Yes, a really bad resistor could actually have enough distortion to show up. Any modern resistor probably not. Except of course for some of the special audio resistors may still have enough distortion.
This is a rebuild there certainly can be parts that are not equal to modern parts.
Or haven't you seen the newly made beeswax capacitors?
Lousy then lousy now. But some folks like them.
SY
Yesterday there was a service call for crackling in a pair of loudspeakers. The main system worked fine. The system in question was a radio shack copy if a Bogen and two radio shack loudspeakers. A quick look showed the cosmetic gold plated RCA connector feeding the amplifier had some nice crudy crystals growing around it. No sign of any direct water leak just very high humidity from the basement location.
Of course cleaning the crud off the connections fixed the problem. Now the signal level would have been around 100 millivolts. Note there was no interruption of the signal just added distortion.
So my OINION is that even at low signal levels you can get distortion from pretty much anything. Now if one tests the old resistor I suspect it will show a reasonable cause for the observation. There is no magic nor is it a general case.
But you are welcome to show your calculations.
Yesterday there was a service call for crackling in a pair of loudspeakers. The main system worked fine. The system in question was a radio shack copy if a Bogen and two radio shack loudspeakers. A quick look showed the cosmetic gold plated RCA connector feeding the amplifier had some nice crudy crystals growing around it. No sign of any direct water leak just very high humidity from the basement location.
Of course cleaning the crud off the connections fixed the problem. Now the signal level would have been around 100 millivolts. Note there was no interruption of the signal just added distortion.
So my OINION is that even at low signal levels you can get distortion from pretty much anything. Now if one tests the old resistor I suspect it will show a reasonable cause for the observation. There is no magic nor is it a general case.
But you are welcome to show your calculations.
SY
The crud was shunt! That is what was so interesting. Series crud reduces signal level. That wasn't happening.
Now if you could apply your expertise and explain why the cosmetic gold plating disappeared under the crud leaving the brass base exposed and the quantity of crud a semi-sphere about 1 mm diameter. The crud was white and grainy and left my skin feel as if it was not a very neutral ph. No sign of any source of water other than humidity. And the interesting part was no crud in the contact area. The jack was the standard silverish chrome like plating. It was bright and shiny with no sign of oxidation.
The crud was shunt! That is what was so interesting. Series crud reduces signal level. That wasn't happening.
Now if you could apply your expertise and explain why the cosmetic gold plating disappeared under the crud leaving the brass base exposed and the quantity of crud a semi-sphere about 1 mm diameter. The crud was white and grainy and left my skin feel as if it was not a very neutral ph. No sign of any source of water other than humidity. And the interesting part was no crud in the contact area. The jack was the standard silverish chrome like plating. It was bright and shiny with no sign of oxidation.
a secret of metallurgy ... Why does SnPb solder joint so bad in comparaison with wrapped junctions ? OT... Anymay did somebody else try higher wattage resistors ?
That seems miraculous. Lots of shunt crud but nothing in series. May I guess that you didn't determine the impedances?
So, stepping away from your side show and back to the question at hand. You have (let us say) a 10k source impedance and a 300k load. The load is a really awful comp resistor with a 0.01% VCR (that's double the value in a new resistor). What's the distortion? Now double the size of the load. What's the distortion?
Getting to things which are actually audible, what's the gain change?
Distortion and intermittency of small signals on dirty contacts is a well known phenomenon (that's why you have to use hermetically sealed relays for small signal work). It only takes oxidation on the atomic scale to cause problems, so just because it looked like it was only in shunt, doesn't necessarily mean it was. If it was that badly oxidised you can be pretty shure the whole part was affected to some degree. Even it it was purely in shunt, it could still cause problems by creating a flluctuating load impedance for the device driving it.
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Nice to know that I am now so famous that I have already contributed to a thread without posting!
Changing from 300k to 600k might change the sound a little (apart from the volume pot loading issues which others have mentioned) if there is a coupling cap and the valve is gassy so has significant grid current and is also low in emission so needs a little boost from a bias shift. With a correctly designed and functioning amp you should not hear much difference
Changing from 300k to 600k might change the sound a little (apart from the volume pot loading issues which others have mentioned) if there is a coupling cap and the valve is gassy so has significant grid current and is also low in emission so needs a little boost from a bias shift. With a correctly designed and functioning amp you should not hear much difference
Without the situation drawn out in detail it'll stay guessing and eliminating possibilities. Why not have a look at the circuit at hand and educate the readers with actual numbers?
The reason why I feel it was shunt was that the audio was unaffected. It also was a bit moist.
But I think the actual area where we differ is on how a bad resistor behaves.
A good resistor has some distortion related to temperature coeffcient. Now that shows up as third harmonic distortion. Now second harmonic also shows up sometimes on a decent resistor but at a lower level. When you start seeing lots of harmonics there is more wrong than simple thermal distortion.
Now since neither of us have seen the resistor in question or measured the distortion profile there is no data on if the reported change is due to a bad resistor or observer bias. Now if the possibly bad resistor is replaced by a new resistor of the same value and even type and the observation is that the performance is still improved, would you continue to doubt it could have lust been a bad resistor?
Next time I find crud I'll take a picture for you!
(Different subject, i recently measure some mylar capacitors for distortion. I now have them in a gallon can full of silica gel packets. In a week or so I will retest them. Should show if moisture is the issue.)
Roast on a moderate heat..
Save juice to make gravy...😀
Allen Bradley RESISTORS special treatment method - DIY Audio Projects - StereoNET
Is the sound dependant on the end caps or element type or element material..(They all sound the same..no they don't..yes they do!)..OK well why isn't there only one type..ie the best one..well because its cheaper to make them...well why doesn't every manufacturer make them the cheapest way then?..well er.. 😀
Well its because some need to be accurate...OK so they sound the best then..well not always..but if they all sound the same then that's not relevant..
Well some resistors make harmonics ..no they don't they are all the same..and so it goes on..😀
Regards
M. Gregg
Save juice to make gravy...😀
Allen Bradley RESISTORS special treatment method - DIY Audio Projects - StereoNET
Is the sound dependant on the end caps or element type or element material..(They all sound the same..no they don't..yes they do!)..OK well why isn't there only one type..ie the best one..well because its cheaper to make them...well why doesn't every manufacturer make them the cheapest way then?..well er.. 😀
Well its because some need to be accurate...OK so they sound the best then..well not always..but if they all sound the same then that's not relevant..
Well some resistors make harmonics ..no they don't they are all the same..and so it goes on..😀
Regards
M. Gregg
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That link might be the single dumbest thing I've read today, and there's been a lot of competition.
..but isn't that a resistor?? - Status
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