I have a question.
In many of the amps I've made, I found that if I played a treble tone at mid power with no speaker, something in the amp would be making that tone. I couldn't find any specific components that would do that though. What components would do this?
In many of the amps I've made, I found that if I played a treble tone at mid power with no speaker, something in the amp would be making that tone. I couldn't find any specific components that would do that though. What components would do this?
Audio polarity
Oddly enough, those speaker bullets come in a positive and negative pair. Why? Is there something different about the current through the positive and negative terminals at any given time other than polarity? Kirchoff's current law would seem to contradict this.
John, Does Bybee have an explanation for that?
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
Oddly enough, those speaker bullets come in a positive and negative pair. Why? Is there something different about the current through the positive and negative terminals at any given time other than polarity? Kirchoff's current law would seem to contradict this.
John, Does Bybee have an explanation for that?
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
I had exactly this when I was developing my e-Amp (http://hifisonix.com/ovation-e-amp/).
When the output voltage exceeded about 20V pk-pk, into a dummy load, the amp board would 'sing' and as I changed the frequency, the tone would change and then if I changed too much, disappear.
The culprit was a 1nF 1kV leaded ceramic capacitor used in the damper network betwen my driver and the output stage devices. Just by clamping it between my thumb and forefinger would stop it. I changed to a film capacitor, and the problem went away. I suspect if you use this type of capacitor in a Zobel, you will get the same problem.
I learnt a lesson that day, and now NEVER use ceramics other than for rail decoupling in digital applications - but, see Kendall Castor-Perry for some useful guidelines on how to apply them.
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That is the standard audiophile nonsense, often said by snake oil merchants and their fans to cover themselves when normal people with normal competent equipment hear no change with their ears alone.a.wayne said:
High-K ceramics are non-linear, piezoelectric etc. - useful for supply decoupling but not much else (although OK for coupling caps in low-fi applications such as valve radio sets). Low-K ceramics (NP0, C0G) are linear, stable etc. and fine for audio.
No - I should have clarified . It is indeed the high types like Y5G, X7R etc that are the problem.
The COG/NPO are very good.
No. They are showing a simple functional diagram, not a full blown schematic. The diagram has been optimized to simply show how the injection current opposes the measuring current, so the amp is tring to quiet the differential input..bog standard feedback theory.
A simple mass produced module can be embedded within the front of any power amp to zero it's ground current.
Bingo.
That moves the input to compensate for the ground. The active circuit tries to zero the ground current.
If the ground current is attacking other parts of the equipment, zeroing it is better. For example, loop coupling at the output stage of the source, ground path to circuit coupling in the amplifier. Whitlock only considers IR drop in his presentations, so not removing the current may not remove the problem, and two channel inputs may be worse. The active solution can be applied to multiple channels as well as differential inputs, eliminating the pin 1 problem.
While your point is correct, the purpose of the diagram is to provide the solution theory, not specific implementation. That's what all of us are supposed to do.
jn
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Works well at receiving AM radio stations and injecting the broadcast front ends. Some FM in phono as well if your to close to the transmitting tower. I disagree about fine enough for audio the cost of quality polyprops from non audiophile sources is low enough and they are better caps. There is too too much quality surplus film cap to use ceramics out side of the RF tuning range since cost is not that much of a factor to the DIYer.
Normal !
What about those with paranormal or subnormal systems 🙂 who set the standards and can subnormal plebs call the "competent normal " snake oil reps with overpriced BS stereo products because they hear well enough with their $15 ear buds ..
Just saying ....
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(even new, a polypropylene capacitor in the pF range, with a 100V or higher rating and <5% accuracy, is likely cheaper than a comparable through-hole COG/NPO)
I have seen that with heatsinks. Play a sweep and there is a frequency area where the heatsink fins apparently resonate, loud enough to hear.
Jan
It would seem that all airborne excitations have to propagate from a mechanical source originally?
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