Very often, the wipers will not reliably handle current flow. Multi-turn pots are designed as voltage dividers.
The normal single turn controls perform very well, otherwise they would have used a multi-turn control. Sometimes the range is too great, but that is a design error and can be corrected by changing fixed resistor values and some times the value of the pot. Yamaha was famous for this problem. The contact on a single turn is much larger and can better handle current flow, that part is pure physics and common sense.
Finally, real common sense. If you don't need to replace something, why on earth would anyone consider doing that?
The normal single turn controls perform very well, otherwise they would have used a multi-turn control. Sometimes the range is too great, but that is a design error and can be corrected by changing fixed resistor values and some times the value of the pot. Yamaha was famous for this problem. The contact on a single turn is much larger and can better handle current flow, that part is pure physics and common sense.
Finally, real common sense. If you don't need to replace something, why on earth would anyone consider doing that?
Mark, you are almost correct.
The wiper and slide are much smaller in a multi-turn control. Use a hammer and prove it to yourself.
Multi-turn controls are designed for very fine adjustment. Normally process control and test equipment. Things like bias current and DC offset are not carefully set as they both drift a great deal with temperature. The very notion of a fine setting that will stay is misguided at best. On top of that, these values when in the ballpark will make zero difference in sound quality.
So tell me, exactly what is the entire point of using a multi-turn control in audio equipment? I'm serious, what are people attempting to gain here?
The wiper and slide are much smaller in a multi-turn control. Use a hammer and prove it to yourself.
Multi-turn controls are designed for very fine adjustment. Normally process control and test equipment. Things like bias current and DC offset are not carefully set as they both drift a great deal with temperature. The very notion of a fine setting that will stay is misguided at best. On top of that, these values when in the ballpark will make zero difference in sound quality.
So tell me, exactly what is the entire point of using a multi-turn control in audio equipment? I'm serious, what are people attempting to gain here?
I just figure out the range for whatever adjustment and use single turn where possible. If the adjustment is very fine I'll use a multi-turn. I never replace single turn with multi-turn in audio equipment, not ever. I have had to remove the darned things and reinstall a single turn. Endlessly turning a control for an adjustment that drifts isn't very intelligent.
A CCS is normally temperature compensated so that application can make sense. Yes, wipers in multi-turn oxidize exactly the same as with single turn, but single turn control respond better to cleaning.
A CCS is normally temperature compensated so that application can make sense. Yes, wipers in multi-turn oxidize exactly the same as with single turn, but single turn control respond better to cleaning.
Thanks for the quick replies,
Chris, " if it passes audio it is working fine in many people's minds. They were honest in that regard." - thats what i was thinking, just that different people have different standards, i wasnt worried about them not beeing honest.
"Is the spark killer bad? If not, leave the poor thing alone. -
i had one exploding in my old analog scope a few years ago, i thought for this cap , as well as for other caps, like the electrolytics in the supply (which are bulging at the top) it might be a smart thing to replace them before they go up in a loud bang.
The multi turn pots were mentioned earlier on, and i thought replacing the pots could alsos make sense,
after all the amp is 25 years old.
maybe i worry too much..
"Polyester capacitors aren't very good either" - i have never had the chance to compare differnt caps, and after reading that people prefer film caps to electrolytics i thought this could be a good chance to try. i guess i stick with the electrolytics then.
The amp must have gotten worse over the years, its hard to imagine anyone finding the sound of my rotel enjoyable.
There are other things you can do that solve the issue I think you're trying to protect against." this is what i am asking, where would you start?
Jürgen
Chris, " if it passes audio it is working fine in many people's minds. They were honest in that regard." - thats what i was thinking, just that different people have different standards, i wasnt worried about them not beeing honest.
"Is the spark killer bad? If not, leave the poor thing alone. -
i had one exploding in my old analog scope a few years ago, i thought for this cap , as well as for other caps, like the electrolytics in the supply (which are bulging at the top) it might be a smart thing to replace them before they go up in a loud bang.
The multi turn pots were mentioned earlier on, and i thought replacing the pots could alsos make sense,
after all the amp is 25 years old.
maybe i worry too much..
