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Vintage threads from the first ten years

Marshall Plexi RI Vol. Pot. Linear Or Audio?

8/19/2000 9:07 PM
Spencer	Marshall Plexi RI Vol. Pot. Linear Or Audio? Why does the volume on Marshall 1987X Plexi RI's come up so quickly? Is this due to a linear taper volume pot? If so, can it be replaced with an audio taper pot for a more useable volume control? Thanks.

8/20/2000 10:00 AM
Liam	Can't remember, but I've got a feeling they're audio taper, and it's the circuit design that pulls the volume up so quick. Might be worth trying a handful of audio taper pots from different sources. I'll be trying this on my 1987 in a few weeks, so I'll let you know what happens. Liam

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8/21/2000 11:01 PM
Ken McGill	If you take the bright cap off Channel 1 volume pot or put in a reduced value cap ie:100pf or 470pf the pot tapers more smoothly.This is a quite usefull and easy mod for tone as well at less than full on volume.I own a 1987X and did this simple mod and have been happy with the results. Ken

8/27/2000 4:32 PM
Cliff	For what it's worth, I tried this on my 1987X with a 250 pf cap... big improvement in manageability; very effective !!!

8/29/2000 3:28 AM
Gord	I've never played on any of my amps through a channel with a cap across the volume pot. Way too thin sounding for my tastes. Whatever that may be worth. GOrd

8/29/2000 6:40 AM
Peter S	Spencer, You can take the 500pf cap off and it will help alot.....if you use the amp at low volumes and find the sound too dull, put a 100pf cap on the volume pot. This will give you the high end sparkle without the overbearing midrange of the 500pf. Also, the taper of many audio taper pots frankly sucks. Stick a good audio taper pot in there with 30% taper and you will have much more control over the volume, and the amp will distort much later in the rotation. The lower gain distortion sounds will also be much smoother if you are still using a bypass cap on the volume control. The only pots I use are Clarostats and I can turn my amps up to about 6 before they really start to breakup. Between 7 and 10 is where all the distortion lives. By the time you are up to 7 or so the brightness cap is already out of the circuit and the distortion is much better sounding. Peter S

8/29/2000 6:40 AM

Peter S

Spencer,
You can take the 500pf cap off and it will help alot.....if you use the amp at low volumes and find the sound too dull, put a 100pf cap on the volume pot. This will give you the high end sparkle without the overbearing midrange of the 500pf. Also, the taper of many audio taper pots frankly sucks. Stick a good audio taper pot in there with 30% taper and you will have much more control over the volume, and the amp will distort much later in the rotation. The lower gain distortion sounds will also be much smoother if you are still using a bypass cap on the volume control. The only pots I use are Clarostats and I can turn my amps up to about 6 before they really start to breakup. Between 7 and 10 is where all the distortion lives. By the time you are up to 7 or so the brightness cap is already out of the circuit and the distortion is much better sounding.

Peter S

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