#1
I read a thread awhile back that talked about swapping a 12AX7 in V1 for a 12AT7, and the result was at least a partial elimination of some of the top-end fizz that the 6505+ has.

I have all JJ 12AX7s in my 6505+ 112 right now, but am interested in getting rid of some of that fizz. (It's not that bad, but if I could get rid of it, I would.)

The question I have is, seeing how a 12AT7 has a gain factor of 60 as opposed to a 12AX7's 100, would that cut too much gain?

I mean, I really want the same tone, just without some of that fizz. I don't want it to sound like a hard-rock amp -- I still want the Br00tz!

I realize the $10-12 I might spend finding out may seem trivial, but money is hard to come by these days...

Thanks for any help/insights anyone might have! *Cough, Cathbard, Cough*
Atmospheric dark metal w/ black and death metal influences:
(My Soundcloud page):

Pestilential Flood
#2
It would thin out the amp considerably, but as you said, for 10-12 bucks why not?

Sounds to me like more of a speaker problem.
#3
If you just put a 12at7 in V1, you won't lose that much gain. V1 has the most effect on the overall tone of all the preamp tubes, but with so many gain stages after V1, you won't lose much gain. Besides, you're not running the gain maxed out are you?

For a comparison, I have a Peavey Ultra+, which is similar to the 6505/5150, and I replaced my 12ax7s with GE and RCA 5751s, which are about 70-90% of a 12ax7s gain, and I only had to turn my gain knob up 1 or 1-1/2 to match the gain I had with all 12ax7s. Obviously I had to spend more than $10-12 on that, but that's just a comparison to show you shouldn't lose much gain with the at7.

EDIT: ^ that Eminence is a pretty good speaker, so I don't necessarily think that would be the problem IMO. If it still had the Sheffield in it, I'd say yeah, but not with an Eminence.
Ibanez UV777 - Carvin TL60 & 727 - Jackson KE3
Splawn QuickRod - Mesa Stiletto & RoadKing - Peavey Ultra+ - Peavey Bandit
Some pedlulz & cabz


7 String Legion
Last edited by BCKRedBaron at Feb 29, 2012,
#4
As you know, it worked for me. Admittedly, with some guitars i still have some fizz, but it definitely reduced the fizz, and i really leave the knob about the same. No real loss of brootz, no need to worry
I'm just a kickin' and a gougin' in the mud and the blood and the beer.
#5
Quote by Strats&Cats
It would thin out the amp considerably, but as you said, for 10-12 bucks why not?

Sounds to me like more of a speaker problem.


If your using the Peavy Cab I would try using another. I played a 5150 through an Engl cab and it sounded like a totally different amp.
#6
@BCKRedBaron:

No, I'm not running the gain even close to maxed out. My standard setting (lead channel, of course) is between 3 and 4 depending on what I want to play, with a TS9 as a boost (gain: 0, level: 10). Sometimes I'll turn the TS9 off and turn the gain up to 7 for a different tone on some stuff.

Actually, I didn't even notice the fizz until a recent purchase of a Boss Hm-2, which I use in the loop with the lead channel. That pedal takes away all the fizz and adds this super deep, raunchy distortion which is great for death metal. But my main metal tone with the TS has a more midranged voice, and would be perfect without the fizz.

Even with the presence knob on zero it still has it, but it's definitely worse with the presence at 6 or more. I'd rather have to turn the presence up to get more bite than fight to get it under control.

@dementiac captain:

I think it was your thread I was reading. Thanks for the comments; I think I'll try it!
Atmospheric dark metal w/ black and death metal influences:
(My Soundcloud page):

Pestilential Flood
#7
Another possibility you could try is an EQ pedal, like an MXR 10-band, and cut the highest frequency shelf and see what that does. From some of what I've read a tubescreamer in front and an EQ in the loop really work wonders.
Ibanez UV777 - Carvin TL60 & 727 - Jackson KE3
Splawn QuickRod - Mesa Stiletto & RoadKing - Peavey Ultra+ - Peavey Bandit
Some pedlulz & cabz


7 String Legion
#8
Try a 5751, they have a gain of 70. A 12AT7 may be going a bit far. You could always boost it to get back to the brootz but I think you'd be better served by a 5751.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
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Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#9
^^Any specific brand of 5751? I like the dark character of the JJs I have, but I don't think they make a 5751. I definitely don't want anything too bright. Something very rich in harmonics would be the ticket I think...
Atmospheric dark metal w/ black and death metal influences:
(My Soundcloud page):

Pestilential Flood
#10
Well if you can find an RFT I'd grab it but otherwise go for a JAN Phillips or even a GE.
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#13
I don't have a 6505, but I've done a V1 swap from 12ax7 to 12at7 in a couple different amps and had the exact result you're looking for--a cut to the highs and mild drop in overall gain that left me with a lot less "fizziness' when I finally adjusted everything back up to the gain I used before.

I understand that it might be a bit too far in some cases, but if you're not really using a lot of the gain on tap to begin with, it's not going to be an issue IMO.
#14
^^Well, I realized a while back that too much gain just doesn't let the natural sound of the guitar go through. I figure if I have much of a gain cut, I've still got 3/4 of the gain on tap to bump it back up. Plus, I'm running my TS with zero gain; I could add a little there.

I like the tone I'm hearing from my amp, but cutting those really high frequencies would probably be perfect. I actually ordered a JJ 12AT7 last night, just because they're cheap and I'm in the experimental stage right now.

If I like what it does I'll probably consider getting a more expensive NOS tube in a 12AT7 or 5751. I just didn't feel I could justify $35+ until I'm sure it's what I want.

Thanks to all who responded!
Atmospheric dark metal w/ black and death metal influences:
(My Soundcloud page):

Pestilential Flood