The phase inverter

[JeffB]

Frankly, idk much about these..only that it affects how the pre works with the power amp.

I never gave the pi tube much thought. I jammed in the mullard ri I had as internet scuttlebutt says that it is a good choice for that position. Ive been playing for months with it. I came across some more scuttlebutt that said in some amps it can make a large difference what tube is in the PI and you can try subbibg something lower gain to change how the amp feels and whatnot.

I can tell ya in the OR15, that is the case. I slapped an old JANGE5751 in therr and its like I got a new amp. The amp feels spongier and opened up in the top end. In fact, I did not like it with a pair of H30s cos it was too stiff and too dark and low notes mushed together in an unpleasant way under distortion.. Completely opposite now..I LOVE it with the h30s.

I gotta try and get a clip made. I think I have dialed up my best tone maybe ever. Even better than my old 1987.

 

[Gone_Shootin]

Re: The phase inverter

The PI is actually part of the poweramp, so I guess you could look at it as the input stage of the poweramp. In layman's terms, the PI tube along with it's circuit, takes the mono signal coming out of the preamp and turns it into two equal signals, or at least in theory because variances tend to leave things slightly unbalanced, even in tubes with "matched" halves, and feeds each half of the signal to each half of the poweramp. It's actually a little more involved than that, but that's the basic jist.

As far as gain ratings and types go, they effect how much headroom a poweramp has. A higher gain PI tube will break up earlier, whereas a lower gain will give you more headroom and later breakup. Here's a page that explains it all better than I can. http://www.thetubestore.com/Resources/Guitar-Amp-Info/Gain-Factor
And this one has a chart with gain ratings of various tubes. http://www.300guitars.com/articles/preamp-tube-gain-factors-and-substitution-chart/

As far as my personal preference goes, JJ 12AX7s have become my fovorite for the PI, because I've discovered that they make my distorted tones growl a little more than other tubes. Which leads me to another point. The PI tube is one of the key positions for putting the final touches on an amp's tone, as you have discovered.

 

[Demanic]

Re: The phase inverter

Love JJ's. They sell the best balanced PI tubes. That little bit of variance is what gives tube amps their depth.

 

[JeffB]

Re: The phase inverter

The PI is actually part of the poweramp, so I guess you could look at it as the input stage of the poweramp. In layman's terms, the PI tube along with it's circuit, takes the mono signal coming out of the preamp and turns it into two equal signals, or at least in theory because variances tend to leave things slightly unbalanced, even in tubes with "matched" halves, and feeds each half of the signal to each half of the poweramp. It's actually a little more involved than that, but that's the basic jist.

As far as gain ratings and types go, they effect how much headroom a poweramp has. A higher gain PI tube will break up earlier, whereas a lower gain will give you more headroom and later breakup. Here's a page that explains it all better than I can. http://www.thetubestore.com/Resources/Guitar-Amp-Info/Gain-Factor
And this one has a chart with gain ratings of various tubes. http://www.300guitars.com/articles/preamp-tube-gain-factors-and-substitution-chart/

As far as my personal preference goes, JJ 12AX7s have become my fovorite for the PI, because I've discovered that they make my distorted tones growl a little more than other tubes. Which leads me to another point. The PI tube is one of the key positions for putting the final touches on an amp's tone, as you have discovered.

Thanks for the explanation and links. Very helpful :bigthumb: Im amazed at the difference it made. Much more open, less congested and overly gained out. And it has a nice bouncy feel, not stiff. It sounds and feels more "vintage", if you will.

 

[JeffB]

Re: The phase inverter

Love JJ's. They sell the best balanced PI tubes. That little bit of variance is what gives tube amps their depth.

The amp came with JJs ecc83s' allaround. I have never liked them in the V1 spot, so when I got the amp I immediately started tube rolling and thats when the Mullard RI went in the PI. I may give the JJ a try again in the PI at some point.

 

[ken361]

Re: The phase inverter

I use a Sylvania Baldwin in the PI in my DSL , PI's are important the LPS is a decent tube also

 

[jeremy]

Re: The phase inverter

i like the sovtek lps as a pi tube for lots of amps

 

[Darg1911]

Re: The phase inverter

It was suggested to me by Doug (Dougs Tubes) that the Sovtek 5751 was also worth a try as a PI. He didn't feel that it was worth a chitlin for much of anything else. I haven't tried it.

 

[Rex_Rocker]

Re: The phase inverter

I like the Sovtek 12AX7LPS if I want to fatten up the sound of a brighter power section or the JJ ECC803S if I want to brighten up the sound of a warm power section.

With my amps (Peavey XXX and Krank Rev Jr.), I like the Sovtek better, but it can get a little tubby, and I have to back off the lows a little compared to other tubes. Nice smooth tone and open-ness, though.

 

[Gone_Shootin]

Re: The phase inverter

Love JJ's. They sell the best balanced PI tubes. That little bit of variance is what gives tube amps their depth.

Yep, and the extra depth that those variances create is exactly why I don't use balanced PI tubes.

 

[Gone_Shootin]

Re: The phase inverter

Thanks for the explanation and links. Very helpful :bigthumb: Im amazed at the difference it made. Much more open, less congested and overly gained out. And it has a nice bouncy feel, not stiff. It sounds and feels more "vintage", if you will.

Yep, it's amazing how much difference it can make. And don't be afraid to try different brands and compatible types, you may find something you like more.

Tube rolling is fun.