6G15 reverb unit in a Valve Jr head ??'s

[tommytornado]

I just picked up a used Valve Jr head cheap with intentions of trying a 6G15/reverb unit type circuit in it.  I was planning on using the existing PT & OT.  I have a choke I pulled from a DRRI.  An Accutronics 8AB2A1B Reverb (short) Tank (input imp 10 ohms, output 2575 ohms).  I have a couple questions for those who know much more than I do.

1.  What opinion's/suggestions might you have for going with an EL84 instead of a 6V6 to drive the tank?

2.  Would it be worth it to go with DC heaters?  Or maybe I should ask, any suggestions to make the unit as quiet/hiss free as possible considering the stock 6G15 circuit? 

As always, thank you!

[HotBluePlates]

1. If you want to use an EL84, go for it. It will work fine.

2. I had a reissue 6G15, and it had no hum or significant noise. There might have been a little background hiss, but not enough for me to take notice of it in use. Fender didn't do anything special in that chassis, so I don't think you'll need dc heaters or much of anything special to be reasonably low-noise.

[FYL]

1.  What opinion's/suggestions might you have for going with an EL84 instead of a 6V6 to drive the tank?

Fender used EL84's as reverb drivers in a number of amps, when 6V6GT's weren't readily available. Check for instance the Vibro-King.

2.  Would it be worth it to go with DC heaters?  Or maybe I should ask, any suggestions to make the unit as quiet/hiss free as possible considering the stock 6G15 circuit? 

No need to use DC heaters. Doug's version of the 6G15 is quiet as a mouse, better than Fender RI's and much better than vintage models.

[sluckey]

Fender used EL84's as reverb drivers in a number of amps, when 6V6GT's weren't readily available. Check for instance the Vibro-King.

That's the only Fender schematic I've ever seen with an EL84 reverb driver. Can you point out another one? And was there ever a time when 6V6s weren't readily available?

[tubeswell]

If you are using an EL84, I think the cathode resistor needs to be around 100R-200R (bypassed with a 47uF) 2CW. And make the RT 5k.

The stock 6G15 uses a 6K6 with a 1k cathode resistor, and this works for a 6V6 quite well, but I have my doubts how an EL84 would sound with 1k.

[FYL]

That's the only Fender schematic I've ever seen with an EL84 reverb driver. Can you point out another one?

A few Zinky-designed amps, back when he ran the Fender Amp Custom Shop in Scottsdale.

And was there ever a time when 6V6s weren't readily available?

Yes, beginning to mid '90s. Supplies were dwindling - New Sensor wasn't big then, prices skyrocketed.

[Geezer]

Yeah, that should work nicely for a reverb unit, just be sure to get the right size reverb pan (shorty). 

[sluckey]

Yes, beginning to mid '90s. Supplies were dwindling - New Sensor wasn't big then, prices skyrocketed.

I totally missed that. I wasn't into guitar amps at that time. I was totally acoustic and very much into windsurfing and catamaran racing. And the FAA depot must have had a big reserve because I never remember any backorders.

[HotBluePlates]

And was there ever a time when 6V6s weren't readily available?

Yes, beginning to mid '90s. Supplies were dwindling - New Sensor wasn't big then, prices skyrocketed.

Fender makes new amps, and needs new tubes to stuff in the sockets before shipping to dealers. At that time, the just about only "new 6V6's" were a russian tube type that was rated for something like 250v on the screen. Tons of these tubes routinely failed in guitar amps, to the point that people really started looking for NOS 6V6's. Until that point, I could walk into a TV repair shop in Charlotte, and buy all the old-stock RCA12A_7's, rectifiers and output tubes I could carry, for like a buck a piece.

Remember also that the on-board reverb circuit typically works the tube near 400v. The russian EL84 sub that was available easily handled the chore, the russian 6V6 sub didn't. So we wound up with a reverb circuit with an EL84 driver.

Things are different now. But it is still proven to be a workable route.

And the FAA depot must have had a big reserve because I never remember any backorders.

Well, sure they did! And so did the military at the time. I wish I had the money and the knowledge of how to buy from DRMO, because I coulda bought a metric sh!t-ton of late production american tubes for nothing in the military's big sell-off around that time.