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In Reply to: RE: Has anyone else tried this experiment? posted by vinnie2 on July 07, 2017 at 13:15:10
I admire your integrity in the test (not saying it's the be-all and end-all, but many audiophiles seem to pull out excuses when this happens rather than just reporting the result).
If you replace your resistors with something like a 33 ohm resistor to protect the power amps, you may find yourself hearing more of a difference, though. Because SET amps in particular tend to have rather high output impedance so their frequency response (and even output level) can be very much affected by the impedance of the speaker load which is usually not very flat. Putting an 8 ohm resistor across the speaker makes the impedance variation quite small, so would hide that particular effect. Of course if that did suddenly make the differences clearly detectable, it would be hard to argue that the SET was the better amp than the PP since it can be more messed up by speaker impedance curves.
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Thanks for the kind words.
I don't see any point in this forum if we don't report results honestly and leave them open for discussion and further experimentation. I just wish a couple of other folks out there would do the same experiment and report THEIR results. It can be easily done.
Another poster recommended higher value resistors too, so I put some 25 ohm units on in place of the 8 ohm units and repeated the test runs. My ears still could not hear any difference between the amps.
Are you saying that the once 8-ohm, now 25-ohm resistor is in parallel with the output of the amplifier that is being auditioned? I was previously under the impression that only the amplifier NOT connected to speakers was seeing the load resistor. So, even if the impedance seen by the amplifiers is now likely to be within a reasonable lower limit (for an SET, greater than 8 ohms), there is still the probability that the resistor is coloring the sound. Please don't be angry, but this is just not a good way to evaluate an amplifier, let alone to compare two amplifiers, in my own opinion, of course.
To lessen the resistor effect, you could use a much higher value, like 100 ohms. Or better yet, re-arrange your switching such that only the amplifier not connected to the speakers is instead connected to the load resistor. The latter might require two switches but could be done easily. At that point, you may be able to perceive differences that thus far elude detection.
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