Mono Stereo

With more than half my records in mono, and a stereo system with no mono switch, some attention to the mono-stereo issue has been long overdue.I am not wanting (at this moment anyway) to get drawn into the arguments about artistic intent, dedicated mono and stereo masters vs fold-downs, studio monitors.

Mixing console which would have been used by Rudy Van Gelder:

Van Gelder had to work with the technology available and in the early days this is what he had. Stereo was a by-product of the emerging technology for multi-instrument recording – mic-ing and mixing – before committing to tape. Hence ” Lead instrument Left, piano and bass Centre, drums Right” Stereo. I wanted to be able to listen to some of my “primitive stereo” records in mono. What I hadn’t bargained for is that the solution had a large number of unexpected other benefits, more on which later

What no mono switch?

The manufacturer of my hi-fi, Linn, does not provide a mono switch anywhere in the system, and not for just for minimalist aesthetic reasons.

From a purist performance point of view, any kind of physical switch in the signal path degrades that signal, and there are no mechanical switches apart from power on/off (volume is digitally managed – no moving parts). That makes sense. The idea of tone control knobs, or a bass-boost switch is risible. But the need to address the issue of mono meets with “hardly anyone has mono nowadays” (or so the Linn Marketing Department informs them, demanding an ipod connection point instead) An absent mono switch is a casualty of their philosophy and it has been necessary to listen to mono records in stereo.

One solution of course is to spend many thousands of pounds on a dedicated mono cartridge, an additional arm, and a new deck able to host both stereo and mono arms. I am sure it is wonderful, no issue, but what if you could get a similar benefit for just £30? Linn had not bargained for man-in-a-shed, whose solutions work around obstacles created by organisations who think they know better than you what is good for you.

Man-in-a-Shed Productions, a friend who understands how to hold a soldering iron by the correct end (which is where I go wrong) came up with a solution to the problem of L-R-C stereo: a simple mono/stereo switch, constructed from demanding audio-grade components, sited discretely between the turntable output leads and the preamplifier. From opinion circulating in the hi-fi community he thought there would be other benefits, but neither of us was fully prepared for what followed.

I’d rather switch than fight

With the toggle switch set to Stereo, left and right channels simply pass through as normal: the signal from the cartridge – whether the record is stereo or mono – heads off for the preamplifier in “Stereo”. However flick the switch to mono, and interesting things start to happen.

The Left and Right input signals are merged with their positive or negative opposite numbers. Left Output comes from L+ and R+ Inputs, and Right Output comes from R- and L- Inputs. Variations between the two signals are “cancelled out” (an idea which I still have difficulty grasping) Importantly, this “cancelling out” includes a proportion of unintentional variations such as surface noise, imperfections in stylus tracking and any hifi-induced asymmetry in the phasing or processing of left and right channels.( If that made sense to you I probably haven’t written it right)

Here’s the thing. Banished from the left speaker, Monk or Coltrane emerge centre stage, while sidemen return to their natural spatial and musical relationship in supporting the lead. Grandissimo.

The unexpected benefits

Converting a stereo record back to mono eliminated the “eccentric” placement of instruments in primitive stereo, as expected. However I was somewhat taken aback by the improvement in sound on mono records when played in mono.

Playing a Mono record in mono results in a significant improvement in sound quality compared with listening in stereo: fuller more tuneful bass, brighter top end and more forceful sound image overall. All that cancelling out really does eliminate unwanted noise and phasing differences between left and right channels. (Illustration not to scale, but for illustration. That’s what illustrations do. Illustrate)

Even more benefits

Far from the signal degradation expected from sending the turntable output signal through an extra phono connection and length of cable, by using a very high-end copper woven cable (Kimber 1030) the previous turntable signal would appear to be cleansed of some extraneous signal contamination (controversial, but in an A:B test using a simple “Linn Silver” cable, Linn’s cable throttled most of the benefits) Both mono and Stereo sound better (though stereo is a tad quieter and needs a nudge on the volume)

Surface noise reduced by about 50% on mono records, as the “bad signal” is often asymmetrical between left and right channels and is cancelled out or much reduced in the merged signal.

Hissy vinyl of some Prestige and New Jazz Sixties pressings – manufactured with vinyl incorporating a quantity of recycled vinyl, is significantly reduced, from an intrusive level to a lower level which is fairly tolerable on a lot of them. I can only assume the foreign matter and detritus suspended in the vinyl is asymmetrical in its distribution and therefore a candidate for “cancelling out”.

The overall improvement in mono top end – brighter and clearer – is particularly welcome. I have a theory, not that explanation is necessary. I wonder if the upper frequencies encoded towards the top of the groove wall are more prone to differences between the left and right groove wall than the bass towards the bottom of the groove wall. Who knows?

Burn in

As with all interconnects, time is needed for burning in (another experience-based idea) I fully expect this solution to get better and better as the wires and components get used to the new properties of each other. And that is very good news indeed.

Postscript –

Renegade action by US postal service

Attempt to manufacture a mono- stereo switch and post to the US was sabotaged by the US Homeland Security who must have played fun and games with this switch. Despite being obviously “empty” and no threat, someone decided to snip the wires anyway, destroying a legitimate electrical product  for no purpose.  Assholes. Inconsiderate people.

UPDATE July 30, 2013

The stand alone mono/stereo switch has been retired, by the function being incorporated into the new custom-built phono-stage preamplifier, shown here (left, centre micro-switch):

The rationale and function remains the same, is equally effective in audio performance terms, and ergonomically preferable. In an ideal world there would be an led indicating whether the switch was set at mono (red) or at stereo (green), and a microprocessor which analysed the incoming signal according to mono or stereo.

The high-end reference model, the Boop-poop-pidoo,  would have an energy-saving curvaceous blonde to set the switch for you, and then mix your martini, very dry. But of course, this is a far from ideal world. What actually happens is you forget to set the switch correctly when changing records, and wear out the carpet trudging to and fro to change it. Still, it’s good exercise.