Please help me understand!

[Deleted]

OK, A long, long time ago I was taught that if you have a... let's say 500k pot. You need to measure the resistance of that pot to get the true value of that pot.

 So let's say that pot measures out to be 519 resistance. Then you have a 500k pot of a plus factor. Right? All the better of having a true 500k pot.

Now here is where I need some help in understanding. Many pots are sold with a 9%, 10% 15% and so on tolerance. Now the problem I have with a "tolerance" in the way of late I was told is you add what ever tolerance to the resistance is. That to me make no sense at all.

 You could take any pot and add what ever number to it and then say oh that's a 500k or 550k and so on. But the resistance is what you are really getting. Right?

 You are only going to get the output or resistance that is on the meter. Nothing more, nothing less. Just because you can add a number to that pot is not going to give you that resistance. I cannot make a pot that reads 519k and make it read 550k just because I add a number to it.

 Now that being said... I was also told a long time ago from a seller that I had bought 4 500k matched set pots. That there was a 10% tolerance between the pots. I got the pots and all of them had the exact resistance in them. All of them. So they all measured out to something like 509. I paid a lot more for them pots only because I was curious of how close they would be.

  See, I can understand a "tolerance" if you are trying to compare one pot next to another. But now when it comes to the pot itself, that is another thing. I did watch a video and on that video he showed how he measured a "tolerance" He measured by placing the probes at each end of the pot. Then he finds the center of that pot with the meter. Then he takes one probe and puts in the center. Then measures the difference between the two points. That tells him the "tolerance" of that pot. He did not add a tolerance to the resistance.

 So, what do you all think? Am I out of the water in the way I see it? This has been bugging me since that guy went off on me when I questioned his way of what a "tolerance" is or isn't.

 In his way of thinking, I think, is a way of copping out on what is a real 550k pot. To me, a reading of 519 does not equal a 550. Yes you can add the numbers to it and say it's a 550k but again when it comes down to it. I am only going to get 519. I cannot turn the pot up to get there. LOL!

  Been doing this stuff for a long time. Don't forget, I used to build guitar amps and work on them. So I do have a little idea about this. But I may have been wrong in the way I have gone about all this. Hum...

 Please help me understand.

EB

[antares]

Well I'll try! First, ignoring a traceable calibration source, you're pretty much OK with a digital read out meter because even the cheapest and cruddiest example will exhibit a sensitivity of at least 1 MegOhm per Volt. If you use an olde worlde analogue meter, you'll want to ensure that it has a sensitivity of at least 20 kOhms per volt (eg, an AVO 8 or similar) otherwise the meter's low sensitivity will load the circuit under test and give misleading readings. This value is frequently inscribed somewhere on the meter's dial invariably in a tiny font. Remember that meters don't actually measure resistance- they measure electrical potential, but conveniently display the measurement on a scale inscribed with Ohms to save us some leg work with a calculator.

Regarding tolerances generally, the closer the tolerance, the more any component will cost and often the harder it will be to source because in general terms the objective accuracy is not required for the job in hand. Amongst other things, the increased cost reflects more careful manufacturing and the degree to which the items are inspected, but also the implied economies of scale. Batch inspection is not generally conducive to close tolerance manufacturing. The basic question is regarding the marginal propensity to consume, or in other words- how deep are the target consumers' pockets?

Any component has a nominal value. In the case of these potentiometers, although not restricted to, that could be 500k or 550k. If the items are quoted to be +/-10% tolerance, then the former could tumble off the conveyor belt measuring anywhere between 450k and 550k and still be considered acceptable within the manufacturer's exposition. In the latter case for the same +/-10% tolerance, it could measure anywhere between 495k and 605k and it would still be within accepted tolerances. From the foregoing it should be clear that a potentiometer that measures 519k using a meter that doesn't load the circuit under test with its own inherent resistance would be within acceptable limits, irrespective of whether it was marked as 550k or 500k. On the other hand, if the quoted allowable tolerance stated by the manufacturer was +/-5% that would no longer be the case, but you can do the sums.

As an aside, it is of interest to me that potentiometers are not sold in the same preferred nominal values as discrete components, eg 100, 150, 220, 330, 470, 560, 680 and 820 etc.

