Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

[STRATDELUXER97]

Curious? I've read several posts on other forums where guys have used either of these tubes in the phase inverter spot to "clean up" the overall tone of their NMV Marshall heads>>>>I've not tryed this,but my amp does get pretty aggressive pretty quickly!

What were the results and was it worth trying?

 

[marvar]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

haven't tried a 5751, but I've tried just about every other tube out there- any PI with a lower gain, such as a 12AT7, or AY7, will give you more clean headroom before the onset of tube distortion, In other words, you can turn your master up higher. You will probably have to turn it up to get the same amount of volume that a AX would give. Give it a try, you may or may not like it. One other thing, most tubes that have less gain, will pass more current.

 

[STRATDELUXER97]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

haven't tried a 5751, but I've tried just about every other tube out there- any PI with a lower gain, such as a 12AT7, or AY7, will give you more clean headroom before the onset of tube distortion, In other words, you can turn your master up higher. You will probably have to turn it up to get the same amount of volume that a AX would give. Give it a try, you may or may not like it. One other thing, most tubes that have less gain, will pass more current.

Once you got your volume up to compensate for the lower gain AT7 though,did it change the overall tone of the amp? Or did it just sound the same,but with lots more headroom? Headroom was where I was leaning....Most of today's 12AX7s are pretty gainey!

 

[kevlar3000]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

I do it often. I actually have a 12Au7 in one of my Traynors. That thing is a screamer. It can really give some clarity w/o neutering the nasty. . I would say I do this in 4-5 of my amps, the 68 Traynor is the only one with the 12AU7 though. It will lower amp volume a bit. Very cool stuff to mess with. I really find every tube position dramatically effects the overall 'feel' of an amp. I am always trying different combos out. I only have a couple amps with the same brand tube in all positions. The rest were just what my ear liked....

Have you messed with the neg feedback wire on different taps? You have it on the 4 ohm right??

 

[marvar]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

Yes, as kevlar says, it affects the 'feel' of the amp- if you are going for a more bluesy tone, give it a try- the PI isn't really a tone shaping stage, except for how hard the signal drives the power tubes.
Most of your older Fender tube amps use a AT7 in the PI position.

 

[kmcguitars]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

I just put a 5751 in PI of my HRD. That with a 12AT7 in V2 makes the harsh O.D. channel very usable. So I imagine it would have a similar effect in a Marshall

 

[STRATDELUXER97]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

I do it often. I actually have a 12Au7 in one of my Traynors. That thing is a screamer. It can really give some clarity w/o neutering the nasty. . I would say I do this in 4-5 of my amps, the 68 Traynor is the only one with the 12AU7 though. It will lower amp volume a bit. Very cool stuff to mess with. I really find every tube position dramatically effects the overall 'feel' of an amp. I am always trying different combos out. I only have a couple amps with the same brand tube in all positions. The rest were just what my ear liked....

Have you messed with the neg feedback wire on different taps? You have it on the 4 ohm right??

I've gone back to the 220k splitter resistors(PIMV Pots now) from 100k that I had before to my output tubes and yes,I'm still 100k NFB resistor at the 4 ohm tap...Thought about trying the 8 ohm tap? Haven't though...Since I can't crank this baby up(Shame really) at our gigs,I'm having to rely on keeping the amp clean with some headroom and use pedals to get my grind...I know I need an attenuator but I have to wait until I have the $$$$$ again! :crying:

 

[STRATDELUXER97]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

I just put a 5751 in PI of my HRD. That with a 12AT7 in V2 makes the harsh O.D. channel very usable. So I imagine it would have a similar effect in a Marshall

Cool thing about my amp....It isn't at all harsh,but I do feel it wants to break just a bit too soon into the "grind" department....The MM choke and OT did this....LOL

 

[Lake Placid Blues]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

Iv'e done it when a Marshall type amp head is needed for bass work, but I like the AX for guitar work. I will swap in the AX in Fenders for guitar work too. Nothing wrong with earlier breakup in my book. Earlier breakup works well with single coils and vintage output pickups. I think the vintage output pickups can be more dynamic and soulful this way.

 

[STRATDELUXER97]

Re: Anyone Ever Try A 5751 Or 12AT7 In Their Marshall's PI Spot?

Iv'e done it when a Marshall type amp head is needed for bass work, but I like the AX for guitar work. I will swap in the AX in Fenders for guitar work too. Nothing wrong with earlier breakup in my book. Earlier breakup works well with single coils and vintage output pickups. I think the vintage output pickups can be more dynamic and soulful this way.

I Like breakup also,but I'm currently using my Marshall at lower volume levels in smaller clubs with pedals and I need the amp round and clean....Unless I get an attenuator?:bigthumb: