John Curl's Blowtorch preamplifier part II - Page 3491 - diyAudio
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Old 12th February 2013, 01:06 PM   #34901
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When you had finished to test and tune a DIY device, and before to screw the cover, it is a good practice to hit all circuit boards, with some non conductive tool while you look at a sinusoidal signal. A good way to verify all your weldings at a glance. Do the same for your wirings. As SY said, the vibrations will be hundred time higher than any acoustical or mechanical vibrations in normal use.
Marce, yes, you're right about SMD litics. A good practice is to secure them with some varnish or glue once welded.
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Last edited by Esperado; 12th February 2013 at 01:15 PM.
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Old 12th February 2013, 01:09 PM   #34902
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. But mass on springs would help, but springs on there own have a resonance, hit that and the fun starts
.
Sure, in practice 20 kg mass on valve springs gives a pretty low (and benign) resonance frequency.
Icing on the cake might be filling the springs with cured silicone or other substance....maybe Crazy Putty.

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Old 12th February 2013, 01:22 PM   #34903
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Marce, yes, you're right about SMD litics. A good practice is to secure them with some varnish or glue once welded.
Just be wary of yellow contact glue that breaks down with heat and time, becomes corrosive, conductive and eats pcb tracks.

Dan.

Last edited by Max Headroom; 12th February 2013 at 01:29 PM.
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Old 12th February 2013, 01:32 PM   #34904
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On the contrary, transports, and specially optical devices like CDs are very sensitive to vibrations. I have two experiences on this.
First, in my car, i used, long time ago, a portable CD player. Isolated with a support mounted on springs (damped with foam) at low resonance frequency in all directions: perfect, even during very aggressive drive or paved roads.
I use an old Marantz CD player in my hifi system. I had dumped with lead all the mechanical parts of the transport, until everything sound deaf. Including the motors and the tray. With great benefit. The all transport part itself was mounted on floating silicone suspension.
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Old 12th February 2013, 01:37 PM   #34905
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.....but higher up the list would be 'common' CD players that typically exhibit audible modulation due to vibration.
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Old 12th February 2013, 01:43 PM   #34906
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As SY said, the vibrations will be hundred time higher than any acoustical or mechanical vibrations in normal use.
Maybe not so....acoustic induced vibration can be pretty high amplitude in a high SPL situation.
If the acoustic feedback excites a high Q mechanical resonance, the modulation might be more than we might reasonably expect !

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Old 12th February 2013, 01:59 PM   #34907
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what is this CD thingo of which you speak?
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Old 12th February 2013, 02:10 PM   #34908
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what is this CD thingo of which you speak?
i don't understand the question, witch model ? Marantz CD-53.
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Old 12th February 2013, 02:21 PM   #34909
marce is online now marce  United Kingdom
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400lb hammer. 6 foot arc, unit bolted to a metal plate, not many SMD can type electroylitics survived, ferrites and transformers have to be filled with gunk and can still crack. Great fun, open the box and see whats survived, after you plug the gear in and see if anything still works.
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Old 12th February 2013, 02:28 PM   #34910
SY is offline SY  United States
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Quote:
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Maybe not so....acoustic induced vibration can be pretty high amplitude in a high SPL situation.
If the acoustic feedback excites a high Q mechanical resonance, the modulation might be more than we might reasonably expect !
Nope, not even close. Here's a way to demonstrate it: mount an accelerometer on your amp/pre/DAC. Play music while recording the output of the accelerometer. Now tap on different places on the amp/pre/DAC. Look at the accelerometer output.

For this purpose, you can either use a MEMs device or a cheap PVDF film sensor.

Once you've convinced yourself that the tapping is a much more rigorous test, you now have a cheap way of tracking down your construction errors!
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