でつ e&oe ...

[Deleted]

I think I am getting there. But, I still can't see how when the resistance is at 519 how that can be called a 550k pot. Out of the 4 I got that are supposed to 550k, only one came out at 550k. The other 3 were way under that. To me, at best they are 500k with a plus on them. One of them measured out at 507k. I know about the +/-.

 Again, I think that a tolerance is a cop out. So, because of the tolerance of the 4 pot that I have, can they all be a real 550k? Now in the past I have bought 525k and 550k, and they were marked as such on the back of the pots. When I tested them, they were all or just above what they were marked at. The new pot I have are not marked as 550k They have a number 500 on them. So to me, they are 500k with a little added plus to them.

 I have never once, in all the years I have buying pots, had this much problem with pots. I have always measured them for resistance, and they all have been spot on or just above what they were marked as. I just can't get over I was taken on the new pots. I feel that someone is hiding behind the tolerance thing. Making claims that are not true. This is the reason I am asking. I hate it when someone is taking a product and trying to make it something that it is not.

Thanks so much for your response, Steve.

EB

[dnic]

My take on this is the same as Steves. +/- 10% gives a 50K on a 500K pot. So a 250 pot would have an range of 25K above or below. So if a guy says it's 550K and it measures 519K technically it's within range. I agree I think this seller is miss representing his product, he should call it a 500K. It seems more legit. But technically he's within range.

My new kick is 300K pots with .033 caps. Like the old Gibson set up for hummers. I'm gonna try them on SCs as well. I really like the set up with by Route 66 Strat with Johns classic buckers.

[Deleted]

OK, one last thing. First, I am sorry if I am being thick-headed about this. This is how I have to go through things at times for me to understand.

 Alright, If you have a pot that reads 550k, and you have one at 500k Is there going to be a volume différance between the two (if the pots are being used as volume)?

 If I was to use them in a guitar, does that mean that one will out do the other? If so, then in my thinking a tolerance is bogus. I would rather have pots that are close to each other than a far apart reading. That is why I measure resistance over concerning myself over tolerances. Otherwise, there is no need to be measuring the pots at all. But then it becomes a crap shoot.

 Well, anyway... I can't help but think of other things, like when I used to build cars. A 650 single pump carb will not act like a double pump carb. No mater how many times you change the pill in it. This is my thinking on the pots. You are not going to get a 550k out of a 500k pot. Or 300k out of q 250k pot. To me, it's not going to happen no matter what kind of tolerance you add to it.

 I understand the tolerance thing. But I still think it's a big cop out and that many are using it to mask what the pot really is. Same as the 33 tone caps. They, too, have a tolerance, so are we really getting what we pay for? Hum...

 Kind of like... Oh, it's a four-string guitar, but it sounds and plays like a 6 string. LOL!

EB

[antares]

A potentiometer is a discrete passive component. a higher value potentiometer will never make any guitar any louder, but it certainly will make it quieter when set at full resistance.

The bottom line for the consumer is what's stamped or engraved on the potentiometer case, and then add or subtract the quoted tolerance to see whether the measured value is still within limits. If it states 500k and is quoted as 5% then 519k is within tolerance. If it stated 550k on the casing and quoted as 5% then 519k is out of tolerance.

If on the other hand the tolerances are 10% then your seller is correct to say that what you received was effectively amounting to the same thing whether it is marked 550k or 500k. It's a crackpot way to do business because you had every right to expect a potentiometer ENGRAVED or STAMPED 550k if that's what you bought, but at the end of the day, you could have either and it could still amount to the same thing so it's a waste of breath arguing about the what's written on the casing. The bottom line here is that you are right, but he is also right in saying that you can dig your heels in, get replacements stamped with the other value that you bought and end up with the same 519k, so why bother? As I said- you're both "right" but you're approaching it with different terms of reference. My take? The guy is an AH. He should place the customer first, acknowledge he's sent the wrong thing. Make amends, put it right and avoud doing it again. But he's correct to say that after all that cost to him, you could easily end up with a 519k potentiometer. It's a delicate balance but who is being more unreasonable?

