5751 Twin preamp tube

Brad Sarno · Post by **Brad Sarno** » 30 May 2004 7:40 am

Has anyone tried a 5751 tube instead of a 12AX7 in their preamp tube position in a Twin (V2 usually)? I've read that this was a SRV choice. Here are some quotes:

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Tech info: Unlike a 12AX7, the 5751 has a lower gain of 70 (100 for a 12AX7) just like the originals. The tube is lower impedance, and has predominent 2nd harmonics for a sweet, smooth tone. The 5751 is famous for its linear response and good transconductance and this tube holds true to that specification.

The 5751 has a bit less gain than a 12AX7, (30% less) and a more linear tone, Smoother, with outstanding clarity and "chime." Overdrives in a different manner when compared to other tubes (not as harsh) Very cool.

Stevie Ray Vaughan preferred them in his Super Reverb and Vibroverb in tube #2 (reverb preamp) for a clean tone with far more headroom than a 12AX7. It is one of the Characteristics of the "chime" tone.

The 5751 is not a 12AX7, it is a different tube with different character.

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So far I like it in my Twin. Anyone tried it?

Brad Sarno

Mark Herrick · Post by **Mark Herrick** » 30 May 2004 10:25 pm

I think some of the difference is going to depend on which 12AX7 you compare to. I'm using a JAN Phillips 12AX7WA in my Custom Vibrasonic and it sounds very nice. I swapped it today for a GE 5751 and it was similar but not quite as sweet/warm. I tried the new Groove Tube 12AX7M (the Mullard copy) and it has significantly higher gain, but not as sweet.

So now I have a Phillips 12AX7WA in V1 and the GE 5751 in V3. It sounds pretty nice. Tomorrow I will go back to a 12AT7 in V3 and see what difference that makes.

BTW, several years ago I had an amp tech service a Mesa Boogie Mark IIB. When I told him I was using it for steel guitar and wanted clean headroom, he replaced ALL the preamp tubes with GE 5751's. Whereas previously you could get nice distortion at low volume on that amp, afterwards it was difficult to get distortion at all.

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jim milewski · Post by **jim milewski** » 31 May 2004 5:52 am

would it work in the Black Box?

Donny Hinson · Post by **Donny Hinson** » 31 May 2004 10:04 am

Brad, want sweet? Try a (hard-to-find) 12AY7.

Low gain, but an oh-so-smooth sound!

Dan Tyack · Post by **Dan Tyack** » 1 Jun 2004 1:21 pm

I use AY7s a lot in my THD BiValve. The're pretty easy to find on the internet.

Brad Sarno · Post by **Brad Sarno** » 1 Jun 2004 1:32 pm

Jim, I haven't looked into putting one in the Black Box yet.

Donny, I've actually been using a 12AY7 for a few weeks and I really like it. The gain is much lower so I set my volume knob higher. It really seems to relax and sweeten up the tone. I agree!

Brad

Jerry Van Hoose · Post by **Jerry Van Hoose** » 2 Jun 2004 3:24 am

Does the 5751 sound better for both guitar and steel or just for guitar? With 30% less gain, wouldn't they be more likely to break up earlier? ...or... if you don't drive it too hard, a pedal steel will also sound smoother? Thanks. (SRV fan here too)

Erv Niehaus · Post by **Erv Niehaus** » 2 Jun 2004 6:48 am

I run a Tube Works rack system and I put 5751 tubes in the preamp and reverb a few years ago and really like it. Seemed to smooth it out.
Erv

Brad Sarno · Post by **Brad Sarno** » 2 Jun 2004 7:13 am

Jerry, what happens with a lower gain preamp tube is that the preamp will remain clean and the power tubes will start to max out and overdrive before the preamp ever gets into clipping. It basically cleans up the preamp. I was just told by someone that the 5751 will sound great on guitar, but on steel it kind of gets funny as you work your way up the neck. I haven't messed with it enough to concur. He wasn't a fan of it on steel.

My understanding is that this tube is a military grade 12AT7 and works better in the V3 (reverb driver) circuit or as the final phase splitter tube. Since these are positions for a 12AT7 anyway, it's a natural choice.

Playing strat into my Deluxe Reverb with the 5751 in the preamp tube position sounded amazing. Made me want to play SRV's Lenny all day.

Brad Sarno

Jerry Van Hoose · Post by **Jerry Van Hoose** » 2 Jun 2004 8:24 am

Brad, thanks. I always enjoy reading your posts.