PPIMV question

[hebaton]

IN the PPIMV installation, the two 220K resistors on the bias are removed before going to the Pot.
How does not affect operation / tone. With the pot at max ( supposedly no influence ) the system is not operating as if those were in place .
I am considering removing this Master since, I don't use it anyway, I find that maybe the first 10% attenuation does not affect tone to much but past that, it s destroying the tone, at least to my ears.

The is also an effects loop in the unit I have. I am told it is the Metropoulos solution. I don’t understand why it has connections to the Treble and mids pots ?
Anyone can explain ?

Thanks everyone.

[thetragichero]

i think you're misinterpreting what the master volume does. take a look where lugs 1 are connected... do ya see it?

[hebaton]

You are probably right. I hve very little knowlage of thgese things. But If I look at a stock JTM45, there are a couple 220K reistors where those lugs are no ?

[pompeiisneaks]

There are always 2 high resistance resistors like 1-2M range added to the circuit as 'safety' to guarantee the bias voltage stay's there in circuit, i.e. it's not going to make the bias disappear, even if the wiper somehow loses connectivity.

~Phil

[romberg]

In a LarMar PPIVMV the 220k grid leak resistors are *replaced* by a 250k pot which also has a 2m2 safety resistor from the bias suppy to center wiper. The pot does exactly the same thing in the circuit that the 220k resistors did. When the pot is all the way up you have a resistance of 250k in parallel with 2m2 which comes out to 224k. There is little chance that your ears can hear the difference between 220k grid leaks and 224k grid leaks . For all intents and purposes the master volume is not even there and the circuit is identical to the non-MV one.

Mike