I think I mentioned that I bought those high quality audio capacitors listed as 1uF +/- 20%. They measured variously up to +43% and not one was below let alone correct. I wrote and told the seller that they were wildly outside of an already very lax tolerance but "hey- it's Christmas so let's forget it." He offered to RMA and refund. I declined and wrote back "Many thanks but no- you're OK. I just felt you ought to know because many eBayers would not accept it." We parted on happy terms. Well, it was the season of goodwill after all. Sure I was out of pocket, but I wasn't going to let it screw my mind up.

A "no load" potentiometer has the track terminated before the rotary travel ends. You can just feel the wiper dropping off the end of the track. At minimum value, there is still a tiny bit of resistive track in play and because some folks reckon it rolls off some of the pickup's highs they opt for no load potentiometers. I have one in one of my Teles and I think it's a pointless exercise.

I file it in the same drawer as chasing down PiO capacitors or insisting on beehive this and orange drop that. Each to their own of course. Not saying they're wrong, but I'm not buying into it. Capacitance is a physical property. The only real variable is the dielectric material and a double blind listening test would soon level that playing field.

I'm with Dane on 300k potentiometers for tone pots. Because you are supposed to need 250k for single coils and 500k for hummers (theoretically) the 300k works as a happy medium for guitars sporting both types of pickups. I first encountered this in my Yamaha Pacifica 904 with its very wonderful Yamaha proprietry push-push 300k pot for isolating one of the humbucker's coils, supposedly giving a single coil sound. Unfortunately, as expensive as they were, Yamaha ceased from using and selling them which in my view is deprecable and reveals volumes about a manufacturer's commitment to serving its customers and product line. I've broken two of them by pulling off knobs without first popping up the switch. They are irreplaceable and unobtanium.

I used 1 Meg pots on my Danny Gatton Tele simply because I read that Danny did for a really bright spangly Tele "tone". It sounded dreadful. I wrote and asked Joe Barden himself both about that and 4-way switching and he advised me to use standard 3-way switching vanilla Tele wiring and 250k potentiometers. I did as instructed and he was totally correct.

でつ e&oe ...

[Deleted]

Steve, this was my whole thing. The pots I got has 500 on the casting. Not 550. But the seller told me that the 500 is a part number, not the actual value of the pot. So at best what I got was 500k pots with a plus value.

 So the seller went off on me and posted in 3 places on the net, said some terrible things about me. So bad that I will not repeat. He posted my full name, address and phone number on these sites. So right there shows me he is wrong in so many ways. He was using the tolerance as a way of not wanting to do anything on his part. He would rather post faults things about me and slander my name to the point he even brought my wife into it.

 But anyway, I still don't quite understand it all about the tolerance. I will still measure for resistance and forget the tolerance. Like you said, if it's stamped 500k then the resistance should fall somewhere close to that. I have never had a pot read under what is marked on the case.

 I have never encountered a seller like I had on eBay. Hope to never have another one ever anywhere! The so-called person needs not to be selling anything if that is the way he's going to act when someone questions him on something he sold.

 I still feel he sent me the wrong pots, I even showed him pictures of what he sent. He told me I was stupid and didn't know my head from a hole in the ground. He did say I could return them. But after reading some of the negative feedback he has, he never did give them a replacement or their money back because he made claims that the buyer did something to the items. Then I read his return policy. It says that he would only accept returns if the items are returned unopened and in the original package.

 He is the one that told me to take them out to measure the resistance. LOL! So I didn't return them. He would have made some excuse not to give me my money back, nor would he had ever returned them to me. Plus, he wanted me to pay for all the shipping.

  So, again, thanks for your input.

I have used the 300k pots as well. But that was a long time ago, and I can't remember what I thought of them. I have used 33 caps forever, it seems like. That is my go-to caps for everything guitar wise.

 For me, I still like the PIO caps. I can hear the difference in them from an orange cap. But they are expensive and for the cost I can buy the other caps and get more of them. Not many people can hear the sound difference, so, why brother with the PIO caps.

