View Full Version : Epicure's Hoss: the mighty M-1 amp (and matching M-4 pre-amp)


geaugafletcher
11-30-2007, 01:15 AM
Many people have no idea that the same EPI that made their beloved model 100s also sold the M-1 and M-4, albeit for only a few years. Word from an old former employee is that the units were _never_ cost effective and quickly went out of production as a result.

Scroll to the bottom of this page for details:
http://www.humanspeakers.com/e/epimodels.htm

In a nutshell, the amp is 120 solid state watts / channel with provision for three sets of speakers. Both channels have a pot to adjust levels as needed. Inputs are via 1/4" jacks, outputs by the same kind of 4- or 5-way binding posts you see at Rat Shack.

The chassis is wonderfully put together, lots of thick aluminum panels with numerous screws holding things together. The two boards and their heatsinks come out as units. Pull one input wire and separate a white plastic connector and they're free. The boards have labels for the collector, base and emitter of each transistor as well as a number of other sundry helpful notes. Everything about the amp's build speaks of hefty quality. Buttons/switches have a very satisfying, positive snap to them, as do those on the pre-amp. Near the binding posts are RCA jacks meant for hooking up an oscilloscope.

I've set about exploring the innards and topology of the amp. Armed with the schematic and a little flashlight, I've pinned down values or part numbers for just about all the caps and transistors on one board. Resistors will have to wait for another day, it's tedious work. See my thread over in DIY for the burning questions of the hour: http://www.audiokarma.org/forums/showthread.php?t=136753

The pre-amp has the usual inputs for 1976 as well as a bunch of silly buttons to press. You can have normal stereo, reversed stereo, mono, left channel only mono or right channel only mono. There are two phono inputs and two amp outputs. Humanspeakers has a full list of specs. My M4 differs from the one pictured - I have just three AC plugs on the back. Volume is adjusted by two sliders, one for each channel. Bass and treble are also adjusted by sliders, one for each channel. "Elbow" frequency as well as magnitude of boost/cut are selectable via a few somewhat less-silly buttons.

AKer Saltwater is the proud owner of an M-1. He took a bunch of pictures that can be seen in this thread: http://tinyurl.com/27ju3o I have a few more to add, mainly of the guts.

See my photobucket page for pics: http://s228.photobucket.com/albums/ee236/geaugafletcher/

Pics include a few shots of the M-4 and several shots of M-1 guts. Note the enormous transformer and towering power supply caps... New caps are on order, just on principle...new PS caps for the M-4 are also on the way. The power light "EPICURE" is out on the M-1 - burned up lamps. The light gets 20vac right from the transformer, I plan to change it over to a little row of LEDs and ditch the old bulb setup.

The amp has a good sound, robust like one would expect. I haven't done any real critical listening with it, just enjoying that it functions as it is. It sounds not unlike the Audire Model 2 that was hanging around the house for a while...

The pre-amp is noisy. Lots and lots of static...cold spray made two transistors in particular get noiser. Odd, I thought you'd pick out noisy transistors when the cold _quieted_ them. In any case, a helpful eBay member noted my purchase of the amp and offered for sale a copy of the M-1 owner's manual and schematics for both units. :) I have a feeling the M-4 will wind up on a tech's bench, but I'd like to take the opportunity to learn about it first...and maybe even fix it! In spite of the background noise, the phono stages sound very good indeed, bringing enjoyable sounds from my cheap Hitachi player.

edit: Can't seem to get attachments working...see photobucket for pics...

thedelihaus
11-30-2007, 01:34 AM
Pretty rare units, however one recently sold on eBay the last month or two.

Well-regarded, well-built pieces.

saltwater
11-30-2007, 10:25 AM
The amps not bad, I like the style. I would however like to learn more bout the preamp, if you have tried other preamps w/ the unit, or just the m4. I was wondering how good of an aker ya are regarding a maual, if ya got one? I understand ya paid for one if ya got one, and not trying to freeload just find one.Ive torn mine apart like you, also those lights are not bad to work on once you get them out, the test switch is sure a plus for testing bulbs, one thing i did for the epicure light was took it out and put a kind of thick peice of paper behind it to disperse the light around so all letters light up, i couldnt stand how the middle of the word was brighter. also looks better at night. also is your dc offset a prob. Im sure well get into more later but thanks for sharing! Finally someone else...

