Pro Tone Pedals and rockabilly guitarist Danny B. Harvey have developed an all-analog Tremolo pedal using a Vactrol opto-isolator design. Its lush tones recall American made amps of the 40's and 50's. Operation is dead silent, and the signal is bell-like in its clarity. Available here: http://www.jetcitymusic.com/index.php?page=shop.product_details&flypage=vmj_naru.tpl&product_id=281&category_id=46&manufacturer_id=20&option=com_virtuemart&Itemid=89