Which Pots with APS-1's

[Robert Delahunt]

Re: Which Pots with APS-1's

I'll be the "Prell" here and fix the split ends.

Chip is correct as it pertains to a volume pot. TR is correct as it pertains to a tone pot. They're wired differently. A pup will always "see" the full value of the volume pot, but a 500k and 250k tone pot, both set on 200k, will sound identical.

That's electrically impossible. That's why I specifically said "set to 200k", i.e. adjust the pot so it's 200k while watching a meter. I was talking about non-linear pots (i.e. volume). Still, it applies to both, really. The amp and pickup both see what the pot is set to, regardless of what the total possible value of the pot is.

 

[Artie]

Re: Which Pots with APS-1's

That's electrically impossible. That's why I specifically said "set to 200k", i.e. adjust the pot so it's 200k while watching a meter. I was talking about non-linear pots (i.e. volume). Still, it applies to both, really. The amp and pickup both see what the pot is set to, regardless of what the total possible value of the pot is.

Connect a meter to the same terminals that a pup connects to, and adjust the pot. You'll see no meter movement. (Assuming volume function here.) Doesn't matter if its linear or log.

As for tone, a 500k tone pot, adjusted to 200k, will have 300k of unused carbon trace. A 250k will have 50k of unused carbon trace. The circuit will "see" the 200k only. Again, lin or log doesn't matter. 200k is 200k.

Not sure which you were refering to as "impossible".

Edit: Of course, if we're refering to the oddball dual-volume wiring where the pup connects to the wipers, thats different. Then what you're saying is true. But thats the exception rather than the rule.

 

[Robert Delahunt]

Re: Which Pots with APS-1's

Connect a meter to the same terminals that a pup connects to, and adjust the pot. You'll see no meter movement. (Assuming volume function here.) Doesn't matter if its linear or log.

Then connect your meter to the "amp side" of the volume pot (i.e. output). Assuming the two different pots you're describing are set to the same resistance being seen by the amp, they should sound identical.

However, that's just resistance, I admit. It's possible that the capacitance of the pots (even if it is a minor issue, or one that shouldn't make a difference) could also come into play.

But still, electrically speaking, being equal in resistance should make them equal.

 

[Fresh_Start]

Re: Which Pots with APS-1's

The amp and pickup both see what the pot is set to, regardless of what the total possible value of the pot is.

(emphasis added)

No they don't. Please look at the schematic: Strat
The resistance between the switch (pickups) and ground through the volume pot is always the total pot value, regardless of the position of the wiper.

The pot acts as a voltage divider in this case with the wiper position determining what percentage of the signal from the pickups continues on to the amp (and what percentage goes to ground).

The amp doesn't "care" what value volume pot is in the guitar. Look at the schematic again - one end of the pot is attached to ground. The wiper is connected to the output jack. The resistance between the wiper and ground changes as you adjust the pot, but this has no effect on the amp. It simply controls the amount of pickup signal going to the jack.

On a Les Paul or other 2-volume guitar, the pickups are connected directly to the volume pot wipers. In that case, the setting of the pot does directly affect the resistance between the pickups "output" and ground. IOW the load changes. But this thread is about a Strat...

Chip

 

[Wi66Pro]

Re: Which Pots with APS-1's

Thanks for everyones input to my original question(s). It's very much appreciated.

I've ordered three 250k CTS vintage style pots which should arrive tomorrow, so I'll update this thread once I have installed them.

Having the 500k CTS pots installed has improved the tone throughout the range (stock korean pots were like an on / off switch), however, I find the 500k pots a bit to bright for me.

 

[Robert Delahunt]

Re: Which Pots with APS-1's

(emphasis added)

No they don't. Please look at the schematic: Strat
The resistance between the switch (pickups) and ground through the volume pot is always the total pot value, regardless of the position of the wiper.

The pot acts as a voltage divider in this case with the wiper position determining what percentage of the signal from the pickups continues on to the amp (and what percentage goes to ground).

The amp doesn't "care" what value volume pot is in the guitar. Look at the schematic again - one end of the pot is attached to ground. The wiper is connected to the output jack. The resistance between the wiper and ground changes as you adjust the pot, but this has no effect on the amp. It simply controls the amount of pickup signal going to the jack.

On a Les Paul or other 2-volume guitar, the pickups are connected directly to the volume pot wipers. In that case, the setting of the pot does directly affect the resistance between the pickups "output" and ground. IOW the load changes. But this thread is about a Strat...

Chip

The pickup does put out a small voltage. However, from what I've read, being passive, it's connected to the amp and becomes part of the circuit with it, hence the pots function more as a load (i.e. the higher the value, the more load) on the pickups.

I'm going to stop short of outright disagreement because I do not design these circuits for a living. However, being that I have been taught electronics and I work on electronics for the military, I am saying "should".

There's a lot that's said about electronics on the internet that is simply not true. Not saying you're wrong, but I'm saying I've seen it from others before. I'm going to have to do more research and possibly contact some engineers I know.

 

[ErikH]

Re: Which Pots with APS-1's

TR, Artie and Chip are right. I had thought the same as you do and totally disregarded the wiring of the volume pot in a Strat. In that case, they are 100% correct.

The higher the volume pot value, the LESS load on the pickups. Higher resistance to ground (through the voltage divider wiring), the less signal goes to ground.

Now, for the OP, try a 500k volume with 250k tones. It works well for me with Texas Specials in one of my Strats.

 

[Wi66Pro]

Re: Which Pots with APS-1's

Just a quick update on the 500 / 250 pots question.

I have now installed a set of CTS 250k Vintage style pots, I have kept the two caps as per the original and I have upgraded the wiring to wax covered type to match that of the SD's.

Before I opened up the Strat, I recorded each pickup for a comparison.

After installation the new recording has a slightly warmer tone but the biggest difference is the gradual increase and decrease of tone and volume.

I'm not sure if it's better quality pots (previous 500's were CTS as well), or whether it's because being 250k it differentiates more accurately the position of the dial. (That's a very none technical way of describing it).

But the bottom line is, a warmer tone and absolute control over volume and tone control. Each number on the dial has a noticeable impact.

Thanks' for all the very useful advice. I have learnt a lot.

 

[Butch Snyder]

Re: Which Pots with APS-1's

I have never seen Fender use 500k pots with their singlecoil guitars. Maybe because the pickups have Alnico 2 magnets, they thought they needed to. Personally, if I would have removed the pickguard and seen that, I would have promptly replaced them with 250k all around.