I recently acquired this power amp with an unknown history but learned through a member on the Audiokarma forum that I might find info on this site. The amp claims 500 watts or 250 per channel, weighs considerably and appears very well built. After cleaning up the exterior I opened it up and found the transformer was loose and some small black plastic pieces were on the bottom of the chassis along with some small but long machine screws. Removed the screws, vacuumed up all the plastic bits, tightened down the bolts securing the transformer, traced those screws to the back of the output meters, sprayed the pots with Deoxit then visually inspected the circuitry for any abnormalities with all appearing fine. Another thing, those heat sinks extend way out and have sharp edges, I've the scratch marks on my arms to prove it!
Powering it up using a DBT with a 100 watt bulb and 8 ohm dummy load per channel with gain pots set at a minimum, the bulb was first bright then momentarily darkened then came back on at about 3/4 the original brightness. there was no Magic Smoke or explosions! That's about all I had time for today but it looks like a promising project.
Found some info on the bias and offset from a restorer online who thought it should be set to 100mv but this applied to the model 200, haven't found much info on the model 400. Do you think the 100 watt bulb is insufficient for testing this powerful amp or should it be a greater wattage? The transformer is massive and rated at 1.5 killowatts, pretty intimidating and approached with caution! I've some info on this and will have to read it carefully before proceeding further but so far don't see any info on how to go about setting the bias or offset, any info regarding doing this would be most appreciated!
Powering it up using a DBT with a 100 watt bulb and 8 ohm dummy load per channel with gain pots set at a minimum, the bulb was first bright then momentarily darkened then came back on at about 3/4 the original brightness. there was no Magic Smoke or explosions! That's about all I had time for today but it looks like a promising project.
Found some info on the bias and offset from a restorer online who thought it should be set to 100mv but this applied to the model 200, haven't found much info on the model 400. Do you think the 100 watt bulb is insufficient for testing this powerful amp or should it be a greater wattage? The transformer is massive and rated at 1.5 killowatts, pretty intimidating and approached with caution! I've some info on this and will have to read it carefully before proceeding further but so far don't see any info on how to go about setting the bias or offset, any info regarding doing this would be most appreciated!
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I believe these were made for Gargantuan ESS system having one box biiiig sub and big panels - lateral moving mids and big AMT on top
I wonder if this amp was around at the time when Mr Pass started his long and illustrious career at ESS?
only question is - did he left ESS before this amp was made
dunno for sure, but I believe he was gone Treshold then
dunno for sure, but I believe he was gone Treshold then
Absolutely. The amp was created in '72 by Pete Werback, who greatly
assisted moi in moving from speaker to amplifier design. I paid him
the favor back when I gave him my little car amp business, which he
turned into Linear Power.
He was a genius. Unfortunately he died in a plane crash in the 80's.
Like the Phase Linear 400 / 70, the ESS 500 was based on the Lin
topology (1956) writ large, and with a couple of improvements, mostly
the use of constant current sources in the front end. After Pete left ESS,
it was revised again to use the more rugged output devices that were
being introduced around 1973.
Thanks for the history lesson Nelson, they look a bit like the Phase Linear amps as well in build style.