Another PI question - 12ax7's

[CTN]

For those who've experimented with PI's in high gain amps:

could you give me a run down of the types of characteristics brought to the table by various brands of 12ax7?

Cheers!

[mwalluk]

Re: Another PI question - 12ax7's

I would like to know as well. Also what charecteristic / brands are the best for V1, V2, V3, V4....................... sorry for thread hijack

[Maynardo]

Re: Another PI question - 12ax7's

Best to me at least in v1, RCA short grey plate... spongy, full with enough bass, treble and mids and kind of a 'chorusy' character to cleans.

[misterwhizzy]

Re: Another PI question - 12ax7's

Convoys, I did quite a bit of experimenting with the PI in my Jet City, and by FAR the best change I EVER made to that amp was putting a 12AU7 in that slot.

I put a Tung-Sol, an EHX, a Mullard RI, a Sovtek LPS in there. There were minor differences. Then I paid $10 on the recommendation of a very knowledgeable guy on a JJ 12AU7, and it's the best thing I have done to that amp, including replacing all tubes and biasing properly.

[glassman]

Re: Another PI question - 12ax7's

There isn't a lot difference between different brands of 12AX7 in the PI position. Subtle is about a good as you're going to realize. Like Will (Misterwhizzy) said, switching to a different type will be more dramatic. 12AU7s and 12AT7s will give you more of a difference but it's still not going to be dramatic. 12AY7s aren't a great choice though; they tend to sound like a worn out 12AX7. I do have a few customers that prefer the midrange focus of a worn out tube so I can't really say nobody would like that tone. I actually do in some amps.

The PI isn't really very sensitive to tube substitution. Going from a worn out tube to a fresh tube of the same type will make quite a bit of difference; primarily in bandwidth but overall, it's a small swing and not a big one. Don't be afraid to experiment.

[FretFire]

Re: Another PI question - 12ax7's

I'm a fan of the Sovtek 12AX7LPS in the PI spot. I have one sitting here waiting to go in my new amp when it lands!

[ken361]

Re: Another PI question - 12ax7's

Lps also

[CTN]

Re: Another PI question - 12ax7's

Convoys, I did quite a bit of experimenting with the PI in my Jet City, and by FAR the best change I EVER made to that amp was putting a 12AU7 in that slot.

I put a Tung-Sol, an EHX, a Mullard RI, a Sovtek LPS in there. There were minor differences. Then I paid $10 on the recommendation of a very knowledgeable guy on a JJ 12AU7, and it's the best thing I have done to that amp, including replacing all tubes and biasing properly.

What'd the change sound like? what'd it sound like before?

There isn't a lot difference between different brands of 12AX7 in the PI position. Subtle is about a good as you're going to realize. Like Will (Misterwhizzy) said, switching to a different type will be more dramatic. 12AU7s and 12AT7s will give you more of a difference but it's still not going to be dramatic. 12AY7s aren't a great choice though; they tend to sound like a worn out 12AX7. I do have a few customers that prefer the midrange focus of a worn out tube so I can't really say nobody would like that tone. I actually do in some amps.

The PI isn't really very sensitive to tube substitution. Going from a worn out tube to a fresh tube of the same type will make quite a bit of difference; primarily in bandwidth but overall, it's a small swing and not a big one. Don't be afraid to experiment.

What kind of differences can I expect with a 12au7 vs a 12at7?

[ken361]

Re: Another PI question - 12ax7's

What'd the change sound like? what'd it sound like before?



What kind of differences can I expect with a 12au7 vs a 12at7?

they have less gain then a 12ax7

[misterwhizzy]

Re: Another PI question - 12ax7's

What'd the change sound like? what'd it sound like before? What kind of differences can I expect with a 12au7 vs a 12at7?

It just drove the power section too hard. It was less detailed, and there was a little less headroom. When I put the Mullard in there, it almost sounded like Queensryche's post production sound. It was too smooth, not as much response to what was going on on the fingerboard, etc.

When I got the 12AT7 in there, it made a little bit of difference, but not that much. The 12AU7 filled out the sound, increased the headroom, and gave more detailed preamp structure to the sound. If I understand it right (and Jerry, feel free to correct me), Soldano's preamp design tends to drive the PI pretty hard, and if you lower the gain out of that section, it lets the power amp do its job a little more easily.

[CTN]

Re: Another PI question - 12ax7's

interesting...

I think I'll pick up a couple of 12au's and have at it!

[glassman]

Re: Another PI question - 12ax7's

+1 to Will's explanation.