"Polyester capacitors aren't very good either" - i have never had the chance to compare differnt caps, and after reading that people prefer film caps to electrolytics i thought this could be a good chance to try. i guess i stick with the electrolytics then.
The amp must have gotten worse over the years, its hard to imagine anyone finding the sound of my rotel enjoyable.
There are other things you can do that solve the issue I think you're trying to protect against." this is what i am asking, where would you start?
Jürgen
Never had a properly implemented one go bad but open wiper single turns were often a hassle when I was a bench tech repairing all manner of tape machines. No mourning their disappearance here.
Hi yurgs,
Some capacitors were known for failing. Not all and most are fine.
Yep, you worry too much. On amplifiers exceeding 40 years old, I rarely have to replace bias controls. Some yes, so I put in original single turn as close to the same size as I can. I never install multi-turn controls as this is both not what they were designed for (circuit type), and also they are unsuited even if you simply look at how many turns are required.
Coupling capacitors are large enough in value so they do not develop signal voltage across them. Now, if they are defective (like leaky or low value), you replace them. Electrolytic capacitors have DA issues, but so to polyester types. Polypropylene are too large physically (which is why they use electrolytics normally). If the part is too big, you can't use it. They do not affect sound quality anyway. I've done a lot of testing in this area as have many others.
Yes, equipment can degrade over the years. Issues can occur with any components, transistors and matching. Resistors, capacitors. They all have odd failure modes, even some solder connections (remove old, use new and not too much). Like people, they can have individual personalities.
Sound quality issues. This is where many years of experience and test equipment comes in. No one can give you a "hit list", but there are common things. You can't replace a really good technician with the internet or artificial intelligence yet. I have always written what I have learned and experienced.
Some capacitors were known for failing. Not all and most are fine.
Yep, you worry too much. On amplifiers exceeding 40 years old, I rarely have to replace bias controls. Some yes, so I put in original single turn as close to the same size as I can. I never install multi-turn controls as this is both not what they were designed for (circuit type), and also they are unsuited even if you simply look at how many turns are required.
Coupling capacitors are large enough in value so they do not develop signal voltage across them. Now, if they are defective (like leaky or low value), you replace them. Electrolytic capacitors have DA issues, but so to polyester types. Polypropylene are too large physically (which is why they use electrolytics normally). If the part is too big, you can't use it. They do not affect sound quality anyway. I've done a lot of testing in this area as have many others.
Yes, equipment can degrade over the years. Issues can occur with any components, transistors and matching. Resistors, capacitors. They all have odd failure modes, even some solder connections (remove old, use new and not too much). Like people, they can have individual personalities.
Sound quality issues. This is where many years of experience and test equipment comes in. No one can give you a "hit list", but there are common things. You can't replace a really good technician with the internet or artificial intelligence yet. I have always written what I have learned and experienced.
Hi rdf,
I have had many muti-turn controls go bad. Probably about the same ratio as single turn. These are all basically the same idea, construction differs. The multi-turn parts have smaller conductive surfaces, that is the big difference.
I have a couple pieces of test equipment that need wholesale trimmer replacements. These are voltage references, so that means a complete (very expensive) adjustment and recertification. If you think for a moment that multi-turn controls are immune from oxygen, you are sadly mistaken. This is the main issue with metallic contacts, and the problem in adjustable resistors. The one thing the standard open style trimmers in stereo equipment have going for them is that you can clean them. You cannot easily clean a multi-turn control.
I have had many muti-turn controls go bad. Probably about the same ratio as single turn. These are all basically the same idea, construction differs. The multi-turn parts have smaller conductive surfaces, that is the big difference.
I have a couple pieces of test equipment that need wholesale trimmer replacements. These are voltage references, so that means a complete (very expensive) adjustment and recertification. If you think for a moment that multi-turn controls are immune from oxygen, you are sadly mistaken. This is the main issue with metallic contacts, and the problem in adjustable resistors. The one thing the standard open style trimmers in stereo equipment have going for them is that you can clean them. You cannot easily clean a multi-turn control.