linear pots in tone stack

[JoshBernstein]

Im currently building a princeton reverb, and have accidentally ordered 250k linear pots for the treble and bass controls instead of logarithmic. What would be the effect of using these anyway? Ive also read that you can make a pseudo-log pot by paralleling a resistor across the linear pot. Could i do that? If so what value resistor should i use?
Thanks!
Josh

[pompeiisneaks]

I don't know about the pseudo pot, but for linear, you'll just get weird behavior on how the pot adjusts your tone pots, Instead of feeling like it impacts tone consistently with the roll of the pot, it will feel like a large portion does very little, and then all of a sudden, you get major change in a very small portion. The audio taper is logarithmic and smooths this out so you get a more linear 'feel' to the dialing of the pot. (i.e. the actual tone circuit is logarithmic, and therefore your pot should be as well, or you get odd behavior.)

There is no change to the actual operating range of the pot itself, just how difficult it is to dial in a specific tonality in some ranges.

~Phil

[brewdude]

http://www.geofex.com/article_folders/p ... tscret.htm

[pdf64]

A linear 250k pot is fine for a BF treble control.
Linear is a 50% taper, BF amps tended to use 30% audio.
Modern standard audio tapers are 10 or 15%.
So linear is as close to the 'correct' taper as a modern audio pot.

It's a different story with the bass; BF tended to use a 10% audio taper, eg so at halfway it's only on 25k.
A linear pot won't work out well there; most of the useful range of control will be in the 1st 1/4 rotation.
The DrZ EZG50 uses linear pots, and its bass control seems a hair trigger.

[M Fowler]

I have notes on the EZG50 using linear taper tone controls and he had changed those out to audio taper which was better.

I regularly work on a local guitarist EZG50 doing both maintenance and some repairs to ground buss broke near pots, recto's burning up and replacing 8AB3A1B reverb pan and uses insulated RCA jacks on the chassis.

These amps are bias shunt method 455v on plates and set to .028mA.

The owner loves this amp because it stays clean for his country band.

I have an original EZG50 head cab in red but after Doc and I talked he decided not to sell me one of his EZG50 chassis, darn it. But I have the correct OT and looking for PT and choke to build a replacement head.

[M Fowler]

Refer to my photo and notes regarding pots in this post, thanks.

http://ampgarage.com/forum/viewtopic.ph ... 6&start=15

From beginning of the thread http://ampgarage.com/forum/viewtopic.php?f=6&t=21056