Master Volume on old valve amps , a new idea?

[pete1951]

Many new amps have master volume controls. This let’s you get a bit of ‘crunch’ without turning the amp up so much your ears bleed. Retro fitting one to an existing amp can be done though it is a compromise, the ‘best’ distortion usually comes from the power valves and a master allows the preamp to be overdriven. That said, I have a master on my ‘67 Fender Princeton and like the sound it makes ( at low-ish volume) .
I have just been given a WEM dominator with a very customised amp. It has no master, but does have a spare ‘pot hole’.

Normally I would put in a dual gang pot, this would turn down the signal going to the power valves as it leaves the phase inverter. ( this of coarse only works on amp with 2 or 4 power valves)
But what if I were to use a dual concentric pot rather than a dual gang? This allows you to turn down one or both of the dual pots separately.
Turned down together will give a conventional master volume.
Turn down just one and you suddenly have a single valve working, so a 15 watt amp turns into about 5 watt and turning the other part of the dual concentric down will give even more control.
Does any other amp have this ?
My friend Barry (@ampmaker) says it won’t harm the amp and he has a switch on his latest amp that turns one valve off, which my control can do.

I am waiting for some parts but hope to have the amp running in a few weeks, hopefully I will like the asymmetrical tones that my control will give.
Pete

[archtopeddy]

Interesting idea Pete. Looking forward to hearing about how it sounds.

[Michael Messer]

WEM Dominator amps are pretty good. I had one in the early 80s and it was great until it was stolen from a gig off the stage while we were clearing up. At the time I wished it was called a WEM Detonator that I could have detonated remotely!

Shine On
Michael

[mitchfit]

leary about recommending these recently developed 6BQ5/EL84 lower powered substitutes as they don't seem to have any middle ground in the user reviews. i have never used them myself. JJ mfg valves don't have a sterling reputation in the US market either.

if over-driving the preamp tubes doesn't sound that good to you, or still louder than hoped for after lowering voltage to power valve(s) perhaps one (or two) of these could help? how does it still push-pull with one leg only?

JJ's claims about them:

JJ Electronic has introduced an EL84 vacuum tube with a twist! The new JJ EL844 power tube provides about 25% less headroom than a traditional EL84, but can be used in any EL84 tube amp without modification to the amp. If you need less headroom for your bedroom amp consider the EL844 tube.

From our review: "The EL844 does exactly what the manufacturer claims. You get all the tone of an EL84 with less volume overall. The difference doesn’t end there. Because the tube has less power to give, you end up with very nice distortion at lower volumes. I ran the Pro Jr. up to a point just at the start of audible breakup. With EL84's, the Fender Pro Jr. was loud and punchy. Switch to the EL844's and cool stuff starts to happen. At the same settings the distortion was now very nice. The EL844 adds a bit of compression so the distortion was smoother and more focused. These tubes have excellent response to pick attack. With a lighter touch you can get sparkling shimmer, dig in with the pick and you can push the tubes into overdrive."

[no affiliation]

www.thetubestore.com/jj-el844-low-power-el84

mitchfit

[pete1951]

Th EL844 looks interesting, every suppler in the UK seems out of stock at the moment. I will get a pair as soon as I can . How they ( or one of them ) will react to being in a push-pull amp with an standard EL84 will be very interesting. With my dual concentric pot I could then go from a 5watt single EL84 to a 3 watt?(not sure how powerful) EL844. Plenty of ‘ crunch ‘ at bedroom volume.
Pete


Just found one on line, hopefully will be testing it on Wednesday!

[mitchfit]

could have a useful experimental application in an olde school Vox AC also? [after switching from EL34 twins used in short lived original models] would love to hear resulting impressions from one who has no monetary horse in the valve sales race.

has me wondering about a single ended EL 84 Winfield Thomas built based on the Supro Dual Tone P-P circuit without trem. and/or his "Winfield" 2X4 optional circuit with Marshallesque preamp flavoring.

also, Mark Baier once told me via email that he had gotten some surprisingly pleasant sounds from grossly miss-matched 6L6 twins he had tried in his amps.

mitchfit

[mitchfit]

^^^^
brain flatulence alert!!!

the supro clone uses a 6973, not an EL84. must be olds timer's setting in. they do kinda look alike. from ten feet away.

the sun was in my eyes, and there was a tree obstructing my view.

yeah, that's what happened...i remember it clearly now.

:^)

mitchfit

[pete1951]

The el844 arrived today. There is a small volume drop . Have not had time to do a proper test yet and still waiting for parts for the Dominator.
Pete