EL844 Amp Based on 5f6a?

[The New Steve H]

Well, I'm stupid.

Isn't it possible to drop the voltage with big resistors, or should I be looking for an OT that already likes EL84s? They have one for the Vox AC15, but it has no 5V taps. They also sell one for the Vox AC30. It has 5V, but it's pretty expensive.

http://www.classictone.net/40-18050.pdf

I guess I could use the AC15 job and find an additional transformer for the rectifier heater.

[The New Steve H]

Dude on another forum says you can lower plate voltage with Zener diodes in series. Would that work? I would probably use an aluminum chassis, so I think it would sink heat okay.

[The New Steve H]

Now I'm reading that Fender uses EL84s at high plate voltages, and that you just have to keep the screen voltage low.

[sliberty]

Now I'm reading that Fender uses EL84s at high plate voltages, and that you just have to keep the screen voltage low.

That is often the case. Fender ran 6V6's at well over the published specs too. Keeping the screens low seems to help lengthen tube life under such circumstances.

[10thTx]

Fender and Carvin run EL84's over specs with low screen voltages.

How do those amps sound to you?

Do you like the Blues Jr or Carvin Nomad tone?

You can install a VVR and make sure the voltages never exceeds 330v or something like that. Or you can try the zener method.

Or ........ you could look at a PT that is better suited for those tubes.

It's your amp and your call. I personally would prefer the correct PT.

With respect, 10thtx

[The New Steve H]

The big Vox-style PT will work perfectly with no aggravation, but it's danged expensive. I wonder if I could set this thing up so it could run two or four EL84s, with a switch. That would make the bigger PT worth the money.

As for whether I like the sound of Fender and Carvin amps, I don't know what a Carvin sounds like. I obviously like Fender, since I'm trying to make a tiny Bassman!

[ToneMerc]

Well, I'm stupid.

Isn't it possible to drop the voltage with big resistors, or should I be looking for an OT that already likes EL84s? They have one for the Vox AC15, but it has no 5V taps. They also sell one for the Vox AC30. It has 5V, but it's pretty expensive.

http://www.classictone.net/40-18050.pdf

I guess I could use the AC15 job and find an additional transformer for the rectifier heater.

Why not just use the 18W PT?

http://www.classictone.net/40-18035.pdf

[The New Steve H]

I hate to have to say I'm stupid twice in the same thread, but I guess it's time. That PT is perfect, and I should have kept looking until I found it. Thanks.

The 4-tube idea is kind of interesting, though.

[Zippy]

There are several versions of the half power switching for cathode-biased EL84s. Just look 'round the Rocket/Liverpool pages.

Just lift the cathode resistor for one pair and ensure to correctly bias the remaining pair.

[The New Steve H]

I keep turning this idea over in my head.

The idea was to create something which is essentially a 5F6A Bassman, except that it would have EL84 or EL844 tubes and lower output. I can do that with the 18W PT that was suggested.

Now, of course, I am having new ideas. The Bassman I already built has 6L6 tubes, and it sounds wonderful at low volume. Maybe I should just build a 5F6A with a 4-tube EL84 output section. I don't know enough about tubes, though. Does the Bassman sound good at low volume because of the preamp, or does it depend on the 6L6s, too? What if I build this thing, and it sounds like crap at low volume?

Classictone makes a nutty PT that will do just about anything, so I could give this amp a try, and if it turned out to be stupid, I could recycle it:

http://site.triodestore.com/Convertible ... CSHEET.pdf

That PT would let me do just about anything with the B+, it will run two tubes or four, and it has heater current out the rear end.

Then the following thought ruins the whole thing: why not build a Fendery JTM50 instead of driving myself nuts with four tubes? I guess I need to find out what EL34s sound like. I know I like EL84s, but the only EL34s I've heard were in my church's AC30s, which I hate.

[Zippy]

How 'bout a 5F6A with 6V6s and 2-10"s?

FWIW, I have a Mission Amps tweed Super that I built with a hi/lo power transformer that lets me run 6L6 (KT-66) at tweed voltages or 6V6 at black face voltages.

[The New Steve H]

Man, I think I just steered myself back to the Rocket.

[The New Steve H]

And I just realized the Vox has EL84s in it.

[Zippy]

That's not a bad place to be.

Call RJ and get the right parts and do it!

'course you still need to consider the Rockster 66 option...

... and whether to drill an extra hole for the missing tone control.

[Zippy]

And I just realized the Vox has EL84s in it.

I was hoping that was a typo and not a brain fart.

Oh well...