Hammond tubes

Dave Zirbel · Post by **Dave Zirbel** » 4 Jan 2002 10:23 pm

A friend of mine gutted an old Hammond organ and gave me some tubes. I got 2 6V6's, 2 12AX7As and a handful of 12AU7As. Have any of you tube fanatics tried Hammond tubes in your Fender amps? Can the 12AU7As be used as substitutes for any of the standard pre amp tubes, like the 12AT7s or 7025s? Thanks, Dave

Paul Graupp · Post by **Paul Graupp** » 5 Jan 2002 7:59 am

Dave; Chances are Hammond tubes were made by some other manufacturer of tubes. There was a lot of that going on. A 12AU7 will not work properly in a 12AX7 (7025) slot. It's a different gain tube and as I recall the series went from AU to AT and then AX with different mu characteristics for each.
The components used in one may be incorrect for another.

Regards, Paul

Steve Feldman · Post by **Steve Feldman** » 5 Jan 2002 8:08 am

I'm no amp tech, but I was under the impression that a 12au7 was completely swappable with a 12ax7 - particularly if you wanted to lower the gain. Is that not right?[This message was edited by Steve Feldman on 05 January 2002 at 08:09 AM.]

ajm · Post by **ajm** » 5 Jan 2002 8:31 am

From what I remember:
12AU7 = gain of 20
12AT7 = gain of 60
12AX7 = gain of 100

You can swap any position without hurting anything but you may not like the sound; that's up to you. I also believe that you can swap the 12xxx series tubes with 7025, ECC83 and a host of others. The Groove Tubes book has a pretty good chart for this.

Over at Harmony Central, a lot of guys talked about swapping the AX7 with an AU7 in their Tube Works Real Tube overdrive pedals. I tried it and it makes a world of difference. I like the 12AU7 much better.

Jack Stoner · Post by **Jack Stoner** » 5 Jan 2002 8:37 am

The old Hammond tubes are probably made by either GE, RCA or Sylvania - the three main US tube manufacturers back then.

To add to what has already be said about the different types, the 7025 is a low noise version of the 12AX7. A lot of the old "Hi-Fi" equipment used 7025's in the preamp sections.

Ken Fox · Post by **Ken Fox** » 5 Jan 2002 8:57 am

A lot of guys I've talked to on the Fender forum have tried lower gain preamp tubes in the Hot Rod Deluxe, Blues Deluxe with great results. I tried it in the tube that was used for "Crunch" and "Ultra" mode on a Peavey Triumph 60. It really mellowed out the raspy overdrive sound! It might be interesting to try a 12AT7, 12AY7, or a 12AU7 in a Tubefex to see what the results would be.

Dave Zirbel · Post by **Dave Zirbel** » 5 Jan 2002 9:30 am

Jack, the tubes say Made In Holland. DZ

Jon Light (deceased) · Post by **Jon Light (deceased)** » 5 Jan 2002 9:52 am

Dutch? Could be Philips. Or Amperex Bugle Boy. I had a mystery 12AX7A/ECC83 tube. It still had a bugle boy logo and the code and 'Holland' on it but the name was worn off. A search turned up an intact picture and the Amperex name. The tube sounded so much better than the new Sovtek in the Vibrosonic. Then I pulled it and shorted it out. *#@*!&%^&#*!&$!!

Here the site with ID'ing pictures--
http://www.tubeworld.com/
[This message was edited by Jon Light on 05 January 2002 at 09:55 AM.]

Steve Feldman · Post by **Steve Feldman** » 5 Jan 2002 10:18 am

I recently bought a couple of Sovtek 5751 (12ax7/ECC83-type) tubes to go into a used Mesa V-Twin rackmount that I got on the cheap because it needed a repair. So far, I havent't tried the 5751s because I just got the V-Twin working and it already sounds VERY good with the stock tubes.

The 5751s are supposed to have ~70% of the gain of a 12ax7 with a very low noise floor and little to no microphonics. Anyone else try these critters?

Michael Holland · Post by **Michael Holland** » 7 Jan 2002 5:46 pm

What a coincidence! I just bought a lot of vintage Hammond 12ax7's in an eBay auction. They sound incredible in my Mesa Heartbreaker and Mavericks; really full, with perfect mid-range. And they cost the same as new Russian or Chinese tubes! I've also recently tried some Telefunken, re-labeled Mullard (Audiovox and Bogen), and some G.E.'s. And I have some vintage Sylvania 6V6 in the Hearbreaker. Sounds great!