Metropoulos Forum

Hi Guys,

The standard Rich Mod puts each 500K pot in parallel with a 220K bias resistor. When dimed, this gives an effective resistance of 153K which is quite a bit off the stock 220K. Has anyone tried this mod while replacing the 220K resistors with 470K resistors? This would give an effective resistance of 242K which is a bit closer to stock. I think the Alpha pots are more like 450K a side anyway which would get you to 229K (assuming that the 470K resistors are actually 470K, which they may not be). I'm interested in getting fully cranked tones at about 3/4 or higher of full volume (ie. just knocking a bit of volume off) out of my 1987 while still being able to remove the MV as much as possible from the circuit when dimed. I'm playng rock and not blues so a bit of gain at lower levels is not a bad thing.

Is it worthwhile swapping the resistors or will biasing with the mod dimed make this largely unnecessary? Anyone tried this?

I suppose I should ditch the PCB and buy a PTP board from George so I can try these things when the mood strikes me...

Cheers,
Daz.

Thats exactly what I would do. But I would try to make it so that if anything the max resistance will be close as possible without going over. I would use something like 400k. With a 500k resistance it would give you 222k but we know the pot wont be exactly 500k so it could be as low as around 211k. Obviously you should measure your pot first to know what your dealing with.

will changing those resistors have a significant effect on the sound? just curious, is it possible to push/pull the rich mod out of the circuit?

That is how I have my PPIV master installed with the two 470k resistors. It sounds pretty much like the stock amp all throughout the sweep of the master except at very low levels. I tried the master without replacing the resistors initially and the tone was squashed severely. Its a noticible difference. When you attenuate using the master I think it allows the amp to breath more uisng the 470k resistors.