el84's in a tweed deluxe

[riscado]

is it possible to wire, a couple of sockets in parallel to be able to run a either a pair of 6v6 or el84 in a deluxe?

thanks

[carl gigun]

Sure, sounds like a fun idea. As long you take some care that the el-84 are operating safely, they should work with the same output transformer. You'd have to do a new cathode R and bypass C, grid stoppers, and screen resistors (if used) on the sockets for the el-84s but not more 220k bias resistors. Then jump the grid, plate and screen leads over from the 6V6 sockets.

Of course you'll need a suitably threatening label to make sure nobody ever puts a mix of the two tubes in at once.

[clyde]

switch

Would it be possible to run a switch that would switch between the two different pairs? Throw the switch one way and you get 6v6, throw it the other way and you get el84?

[Arthur B.]

Would it be possible to run a switch that would switch between the two different pairs? Throw the switch one way and you get 6v6, throw it the other way and you get el84?

You mean something like the Mesa Boogie Blue Angel? Yes, it's possible to do so.

[Bruce / Mission Amps]

is it possible to wire, a couple of sockets in parallel to be able to run a either a pair of 6v6 or el84 in a deluxe?

thanks

I'm sure it's possible to do that.
The OT is about the same for both 6V6s and El84s.
All you'd need is a way to lower the B+ a little or, use a power tranny that is down in high voltage AC so the EL84s are not overvoltaged.

By the way, we have octal to 9pin EL84 adapter kits for the 5E3 kits which includes stainless steel adapter plates, 9 pin tube sockets, wire El84 hold down clamps and all the nuts and bolts, etc.

[clyde]

el84 B+ with 6v6

What would be the effects if someone where to permanently lower the B+ for use with el84's and then change back to
6v6's with the same B+ for el84's?

I've got a MA Deluxe with 6v6's (stock circuit) that sounds great with 6v6's. The only amp with el84's I have any experience with is a Fender Pro Junior and that thing sounds straight and clean, whereas the 5e3 can get kind of hairy. Would swapping el84's tend to clean up the sound of a
5e3? Just curious about the tonal possabilities since you mention the adaptor.

[Satamax]

Would swapping el84's tend to clean up the sound of a
5e3? Just curious about the tonal possabilities since you mention the adaptor.

Don't think so! If you want EL84 try yelowjackets of teh like

[Bruce / Mission Amps]

Would swapping el84's tend to clean up the sound of a
5e3? Just curious about the tonal possabilities since you mention the adaptor.

No not without tweaking the amp.
If you want a much cleaner sound with a 5E3 and 6V6s you need to turn it into a different amp, an amp that ends up just having some tweed 5E3 tone when driven hard.
Going to fixed bias 6V6s, a small choke and a tweak to the coupling caps and cathode bypass caps will do that and more.
Another possibility is to rebuild the amp with a beefed up B+ rail, 6L6s and a reissue OT for a BF Pro Reverb.
This configuration will net you something like a slightly lower powered version of tweed Pro but, with single 12" speaker... still a great sound.

[allsavy]

What if you did want to have both sets of tubes in at once?

[Dave H]

6v6 + el84

What if you did want to have both sets of tubes in at once?

You could do it like this. It's either 6V6 or 6V6 + EL84. The 6V6 + EL84 combination sounds great.

Dave H.

[Bruce / Mission Amps]

You could do it like this. It's either 6V6 or 6V6 + EL84. The 6V6 + EL84 combination sounds great.

Dave H.

I don't have the amp to measure anything so this is all speculative...
the EL84s, biased at 12v in this amp, might make, say 14-16 watts output but probably go into Class B distortion at +24vac PP drive on their grids.
That's a little more then half the drive level needed to make full power in the 6V6s which are biased at 24vdc.
It would take 48vac PP at the 6V6s to make full power before clipping.

So... assuming the 6V6s will only make maybe 6-8 watts at that same drive 24vac PP drive level (of course I don't know) .... how do you keep the amp as a whole from sounding clipped and buzzy with EL84 + 6V6 when driving at higher power levels, or is that the whole idea?
In other words, the total clean output power seems like it could only be about 18-24 watts with both sets of tubes running due to conflicting bias levels with respect to the same peak to peak drive level at their respective grids. Limited by the EL84s being driven into Class B cutoff.
HA ha... that was a mouthful....

[Dave H]

Hi Bruce,

It was originally a 30W, 4 x EL84 amp but after over 10 years of EL84s I felt like a change and rewired it to be either 16W, 2 x 6V6 or 16W, 2 x EL84 but I found I wasn’t using the EL84 setting and sometimes missed having the extra power so I changed it to be either 2 x 6V6 or 6V6 + EL84 as the schematic.

I didn’t expect it to sound very good and thought I’d end up wiring it as a 30W, 4 x 6V6 amp but it sounds fine. It doesn’t sound any more clipped or buzzy than my other amps and it looks OK on a scope but I don’t ever run heavy distortion. I’m too old for that I try to always have it just at the point of breaking up. I did think of splitting the 220k grid load resistors into 120k and 100k to reduce the drive to the EL84s to balance with the 6V6s but as it sounded OK I didn’t bother. I thought that having an extra 100k or so resistance in series with the EL84 grids would roll off the highs but people do use 1M post PI master volume pots. Does that roll off the high end?

It does work as you said. It will only put out 25W clean not 30W but it does sound more solid and punchy on the 6V6+EL84 setting than it ever did with ether 2 EL84s or 2 6V6s. I guess the EL84s are clipping the PI output at about 14V peak so that 25W is 16W from the EL84s but only 9W from the 6V6s.

Dave H.