The more i look at the m4 i just say damn you, i had a chance at one but the seller was in australia and would not ship overseass=, i even put out a wanted epi m4, on ebay for eveyone to see, and she found me and would not sell it to me. wtf????

Blue Shadow
11-30-2007, 11:11 AM
I have always liked the looks of this equipment.

Interesting that the M1 caps in your unit are 25k and the ones in saltwater's are 20kf.

Why do you call the mode switches "a bunch of silly buttons to press?" These are useful for diagnostics and for other reasons. I don't like not having them.

geaugafletcher
11-30-2007, 11:27 AM
I suppose the stereo/manual/etc. switches would be useful for diagnostics, but they're really not necessary and seem superfluous to me. Maybe 'silly' was a bit much... :)

The power lights in mine already have some kind of plastic diffuser sheet in them, albeit pretty roughly cut.

DC offset on the M-1 is about 30mv on one channel, 11mv on the other.

There's at least one cap omitted from my amp's boards that does appear on the schematic. (cap 21 - there's a jumper on the board where the cap should be) There's something that looks a lot like a version number in the bottom right corner of the schematic, one that doesn't correspond with the number on my amp boards. What with my M-4 having 3 AC receptacles instead of six, I figure both units underwent revisions over their short lifetimes.

I've paired the M-1 with the pre-amp section of an SX-838. In spite of all the noise coming from the M-4, it sounded better with the M-1 than the Pioneer did. There's something about the design of the M-4's phono stage that I like better than the Pioneer's - although Markthefixer's work on my 838's phono pre-amp rendered it very, very quiet indeed.

Random note: These two units had a combined MSRP that today would be somewhere around $3,000.00, depending on inflation and so forth.

Blue Shadow
11-30-2007, 11:56 AM
From the inflation calculator:

"What cost $1050 in 1975 would cost $4146.56 in 2006."

I used the lower price of the amp and the first year of the preamp per the humanspeakers site.

saltwater
11-30-2007, 12:43 PM
the money is what wowed me, i was gonna sell it when i first got it, but finding some speakers in the trash week or so later rendered me to use it.

Also the diffuser it what clear plastic, mine was, and i said to thin and clear so the white paper came in.

also what # is yours mine is 1901....
so basically the only thing you got is the schematic,

geaugafletcher
12-01-2007, 11:05 AM
Saltwater's 20,000uf caps are more likely original. The 25,000uf in mine just _barely_ fit. In fact, the cap screws are close enough to the board that I put a strip of electrical tape over them just to be safe. I would've used some of that big roll of Kapton I have, but I think my brother made off with it... hm...

The new caps are Mallory and exactly the same dimensions as those I removed, a pair of Sprague "Powerlitic"s.

Saltwater, I'll have to look up the serial number for you. I only have the schematic at present, but the owner's manual will be on the way to me shortly. You'll get a PM from me when it arrives.

saltwater
12-01-2007, 11:39 AM
the serial number is on the top lip where the speaker connects are and power cord are!

geaugafletcher
12-03-2007, 03:10 AM
Serial number is 1780.

saltwater
12-03-2007, 06:54 AM
cool, so we know of 2 out of 1901... and radio knows where one is

spunkeee1
09-21-2008, 12:00 AM
just came across an M1 in a customer's barn. Blew off the dust...removed the mouse nest from behind the terminal access plate and hooked it up. Love it !! Any idea what these beasts are worth nowadays?

MarZutra
06-24-2014, 04:13 PM
just came across an M1 in a customer's barn. Blew off the dust...removed the mouse nest from behind the terminal access plate and hooked it up. Love it !! Any idea what these beasts are worth nowadays?

I chose to respond to this old reply - knowing it is old and that also no one in the thread bothered to answer this poor guy's question.... Should the person return to seek an answer. One can get working examples - for $75-100. Decent ones go for $200-$300.00 and exceptional ones I've seen sold for $650.00.... That's in mint serviced condition with original literature...
Regards...

jdurbin1
06-24-2014, 04:27 PM
Likely nobody answered because the question was one about the value of these amps, posted in a forum where that's not supported, instead of in Dollars and Sense where it is. Didn't help it was his first post, either.

John

MarZutra
06-25-2014, 07:08 AM
Thanks John. You are right. Just trying to be a bit of help wherever I can. I also own one of these amplifiers and have had the same questions as well. Took a bit of research and time but came up with an answer.
Kind regards...
Jer