2. analog
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Question on Output Music Hall MMF-5 / Sumiko Pre

I have recently gotten back in to Analog for fun and on a budget and it has been great. However, on a couple of records I have been listening to my woofers will start to flap forward in long strides yet I hear nothing. They are moving so violently fast and with long strides it is flat out scary looking.

Is this due to a lack of a subsonic filter in the phono pre? Am I going to damage my speakers. It is just wierd.. I have never experienced this with any other source. My system is below and I would truly appreciate any feedback.

Thanks

Chris

Electrocompaniet ECI-3
Tyler Acoustics Taylo Reference Monitors
Music Hall MMF-5
Sumiko Phono box
AQ Diamond Back from Sumiko to my Int. Amp.
the_kid

Showing 1 response by jcbtubes

jcbtubes
400 posts
 
Your assumption is entirely correct. Warped records (and non-concentric punched records) can produce high amplitube subsonic distortion. It can damage drivers if someone were negligent, particularly with smaller mid/bass drivers and high power amps. Use common sense which means turning down teh volume, or get a phono unit with a subsonic filter, or even buy an in-line subsonic filter. This might be your least expensive solution at this point. If you know the input resistance of your pre-amp (usually 47K or 50K ohms), the filter can be as simple as a series capacitor. Without getting into the math, a .1uf cap in series with a 50K input resistor should yield about a 30 Hz corner frequency. (Now, this is a simple analysis without all possible parameter considerations, so no crucifixions please);^) Any value between .1uf (about 30Hz) and .15uf (about 20Hz) would work, but keep in mind that the higher cap value allows more low frequency to pass. Good luck.
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