1M pots measuring 500k...? And other pot problems.

[wcrankshaw]

I've had a 5G9 tremolux for a while now that I built. It works just fine, but it's always seemed like the volume and tremolo controls were a little "off". The volume gets too loud too fast with just the slightest turns of the knob. I just opened it up to take a look again, and when I measured the volume pots they both read ~500k between the outside tabs, but should be 1M. The odd thing is that the 1M tone pot is accurately measuring 1M and has the same labeling on the casing as the other two (all three read Alpha - 9E4). Am I missing something here, or are the two volume pots actually mislabeled 500k pots? Would this cause the hyper sensitive volume changes I've been experiencing?

Also, I put in a 2M audio pot for the speed control because at the time I hadn't seen any recommendations for reverse audio taper, and the schematic doesn't specify. Will this make a significant difference if changed to RA? Or will it just reverse which side of the pot is fast and which side is slow? It also doesn't get very slow in general...is this related to the fact that the 2M pot is actually reading 1.6M?

Lastly, my depth pot is measuring accurately, but is linear rather than audio taper. Any opinions on this? Have I just completely done everything backwards here?

Any help with this rambling post would be greatly appreciated. Thanks.

[diagrammatiks]

are you measuring the pot in circuit?

the reading you have is going to be in parallel with anything else attached to the top wiper and going to ground.

[Jazz P Bass]

Yeah, agreed.
The best way is to remove the pot for measuring.

[Bruce / Mission Amps]

In circuit the two 1m volume pots are in parallel with each other. So two 1m pots would measure 500K or less.
Look at a 5G9 schematic.

[wcrankshaw]

In circuit the two 1m volume pots are in parallel with each other. So two 1m pots would measure 500K or less.
Look at a 5G9 schematic.

So that solves that non-problem. Thanks guys.

Any thoughts on the taper situation regarding the tremolo controls?

[Kazooman]

So that solves that non-problem. Thanks guys.

Any thoughts on the taper situation regarding the tremolo controls?

Well, going with the parts specified on the schematic would seem to be the correct course. There have been thousands of successful builds of this circuit using the originally specified parts. You seem to be substituting parts because you can't find an audio taper or a reverse audio taper and then expect to get an amp that performs like the original.

Go get the original spec parts, put them in your amp, and then we might be able to help you get the sound you are after.

[wcrankshaw]

Well, going with the parts specified on the schematic would seem to be the correct course. There have been thousands of successful builds of this circuit using the originally specified parts. You seem to be substituting parts because you can't find an audio taper or a reverse audio taper and then expect to get an amp that performs like the original.

Go get the original spec parts, put them in your amp, and then we might be able to help you get the sound you are after.

I put in what the original schematic says. The values are correct, but I'm curious about the tapers since the schematic doesn't specify linear, audio, or reverse audio for any of them. I'm trying to find an answer regarding the effect of different tapers on those particular controls. I've read a lot of places that tone is better with a linear taper, but it all seems to be personal preference.

Otherwise, I'm curious what it would take to get a slower starting tremolo speed. It's roughly 120Hz at the lowest setting.

[Kazooman]

If the schematic doens't specify otherwise I think it calls for linear taper. I don't think that the audio taper you used for the depth pot would make a difference, but if it is really only 1.6 M out of the circuit I would relpace it.

[Bruce / Mission Amps]

A lot of vibrato circuits use reverse taper pots.... RG where is that article you wrote up about how to mod pots for different tapers!??

[Kazooman]

A lot of vibrato circuits use reverse taper pots.... RG where is that article you wrote up about how to mod pots for different tapers!??

It's at his geofex.com website. Select FX-tips/how-tos and then select "The Secret Life of Pots".