 So, here is my conclusion;

   I am going to move on from this. After reading and watching videos on this subject, it seems to be something to let stay in the air of nothingness. No mater what I say or try to understand it all, it makes no real sense to me in how something like pots can have one thing stamped on them only to turn up as something else because of a tolerance that someone puts on them. The pots I got are supposed to be 9%+ No negative was ever talked about until many emails later. He did change his ad to say +/- after I called him on it.

  I will never understand how anyone can put a % of a tolerance on a pot and then say that is what it is. That means I can use a 250k pot, add 20% tolerance to it and get a 300k pot.  I have measured a lot of 250k pots that came out to be 275. So are they 250k or 275 or 300K Hum... No, I think they are in deed 250k pots, just like they are marked.

  So, from here on out, I will make sure of what I am getting. I don't care who I buy from. I will even question Stew Mac. I will trust no one!

 OH, the art of trying to have fun! LOL!

EB

[antares]

In this case the value is a part of the part number, something that is extremely common in my experience. You've got it Eddie- the 250k potentiometer with 10% tolerance is nominally 250k, but can actually measure up to 275k. It passes batch testing. If it measured 1k more- 276k AND you could be confident of your meter's accuracy, it fails and cannot be sold as 250k +/- 10%. We have to draw a distinction between what they are sold as, and what they actually turn out to be- they're two different things, and the quoted tolerance is like a mutually accepted guideline between manufacturer and consumer so that each party knows what to expect.

Manufacturers produce these things in 7- figure batches and no doubt higher. They simply cannot pluck each one off a production line and test each one as being accepted or rejected AT THE PRICE POINT. If the end user is prepared to pay proportionately more that reflects the higher accuracy in assembly and smaller batch testing then they will happily fulfil that market demand, but certainly for guitars, no one is prepared to pay for that accuracy. Bourns pots tend to be of better manufacturing quality and frequently of closer tolerances, and that is reflected in the higher prices they tend to command and relatively lower useage in guitars and probably more stock left hanging around in storage waiting to be sold.

Regarding capacitors, I confess that after a lifetime working in factories with hammers banging, radios blaring out on different channels and a symphony of leaking airlines, I cannot hear any difference between capacitors.

The capacitor is connected across a potentiometer in a tone control in a variable RC circuit. The potentiometer is literally that- a potential divider, but it is variable. As it is rotated, the sound we hear changes as progressively more and more of the high(er) frequency component finds a lower and lower impedance to "ground" at audio frequencies (there is no true ground or earth in a guitar- it is an AC signal. Any "ground" is at the other side of the amplifier circuitry at the supply outlet in the house wall. In a guitar, it is better to think of it as a signal return to constitute a circuit and thus satisfy Mr. Kirchoff.) Basically, the potential divider provided by the potentiometer funnels more and more of the treble components to "ground". Since the sound (shall we say "tone"?) is constantly changing as we rotate the potentiometer, how can we say the capacitor sounds different? Different from what?

If we were to set up fixed capacitors, matched exactly for uF value, one (eg) PiO and one (eg) Orange Drop, each wired to one tag of a changeover switch, we could switch back and forth and perhaps hear some difference- they have different dielectrics after all, but what we are thinking of there is creating a circuit topology a bit like a sawn off Varitone (as in missing the lumped component inductance). Leaving aside Varitones mostly found in Gibsons, no one deploys capacitors that way in a guitar. For me, it's not possible to say one sounds different from another all the while they are connected across such a variable potential divider. Where's our reference needed to say that?

Then we come along and plug in a perhaps 3 to 6 metres long coaxial lead that exhibits more capacitance in parallel with the tone control. This can be anywhere between 50 pF and 200pF per metre in parallel with the .033 uF in the guitar. Then the signal encounters more capacitance due to the amplifier's input circuitry. It's a minefield!

でつ e&oe ...

[Deleted]

Jan 6, 2023 12:25:43 GMT -6 antares said:

You've got it Eddie- the 250k potentiometer with 10% tolerance is nominally 250k, but can actually measure up to 275k. It passes batch testing. If it measured 1k more- 276k AND you could be confident of your meter's accuracy, it fails and cannot be sold as 250k +/- 10%. We have to draw a distinction between what they are sold as, and what they actually turn out to be- they're two different things, and the quoted tolerance is like a mutually accepted guideline between manufacturer and consumer so that each party knows what to expect.

