Ampeg reverb - parallel 6SN7

[Sonny ReVerb]

I've built an amp using an Ampeg reverb circuit. It only uses one triode of the 6SN7 for driving the reverb tank. Is it possible (beneficial) to use both triodes in parallel to drive the reverb? Just considering a possible use for the unused triode.

Merlin addresses a parallel 12AT7 current driver under Cheap current source drivers

[sluckey]

Very easy to try and see. The Ampeg R15R has a nice reverb effect using only  half of a 6SN7 to drive the tank. The other half is used as a gain stage just prior to the driver. Maybe that's a consideration?

Could we see your entire schematic?

[PRR]

> possible (beneficial) to use both triodes in parallel to drive the reverb?

Possible? Of course. You could harvest an organ and lash 2 dozen 6SN7 together.

Beneficial? What benefit do you need more of? Gain will go up *very* slightly; a lesser tube in front would give gobs of gain. (Or bypass that cathode R.) But if you are not reaching fully-soaked-wet Drive because of lack of drive Power, a parallel tube just might make a useful difference. (Choke-load would be, not 1.4X-2X, but 10X stronger...)

[Sonny ReVerb]

Thanks, Gents.

This amp could use more reverb. It seems like it has plenty of signal going into the tank, but not much after recovery. I tried two different tanks to rule out a bad tank. I changed the plate load resistor (47k to 100k), bypass cap (0.1uF to 2.2uF), and grid leak (22k to 220k) of the 6SL7 recovery stage. I considered using the spare 6SN7 triode for an additional recovery stage (as Ampeg did), but this amp uses a tube mixer for the dry and wet signals. An extra stage on the wet side would put it out of phase with the dry side. That's why I thought of the two parallel triodes (no phase change). I also changed R27 and R42 to 100k to try to get more signal from the wet side.

 I'm on the road this week, so I don't have access to the schematic at the moment. To get you started, it's the amp in the attached PDF with the attached reverb.

 Maybe I will try a bypass cap on the drive stage, as PRR suggests, when I get back.

[sluckey]

The circuit you asked about initially uses a cap coupled reverb tank. But your wunderbar uses a transformer driven tank. Cap input tanks are not interchangeable/compatible with transformer driven tanks.

[Sonny ReVerb]

This amp uses the proper high impedance Ampeg Type C tank - 4FB3D1B

[Sonny ReVerb]

Here is the amp schematic:

[Sonny ReVerb]

and gut shot...

[tubenit]

I really like that amp design!  THANKS for sharing the schematic!  Very innovative and interesting build. 

With respect, Tubenit

[Sonny ReVerb]

Thank you. It's derivative, of course. I'm just a cookie cutter builder. It's based on an Amplified Nation Dirty Wonderland which is based on a Wonderland which is based on a Two Rock John Mayer Sig which is based on some Dumble variant which is based on...  You get the idea. I subbed in the Ampeg reverb and 7591A's.

[sluckey]

Looks very clean and neat. 

[pompeiisneaks]

Very nice!  Looks like the blue FR4 garolite I get from mcmaster carr :D (had to have blue myself, I love the color).

~Phil

[Sonny ReVerb]

Looks very clean and neat. 

Thanks. This is the first amp I built with the 'elevated' heater wires. It was also pretty labor intensive with all the off board components.

Looks like the blue FR4 garolite I get from mcmaster carr :D

That's the stuff! McMaster 20ga solid core wire, too.

[DummyLoad]

nice work!


--pete

[tubenit]

BTW,  I like it that you used turrets and not eyelets on that board.  I think that was a good choice.  Would love to hear a soundclip when you get it tweaked to your liking.

With respect, Tubenit

[Sonny ReVerb]

Thanks, Gents. I finally had a chance to experiment a bit more with the amp. I placed a 1uF cap across R33 - the cathode resistor of the reverb driver tube. The reverb level was better. I ended up with a 2uF cap there. That gives a usable reverb level. Certainly not surf levels, but probably enough for most players. You have to set the SEND level around 7-8, though.

Next, I'll get it cabbed up and have some other players try it. I've got a 12" WGS ET65 and a 12" Celestion Gold to use with it. I'll build separate cabs for each. Three cabs to build - I better get busy. Any tolex application tips for cold weather? ;) I usually build cabs in the summer.

[Sonny ReVerb]

Finally got two cabs done. The speaker cab has the WGS ET65 in it. Sounds good. I'll try to get some sound clips up sometime.