Gazzip said:
andyjm said:
The capacitors and resistors found in HiFi equipment are microphonic, but these days with small surface mount components stuck onto a rigid board, the effects are probably inaudible.
A quick way to check:
1. Put your CD player on pause.
2. Turn the volume way, way up
3. Tap each device in the signal chain with the end of a pencil. A 'boing' out the speaker indicates the device has microphonic components in it and possibly some sort of acoustic feet might make a difference. No 'boing' (and there probably won't be), then any money you have spent on feet will have been wasted, and I am afraid any improvement you have heard is just suggestion bias.
I would have thought that the materials used to make the capacitors, resistors and even the rigid circuit board inside our electronics would each have their own acoustic resonant frequency. This could be down in the 20Hz region and below or right up in to the KHz region and beyond, and could potentially create a microphonic effect through self-vibration at their given resonant frequency. (Look up Tacoma Narrows on YouTube for an dramatic example of resonant frequency)
Tapping a pencil on your kit isn't going to expose it to the full range of frequencies that a loudspeaker can produce, but playing recorded music will.
I have bought a couple of sets of CeraDiscs on ellisdj's recommendation and I am very happy with them under my DAC and valve amplifier. DAC's are full of sensitive oscillators don't forget...
A tap is very similar to the type of theoretical pulse used to characterise impulse response, and actually comprises a very wide range of frequencies. If you have the volume way up, and there is no sound when you tap a device, it is not microphonic.
You can try this by comparing your DAC (which isn't full of sensitive oscillators) and almost certainly isn't microphonic, with your valve amp which will be very microphonic. I would suggest you don't have the volume up too high when you tap the valves, it might startle the cat.
There is an argument that a valve amp should be in a separate room to the speakers. The characteristic sound of a Marshall valve combo was in part due to the feedback from the speaker to valves in the amp.
- just to add, 'self vibration' would require the components to change in shape with applied voltage. This is something piezo crystals do, which is why they make good oscillators. Capacitors and resistors do not.