It's the differential receiver that's critical for common mode rejection. The output driving it just needs balanced impedances. Signal symmetry is irrelevant as common mode rejection works even in the absence of any signal.
ee
@Billshurv:
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So why is a headphone not a differential receiver? Common mode with a balanced impedance has no net movement? Or are we heading down a symantic rabbit hole?
Sure, a headphone driver is essentially a balanced, differential input. But for what purpose? You think you're going to pick up audible noise on your headphone cable? And my point was that the input of a bridged amplifier is not a differential input.
By the way, the first "balanced" amp from HeadRoom never mentioned common mode rejection. It was all about the bridging. Increased power, etc. though the increased power was irrelevant. A single ended amp can have whatever power you want.
It was just a naive misapplication of the term "balanced," but it has stuck.
se
Common mode rejection in the lower AM band, duh. Not that I can hear that high anymore without a radio.
Thats how patent reads to me.... the + and -45 degree stuff. But, I can easily measure that affect if I had the unit to measure. SY can do it also.
Since the patent is so old.... expired now (?). we can measure and listen and see how to do IT better..... assuming it makes an audible improvement.
Anyone have the actual values used by MIT? I am more interested in the RC circuit affect than CM rejection et al which has not been a problem in my systems.
THx-RNMarsh
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Also, if things weren't confusing enough, in the United States a "patent" covers other Intellectual Property that is not an invention. So, for example, what in other nations is referred to as an Industrial Design ... which covers things like the shape of an automobile, for example ... are called "Design Patents" in the US.
Shady companies imply that the Design Patent refers to a form of invention; the classic example is the Q-Ray Bracelet.
You can't make a bracelet that looks like the Q-Ray because it has a registered Design Patent. But Q-Ray in their television advertising implies that it has a patent on the function of a "healing bracelet".
It seems that Design Patents are ideal for the Cable "industry". I'm surprised they haven't jumped on that one yet.
Brisson's application is for a utility patent. He's managed to keep the application alive for nearly ten years now. The fact that his attorney is Timothy Brisson is, I'm sure, just a coincidence.
I haven't read the file wrapper, but I'd guess that it's highly entertaining.
Tim is, of course, Bruce's son.
If you can add value or 'improvement' or other modification to the patent, you could keep extending the application and/or patents life.
Still, the patent is about the Network. Does anyone know the values he used in that network?
THx-RNMarsh
Not specified as a preferred embodiment, which is unlikely to fly if they ever want it to be issued. One claim, and it looks completely meaningless. It appears to be a "show" patent rather than a serious one. That's viable if you have a cheap or free lawyer.
I love Roger Modjeski's comments in his BAF talk.
I love Roger Modjeski's comments in his BAF talk.
Here you go. Far less here than meets the eye. The titles should be self explanatory. Data taken with 300R load on the headphone end. 1V magnitude. The dominant effect is merely the capacitance of the cable.
edit: 50R source impedance.
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