Subject: S/500  my review
Date: Tue, 15 Feb 2000 12:09:15 -0800
From: "scottalowell" <>
To: "Threshold Amp Repair" <>

What would $4,895 buy In 1987? A Threshold S/500 A-A/B Stasis power amp.

    This amp features a 1000KVA toroidal power supply, backed by 116,000 uF of
storage.  The design of this optical bias amp is to have no global negative feedback. It has a bipolar transistor output, and a generous area of heat-sinks around the case. What you end up with is an 82-pound battleship, with about as much firepower.  Since the S/500 was introduced in 1984, the audio community and media have given it nothing less than stellar reviews, placing it among the most topnotch "A" list equipment. This is deservedly so.
    I purchased my S/500 in used/mint condition in 1999 for a paltry $1,300 . I felt like I stole my way into the high-end.  I have heard a number of new power amps costing upwards of 9 kilo-bucks that I didn't like better.  That says a lot about the original design genius of a 13 year old amp!  This old amp extracted every bit of detail off a source.  It reproduced music in a neutral, grain-free, non-fatiguing manner.  I used material like Linda Ronstats "For sentimental reasons" for vocals.  The midrange was a liquid, transparent presentation, which unlike many SS  designs didn't sound flat, sterile, brittle, grainy, opaque, or cold.
    On classical material like "Mars, Bringer of war" and "Hut on Fowl's legs" the bass proved to be the tightest, deepest, most unblinkingly powerful I could hope to extract from a sound system.  The very deepest notes had incredible control and definition.  During a net search for Threshold information, I found Jon Soderberg's website. He offered repair and upgrade to Threshold/Forte products.  I thought, if nothing else, maybe I could get the chassis freshened up on the inside, - 13 years can be a long time for some internal components.  What does $425 buy in the year 2000?  As far as amp mods go, a functional bargain-basement tweak that really works well.  I dropped my amp off on a Monday, and picked it up on Saturday.  The modifications included upgrading the four 29,000uF/80v storage caps to 37,000uF/100v caps . The power reservoir was now kicked up to 148,000 uF . The bias was adjusted for modification to the front end circuit, and the aged power switch was replaced for good measure.
    Almost immediately, the effects of this modification were obvious. No need for extensive DBT here.  The same source material was now more forward. By that, I do NOT mean "bright." I mean that the air around instruments increased, and the soundstage was markedly improved. It's like you went from row "E" to row "C." The conveyed sense of room dimension was now more defined, and fine details became more prominent. Michael Bromek's "Celtic Guitar", track 2 - "Second two O Carolan's pieces" simply bloomed.  The strings expanded outward magnificently, and when he taps his hollow-bodied guitar, the sound of flesh on wood is very realistic. Horns on "The best of Maynard Ferguson" and "The best of Chuck Mangione" from the stock amp were fluid, but now it feels like you could step BEHIND the horns. You sense the heat from staccato horn hits. The bass test came via Telarc's "Space spectacular" the main theme to "Battlestar Galactica " , "Star Trek TMP " and "Superman the movie." The bass impact was there as before, but now with an edge. It's like the information was more finely separated and etched. The visceral slam was improved. Zaranthrustra REALLY spake…loudly.
    I've seen companies offering questionable amp upgrades that are also very expensive. They are nothing more than replacing all the guts of an amp for the price of a new one. By contrast, this is a cost-effective deal-and-a-half. I highly recommend this upgrade to any owner of a Threshold product. It merely makes the already excellent amp more of what it already is. It is like a product evolution. Nelson Pass has over-designed superb products for years. Threshold provides the tube community with a solid state alternative for detailed musicality without fatigue. For those of you looking for a means of increasing personal enjoyment of a Threshold amp, this upgrade will not disappoint!
Scott A. Lowell