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This is more of an academic inquiry regarding anti-vibration devices for an integrated amp or cd player): assuming that acoustic and structural vibrations or micro vibrations can cause resonances within the amplifier or other component and assuming that what is actually vibrating or resonating in the amp is the chassis, the amp cabinet enclosure or the individual componentry such as circuit boards and individual parts such as resistors, capacitors, transformers, transistors and the like, how do such micro vibrations cause the sonics to be altered or affected given that the amp has no actual moving parts (the cd player with its actual mechanically moving parts and jitter issues is easier to comprehend, however) - what actually causes these vibrations or resonances to affect the sound output signal going from the amp to the speakers? Thank you
Follow Ups:
What David Aiken is describing is Faraday's Law of Induction. Discovered in 1831, it is the basis of our electro-technical civilization.
Any motion of conductors in an amplifier in the presence of magnetic fields will result in induced voltages. If these motions are correlated with the audio signal, the artifacts they produce will be more noticeable than if they were random.
I've had experience with two completely different amp designs, where reinforcing and damping the support of the heavy power transformers resulted in marked improvement in deep bass clarity.
Keep in mind that power transformers are not the only sources of magnetic fields. Any DC bias currents that flow in loops will generate static fields.
There are other sources of vibration besides the speakers. Most synthetic-film capacitors are transducers, as the film compresses and expands when the electrostatic force between the electrodes varies. It is sometimes possible to hear the audio signal directly from a capacitor in the circuit. If these capacitors are mechanically coupled to other circuit elements, then they can affect the signal. External damping will not help this issue very much.
I have to second the comments regarding capacitors. If you replace a speaker with a simple 8 ohm resistor and examine the crossover with music flowing through the signal path, you may feel the capacitors vibrating to the music and also hear those vibrations.
Bill
The prevailing theories suggest that individual electronic parts (such as transistors, resistors, capacitors, wire, pc board traces, etc.) can produce small amounts of voltage when subjected to mechanical vibration. In addition, eddy currents and hysteresis distortion are created when vibration is present within an electronic component. These conditions can affect the flow of electrons through a conductor which would alter the signal flowing through the component.Vibration can affect a component that utilizes a digital optical disc. The laser reading a spinning disc can have a more difficult time focusing on the information spiral if vibration is present. When this occurs, the servo sled must utilize corrective motors which will tax the power supply. If the vibration is severe, some digital information may be unreadable by the laser and interpolation can be brought into effect. Interpolation is when the processor ‘makes up’ the information that should probably be in the unreadable section by comparing what came before the unreadable section and what comes after the unreadable section. It might guess correctly but it also may not. In any case, the power supply will work harder than necessary during this occurrence. Also, digital components are based on master and sub-clocks (oscillating crystals) and extra vibration can interfere with their accuracy. Unwanted vibration can cause timing errors (corrupted ‘settling time’) of the bits which can increase jitter.
Vacuum tubes can become microphonic and turntables exhibiting excess vibration can cause unwanted motion of the stylus within the groove which will add unwanted artifacts to the signal.
Loudspeakers are a complex source of vibration which contaminates other components within the system. Loudspeakers also self-induce vibration which results in many sonic problems that interfere with their own ability to perform optimally.
There are three main sources of vibration that affect an audio or video system:
1) Floor-borne vibration sourced from loudspeakers, subwoofers, heating & AC systems, external traffic (cars, trucks, trains, freeways), geologic seimic activity, etc.
2) Air-borne vibration coming directly from the speakers through the air and exciting the chassis of the components within a system.
3) Internally-generated vibration resulting from spinning motors, humming transformers and cooling fans built into the component.
Best,
Barry
Edits: 10/08/08 10/08/08
Well, off the top of my head and probably among other things, there's usually a strong magnetic field emanating from the power supply transformer within a component. If you move a wire that forms part of the circuit within that field (or a circuit board since the signal path on the board replaces wire), you induce a current in the lead that fluctuates with the movement. That's effectively how some pickup cartridges work: wires or coils moving within a magnetic field. Since the moving lead is part of the circuit and your signal is, among other things, current in the circuit, any additional current introduced by movement is added to the music signal. So, if the vibration causes signal leads or circuit boards to move slightly within the field, you are going to add something to the music signal.
It doesn't take much movement of a stylus tip to create a signal but cartridge signals are much lower in level than a line source signal which is why they need a phono stage to boost them to suitable levels for the pre-amp stages to work. Since signal travelling within most components is around line source level or higher in some power amp stages, any added signal you induce by this method will be much lower in level than your original signal but that doesn't necessarily mean it's going to be completely inaudible. How much you add to the signal in this way will depend on the strength of the magnetic field, how effectively shielded the circuit traces/wires are, and how much movement results from the vibration.
I suspect there's other mechanisms at play as well.
David Aiken
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