Surround Sound Switch #3: Bulgaria (rotary switches)

Previously:

Mother Of all Relay Boxes
Rolling your own Commutator

Seems there's quite a lot of work in rolling your own commutator. Might it be useful to look at ways of simulating one, using only reasonably priced standard parts more readily available to today's hobbyist? Why yes, yes it might.

Start with a 7P8T rotary wafer switch and electrically collapse it into a 7-pole commutator, by first connecting the seven input signals to the wiper contacts, then connecting all 56 of its output terminals in a septuply nested helix pattern. Despite containing quite a lot of structural redundancy, in terms of the number of potential interconnections versus the number of configurations we actually intend to use, this design at least preserves this nice commutator property: for each of the eight positions on the dial, every one of the seven circuits contains just a single point of dry metal-to-metal contact. So at least we are still minimising contact resistance.

мартеница (Martenitsa - worn for Grandma March)

The Bulgar Fraction

To ebay now, where we find the RFT Palladium contacts 7P8T rotary wafer switches pictured below. Of German manufacture, priced in American dollars, being offered for sale by a gentleman in beautiful Bulgaria.

As you can see from the metric rulers thoughtfully incorporated into their sexy photoshoot, these beauties are about 6cm (2½") in diameter and 15cm (6") from head to toe. Each circuit or pole has its own dedicated 8-output wafer, and the modular design could quite obviously be adjusted to accommodate various other numbers of inputs and outputs. Such stackable wafer components are readily available from various suppliers, but the sheer novelty of finding such an exact, and so steampunk a match, to my very specific 7P8T configuration requirement, simply obligated me to buy one, even if only for a proof-of-concept prototype. Or actually two, since both were in need of some restorative care.

Materials Science

Palladium contacts were developed during the 1980s to replace the too-expensive gold finishes on the contacts of separable connectors used in burgeoning telecommunications systems. To inhibit corrosion by atmospheric chlorine, retard the formation of insulating frictional polymers on the contact surfaces, and improve wear resistance, an alloy, clad 60 per cent palladium / 40 per cent silver (for improved conductivity), with a small amount of protective gold diffused into the surface, and a new palladium electroplating process using a thin gold overplate, were developed:

Palladium contacts do not sulfidate or oxidize, and so offer extremely low electrical noise levels. They have an electrical life expectancy of approximately 10 times that of fine silver contacts. However, because of relatively poor conductivity properties, load currents are limited to about 5 amperes. Palladium contacts require .006” to .012” overtravel to insure good wiping action. Because of this, they are used primarily on telephone-type relays - that is, relays on which the contact arms are parallel to the length of the coil, and on which such overtravel is easy to obtain. Also, palladium contacts should be bifurcated to help insure circuit continuity on contact closure.

-- Tyco Electronics Corporation Relay Products Application Note [PDF]

The term "extremely low electrical noise levels" is relative to context. Telecommunications relays demand much less than audiophile listening! The "poor conductivity" is also cause for concern in our application, where the active load is only a few (typically 8) Ω. We'll return to this thought right after this...

Brief Note on Switch Soldering

After soldering wires to the terminals of a wafer switch, don't be tempted to use solvents to clean away any flux residue. This applies equally to any other soldered switch and relay types, including relay bases, used in your alternative designs (later designs in this series use mostly crimped and screwed connections, for which this advice is irrelevant). Such a solvent wash will indeed dissolve the resin as advertised, however the resultant dissolved resin can then spread over the switch contact area, depositing a thin, hard, and clearly undesirable film of resin as the solvent evaporates. As Ray Skipp's Workmanship Standards Manual advises, "Much less harm will be done by leaving small amounts of flux residue on the soldered joints."

About Ratings

Due diligence demands we check the operating voltages, currents and powers present in our circuit, and for this we need information about the equipment we're interfacing. On one end of our switch will be found a Yamaha RX-V777 AV Receiver/Amplifier (discontinued), sporting up to 160 watts per satellite or centre channel, into 8Ω loudspeakers. At the other end, a mixture of satellite and centre units from two merged harman/kardon HKTS 16WQ/230 5.1 Channel Home Theatre Speaker Systems (currently unavailable), all of which obligingly present an impedance of 8Ω to the passage of reciprocating electrons. So, the ballpark has these dimensions:-

V_rms = √(P × R) = √(160W × 8Ω) = √1280 V < 36V

I_rms = √(P / R) = √(160W / 8Ω) = √20 A < 5A

Actually, these figures should well exceed the voltages and currents produced in practice, possibly by a factor of two or more. This is partly due to manufacturers' traditional systematic exaggeration of the stated output power of their kit. I've taken the quoted wattage to express average power, which is the only figure that can be quoted honestly; anything else is disingenuous and evil! Funnily enough, manufacturers tend to look at this and say well, if that's just the average power, and if the instantaneous power drops to zero on every half-cycle, then the peak music power (a term they invented for purely marketing purposes) must obviously be double that. So they say yeah, double, sounds good. Let's go with that.

