Electro Research EK-1
The Electro Research EK-1 is a pre amplifier in the solid state amplifier category.
Brian D. Smith (February 26, 2006): Made in 1980, the EK-1 was originally part of a very exotic condensor/piezoelectric phono cartridge package, the brainchild of mad(?) genius John Iverson, designer of the famed A-75 power amp. John was a positively brilliant engineer who liked life on the edge, and mysteriously vanished amid strange circumstances a few years back and has never been found.
The EK-1 featured military-grade construction and parts. The chassis was machined from a solid block of aluminum 19"X6"X22", and had a seperate compartment for the power transformer. Glass-epoxy circuit boards with all gold traces and metal potted modules graced the inside, as well as relay switching and 3 levels of regulated supply rails. The workmanship and layout are unbelievable. The package retailed for $3000.00 in 1980(it was made in singapore to keep the cost down!) and would probably be 10 times that today.
Front panel controls were very spartan: Large level and input select knobs(machined from solid aluminum), and two small 'trim' knobs for channel level matching, three lighted pushbutton switches(power, standby/mute, tape monitor), and a set of RCA jacks with a capacitance meter to see if your cables were 'up to par'. NOTE: The two phono inputs are voiced for the special cartridge that came with it and supply PHANTOM POWER(+and-15V!)at the RCA jacks. This will BURN UP any other phono cartridge that is plugged into it! DO NOT plug a turntable into the phono inputs. A VERY experienced hi-end service tech can modify it, but it may still not sound right, due to the unique voicing and output level of the original cartridge. This isn't much of a problem, however, as there are 6 inputs plus one monitor input. In addition, there are 3 sets of individually buffered outputs.
RefurbishingBrian D. Smith (February 26, 2006): The input/output jacks can get a bit loose, but be warned, changing them is NOT for the beginner or tinkerer, as it requires removal of the main circuit board, as well as some talented soldering skills and silver solder. Only experienced hi-end or pro audio technicians should attempt to service these beauties!
Brian D. Smith (August 27, 2012): Hi Johnyun, Azirul, and all other readers. I apologise about the "media blackout"; been rather busy with career-type stuff.
Now,as to your questions about your EK-1 malfunctions:
Generally speaking, if there is ANY audible noise at the outputs, regardless of the volume setting, then there is something wrong. A healthy EK-1 hooked through a typical sensitivity audio power amp with no input signal(inputs shorted to ground) and the volume control fully clockwise should produce a white noise type hiss that can only be heard at all in a very quiet room with your ear within about 18 inches of the tweeter. With the volume control at minus infinity(fully CCW), it is difficult to tell if the unit is even on, as the noise floor of the power amp is all that is audible(ear within 3 inches of the tweeter). I have not measured it with test gear, but experience tells me that this is a signal-to-noise ratio of better than 125 db to 1.
As for the small yellow caps on the bottom board: It has been a while, so I may be a bit off on details, but if memory serves(fingers crossed), the ones with the black band on one end were hooked in parallel across the bigger electrolytics in the power supply. This is a common design trick in hi-end audio; the electrolytics, while absolutely required to remove ripple remaining after full wave bridge diode rectification, produce hf white noise on the DC supply rails. Small value, high quality mylar or polypropylene audio type caps (typically .01 microfarad or so, rated at greater than 2x of the rail voltage) are used to make sure any HF and RF noise is shunted to ground, leaving only pure(well, less contaminated) DC to power the audio circuits. I don't know if the "P" is for "positive" or "poly(-propylene o -styrene)", but I would guess that it is not for positive, as a "+" symbol or a band at one end(ah-HA!)is more universally understood, regardless of language. If you follow the traces back to the electrolytic caps, it will become apparent which end is which; the positive is connected to the positive of the electrolytic supply cap(parallel wired). The black band may denote either positive or negative, but the quick procedure I just described will tell you for sure.
I have(since my previous postings) since had the same EK-1 that I repaired brought to me for safe keeping while its owner was on a world tour, so I took the opportunity to take some pictures of it, inside and out, so I could post 'em here for everyone's benefit and/or enjoyment. I shall attempt this now. Cheers everybody, Brian D. Smith
Brian D. Smith (February 26, 2006): See above regarding experienced hi-end professionals only, but that being said, I recommend having the phono inputs' phantom power disconnected and the input gain modules bypassed(for the phono inputs). This will require a seperate phono preamp, which is usually what hi-end guys do anyway.
Brian D. Smith (February 26, 2006): As a pro audio service tech, I had the opportunity to service one of these a few years ago, and I won't soon forget it. The EK-1 is arguably the finest audio preamp I have ever seen or heard. I had built my own tube/solid state preamp & power amp, and was quite proud of them until I plugged the EK-1 into my system. It was a humbling experience. It sounded a good deal better than my 'reference' unit(which had smoked everything I had compared it to up to then). Cleaner, crisper, smoother, MUCH quieter background, generally WAY more neutral sounding than anything I've ever heard. A good buy at ANY price.
Stanley Pencil (January 29, 2009): Could someone please help me by letting me know what the secondary voltages on the power transformer should be? My unit is totally burned out - can't read anything on or off the tranny!
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