Interesting PPIMV issue...

[MHProd]

So I just installed a Lar/Mar PPIMV in my JTM45 build. I wasn't really convinced this was going to give me a good sound since I read so many people saying it makes the top end fizzy when you turn it past halfway.

Well, I don't have this problem. The MV works really well, even at super low volume I still get plenty of tone, however, all my top end is gone. I have to max out the Treble and Presence. It doesn't sound bad, but even when I'm halfway, I find myself turning the Treble up. And the Bass becomes huge too. In normal operation, the Bass is usually on 4 and Treble on 6 or 7. With the PPIMV, the Bass is on 1 and Treble on 10.

What do you guys think?

[SteadyEddie]

That's my experience.

[coldengray]

Same for me - anything less than 50% and the treble is gone, bass is huge and loose. Fizzy at low volumes too, at least for me.

[Scumback Speakers]

Huh, I was just over at a guy's house where he put this in (dual 250k pot, etc) and when I turned the PPIMV to less than 1/2 I had to turn the bass and mids up because it got too trebly.

What preamp tubes & speakers are you running with the amp?

[stef]

The PPIMV changes NFB and I find the NFB circuit very important for both sound and feel. I hate to have as many different sounding "amp settings" as 10 dials on the PPIMV.

[coldengray]

I read somewhere that a 250pf cap in parallel with the existing 47pf PI cap could tame the side effects of using the LarMar MV.

I'm running new production JJs in the preamp right now...they came with the amp. I have plans to change that soon. Neil told me if you're using a PPIMV you need a solid PI tube...like a NOS CV4004.

[MHProd]

Huh, I was just over at a guy's house where he put this in (dual 250k pot, etc) and when I turned the PPIMV to less than 1/2 I had to turn the bass and mids up because it got too trebly.

What preamp tubes & speakers are you running with the amp?

I know!!

Most reviews of the PPIMV reflect the opposite issue (amp becomes too bright) while here it seems to acts like a Cut control. I used shielded wire and a pot from Valvestorm.

Using a mix of NOS and modern glass.