--- In [email protected], "Jose A. Amador" <[EMAIL PROTECTED]> wrote: > > Bill Meahan K8QN wrote:
> > So what? For anything that includes the human ear and brain as > > part of the system (such as a strictly CW/SSB receiver) "numbers" > > alone don't tell the whole story since, to the audio processing > > centers of the brain, all distortion products are not created equal > > and some are actually preferable. > > Something I find is a must is to have the cleanest possible audio. > > Particularly, low distortion, low noise and properly filtered highs. > Otherwise, it can get tiresome after some extended period under stress, > like in contests or DX pileups. It is the part of stress you can > minimize somehow at will in such a stressful activity. It is something > I have come to appreciate after using a few different radios along the > years I have been a ham. > > 73, > > Jose, CO2JA > I am in 100% agreement. However, what constitutes "low distortion" is an interesting topic. An IEEE study several years back found that even something on the order of 1-3% distortion is considered "low distortion" IF the distortion products (speaking strictly audio here) are primarily even-order in nature. Conversely, distortions in the low fractions of a percent can still sound "unacceptably high" IF the distortion products are primarily odd-order in nature. The brain-ear system finds even-order distortion "musical" and odd-order distortion "harsh" or "consonant" vs "dissonant" to use musical terms. By their _usual_ distortion-producing mechanisms, tubes tend to "soft-clip" and produce even-order distortion products, while solid-state devices tend to "hard-clip" and produce odd-order distortion products. This odd vs even products issue is why I say "all distortion is not created equal" and why I have some problems with the way we tend to evaluate receivers primarily based on IP3 numbers. IP3 is usually measured by hooking up to the audio output of a receiver and measuring the distortion products output without worrying about odd vs even. Hence older tube-type receivers are almost universally thought of as inferior to more recent designs which may well be true IF the IP3 number were the only consideration. However, those old classics were designed to be used by humans, not sound-card inputs or test equipment, and it's often a real treat to listen to one of the better tube-type receivers, even on 40 during a contest. My $0.02, anyway. Closer to the original topic: The MC1496 is a Gilbert-cell device. The latest and greatest from Analog Devices use Gilbert-cells internally, as do similar chips from competitors. Guess they're not *quite* so obsolete after all. That one's free. :-)
