Vibration Test Equipment

[Thorensman]

Hello everyone. This is my first post so please bear with me if it is not relevant. I rebuild vintage analog audio turntables and in the process I try new materials and/or products to improve them. I am in need of some vibration testing equipment so I can validate the results of my labors. The turntables incorporate belts, pulleys, idler wheels, small electric motors, etc. Can anyone recommend equipment to suit my needs? Thank you very much. Jim

 

[GregLocock]

I've got a TD160 with an SME III arm.

Unfortunately lab quality high frequency accelerometers and mics are expensive, as are their conditioning amps. You may be able to get secondhand ones, as people are replacing individual battery powered systems with racks of 24 and 48 channel units.

I'd recommend B&K gear, the 2635 charge amp in particular, choice of accelerometer is tricky as sensitive ones tend to be big and heavy.

I might be being a bit over the top, the only thing that really matters is the signal transmitted by the needle, why not just analyse that?



Cheers

Greg Locock


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[boyze]

are you trying to measure vibration into the turntable? A friend of mine designs and sells isolated tables for turntables that have very low natural frequencies (<1-2 Hz type stuff). Or acoustic frequencies? Or maybe both?

Have Fun!

James A. Pike

http://www.xl4sim.com

http://www.erieztechnologies.com

 

[Thorensman]

I am trying to measure increase/decrease in vibration at each step of the rebuild. For instance, test with bronze bushing and then with Delrin bushing and note the difference. Thank you so much for responding.

Jim

 

[Strong]

"I am in need of some vibration testing equipment"
You have several choices ranging from new purchase, used purchase, rental, and borrow. I could make suggestions, but I would need to know your general ability/experience with vibrations and budget. A tiny, but sensitive, accelerometer connected to a spectrum (FFT) analyzer is probably what you are thinking of. A PVF accelerometer, USB sound card, and PC software could cost less than $500.00 with "some assembly required". Measurements from the audio signal with a precision source record might be more effective than vibrations! Drive components can affect table radial and torsional vibrations (wow and flutter) and also shake the tone arm. You could consider making precision digital recordings of various test configurations and then have someone do the signal analysis for an hourly fee.

Walt

 

[GregLocock]

But presumably the vibrations are tiny, in engineering terms, so you'd need a very sensitive accelerometer, which are big and expensive.

Cheers

Greg Locock


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[floattuber]

Perhaps as a proof of concept, you can download an app for your phone that displays what the built in accelerometers measure. The operative word here is that it's free or at most, a couple dollars. Make sure you remove the phone from the case, first. I have a couple for my iphone, one is called Seismometer and the other is iSeismometer.

 

[rob768]

Can you somehow find/fabricrate an album with a straight groove? any noise/movement of the coil will be related to vibrations from the table, drive motor, arm etc. Changes in that signature will be related to modification to the arm (provided that's all that you modifiy)
Adding measurements equipments will add weight to the arm, affecting its behavior.

 

[GregLocock]

Easier than that, just don't switch the motor on, and drop the needle onto a record. However the venerable HiFi test record did also have silent sections.

Cheers

Greg Locock


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[IRstuff]

Actually, you already have a lightweight, sensitive accelerometer, namely, the pickup itself. There's got to be a test record with all sorts of different sections, including silence. The difference between a "gold" unit playing the record and the unit under test playing the record gives you a comparison.

And ultimately, any vibration not picked up by the pickup is irrelevant, and any vibration picked up by some other sensor will need to be proven to be a problem during playback, wouldn't it?

TTFN
faq731-376

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[Strong]

Following up on IRstuff sage advice, here are some links:
Audio system measurements
From Wikipedia, the free encyclopedia
Pasted from <

http://en.wikipedia.org/wiki/Audio_system_measurements>

The Ultimate Analogue Test LP
Pasted from <

http://www.analogueproductions.com/index.cfm?do=detail&Title_ID=35532>

ARTA software - a collection of programs for audio measurements and analysis in acoustical and communication systems. ARTA software uses standard and professional PC sound cards and interfaces for audio signal acquisition and generation.
Pasted from <

http://www.artalabs.hr/index.htm>

You can always add an accelerometer for vibration measurements, but you need to know what background frequencies are affecting sound output first.

Walt