Blues Deville conversion

[bulldogguitars]

Has anyone converted a blues deville or similar amp to run on el-34s. What is involved in this conversion. Thanks in advance for your help. Danny

[Enzo]

You'd have to determine if the power tranny could hancle the heaters, they draw about 50% more current than 6L6. Plug them in and leave the standby OFF so there is no B+ on the tubes. Now measure the 6.3VAC heater voltage. If it is still up to 6.3 or so, then the transgormer is handling it OK. If it is low, then it is not.

You'd have to make sure pin 1 of each EL34 socket was wired to pin 8. And not wired to anyting else.

You'd have to modify the bias supply to adjust to voltages the EL34 needs if it doesn't already have the range.

You'd want to make the screen resistors 1k 5watt types.

[bulldogguitars]

Thanks Enzo I appreciate it. I thought their might be some concern due to power requirements. Ill check it out and post my results. Thank You very much Danny

[chocopower]

....Now measure the 6.3VAC heater voltage. If it is still up to 6.3 or so, then the transgormer is handling it OK. If it is low, then it is not.

How do you check this voltage?

From 6.3 tap to "0" (or ground)?

[hasserl]

How do you check this voltage?

From 6.3 tap to "0" (or ground)?

The 6.3 volt tap is actually two taps, each one ~3.15volts WRT ground, or 6.3volts across them. You can measure this across pins 4/5 & 9 on the 9 pin tubes or pins 2 & 7 on the bigger 8 pin tubes.

Note that pins 4 & 5 on the 9 pin tubes are joined together at the sockets.

[JJGross]

I run my HRDx on EL84s using the Groove Tubes "Substi-Tubes" socket adapters. They drop the voltage down from 450 to 370 and reconfigure the pins so it's a true plug & play operation with no re-biasing needed (but I did it anyway). They're the equivalent of Yellowjackets, but unlike the YJs, they're not housed in plastic but machined aluminum.

The only issue I have with the GT-STs are that the pins seem really fat and it's tight fit into the sockets. Not a problem if you leave them in there, but swapping back & forth with 6L6s you'd end up with some pretty loose pins on the 6L6s. The bases on the GTs are also kind of big diameter so if you use tube retainers on the bases, you should remove them to allow the Substi-tubes to seat properly. I just run mine without the base jacket on it to get around this, and I've read that this also lets them run a little cooler but I haven't done any laser thermometer testing or anything.

As far as how they sound, I'll never run 6L6s in this amp again. The boxiness of the HR is gone and the drive channel actually sounds like drive instead of a million gnats. Now it's still got that Fender clean, but it leans a little more toward Vox/Marshall territory on the drive channels. I can also run all my tone controls straight up at noon to start for the room instead of turning the bass almost off and cranking everything else. With the EL84s it's just such a better balanced amp I can't believe it.

If you want to hear it in action, do a YouTube search for "Dirty Ernie Band". Someone came to a gig recently and recorded us with a pocket camera. Not very Hi-Fi by a long shot, but they were sitting RIGHT in front of my amp so you can really hear the guitar.
The sound really isn't much different than most other YT live recordings. If you have a decent sound system on your computer, crank up the bass for a more balanced sound. Obviously a pocket digital camera with a 1/16" microphone in it isn't going to get a lot of bottom end. Songs that probably best show off the clean tone are "Time & Time Again", "Lie No Better" & "Smokin Gun". All the others are with overdrive and show the drive channels better. Most of them have little to no effects, just the amp with a Bluesbreaker clone I built for solos. Guitar is a MIM Strat w/ TS pups and graphtech saddles, otherwise stock. AKG guitar bug makes the connection.

Cheers,
- JJ

[Rob Mercure]

JJ,

If you will note I believe the inquiry was about using EL34s, not EL84s, and Enzo's answer was the straight poop. Now other than rebiasing once the changes are made the tube swap should be fairly simple. As far as using the '84s I'd probably make my own adapters - copper water pipe works well but I love high temp engine enamel for these projects.

But of course everyone has their own tastes and fer myself I'm really not a fan of EL84s but you probably wouldn't like my home made saurkraut either <grin>.

Rob

[hasserl]

They drop the voltage down from 450 to 370

I'd like to know how they do this, that's a pretty good trick. Dropping B+ voltage is one of the common questions that gets asked around here, and the zener diode in the power transformer center tap to ground seems to be the most common response. What are they doing inside of a tube adaptor to drop 80 volts?

a true plug & play operation with no re-biasing needed (but I did it anyway).

Hmmm, don't these convert it to cathode biased? How did you change the bias?