6GE8 as reverb tube, etc.?

[Ray Ivers]

I just came across what seems to be a unique 9-pin miniature tube (but if anyone else finds something similar, please let me know!) - the 6GE8. It's a pentode/triode with the triode as the power tube, along with a pentode voltage-amplifier stage. Apparently every other pentode/triode with one power stage has the pentode as the power unit (ECL82/6BM8, etc.).

This strikes me as a good candidate for a reverb driver/reverb return circuit, as the triode section has serious beef for driving a reverb transformer along with other desirable (IMO) characteristics, and the pentode could be set up for all sorts of return gain if desired. This tube might also make a good pentode/direct-coupled-CF stage, too, especially for driving low(er)-Z loads with large voltage swings.

Ray

[Alexander]

Hey Ray-

Nice to see some interest in something other than 12A_7's! I've been having fun building with 6SJ7wgt's & 6AU6A's for the punch, and have been happy with JJ's 12DW7 as single-reverb tube, with the 'AU' side driving the standard Fender transformer. It doesn't quite do the surf thing but provides at least half the depth or more with the standard 2-spring long tank.

As to your new tube find-

I think I found one reason for its relative unpopularity:
http://store.tubedepot.com/nos-7734.html

yikes!
But if it was in an amp that was used in early Zeppelin albums then who cares, gotta have it!

Alexander
Retrodyne Amplification

[Ray Ivers]

Alexander,

Yes, there's a ton of different tube types out there - most of which are still available for fairly reasonable prices - offering a vast amount of circuit-design flexibility. The 12DW7's a good example; when I first came across this tube a long time ago it seemed strange to me, but nowadays it makes perfect sense.

Wow, I didn't realize the 6GE8's were priced like that - Antique has them for $27, I think, and perhaps one might get lucky on eBay. I searched through all the 6xxx and 12xxx tubes in the GE book and couldn't find another like it, but I didn't check the MIL tubes.

Ray

[imaradiostar]

up from the dead...

anyone ever use a 6678 or 6u8 as a combined drive and recovery tube?

jamie

[mac1amps]

Yet another perspective.........I've had some great success using EL84/ 6BQ5's as reverb drive tubes. They're certainly easey to come by, and reasonably priced these days. They last alot longer than a 12AT7 ever would, and also have a wider dynamic range.......I confess that I stole the idea from the early Vibro-Kings, before they went back to using 6V6's (simulating the "stand alone" reverb heads that Fender makes/made). I've done this to a number of SF Fenders, and a couple of Dr. Z's as well. Every one of my clients that I've done this for have been delighted with the results.

[jbefumo]

I typically use the 6DW7 (or its mirror image, the ECC823), in circuits where half of a triode is used in a common cathode configuration, with the second a cathode follower serving as a buffer (such as in a Marshall). Anyone else tried this?

Alexander,

Yes, there's a ton of different tube types out there - most of which are still available for fairly reasonable prices - offering a vast amount of circuit-design flexibility. The 12DW7's a good example; when I first came across this tube a long time ago it seemed strange to me, but nowadays it makes perfect sense.

Wow, I didn't realize the 6GE8's were priced like that - Antique has them for $27, I think, and perhaps one might get lucky on eBay. I searched through all the 6xxx and 12xxx tubes in the GE book and couldn't find another like it, but I didn't check the MIL tubes.

Ray

[Chuck H]

I don't know just how this thread became a platform for alternative ways to design a reverb??? I thought it would be about the 6GE8 tube. Which I'd never heard of before now. Anyone else unfamiliar with this tube may find this useful:

http://tubedata.milbert.com/sheets/127/6/6GE8.pdf

Since a reverb tank only puts out about 4mV to 8mV it does take A LOT of amplification factor to bump that while still allowing for a volume control. But in the typical BF type circuit there are actually two cascade recovery triodes. This because the "mixer" or summing triode is being fed a full strength signal from the reverb circuit, but a very padded version of the dry signal. There are better ways to chain and mix it all together IMHE and so I find that a high gain tube isn't really needed for the recovery stage. BUT... If one wanted to, say, feed the reverb signal to a PI or multi channel mixer stage direct from a single recovery stage then I think this 6GE8 tube could prove a step up from the 12au7 that is typical for this application. The only rub is that as the tube becomes more expensive and rare there won't be any substitutes that don't require a drastic reworking of the circuit. I think about these things when I build an amp anymore. 'Am I going to be willing to change the circuit completely when I'm 68. Or will this amp become an end table.'