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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Re: Already.. Take a look! Here.... posted by groman on January 6, 2002 at 17:28:13:
This site at least seems to be honestly comparing the op-amps without an obvious bias or agenda. This would be more the case if all the op-amps were operated under identical conditions, with a well designed power supply, good grounding, etc.However, the conditions are rather strenuous.
5.7 VRMS output level, into 600 ohms load with a non-inverting gain of 10 (20 dB) configuration.The highest signal level most any audio component is asked to do is 2 VRMS, the output of a CD player. The worst case load is usually a few k ohms, and typically around 10 k ohms, not 600 ohms.
As with DougS's site, the listed THD numbers are single figure of merit, and interpreting the distortion waveform is not an easy task.
Harmonic nastiness should be weighted for the higher order harmonics, which tend to look rather abrupt and jagged on such displays. A higher level of second harmonic would not be nearly as bad as a much lower level of 7th.The FFT's are difficult to interpret as to levels, and while they appear to show relative level for the various harmonics, how far down the various harmonics are is not entirely clear either.
Something does not seem right about all the numbers here either, as they show the LF356 to be very low in distortion under these conditions, yet it is NOT capable of driving a 600 ohm load at these drive levels. Neither is the TLO81 op-amp.
So these results certainly raise the issue of whether or not the measurement conditions ar ethe smae for all the op-amps.
The bottom line is that you still have to listen to them, to see which one sounds the best in that circuit, etc. You can not go on just specs alone, and certainly not on just a limited number of specs.
Jon Risch
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Follow Ups
- Re: Already.. Take a look! Here.... - Jon Risch 01/6/0221:06:55 01/6/02 (1)
- Thanks, Jon. - groman 00:11:13 01/7/02 (0)
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