Evans amps

[crbowman]

Anyone here know anything about the old Evans amps?
I am aware of the general history of the Evans amp company going back to their starting days in Texarkana, but I don't seem to be able to find any schematics, or any kind of circuit documentation online. I'm curious because there is one for sale on the Bay for cheap as a "project" amp. Seller says the amp works but has a bad 60hz hum that gets worse if you try to use the reverb. What I DO know is that the amp is an FET-500 model. From what I'm able to find online, apparently this amp used 'high-voltage FET's' which were hard to come by which necessitated the change to the FET-500 LV (low voltage) model in subsequent years. Obviously this is a solid-state amp, but the Evans amps have quite a reputation amongst steel players and some jazz players and are pretty rare. If anyone here has any insight on servicing, or maintaining, or playing through these, I'd appreciate hearing about it.
Thanks in advance guys!

[rooster]

You seem to have the chronology correct. The Evans company changed direction with their output section and it seems that all the early models eventually suffered failure. The thing is, if all the people interested in Evans amps would also know this story then there is no resale on the amp. Basically a time-bomb. I suggest a pass.

[crbowman]

Thanks Rooster. That's kinda the impression I've got as well. I was hoping I could find a part number for those high-voltage FETs, but haven't been able to find even a schematic. I'm still curious, but it's starting to look a no-go.

[crbowman]

Just to follow up for those interested. Looks like the JFET was a 300 volt 2N6449. Looks like these are in fact pretty difficult to source. Apparently, Jim Evans originally designed this as a tube amp and he wound up wiring the JFETs right to the unused tube sockets on the earliest models. Amp also has what looks to be an ancient JBL 15 in it which would almost make it worth the price of admission. Interesting, but I'm not quite hooked yet.

[teemuk]

Well, the idea of those amps was uncolored amplification of whatever was fed into them. Switch from tubes to more linear FETs was apparent, as well as the switch from FETs to OpAmps in even later models. (e.g. the LV)

If I remember right, these amps aren't particularly fancy. Pretty much a standard early 1970's textbook power amp design coupled to a preamp with the neccessary amount of gain to support (IIRC) Baxandall-type tone controls and some overall bandwidth limitation. Not even trying to reinvent the wheel or generating something original and unique.

I have schematics for 500LV and some early Evans tube amp somewhere. Overall nothing fascinating or exceptional in them. They might as well be schematics for any cheapish 70's solid-state amp.

In practice the JBL speaker is The feature which makes or breaks that amp. Throw in some other speaker than a highly linear JBL or EV 15-incher and it's an entirely different amp, and then probably more in the cheap and unimpressive -sounding no-name transistor amp than legendary Evans amp category.

High quality 15" to a generic clean solid-state design is a tried and true recipe for Lap Steel -type amps, though. Works fine for that particular applications so nothing bad in that. It probably just won't convert too well for other expectations that people might have on guitar amps.

[crbowman]

Thanks guys, the finger is inching farther and farther away from the "Place Bid" button.