Showing posts from June, 2012

Hammond 125ESE Part 1

Hammond 125ESE
For years I have been searching for a truly affordable SE OPT that is flexible enough for experimentation with various triode output tubes. Last year I found a DIY SE2A3 amp project featured in MJ 2/00 using a Noguchi universal OPT [pri.Z = 2.5K, 3.5K and 7K], the PMF10WS for JPY 6,800. They even have a lower priced model, the smaller, PMF 6W for JPY 3,500 for people who want to build an amp around a 71A or 112A. Unfortunately they do not export and their fax no. specifically states "not used overseas". This is a clear indication of a well developed market in Japan that caters to the audio hobbyist that makes it unnecessary for manufacturers and dealers to look beyond their shores to thrive.
Even if the SE/DIY revolution in the USA started in the early 90s, the availability of a true high-fidelity airgapped SE OPT for under $100/pr. is practically nonexistent. This could be one of the main reasons why in such a huge and progressive country, proportionately, the …

Hammond 125ESE Part 2

Test bench results for the Hammond 125ESE [Tango U808 used as a reference point] Foreword "Reflections of a scope jockey"
These tests are by no means definitive and I still rely on my ears more than anything else. However the techniques I employ have served me pretty well as short cuts in troubleshooting.
Although some tonal aberrations can be recognized on the scope, it should not be taken as the last word. I have tested amplifiers that looked good on the scope but failed to satisfy me musically or two amplifiers with dissimilar circuit topologies that looked and measured the same but sounded totally different from each other. But these were mostly amps with a lot of negative feedback. Negative feedback can extend the bandwidth of an "ill conceived" circuit or output transformer while overshoot and ringing at high frequencies can be "cured" by judicious use of picofarad value caps. So keep these "band-aids" in mind.
I passed up on several opportuniti…

Shop Talk

JE Labs test bench
From right to left: Genrad W5MT3A Variac, Tektronix 2205 20MHZ dual trace scope, Weller WTCPS soldering station, second shelf - right to left: Heathkit IM21 ACVTVM, Leader LAG27 sine/square wave audio generator, Eico 260 AC/VTVM. Hand held DVMs - Fluke 8060A true RMS, Testmate LCR 195 capacitance/inductance meter and Fluke 75 DMM


In retrospect
My first exposure to high fidelity equipment was at The Juilliard School. I entered the pre-college division n the late 70s and the record library/listening room was equipped with at least a dozen Thorens TD150AB, with Shure M7D, Shure phono preamp/headphone amp driving huge Koss headphones as well as a couple of Tandberg reel to reel tape decks for archive tapes while the classrooms had TD124, Shure M3D, Dynaco SCA35 integrated amp driving AR2A speakers. I spent a lot of free time listening to my favorite recordings which was a crucial part of my musical development aside from practicing and attending concerts at Lincoln…

Rek O Kut Tips

....vintage studio equipment in a scene from "The courtship of Eddie's Father", starring Glenn Ford..
Not much information can be found in cyberspace about the original Rek-O-Kut company based in NYC. But the company was a highly regarded manufacturer of turntables, tonearms and cutting lathes during the golden age of Hi-Fi. A lot of these idler driven turntables found duty in radio stations due to their quick start up time, stable speed and simple yet well executed engineering. My 1961 Lafayette catalog lists several idler models starting with the entry level 2-speed 4 pole induction motor driven Rondine Jr. L-34 [33 and 45] and L-37 [33 and 78], 3 speed Rondine B12 with same 4 pole motor as the L-34/L37, Rondine Deluxe B12GH which uses the Papst "flywheel" hysteresis motor and the the top of the line B12H which uses the HUGE hysteresis motor [see picture below]. By 1963 the L-34/37 Rondine Jr. series was replaced by the N33/34H belt drive which usually was fit…