Pot taper

[Don]

I just tried an interesting experiment with my PR clone. The amp never had the gain or brightness of my old '68. It sounded really nice- kinda warm and jazzy but lacked punch.

I just replaced the volume and treble pots with a Fender 1m and 250k J taper pots. These pots have about a 25% taper compared to the 10% taper pots in the Mojotone kit.

The old Fender schematic shows "2-35" next to the value for these two pots and the reissue schematic calls out a 30% taper.

I don't know if it's psychological caused by seeing pot positions that I'm used to or if the taper actually makes a difference in the tone of the amp (beyond just increased volume and treble at lower pot settings) but it sounds great! I'm going to have to research this.

[Don]

I'm pretty sure that the difference is psychological. I think we've come to expect certain amps to sound a certain way at certain knob positions. When they don't, something seems wrong.
I used the amp at a rehearsal last night and it sounded great- better than ever.

I had replaced the volume pot in my 1966 Vibrolux Reverb with a regular 10% audio taper pot a few years ago and had another '66 VR in for a repair recently and noticed that mine didn't have the same volume and gain at the same settings. I put a J taper volume pot in that amp yesterday and got the same results that I did with the PR clone. It sounds great!

For me, these pots are a requirement in a blackface Fender amp.

[Meaux]

I'm pretty sure that the difference is psychological. I think we've come to expect certain amps to sound a certain way at certain knob positions. When they don't, something seems wrong.
I used the amp at a rehearsal last night and it sounded great- better than ever.

I had replaced the volume pot in my 1966 Vibrolux Reverb with a regular 10% audio taper pot a few years ago and had another '66 VR in for a repair recently and noticed that mine didn't have the same volume and gain at the same settings. I put a J taper volume pot in that amp yesterday and got the same results that I did with the PR clone. It sounds great!

For me, these pots are a requirement in a blackface Fender amp.

Hummm... I replaced all the Pots and Caps (except the blue ones) in my 60's Pro-Reverb a few years ago and wasn't all that impressed... It didn't sound bad or anything like that, just 'different'... The thing has been gathering dust ever since... I'm gonna check the old ones and see... Thanks...

[mickeydg5]

Most will tell you that things sound better when turned up. That is because in most cases with regards to frequency control and volume the signal is left more unadulterated.

These are logarithmic type action potentiometers.
A 10% taper potentiometer will approximately at 10% of total resistance when at center/halfway.
A 25% taper potentiometer will approximately at 25% of total resistance when at center.

So with a 1M one would be at 100k while the other at 250k. The 150k variance can make a good bit of difference in some circuits.

[Meaux]

So, I dug up the Original Volume and Treble Pots that came out of my 60's Pro-Reverb and sure enough they say 2-35 on the case...

Looks like I'm gonna have another Job on the back burner tll I finish a lot of other Crap...

[Don]

So, I dug up the Original Volume and Treble Pots that came out of my 60's Pro-Reverb and sure enough they say 2-35 on the case...

Looks like I'm gonna have another Job on the back burner tll I finish a lot of other Crap...

If you can, and if you don't mind, check them with a meter and let me know the
reading when they're turned up halfway.

Why'd you replace them? Were they noisy?

[Meaux]

If you can, and if you don't mind, check them with a meter and let me know the
reading when they're turned up halfway.

I'll dig em' back out and give it a shot in after is finish throwing out old junk...

Why'd you replace them? Were they noisy?

Yeah, a few of them were so I replaced em' all while I had the thing apart...