.

[Bob-I]

Hey mlp, I think using a voltage doubler would result in 2.7 X 335 = about 900 volts, which seems kind of high for most of the normal tubes used in guitar amps. The data sheets say that 2 X 6550 @ 450V on the plates puts out 70W, that seems like plenty to me. If it were me I would make a B-15 clone W 2 X 6550, SS recto & beefed up filtering. I think I read somewhere that Ken Fischer's personal B-15 was that way. I have been wanting to make an amp like that for myself and I came across this website : http://www.billfitzmaurice.com/ and thought that building a tuned bass cab for it would be a good idea.

Bob-I posted an interesting thread about a bass amp he made recently that makes me want to put a piezo pickup in my P-Bass : http://ampgarage.com/forum/viewtopic.php?t=9644.

Yes, that amp has about 480 on the plates of 2x6550. It measured out at about 80 watts when the output is just showing some distortion with a sine wave at 500 Hz. Pretty simple design as well, just 2 dual triodes, one for preamp and one for PI and a bax tone stack.

Yes, and that piezo PU sounds great. There's actually 2 piezo elements in there and the 3rd knob is a blend between the piezo and the mag PU. My friend Dave Wendler installed it based on the MagPi system he designed. Check it out, http://www.electrocoustic.com/magpi.html His basses are amazing, as are the guitars but they're more geared to bluegrass players.

[mlp-mx6]

At this point I'm leaning towards an Ampeg (Baxandall) preamp driving 4 6550s - it seems I'll have enough current to supply 4 6550s with that transformer. Will 2 preamp tubes get it done? I know I only need 1 for the preamp - will 1 12A_7 get it done for the PI/driver?