A reasonable question. I expect a reasonable design would use a resistor at 1/2 of it's power rating or less. So at first I tried to do the tests at 7.74597 volts rms into a 1K ohm, (about 1/4 power rating) as this is not an untypical use. As the signals are around -165db I suspect the level may need to be higher.
A bit more complicated, but basically that. The thermal noise level is around -134 and the distortion -165 from the excitation. A dc or slow ac would separate thermal from intrinsic, level changes vs % would show discontinuities vs non-linearities.
John C, I sent you a PM, btw... (like me, you may not have your PM notify turned on in your prefs here...)
I am all for Simon7000 doing tests. I'm only trying to focus in on what he plans to do and what will actually be tested!
(fwiw, I've seen other sorts of 'tests' where lots of effort was made to set up and control everything, but the thing that was actually being tested and the conclusions drawn did not have a direct correspondence(!) - not that I am an expert of any sort...)
As i said, a separate thread on resistor testing might bring forth some expertise, prior work and new ideas - why duplicate earlier work, if it was done right?
I am all for Simon7000 doing tests. I'm only trying to focus in on what he plans to do and what will actually be tested!
(fwiw, I've seen other sorts of 'tests' where lots of effort was made to set up and control everything, but the thing that was actually being tested and the conclusions drawn did not have a direct correspondence(!) - not that I am an expert of any sort...)
As i said, a separate thread on resistor testing might bring forth some expertise, prior work and new ideas - why duplicate earlier work, if it was done right?
Bear, I would agree, IF we could keep the topic going, but like so many subjects, people don't have the inclination or the ability to make a real contribution in a specific area like this. It is like the non-linear capacitance of jfets that precedes it, most people don't have any follow-through, but the topic is still important to discuss, and this thread is a little threadbare at the moment.
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Scott,
Just for fun try playing pink noise through your system at a comfortable level of say 75 dba. Then add a 3 khz sine wave to it. Let me know how far down you can hear the sine wave. Be use to use a decent true rms meter such as the Fluke 87 or better.
ES
Don't worry about Scott, Simon. He uses IC's for everything! ;-)
Seriously, I DO think that connections to the resistor body are critical, especially the unsoldered aspect of the interface. I also think that thermal shock be VERY important, and this is why I used, almost exclusively, 1/2W Resistas for the Vendetta and for feedback resistors in the Parasound products. I used to specify 1/2W Holco for feedback resistors in power amps, BUT they changed the formula. NOW, they are not as good sounding. This could be a VERY good comparison to make, because they apparently only changed the end caps on the resistors, and ruined the component.
Seriously, I DO think that connections to the resistor body are critical, especially the unsoldered aspect of the interface. I also think that thermal shock be VERY important, and this is why I used, almost exclusively, 1/2W Resistas for the Vendetta and for feedback resistors in the Parasound products. I used to specify 1/2W Holco for feedback resistors in power amps, BUT they changed the formula. NOW, they are not as good sounding. This could be a VERY good comparison to make, because they apparently only changed the end caps on the resistors, and ruined the component.
Been there, not fair stressing resistors at 10-20V rms and comparing them to any resistors in a system reproducing 75dBA on your speakers. I can't hear 100nv rms 3kHz applied to my speakers with or without the noise.
Scott,
The issue is how far the distortion must be below the signal to not be heard. I am still playing to see how much signal I need to get good readings. If you consider the resistor stressed at 1/8 power where do you suggest for a good comparison point.
As to 100nv rms at your speakers it might just be interesting to see how much voltage it takes until you can hear something at all. My bet is 63uv at 1 M 1khz.
John
Holco resistors used to be wholly copper. now they can be picked up by a magnet!
It's in San Jose the 6th of Feb. (Saturday) at Derek Bowers' pub. I promise you that I will give you the secret password
. The company was being cheap this year so I am coming just for the party (and to see some friends) on my own coin. Sorry I can't offer to pick you up this time, though I would normally without a second thought.
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