5751 Preamp Tubes

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Atropos_Project

Atropos_Project

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Anyone have experience using these vs 12AX7's? I'm kicking around the idea of trying them in my EVH 50 watter, which (to my uses) has silly amounts of gain, even at lower levels.

TIA.
 
They have about gain rating of 70, vs the 12ax7's 100. They theoretically should lower the overall gain.
 
Here's my notes from the day I was tube rolling Nov 2016 viewtopic.php?f=3&t=183631&p=2051187&hilit=12au7#p2051187




It is said that Howard recommended 12au7 in V2 & V3 to reduce red channel gain.
Really cool! With gain on full it was less than the blue, so that wouldn't work for me but would likely be cool for less gain freaks.

I then tried
V2: LPS
V3: JJ 12au7

Now this ^was very close to what I wanted, but still just a bit more tame than I wanted. I imagine many players would love this though

I flipped it and found the magic:
V2: 12au7
V3: LPS

This was awesome! It retains most of the ferocious girth and power but allows full use of the gain- cool tones from 9oclock to maxxed. I tried the original 12ax7 in V3 but that brought back some extra noise, so back to the LPS


I have the LPS in V5 and the rest stock

I'll throw some clips up....Red was too much before, but now it may be my favorite! It has gain, low punch, and saturation of a Cobra with a fast attack of a Fortin.

I used to use Blue for this stuff, but now I may knock that down with an au7 and use it for light/mid gain stuff, not sure yet.

Sources:
12au7
viewtopic.php?f=3&t=182542

Sovtek LPS
viewtopic.php?f=3&t=124599&p=1979196&hilit=sovtek+lps+evh#p1979196
 
I found CH3 in my 5153 50 watter unusable because it had so much gain. I think I ran the gain at 9:00 in that amp. I had similar issues with the extreme level of saturation in my Uberschall. 5751s will help but since those amps are designed to ring as much gain as possible out of 12AX7s you can fill every slot for the gain channels with a 5751 and not see a really dramatic reduction. In the Uber I went from gain at 10:00 to gain at noon I think. If you're running your 5153 gain so low that the channel is choking out then you might get 15-20% more flexibility out of it. It wont turn CH3 into CH2 though.
 
with that 1 (or 2) tube swap above, the gain levels are now much closer between ch 2 & 3. The nature of the gain is quite different though
 
I seem to like 5751 tubes more than 12at or 12au to drop gain. Keeps the feel more. Try it in the phase spot too, compresses nicely sometimes
 
crwnedblasphemy":1vtv89fn said:
I seem to like 5751 tubes more than 12at or 12au to drop gain. Keeps the feel more. Try it in the phase spot too, compresses nicely sometimes
Click to expand...

The 5751 is a lower gain 12AX7 type with the same plate voltage so the feel stays the same and the amp operates the same with the exception of the lower gain. If you use the other lower gain types you also change the plate voltage in that slot and thus the way the amp is operating.
 
Oh crap, looks like I want to try some 5751s now
 
I tried a 5751 in my Soldano a while ago, it did lower the gain but made the low end really hollow in a strange way. I like the JJ ECC83MG better for lowering the gain.
 
I put a NOS GE 5751 in the V1 of my Bogner Twin jet... Sounded horrible. Downright awful.
 
I pop a 5751 in and out of the PI in my amps for a different feel just to mix things up.
 
I have never found a liking for 5751 in V1 slot, works in V2......try one in the PI slot though, while you're messing with it.

Favorite is NOS GE 5751..I tried a few, including 12AT7s.
 
jkdsteve":35i1h2iz said:
I have never found a liking for 5751 in V1 slot, works in V2......try one in the PI slot though, while you're messing with it.

Favorite is NOS GE 5751..I tried a few, including 12AT7s.
Click to expand...

I have an NOS GE, and a Sylvania. I've been using the 5751 in V2 of my 5150 III 50 watt, and recently switched it over to V3.

I definitely recommend it. It really cleans up the flabbiness thay the blue channel can get, and while not a massive change for channel 3, I find it less compressed, and gain a little more usable, (though still way too much). I run between 9 and 10:00. Perfect, for me.
 
Damn am I glad I saw this thread! Never heard about 5751's before.

Have an FJA Aldrich modded 1976 100 watt JMP that sounds killer but just had a little too much gain. Went from no signal to balls out at around 2 on the preamp gain with no discernable difference after that.

Ordered 3 JJ 5751's from Tubestore.com after reading this earlier this week and took them to the practice space last night. Replaced the 12ax7's in V1 V2 & the PI...leaving the tubes Jerry put in the added clean channel and buffered loop alone.
Sure as shit it worked perfectly....amp is still voiced the same just the gain is reduced. Get's ACDC+ crunch at 2 now on the preamp dial which i now have around at around 5.

Usually play with the master volume around 7.5 and my Pro Rack G was working overtime squelching the feed back Since I can't get more than 8 or 10 feet from it. Now I can even kick in my midi switched Furman pq3 for leads and the feedback is gone. I'm even happier with this amp now. Sounds the same but the gain is totally manageable. Awesome :rock: :rock: :rock: :rock: :rock:

Thanks Rig Talk! For once this place didn't make me spend a bunch of money for no reason :lol: :LOL: :lol: :LOL: :lol: :LOL:
 
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