Gravity too. But, sometimes, it helps ;-)
I have to add to my portrait gallery, beside those who believe in magic the ones that don't believe in real.
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Hey Pavel, excellent post.
I recall advice of putting a filter right on (soldered to terminals) or at (small SM pcb) the input connector. Is this still 'sound' advice? Could you say more about both aspects of point 3 (air-coupled EMI and supply line)? Circuits?
Could you say more about point 4? (as a dad I love the idea of inherent, post clean-up!) Circuits?
You seem to have a lot of cents!
Happy Holidays!
Thanks,
Jeff
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My humidity at this very moment is 26%. A bit low my target is 30%. So a small adjustment is needed.
No I haven't personally seen the Micosoft one but what I have seen near there is quite interesting and under an NDA.
Dan, Bill it seems I need your shipping addresses. Also it is begining to look like you may need a large box.
That's what she said!
But seriously,
Is the classic 100k, 1st order filter good enough
or do we need more advanced filters (on everything that is inter connected [air emi and supply line]) these days,
Hmmmnmmm
now more than ever?!?
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Hi Tryphon,
I didn't forget. It's a normal part of every design.
The fact that the speaker output is actually another input path is something I taught technicians for years. Most were very surprised as they hadn't thought of this. These things are so old hat that they don't seem worth mentioning unless questioned about every entry point for noise of all kinds. Then you would also include the power supply. It also can couple internal noise between stages and sections.
-Chris
I didn't forget. It's a normal part of every design.
The fact that the speaker output is actually another input path is something I taught technicians for years. Most were very surprised as they hadn't thought of this. These things are so old hat that they don't seem worth mentioning unless questioned about every entry point for noise of all kinds. Then you would also include the power supply. It also can couple internal noise between stages and sections.
-Chris
Could one of the reason be that they somewhat cancel some distortion of common transducers as suspected by Eduardo de Lima?
The problem with this line of reasoning is that by nature the transducers have compressive nonlinearities just like the electronics. The thing to do is use a dummy transducer in the feedback, John can tell you about his experience with that.
Here is a thought-
The capacitance will cause increased current to drive it in the output circuits. You could measure the drain current at a low frequency (10Hz) in the output circuit. Raise the frequency to something like 10 KHz and see how much in increases. Add a known cap to ground and see how much it increases. The increase in current with frequency will be the capacitance plus some other small factors I would think.
I was impressed that they are only 2.8dB above air at STP. I haven't heard lately from the guy who wanted to evacuate the air from one side of a microphone to lower the noise. Someone asked the other day, "How long do you preheat a microwave oven?", what do you answer?
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Mine takes just under 10 seconds to develop full power. Way back (40+ years) when microwave oven leakage energy was a concern I built meter to look at it.
The meter was a 1N21 diode and a 50 uA meter. Easily measured leakage. Dirt on the door seals raised it to almost double the normal reading. But that is when I learned there is a turn on delay.
So if you worry about such things, be sure your door seals are clean.
Keith Johnson used a vacuum to optimize his mods to the Sennheiser RF condenser mikes. It enabled confirmation that the noise was below random air movement.
Toroids have a large winding window area relative to magnetic flux path length. The geometry is ideal if one would like to be able to saturate the core, or to put it another way, one must exercise some restraint so as not to run the core too close to saturation. Core material matters too, of course.
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Ed, thanks for your generous offer but no need, I'm perfectly chilled, send my share to Bill....with seven women around he surely needs it more than I ever will.
Dan.
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