strange volume pot problem

[M P-Bass]

Hello everybody

I have a problem all you electronic whizzes might have a solution to. Here goes. I've just finished building my very own bass from replacements parts, but I've think there might be a problem in the electronics, which I soldered my self. The bass is fitted with Nordstrand nj4 singlecoils and a Noll preamp. The preamp came with all pots, battery-clamp and jack presoldered, so all I had to do was to solder the pu's to the harness. Everything seems to work properly except the volume pot. When I turn the pot there isn't any output until the pot is turned about 80%, and at full the output isn't very loud. Any suggestions?

[PilbaraBass]

Originally Posted by M P-Bass

Hello everybody

I have a problem all you electronic whizzes might have a solution to. Here goes. I've just finished building my very own bass from replacements parts, but I've think there might be a problem in the electronics, which I soldered my self. The bass is fitted with Nordstrand nj4 singlecoils and a Noll preamp. The preamp came with all pots, battery-clamp and jack presoldered, so all I had to do was to solder the pu's to the harness. Everything seems to work properly except the volume pot. When I turn the pot there isn't any output until the pot is turned about 80%, and at full the output isn't very loud. Any suggestions?

this is a common problem on passive basses using linear pots.

That is because volume really needs audio taper to get a linear-sounding signal...my Yamaha RBX170 has this issue and I just live with it.


It does seem a little strange, however, for an active circuit to be doing this, again it is a taper issue, but one would think that the preamp manufacturer (noll) would have designed his circuit with an audio taper on the gain circuit.

As far as the apparent low output...i'm not familiar with Noll pre's so I don't know if this is just a characteristic of their pre

[Scott in Dallas]

It's probably an audio taper pot which is why you don't hear anything until 80 percent. The pot itself is probably good.

[pkr2]

If the pot is the right value, but just the wrong taper, the effect would be nowhere even remotely as severe as this problem. He said that there was NO output through the first 80% of rotation. No way a wrong taper can cause this.

[PilbaraBass]

Originally Posted by pkr2

If the pot is the right value, but just the wrong taper, the effect would be nowhere even remotely as severe as this problem. He said that there was NO output through the first 80% of rotation. No way a wrong taper can cause this.

not necessarily true...he said "..When I turn the pot there isn't any output until the pot is turned about 80%, and at full the output isn't very loud.."

on a linear pot there is SIGNIFICANT drop in volume below about 75% of the pot value. This can be perceived as "no output", especially if you're expecting a linear volume change.

I'm a bit more concerned that there doesn't seem to be much output through the preamp. I haven't come across a preamp yet that doesn't boost the overall passive volume at least a little (+3 to +6 dB is commonplace)

[M P-Bass]

Thanks everybody for the reply. I think after reading your replies it's probably because the preamp is fitted with a linear taper pot. Pilbaras description i actually quite close.

on a linear pot there is SIGNIFICANT drop in volume below about 75% of the pot value. This can be perceived as "no output", especially if you're expecting a linear volume change.

There's output below 80% but it's just very low (not usable for sure). The pot almost work as an on/off switch. just seems a bit of a waste of pot rotation? Maybe i'll get use to it. Or change it.

Concerning the output: The preamp has an active/passive swicth and when active there's a slight boost of treble, probably around the 3-6 db Pilbarabass sugests. It's just when I compare the output with my other bass (active yamaha) it is about 30-40 % lower. Maybe the yamaha is just very loud.

Thanks again