PPIV Master Volume question

Necrovore · Post by **Necrovore** » Tue Jul 13, 2004 11:39 pm

I have just finished installing this mod in my Marshall.
George I am not using the kit that I bought from you, I used a dual ganged 500k pot and two 470 ohm resistors.

I am questioning the overall volume drop that I am getting now. Following instructions from Jon, I swapped out the 220 ohm resistors with 470 ohm 1/2watt resistors.

I removed the orange and green wires that ran to one side of the resistors leaving the 47picofarad disk cap in place.

I ran the green wire to the middle lug on the pot closest to the shaft(a) and the orange to the middle lug on the pot furthest from the shaft(b).

Ran one wire from the right lug on pot a to where the green wire connected to the 47picofarad cap. Another wire from right lug on pot b to where the orange wire connected to.

On the left pot lug I jumped a wire to both pots and from left lug on pot b to where the 470 ohm resistors connect to each other.

With the "new" master volume dimed I rebiased the amp to 37millivolts using the cathode resistor method of biasing. Tone pots were set to 12 o'clock and volume I&II were both at 0 while biasing.

My question is this: When I have the MV dimed and turn up the Vol I or II and dime them I am experiencing a dramatic overall volume drop. I get nothing more now than a nice respectable bedroom level volume. Jon informed me that diming the MV would essentially remove it from the circuit and would act like it was not there.

Oh yeah almost forgot. I had to remove the D.I. jack which called for cutting a jumper wire from one of the speaker jacks to the D.I. jack, removing a black wire from the ohm selector switch and while looking at the ohm selector switch while the amp is upside down the rightmost lug on the top (as im looking at it, yellow wire connected to it)had a 2100ohm resistor tied to a lug directly below it(as i was looking at it). I removed this resistor as well.

I am curious if I have done anything wrong doing this installation. I would like to still be able to have this amp roar and right now it sounds like something is holding it back. I do like the tone though.

Post by **VelvetGeorge** » Wed Jul 14, 2004 12:59 pm

Jon uses a variation on the type II mv tkit that I sell. Maybe he will jump in here.

Jon??????

George

Necrovore · Post by **Necrovore** » Thu Jul 15, 2004 3:50 pm

Ok I figured it out. Dumbass me installed 470ohm resisters in r26&27 instead of 470k. Had it written right there on my schematic too.

flemingmras · Post by **flemingmras** » Fri Jul 16, 2004 2:10 pm

Ain't that a bitch!?!?

The "variation" George speaks of that I do is that with a 500K pot I change the 220K resistors to 470K resistors. With the 500K pot in parallel with these this puts the grid load in the 220K-250K range(about 242.something K). Whereas with the stock 220Ks in parallel with the 500K pot, this drops the grid load down to about 150K. This is why I use the 470K resistors in place of the 220Ks.

However, if you were to use a 250K dual pot, this would eliminate the need for these resistors altogether as the pot would replace these resistors.

Jon

flemingmras · Post by **flemingmras** » Fri Jul 16, 2004 2:14 pm

Ain't that a bitch!?!?

The "variation" George speaks of that I do is that with a 500K pot I change the 220K resistors to 470K resistors. With the 500K pot in parallel with these this puts the grid load in the 220K-250K range(about 242.something K). Whereas with the stock 220Ks in parallel with the 500K pot, this drops the grid load down to about 150K. This is why I use the 470K resistors in place of the 220Ks.

However, if you were to use a 250K dual pot, this would eliminate the need for these resistors altogether as the pot would replace these resistors.

Jon

Guest · Post by **Guest** » Fri Jul 16, 2004 7:22 pm

Yeah you mentioned that to me one time. I like the way this sounds, Now I can finally play without getting a headache. Though I did notice that VolumeII is not as responsive as it once was, BUT what is does now is completely enough.

flemingmras · Post by **flemingmras** » Sat Jul 17, 2004 11:06 am

This is because the amp is at a lower volume. With that master volume cranked, it takes itself out of the ciruit so this should return the amp back to stock so the bright volume should work just as it did before with the master volume cranked. However with it at a lower volume, the ear is less sensitive to higher frequencies, making it seem like it's less responsive, so you can use it as a gain control.

Jon