Version1 vs.V2 PPIMV?

Guest · Post by **Guest** » Sun Apr 10, 2005 5:15 pm

Hi, I got my jtm45 "retrograde" kit in the mail ,and in looking at the technical refrenceCDROM that came with the kit, I see that there are 2 different ppimaster volume mods. V1 has 2 extra caps and a double pot, and V2 has no extra caps and I think a different value double pot. I'm installing the kit in a bluesbreaker reissue so, I can mount a pot in an extra tremelo pot space. What is the tone difference between the two different PPI master volumes? thank you , Chris

Dax-The-Ax · Post by **Dax-The-Ax** » Sun Apr 10, 2005 8:14 pm

Most people prefer the "Rich Mod" It's the one without the extra caps. I put one in my 1987 and it sounds really good. I put in a 1Meg pot at first and it kind of dampened the sound. Went back to stock PPIMV 2 and it rules. Go with PPIMV 2, you will be happy. And, i don't really know the tonal differences, i haven't heard of anyone installing the PPIMV 1.

Guest · Post by **Guest** » Mon Apr 11, 2005 8:11 pm

OK I guess I'll try out the version 2. Thanks for the advice, Chris.

Post by **VelvetGeorge** » Mon Apr 11, 2005 10:16 pm

It seems like I should just stop offereing the type ! kit. Everyone prefers the type II, and for good reason. It sounds better.

I intially offered both because some people take issue with the bias voltage being referenced through a 1/2 watt pot on the type II.

George

erigm · Post by **erigm** » Tue Apr 12, 2005 2:45 pm

Kevin O'Connor suggest to use larger caps in Version 1 type PPIMV. For example, your PI coupling caps come first, then to the dual pot, then to the extra caps (which should be at least ten times (10x) the value of the coupling caps, and should be rated for at least 100V) then to the junction of the bias and grid resistors. This should help with the bass rolloff as the volume is turned down.

Also, there was concern with the bias voltage being fed throught the wiper of the pot, and if that was ever to open the tube would run away. Kevin O'Connor suggests that in this circuit a resistor should connect the wiper to the bottom of the pot, so the grid will always recieve bias, even if the wiper connection fails.

I have tried version 1 and have found it to be very good. I have not tried version 2

Billy Batz · Post by **Billy Batz** » Tue Apr 12, 2005 6:54 pm

erigm wrote:Also, there was concern with the bias voltage being fed throught the wiper of the pot, and if that was ever to open the tube would run away. Kevin O'Connor suggests that in this circuit a resistor should connect the wiper to the bottom of the pot, so the grid will always recieve bias, even if the wiper connection fails.

Thats exactly how the rich version is designed. The fixed bias splitters are still there so that if the wiper and tracks fail to make clean contact the bias is still on those resistors.