Bourns 500K Pot Testing

skinfreak

Recently ordered some Bourns 500K pots from RS. They were stated as sold within 20% tolerance and I got a wide range:

The PDB241-GTR01's range from -10% to +4% tolerance - 454k to 521k - i was gnoig to use for volume.
The PDB183 Push-Pulls range from +1.2 to +7.4% - 506K and 540k. I was going to use these for tone.

Two of the 241's are 500k and 498k. Big question is how much of an impact is this tolerance shift going to make? In reality that is? And on the tones the same question.

These are going into a PRS Tremonti SE - I got a couple of spare 241s so was planning on using the ones that are close to 500k. But then again I am a numpty and don't really have a clue...

wackojacko

skinfreak said:

Recently ordered some Bourns 500K pots from RS. They were stated as sold within 20% tolerance and I got a wide range:

The PDB241-GTR01's range from -10% to +4% tolerance - 454k to 521k - i was gnoig to use for volume.
The PDB183 Push-Pulls range from +1.2 to +7.4% - 506K and 540k. I was going to use these for tone.

Two of the 241's are 500k and 498k. Big question is how much of an impact is this tolerance shift going to make? In reality that is? And on the tones the same question.

These are going into a PRS Tremonti SE - I got a couple of spare 241s so was planning on using the ones that are close to 500k. But then again I am a numpty and don't really have a clue...

Will make sweet FA difference to tone.

500k pots between 450-550 make no difference whatsoever.

i do slightly snigger at people who pay extra for "5-7%" tolerance pots when you could buy 4 from all parts, six string supplies or eBay and get them measuring between 500 and 525k! (I believe allparts 500k pots are 10% tolerance anyway and the vast majority measure between 475-525 so that's actually a 5% tolerance. If you buy from six string supplies they'll even measure them for you and do matched pots if you're that bothered. 

i doubt the audible difference is noticeable until you get beyond the 20% range though. I.e a 400k/600k pot. Even then....barely noticeable.  

ICBM

wackojacko said:

Will make sweet FA difference to tone.

500k pots between 450-550 make no difference whatsoever.

i do slightly snigger at people who pay extra for "5-7%" tolerance pots when you could buy 4 from all parts, six string supplies or eBay and get them measuring between 500 and 525k! (I believe allparts 500k pots are 10% tolerance anyway and the vast majority measure between 475-525 so that's actually a 5% tolerance. If you buy from six string supplies they'll even measure them for you and do matched pots if you're that bothered. 

i doubt the audible difference is noticeable until you get beyond the 20% range though. I.e a 400k/600k pot. Even then....barely noticeable.  

It definitely isn't. I did some direct-switching testing with pots and added resistors to alter the effective resistance above and below the measured value. There was a reliably audible difference at about 25% below the value and 33% above it, and a little closer than that for just about audible that something had changed but not enough to tell reliably without switching on the fly.

There is a good reason why the standard tolerance on pots is 20%.