Manufacturers produce these things in 7- figure batches and no doubt higher. They simply cannot pluck each one off a production line and test each one as being accepted or rejected AT THE PRICE POINT. If the end user is prepared to pay proportionately more that reflects the higher accuracy in assembly and smaller batch testing then they will happily fulfil that market demand, but certainly for guitars, no one is prepared to pay for that accuracy. Bourns pots tend to be of better manufacturing quality and frequently of closer tolerances, and that is reflected in the higher prices they tend to command and relatively lower useage in guitars and probably more stock left hanging around in storage waiting to be sold.

Regarding capacitors, I confess that after a lifetime working in factories with hammers banging, radios blaring out on different channels and a symphony of leaking airlines, I cannot hear any difference between capacitors.

The capacitor is connected across a potentiometer in a tone control in a variable RC circuit. The potentiometer is literally that- a potential divider, but it is variable. As it is rotated, the sound we hear changes as progressively more and more of the high(er) frequency component finds a lower and lower impedance to "ground" at audio frequencies (there is no true ground or earth in a guitar- it is an AC signal. Any "ground" is at the other side of the amplifier circuitry at the supply outlet in the house wall. In a guitar, it is better to think of it as a signal return to constitute a circuit and thus satisfy Mr. Kirchoff.) Basically, the potential divider provided by the potentiometer funnels more and more of the treble components to "ground". Since the sound (shall we say "tone"?) is constantly changing as we rotate the potentiometer, how can we say the capacitor sounds different? Different from what?

If we were to set up fixed capacitors, matched exactly for uF value, one (eg) PiO and one (eg) Orange Drop, each wired to one tag of a changeover switch, we could switch back and forth and perhaps hear some difference- they have different dielectrics after all, but what we are thinking of there is creating a circuit topology a bit like a sawn off Varitone (as in missing the lumped component inductance). Leaving aside Varitones mostly found in Gibsons, no one deploys capacitors that way in a guitar. For me, it's not possible to say one sounds different from another all the while they are connected across such a variable potential divider. Where's our reference needed to say that?

Then we come along and plug in a perhaps 3 to 6 metres long coaxial lead that exhibits more capacitance in parallel with the tone control. This can be anywhere between 50 pF and 200pF per metre in parallel with the .033 uF in the guitar. Then the signal encounters more capacitance due to the amplifier's input circuitry. It's a minefield!

でつ e&oe ...

When I was in AZ, I had a test table set up to test the caps. I used to let my customers come in, so they could hear the caps, and them let them decide what they wanted in their guitars.

  The funny thing was that most of the people would end up wanting the silver PIO Soviet over all the others I had. So I had to ask myself, why is that? Like it or not, there is a smoothness of the PIO caps that other caps do no have. To me and others, they produce a sound/tone that other caps just don't have. It is subtle, but it's there. The sound has an over all creaminess to it.

   But it's the same that some will argue over tube amps or non tube amps. I'll be doing a couple of videos on my amps soon. I'll go more in the tube sound and the digital sound.

 But yes there is only a value difference between caps, 22, 33, 47, and so on. To me, most caps all sound the same with the same value. But I do like the .33 caps for guitars. I bought some cheap ones not too long ago. They are working well, and they produce a good sound, as good as Orange drop or any other non PIO cap,

 I don't know why me and some others seem to hear the difference. But I can tell the difference in the string gauge being used on a guitar.

I had my hearing tested a couple of years ago  (don't forget, I am 68 years old now). The guy that tested me asked me what kind of work I had done and what my hobby was. I told him I ran printing presses for most of my life and played in Rock groups for many years. He could not believe how good my hearing was. He said my hearing was on the level of a teenager and that I could hear frequencies that most people cannot hear.

 My daughter is the same way. My daughter can hear a dog whistle. Do you remember the old TV remotes of the 70s and the 80s? I could hear the pitch of then remotes. They would hurt my ears when someone would use one, I had to leave the room. LOL!

 So I am real sensitive to sound. I think that is why I was always good at playing by ear.

 Well, need to go eat dinner/supper.

EB