Listening #95 Page 3
If you love mono LPs and 78s half as much as I do, you may eventually buy a true monophonic cartridge or pickup head. Such a product has only a single coil and a single pair of active output pins. (Another pair of pins is physically present, but is dead as a doornail.)
The distinction has practical consequences. If you play a true mono cartridge through any modern stereo preamp, only the right channel will produce music, while the left channel will produce a loud hum: the electric sound of nothing. Most mono switches give strangely little aid, because they merely blend together the two disparate sides. Thus you'll get music and a loud hum out of both channels.
My own Shindo Masseto preamplifier was modified by its designer to provide a true mono option, which is how I enjoy my EMT OFD-25 and OFD-65 monophonic pickup heads through a relatively modern stereo system. I touched on that in last month's "Listening," while describing Shindo's upmarket Vosne-Romanee preamplifier: The true-mono modification had yet to be applied to my review sample of the V-R, but it seemed easy enough to do in the field . . .
Then I thought: Why not give it a quick once-over, for the benefit of other monophiles who are struggling with Y-connectors and the like? Distributor Jonathan Halpern, whose faith in my soldering ability is as strong as it is inexplicable, expected me to mod the sample in any event, knowing I'd want to use my EMT pickup heads with the Vosne-Romanee that's on loan from his firm, Tone Imports; editor John Atkinson also gave approval, glad in the knowledge I'd be covering a topic of potential interest to more than nine people.
Here are the basics: If we limit our focus to stereo components without logic circuits, we see that the source-selector switches in most preamps are double-layered things, having both an input plate with many contacts and an output plate with only two. The switch's input plate is arranged with left- and right-channel sides, and the order of contacts on one side is typically the reverse of that on the other: On a four-source switch where the contacts on one side are ordered as phono, CD, tuner, tape, the contacts on the other side are likely to be tape, tuner, CD, phono. For line-level sources, the selector switch's input contacts are wired directly to the hot contacts of the appropriate input jacks. The two phono contacts are wired to the left- and right-channel phono-section outputs, which for the most part are easy to trace. And the two output contacts are wired to the volume control(s), then on to the input of a line amplifier.
Variations on the above abound, none of them too daunting. For our purposes, the atypically beautiful Vosne-Romanee is a usefully typical thing. Our job is to identify a stereo pair of line-level inputs you can do without; disconnect those jacks from the selector switch; connect a jumper wire between the switch's right-channel phono contact and the right-channel contact for the source we've just eliminated; and connect a second jumper between that contact and the left-channel contact for the enucleated source.
Doing it is scarcely harder than writing ithonestly. On the selector switch of the Shindo Vosne-Romanee, I simply clipped off the wires from the TV jacks, then used my Hakko soldering iron and a bit of Kester 44 solder to install two short pieces of insulated wire, as described above.
All usual warnings apply: Neither Source Interlink Media nor any other disinterested party can be held responsible for injury or death resulting from a bungled attempt at this childishly simple task. If your preamp is under warranty, you must first contact the manufacturer to determine if this mod will void it. (It probably will.) Solder contains lead, which is a known health hazard, and solder fumes have been shown to be especially toxic. And don't attempt this modification unless and until your physician has declared you physically and emotionally prepared to experience an entirely new level of playback quality.