Split-load vs. long tail pair: Tonal/Vibe differences?

[dehughes]

Hey there,

I'm contemplating my next build and am curious as to what the tonal/vibey differences are between a split-load and a long tail PI. I'm toying with the following ideas:

1) EF86 preamp (essentially an AC15 preamp) into a long-tail PI into a cathode biased 5881 pair.

2) JTM-45 preamp into a split-load PI into a cathode biased pair of 5881s.

or?

3) EF86 preamp into a full tone stack then into one 12AX7 triode (gain recovery?) then into a split load PI and off to a cathode biased 5881 pair.

I was contemplating building just a 6G6-B, but then changed my mind and wanted to go JTM-45, but now I'm toying with all sorts of ideas yet I'm hung up on the PI and how it would affect change in the amp as a whole. Until this point I've stuck with LTPIs, but I have a thing for Princetons and I know some of that magic is in the PI (same with 5E3, etc...).

Thoughts?

[tubeswell]

I hate to say it man, but you'll have to build all three of them. And then you'll have to tweak them and change them. Nobody here can help you with your problem unfortunately. Start with #1 on your list.

[dehughes]

I hate to say it man, but you'll have to build all three of them. And then you'll have to tweak them and change them. Nobody here can help you with your problem unfortunately. Start with #1 on your list.

HA! Thanks man. I was afraid someone would say that.

I suppose I'm mostly hoping to find someone that's heard a split-load and long-tail PI in the same amp, so that I could know what the differences are between the two in context. I know what the differences are on paper, but not in reality. Once I get a good mental handle on the differences between the two then I'll know which direction to head.

[JoeM]

...
I suppose I'm mostly hoping to find someone that's heard a split-load and long-tail PI in the same amp, so that I could know what the differences are between the two in context....

Well, I kind of did. I have a '65 non reverb Princeton. The AA964 circuit. Even on '10' it was still a bit clean, so I changed the PI to a LTPI. (Took out the trem which I never used anyway). More gain of course, but I dont really think at lower volumes it sounded a whole lot different. Of course I'm going on memory and it must have been over 30 years ago that I changed it.

[dehughes]

Well, I kind of did. I have a '65 non reverb Princeton. The AA964 circuit. Even on '10' it was still a bit clean, so I changed the PI to a LTPI. (Took out the trem which I never used anyway). More gain of course, but I dont really think at lower volumes it sounded a whole lot different. Of course I'm going on memory and it must have been over 30 years ago that I changed it.

Oh! Very cool! So, it was more of a gain thing, then, in your recollection?

I suppose that's good to know...as I'm not looking for clean, really, but rather the opposite: Less headroom, and a smooth transition from clean to overdriven.

[imaradiostar]

I'll say this- I've built #1 and while not a "clean" amp, it rules.

I recently proto'd an amp that was 6au6-volume-6u8 pentode-volume-6u8 triode split load PI-cathode biased 6l6's. It reminded me of Live at Leeds.

Lotsa usable sounds to be had there!

You might try a 6u8 triode into tone controls (matchless style) into pentode into PI of your choosing.

jamie

[melvin]

I think the long tail always sounds better. It allows for more power tube break-up. The split-load always sounds too wooly to me. It can be a bottle-neck.

[tubeswell]

I like both types in different amps I have tried and/or built.

5E3s and AA1164s sound awesome for the case of split load PIs.

5F6As and 5G9s sound awesome for the case of LTPs.

[dehughes]

Interesting. So, there is a reason certain combinations have stood the test of time, huh...

[JoeM]

Oh! Very cool! So, it was more of a gain thing, then, in your recollection?

I suppose that's good to know...as I'm not looking for clean, really, but rather the opposite: Less headroom, and a smooth transition from clean to overdriven.

As I mentioned, it was a long time ago. Seems that I had the impression the sound was slightly 'thicker' with the LTPI, but the overall tone didnt change. In that amp, I like the additional gain.

I like both types in different amps I have tried and/or built.

5E3s and AA1164s sound awesome for the case of split load PIs.

5F6As and 5G9s sound awesome for the case of LTPs

Yeah, I agree with that. For example, I wouldn't personally think a 5E5/5F4/5E7 type circuit would be right with a LTPI or a 5F6 with a split load. But that's just me. There's no reason you can't experiment.

[ben-horn]

Hi,
I'm now on a 5E5-a and tried all 3 pi-Types.
Unfortunately it always takes some time to rewire the PI and so it's not an
quick A/B comparison.

Only my impression:

LTP: lot of gain, very clean and smoth breakup.sadly a tad cold/thin sounding.
My 5E5 sounds like a low power Bassman

Split load: warmer sounding as long it's clean.same gain as LTP(when you use the second triode as gainstage).When it clips itself wich is early,it is very raw
and dirty.I think the Split load is a big part of the 5e3 Neil Young sound.
There is no way to get this kind of distortion with a LTP.

Paraphase: very thick and juicy.less articulate than LTP but very musical.
lot of gain.the clean sound is somewhat smeary.
I like it very much but it is special sounding.

[dehughes]

Very cool, ben-horn. Great summation.

[Iplayloud]

I think the lack of negative feedback makes for a terrible out of control distiortion ALA Neil Young too ?

[Jag]

Split load never really cleans up (or what we call clean anyway) but I like the sound. Woolly and warm describes what my ears hear. Definitely not tight and bright.

Yeah, going without NFB definitely ups the rat factor.