Half-Power Switch on Express?

[Lonely Raven]

I got a DPDT switch and a printed out drawing from Nik that's supposed to help me do a Half-Power switch on my Ceriatone Express.

I'm not following his drawing at all. Is there an example/drawing somewhere that I can look at to help me figure this out?

I'd really like to get a half-power switch going rather then use 6V6 tubes. I'm finding that I just really like EL34 in this amp and would like to keep it that way.

[dartanion]

How are you going to accomplish "half power" on an Express?

Pentode / Triode?
PT Secondary Switch?

I am not sure how you can actually attain half power via a switch on an Express.

With parallel pairs (4 tubes in PP), you can switch out one pair for 1/2 power.

[Lonely Raven]

It's a Pentode/Triode switch. But I don't follow how it works.

[dartanion]

Don't even bother with a pentode/triode switch. Triode mode is very linear and HiFi like. It changes the tone fairly drastically and isn't really half power either.

I think you'd be better served with SE/PP control or a power scaling board.

Also, why not 6V6s? I have a couple of 6V6 based amps, and I love them. I have become a big fan of these little powerhouses.

[Lonely Raven]

Oh, I love 6V6 amps, I just don't like the sound in the Express.

I'm not sure I have the skills yet for power scaling.

I've been reading in the forums about the SE/PP control, and I don't follow that one either.

I guess I'll just leave it alone for now. I finally got off my butt and replaced the defective octal socket that came in my kit, added bias test points and externally adjustable bias pot, and I added a switch to allow me to switch the OT from 5.2k to 6.6k.

I seem to have picked up a bit more hissing, but all the mods went well. So I should probably work on cleaning up my lead dress and work on the hissing issue that I just made worse.

[Tubetwang]

Is this for giging or home fun?

For the later category, i've finaly worked something out that need no modification...and, permits EL-34 it all it's glory.

I simply wait for the time when i'm alone in the house...

ymmv but...

[Lonely Raven]

I'm currently in an appartment...so I technically have to wait for 3 homes to be cleared out of people before I crank.

[dartanion]

SE/PP control + Attenuator = apartment levels

[CaseyJones]

Cadillac did something like this years ago. They had a V-8 that would run on four or six cylinders on light demand. While sound in concept it's stupid in practice, four cylinders tryin' to pull a heavy car suck gas anyway. There's no real benefit and the extra complexity adds cost.

Know what I'm gettin at?

With two tubes and some cheap iron you can build a Derailment. The parts count is about the same as a proper powerscaling circuit.

[dartanion]

What about utilizing the dual PT secondaries for low / hi power. The low power mode would sound better with 6V6s I'm thinking creamier and smoother. I'd also consider a dual primary switch for OT.

[Lonely Raven]

What about utilizing the dual PT secondaries for low / hi power. The low power mode would sound better with 6V6s I'm thinking creamier and smoother. I'd also consider a dual primary switch for OT.

Hmmm, when you put it that way, a dual secondary switch sounds pretty cool. The lower voltage might sound good with 6V6.

I'm running out of room in the chassis though...my wiring is messy enough with the external bias pot, test points, and OT primary switch. Lots of neat ideas...I like the idea of a derailment as well.

Is a derailment as dynamic and touch sensitive as an Express, but on a smaller scale?

[Buschman]

I put a triode switch in mine & feel it is a usable mod. It is still too loud for an apartment & it browns out the highs a bit. I am with you-6v6s seem harsh in my Express. Go here for a diagram
http://www.tone-lizard.com/Marshall_Myths.htm

[CaseyJones]

Is a derailment as dynamic and touch sensitive as an Express, but on a smaller scale?

Nothing compares to the sonic majesty of a dimed Express. Tell that to your neighbors and the cops, the cops are sure to show up if you can't convince your neighbors!

Nothing compares that is except for a Derailment or other truncated SE 'Wreck circuit. Dimed is dimed, beating the crap outta an ECL86 or a single EL84 is as much fun as that brief and shining moment when you get to turn your Express all the way up... except with no cops and no pissed off neighbors.

[John C]

My experience with triode-mode:

-There is less volume
-The tone is warmer
-The tone is better (to me) than 6V6s in pentode-mode in my Express-type amp
-I could easily compensate for changes in tone caused by triode-mode by tweaking some preamp values

In fact, I've hard-wired my amp to triode-mode with no regrets. ...I didn't hear any hi-fi qualities about it. My preferred setup is EL34s wired in triode-mode, and I would recommend triode-mode to anyone considering non-master-volume amps with too much volume, a la EL34s, 6L6s, others...

One other detail - no more attenuator since triode mode...