according to soundstage review of hotrod version
http://www.soundstage.com/revequip/belles_150a_hotrod.htm~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Here’s what makes a stock 150A into a Hot Rod:
* Removal of original large slabs of damping material from all internal chassis surfaces;
* Application of Cromolin constrained-layer damping material to strategic points in the chassis as a replacement for the original heavy and soft damping material;
* Replacement of original plastic-tipped binding posts with deluxe gold-plated oxygen-free copper binding posts;
* Replacement of stock transformer mounting bolt and pads with a proprietary sandwich isolation system that effectively decouples the transformer from the chassis without introducing shipping problems;
* Application of O2 Blocker to all non-soldered connections to maintain maximum performance for many years. O2 Blocker cleans and seals electrical connections and stays effective for many years.
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now, my amp is upgraded with better binding posts so the main difference is in dumping material. all electronic components are identical.
I personally did have a chance to listen to both stock and hotrod version and could not tell the difference. but then again my ears might be not sensitive enough.
thank you
gd