So, I just wanted to give everyone an update. I did some simulating and in my attempt to get a bit more gain from the PI to overcome the additional load of the master volume, what I didn't factor was the PI's reduced output swing with that circuit. It looked like it would be enough still to overdrive the output tubes, but the traditional circuit still gave like 10V more. So I reverted to standard Ra=82.5k/100k with a 470 Rb, and ran my tests again...45W clean with 6L6s!
So ya, the PI just couldn't hang, but I'm happy with that number!
I didn't, but I was going to do this if tweaking didn't work. And you're right, it's Fender derived. That's why I was being stubborn about the output power, the Bassman is supposed to put out 45W clean with 5881s...and I used a solid state rectifier (i.e., should be less sag than a GZ34 supply = more power).
I'll have to get my sea legs before I try AB2, but I've definitely thought about using drivers to see what that and class B is like tonally. The idea of using a transformer to drive the output tubes also seems fun!
So ya, the PI just couldn't hang, but I'm happy with that number!
I didn't, but I was going to do this if tweaking didn't work. And you're right, it's Fender derived. That's why I was being stubborn about the output power, the Bassman is supposed to put out 45W clean with 5881s...and I used a solid state rectifier (i.e., should be less sag than a GZ34 supply = more power).
This set me straight. I went and checked the 400Vgs curves and ya, you can't even get 340mA unless your load line goes way above the knee (Vg1=0V)!
That's insane (in a good way)! I've been wanting to build a bench supply, but the sheer power is a bit unnerving...You aren't careful and with 1100W (!!!) there's going to be trouble, lol.
No, I don't have any 6550's or KT88's. But I did plan to try them at some point, so I made sure I had enough current for them!
I'll have to get my sea legs before I try AB2, but I've definitely thought about using drivers to see what that and class B is like tonally. The idea of using a transformer to drive the output tubes also seems fun!
My 6P45S PPP triode amp makes 112W RMS sine with a B+ of 300V-320V into 1k3
Peak current ratings tell me that I can do this with one pair if I can deal with increased THD.After finding sweep tubes, I'll never design around audio power tubes again
> get my sea legs before I try AB2
A handful of *guitar amps* have worked in this direction.
Before 1940, driver transformers were common, but the driver typically did not have the grunt to get far into grid current. This also covers the Fender Silverface Musicmaster Bass Amp with a puny 12AX7 driver.
Older Ampeg SVT and Fender 300 pushed real grid current. SVT had cathode followers. 300 had a 6V6 pushing a heavy transformer.
99+% of *guitar* amps use cap-coupling and can't sustain grid current even a few cycles. The cap(s) charges-down and throws the power tube toward cut-off. To a point, this may be The Sound Of Rock And Roll-- slamming the caps against the grids. Neil Young takes it to an extreme. Some designs (especially EL84) are too-prone to grid-fart/block and need the driver "lamed" so they don't block-up totally too easy.
Anyway, if you have a Bassman making 45 solid Watts, what more could you possibly want? The SVT/300 "work" because when pushed they are really Too Loud to stay on the same stage, and gross overdrive is self-punishing. The puny amps are both puny and not the overdrive flavor we love. The cap-coupled DeLuxe and Bassman inspired 80% of all the amps people actually play.
A handful of *guitar amps* have worked in this direction.
Before 1940, driver transformers were common, but the driver typically did not have the grunt to get far into grid current. This also covers the Fender Silverface Musicmaster Bass Amp with a puny 12AX7 driver.
Older Ampeg SVT and Fender 300 pushed real grid current. SVT had cathode followers. 300 had a 6V6 pushing a heavy transformer.
99+% of *guitar* amps use cap-coupling and can't sustain grid current even a few cycles. The cap(s) charges-down and throws the power tube toward cut-off. To a point, this may be The Sound Of Rock And Roll-- slamming the caps against the grids. Neil Young takes it to an extreme. Some designs (especially EL84) are too-prone to grid-fart/block and need the driver "lamed" so they don't block-up totally too easy.
Anyway, if you have a Bassman making 45 solid Watts, what more could you possibly want? The SVT/300 "work" because when pushed they are really Too Loud to stay on the same stage, and gross overdrive is self-punishing. The puny amps are both puny and not the overdrive flavor we love. The cap-coupled DeLuxe and Bassman inspired 80% of all the amps people actually play.
I recall playing a bassman head and 4x12(?) Cab set up in school. It was ancient, but what year I couldn't be sure.
The thing was the sweetest sounding amp, despite back then, me and my band mates were into a lot of metal.
When the head went away for repair (not my fault I promise) the cab was left.
Even that alone, blew a modern Marshall cab away, driven by a keyboard combo and (often) a Boss OD1
The thing was the sweetest sounding amp, despite back then, me and my band mates were into a lot of metal.
When the head went away for repair (not my fault I promise) the cab was left.
Even that alone, blew a modern Marshall cab away, driven by a keyboard combo and (often) a Boss OD1
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