Which position is the Phase Inverter?

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ners

ners

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I'm assuming its the 4th tube furthest on the right, but figured I'd double check (and also assuming V1-3 starting left-to-right).

Started fucking around with preamp tubes in all my amps.
 
ners said:
I'm assuming its the 4th tube furthest on the right, but figured I'd double check (and also assuming V1-3 starting left-to-right).

Started fucking around with preamp tubes in all my amps.
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Yep it’s the one closest to the power tubes.

V1 is the first input stage, only uses half the tube.

One half of V2 (V2A) is the second gain stage.

Second half of V2 (V2B) is the switchable 4th gain stage. The extra stage is inserted between the regular 2nd and 3rd stage. Not up front like a lot of amps.

V3A is the normal 3rd gain stage.

V3B is the cathode follower

V4 is the PI

Let us know which tubes you settle on. I actually like JJ’s, which I put in all my amps. They especially make a phenomenal PI tube. Tung Sol and Chinese sound killer too. Chinese have more saturation usually.
 
So I swapped the bad JJ I had in V1 with a Shuguang based on your reco and thought that was a massive improvement, definitely agree with the saturation and maybe some extra freqs or clarity? Hard to tell due to the original JJ going bad. Don't think I'd go back to a JJ for the V1.

Swapped in a Tung Sol for the PI since that was my most balanced 12AX7 on hand, didn't notice much change and the the original JJ was just as balanced and same gain level according to my Orange tester so wound up leaving it in.

I've got a couple Mullards I could try out too.

The amps been noisy lately and I thought it was the tubes but after swapping out a bunch and testing every single one I finally remembered I have the front MV and gains basically maxed lol, so that's on me.
 
Oh yeah, that'd be pretty hairy with them maxed out. I think of it as being a really quiet amp given the amount of gain it's got.

I don't usually run preamp much higher than 6 or 7. Gets too wooly for me and loses clarity. Gain trim can me maxed without losing definition. I'm sure you've already figured out how preamp adds lower frequency gain and Gain trim adds more of an upper frequency gain. They're useful for balancing the thickness and response of the gain.

I've tried Chinese in v1 and my findings were similar. More saturated. They work well in there.
 
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On the modern voicing I find myself maxing the Bass and Preamp, though I suspect if I went lower than Drop C or used a more modern pickup than a PAF then I wouldn't need to.

Planning to pickup something more suited to drop turned metal than my LP and thinking that will help me dial some stuff back.

Definitely a low noise amp!
 
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