All your base are belong to us

All your bases are bolong to us

Vibration absorbing base picture.


  • basetop.jpg
    25.6 KB · Views: 609

Good to hear from you as always Bernard. The E-A-R material is carried by a couple of audio tweak parts houses in the US. I believe the material I mention was developed to quiet submarines. I have seen it used in a high end turntable design and as a CD damper. It is what is on my Caps in the Aleph3 picture on the Pass forum. There are other materials to play with also that are easy to find: poster mounting putty, bluetac, odeling clay (I use it for speaker gaskets), computer mouse pads, closed cell foam ear plugs, felt pads, cork, and several layers of polypropylene packing tape. I like materials with self stick backings. This is a different application than an isolation base but those are useful too. I really like the polyethylene cutting boards for thier high internal losses and easiness to drill and cut. They make great bases to build external power supplies on. I am working on an isolation base too. For a good overview of damping in audio:

Active Feedback Decoupling

I submit my latest project Active Feedback Decoupling Isolation Base (AFD for short). This anti-vibration base was designed to decouple my DVD player from vibrations and acoustic feedback in the listening room. I decided to go to an amplifier actuator accelerometer design after reading about similar approaches for design of active suspensions for cars and microscope isolation stands. I used one channel of a modified phono cartridge for an accelerometer and four modified polycarb diaphragm tweeters as actuators by cutting out the domes and gluing feet to the voice coils as pictured below. The actuator-feet are wired in series to lower the Q of the resonate frequency of the system and equalize the force sent to the feet by the amplifier. Due to the inefficiency of the drivers a bridged 200W amplifier is necessary to drive the system. A "Linkwitz Transform" Biquad network is used to move the resonant frequency to 1 to 4 Hz. The corner frequency and alignment (Q) are adjustable. To keep it Audiophile grade I used pots from Alps. Foil or metalized polypropylene caps and 1% resistors were also used. The op amps used in the filter amplifier were LF 411s. The effect on the sound of the AFD is unbelievable and was well worth the 140 hours of design and testing. Adjusting the roll off frequency and damping make huge changes in the soundstage that defy belief. I would also like to think my good friend Sal Poli for spending four consecutive weekends in his lab without one word of complaint. We used his HP 3562A Dynamic Signal Analyzer for measurement and filter synthesis. Any further dialogue?



  • afd4.1iso.jpg
    34.5 KB · Views: 371

I thought no one was going to notice a very elaborate joke for april fools day! Thanks for noticing, but maybe you missed the most intricate clues...

April Fools Day- Active Feedback Decoupling, AFD, Any Further Dialogue

4-1- LF411, 1 to 4 hz, 140 man hours

anagrams of "april fools"- "Alps. Foil or" and "Sal Poli for"

It was fun and a lot of effort. I even gave a preview hint in the passive preamp post when I said April fools day was weeks away! Only one nibble...... there is another one from another troublemake on the forum for 4-1-2002. Want to find it anyone?