Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Two 12AT7s in 5E3?

8/2/2005 11:15 PM
Two 12AT7s in 5E3?
I was wandering around the Internet and found a reference to a rare Dumble recording amp called "The Angel's Breath." Apparently, the myth/story is that guys like Robben Ford, Larry Carlton, etc. have used this amp for studio work. However, Dumble apparently does not sell any of these designs to the general public.  
OK, so who cares about the perpetuating Dumble legends, right? Well, there was a comment that this secretive amp may be a tweed Deluxe design with all 12AT7 tubes in the preamp. If that is the trick, it is not very creative by any means. On the other hand, it got me thinking that I have never tried two 12AT7s in my 5E3. I use two 12AY7s when I need more headroom with a pedal steel. I have tried two 12AX7s when I wanted to see how much distortion the thing was capable of. I have played around with other tubes in the first preamp slot (such as a 12AU7) but I usually kept a 12AX7 in the second position during those tests.  
Anybody ever tried two 12AT7s in their 5E3? I am not sure of the effect given that a 12AT7 has more gain than a 12AY7 but less than the 12AX7. Maybe it would give better control of going from clean to dirty than a standard 12AY7/12AX7 setup? Any experiences out there? I would try it myself but I do not have two 12AT7s on hand.
And now, a word from our sponsors:

8/3/2005 2:24 AM

It sounds like you've done some experimenting on your own with different preamp tubes. Your guestimation is probably as good as anyones then. But if it's opinions you want...  
I actually don't like 12AT7s in gain stages. I think most of them were/are manufactured as cheap "function" tubes for oscillator circuits and they sound dry as toast. I think if you have reduced gain in the first stages and then more in later stages that is all equates pretty close to what you might get with a more even gain structure. What you might get by increasing earlier stage gain and decreasing the later stages is more preamp distortion. But it would be so negligable that you may not hear a difference. Also, the Deluxe uses a split load PI which has unity gain no matter what tube you use. So there is really only one 12AX7 gain stage in a Deluxe.  
I haven't read much on Dumbles but what I have seen tells me that he (Alexander) would have built a beefed up power supply if he built a Deluxe circuit. If you think about it, a Deluxe with a choke, slightly bigger filters and transformers and a bright cap, using the standard 12AY7/12AX7 setup would not sound unlike a Dumble. Put another way, I don't think it's just the preamp tubes.  
8/3/2005 9:11 AM

It sounds like you and I are thinking along the same lines. I do not typically use 12AT7 tubes in gain stages. Given that I do not have any blackface/silverface reverb amps around anymore, I barely use 12AT7 tubes at all. But when I read the comment about this mythical Dumble amp, I wondered why I never tried two 12AT7s in a tweed Deluxe. I suspect you are correct in stating that the difference is negligable.  
Regardless of whether or not this story about a secret Dumble recording amp is true, this Dumble guy always makes for good reading. Sometimes I will read something about him and think that he is very creative with amp design who truly loves music and loves making and tweaking the perfect amp for his customers and friends like Lindley, Ford, Carlton, etc. Then there are other times where I get the impression that he is a pompous and greedy *ss who got lucky with one circuit design and intends to monetarily milk it and the "legend" for all it is worth.  
Interestingly, I read somewhere that the Deluxe overdrive sound was the inspiration for his amps. He wanted to take that comfortable, low-volume sound and make it bigger and more solid on the bass end and power supply. Of course, he used a completely different circuit to get there. There is a 1985 "Guitar Player" interview with him that makes an allusion to this as well. Maybe somebody could give Dumble $30,000 to list his favorite mods for a Mission Amps 5E3 kit (just kidding)?
8/3/2005 3:04 AM
Dave H

"Anybody ever tried two 12AT7s in their 5E3? I am not sure of the effect given that a 12AT7 has more gain than a 12AY7 but less than the 12AX7. Maybe it would give better control of going from clean to dirty than a standard 12AY7/12AX7 setup?"
I’d give Bruce’s Tone/Vol mod kit a try. It will have all the control you need even with two 12AX7s.  
8/3/2005 5:35 PM

I use a JAN NOS 12AT7WC as my first pre amp tube in my 5E7 build seen on my site, and though my playing talent is a bit weak lol, I think the amp sounds great with this tube.  
On my tube data page I have all of the gain factors listed for most all the guitar pre amp tubes good if you wan't a refference point from tube type to type. Also a sound bite of this amp. It was done really quick and needs some improvment but it gives you an idea of the sound.  
check it out at:
8/4/2005 2:02 AM

That is a great sounding amp. Have you ever tried a 12AY7 in that first tube socket??? Also there's the 5751 tube. SRVs favorite. Same gain (maybe a tad more) as a 12AT7.  
8/4/2005 11:49 AM

No not yet, but now I really have to try one.  
Thanks, glad you liked it!

  Page 1 of 1