Big bottle power amps

[Steve Conner]

But we're not here because it's easy, are we?

No, we're here because we have a screw loose! (You guys that is, I'm perfectly sane )

Yes, a bass amp with 813s and an 8x10 cab would be rather nice, unless you were the shmuck charged with carrying it around. I once saw a joke "Scale of fines for bass players" and one of them was "Bringing an amp bigger than one person can carry in one trip- $50"

And then if you dropped it and broke those directly heated filaments...

[clyde1]

I saw (and heard!) Gordie Johnson last night with his band "Big Sugar". Gibsons, many of them doublenecks, into a Garnet Herzog feeding an Ampeg SVT, thence 2 4x12 cabinets. Impressively loud, great tone. The bass player also used an SVT.

[R.G.]

And then if you dropped it and broke those directly heated filaments...

Yeah. There's that. 813's were available for under $1 at one point as they were produced in huge quantities for the military for WWII, as the finals for long range aircraft radios I believe. I suspect that's no longer true 50 years out.

I think what I would be incredibly tempted to do would be to find a dead SVT, take out the chassis and those pesky transformers, and put in a 1kW or more Class D amp. Then I'd put superbright LEDs inside several opened-up 813s where the glow could be seen easily. Shoot, I'd put in superbright RGB LEDs, and have the color modulate with power output, switching from orange to yellow to yellow-green to green to blue as power went up.

Then wait for someone to say "Dude, I can't imagine how much power that thing is! It was glowing green and blue on the loud notes!!"

[mooreamps]

"Bringing an amp bigger than one person can carry in one trip- $50"

Steve, you idiot...... That's what roadies are for..... :|

-g

[mooreamps]

Yeah. There's that. 813's were available for under $1 at one point as they were produced in huge quantities for the military for WWII, as the finals for long range aircraft radios I believe. I suspect that's no longer true 50 years out.

Is true.. They are no longer a buck a piece, but I can still source them.

I think what I would be incredibly tempted to do would be to find a dead SVT, take out the chassis and those pesky transformers, and put in a 1kW or more Class D amp. Then I'd put superbright LEDs inside several opened-up 813s where the glow could be seen easily. Shoot, I'd put in superbright RGB LEDs, and have the color modulate with power output, switching from orange to yellow to yellow-green to green to blue as power went up.

Ya well, I don't think so. You have no idea just how much light these things put out when you energize the filaments...or what part of its a 50 watt filament power supply were you missing ??

[R.G.]

Ya well, I don't think so. You have no idea just how much light these things put out when you energize the filaments...or what part of its a 50 watt filament power supply were you missing ??

You want to get into this, Gary?

[mooreamps]

You want to get into this, Gary?

no, no, no........ i wasn't trying to start something.... the tubes glow so brightly, you just won't see any leds if you put them in there...
If you did want to put them on there, best to put them on the front panel if you wanted the extra effect....

-g

[Steve Conner]

Steve, you idiot...... That's what roadies are for....

I've never been in a band big enough to employ roadies! Let alone need a 1000 watt bass rig with 813s.

[mooreamps]

I've never been in a band big enough to employ roadies! Let alone need a 1000 watt bass rig with 813s.

then perhaps your talents are under-employed....:}

-g

[Tubebass]

I saw (and heard!) Gordie Johnson last night with his band "Big Sugar". Gibsons, many of them doublenecks, into a Garnet Herzog feeding an Ampeg SVT, thence 2 4x12 cabinets. Impressively loud, great tone. The bass player also used an SVT.

Thanks for the heads-up! I'll be seeing them later this month!

[Wilder Amplification]

I have a design for a 100 watt 2xKT88 and custom iron wound for it. Haven't built it yet...if I can ever get a chassis for it I've got enough parts to get the power side of it going. Planning to run 600V B+ loaded w/300V screen supply. OT is a 5K plate-plate.

[Zozobra]

After much faffing with Antek regarding the PT I ordered for my prototyping rig I should now have something in the mail. This PT looks good for 6550/KT88s with a 4K primary so I'm going to jump in with that rather than use 6L6s which was the original intent. I'll draw something up when I have all the pieces.

[Zozobra]

Power transformer has finally arrived. Started work on the power amp and power supply. I still need to cobble a bias supply and heater elevation circuits which I'll do tomorrow once I've read up on them a little more. What I have so far is something looking a lot like the D60 power amp. I'm after a pretty clean power amp so it looked like a good place to start. I need to have a little think about the NFB controls as I'm not used to looking at cathodynes.

[markr14850]

You might want to add a pair of 220k resistor as balancers across the stacked 220uf power supply caps.

[Zozobra]

I knew I forgot something. I may also add a switchable valve rectifier emulator resistor too.