Anyway, on the unlikely assumption that the quoted power is the true average power, we do get the above quoted rms voltage and current. In reality, what we probably get is a grotesque overestimate. Which at least errs on the side of caution.

Other than to confirm that arcing won't worry any switch arrangement, the calculated voltage is of little interest. The room rotation switch should only ever be operated while the audio outputs are silent, preferably in fact when the power is off, so when its contacts are switched the instantaneous voltage is zero. That's important; the transient voltages (including inductive kickback) produced by making and breaking contacts, even at comparatively low volumes, can blow or otherwise damage both amplifiers and speakers.

The calculated current value is, on the other hand, of great interest. This is the required switch contact rating in amps, and five is a good target. Unfortunately, and although they perform acceptably at low volume and in the short term, this target proves too high for our Bulgarian rotators.

Don't Throw Out The Baby

Such shortcomings can be addressed in the manifest. Check these 12-way NSF rotary wafers: silver plated brass contacts, with an initial resistance less than 10mΩ, and a continuous current carrying capacity of 5A. Seven of these can be stacked to give us a 7P12T switch, and again we can wire it either helically, to perform our commutator switching function, or any other way, to get an arbitrary set of 12 independent speaker configurations.

These wafers also come in several other pole/contact configurations, e.g. 3P4T on a single wafer, just three of which could provide us with a full (up to nine channel!) 4-direction switch. For the purpose of these prototypes, I'll stick with an eight-direction switch just now.

The standard shaft assembly includes a balanced detent mechanism with a life expectancy of more than 100,000 operations. This component can also be "stopped" in order to reduce our 7P12T design to the original 7P8T logic. Alternatively, we just might be able to find a good use for those extra four switch positions...

Here's what I have in mind. Most 7.1 AV receivers can do a reasonable job of audio upscaling - providing seven outputs (and some bass) from any number of sources, even mono. However, and notwithstanding the soundtrack of the forthcoming Star Wars: The Force Awakens blu-ray, it remains true that mastered, curated, dedicated 7.1 channel content still forms a minority (albeit a growing one) of commercially available home cinema fare today. And audio-only surround sound content in particular tends to be mastered for the 5.x stage.

5.x: Rear speakers lost.

All Quiet In Back

This leads to a problem in our octoroom. When we select "Straight Decode" on the AV receiver, so changing its standing orders away from the direction of "Make it wow!" and more towards "Let me hear exactly what the 5.x mixing engineer intended", then all three rear speakers fall silent, as illustrated by the diagram on the right.

This seems one compromise too far for our octagonal arrangement of speakers. Surely that can't be what the engineer - erm - what's the audio equivalent of envisaged? Didn't Steven Wilson imagine that we could at least be trusted to put the "surround left/right" speakers a little way behind the listener? And what about all that concert hall ambience painstakingly baked into the rear of the mix, it that to stop abruptly at our shoulders now, as though we've just managed to poke our heads through the entrance?

5.x: Rear speakers regained.

The Big Reveal - Mode 5

My solution is to allow an alternative switching pattern for 5.x playback (see left), whereby the surround and surround back speakers are interchanged. Speaker 8 is still silent of course, as we have no provision for a central surround back signal. But speakers 1 and 2 have been swapped, as have 6 and 7. The result is a bit more like a traditional 5.x layout. Let's dub it Mode 5.

Admittedly this is different from the recommended layout of such a system, where the sidelining of the surround sound sources is intentional. However, specialist studio recordings custom mixed into 5.x demand to be reviewed and analysed using the extra depth provided by this arrangement. And incidentally, this arrangement can also be used to facilitate deep analysis of retro quadrophonic mixes, increasingly today released in 5.x format, which were patently designed for playback in 4-corner configurations.

Now back to that 7P12T rotary wafer switch solution, where we found ourselves with an extra unused 4 switch positions on the dial. With a few more bits of old wire, we could make this 5.x-oriented configuration available, allow it to be rotated so that any of the four walls is front-of-stage, and declare victory!

Depending on the detailed physical placement of your speakers, you might also consider moving the signals from speakers 3 and 5 down to the recently vacated 2 and 6, so that those two can now be repopulated with front presence feeds FPL/FPR, if such are available on your receiver. Obviously we'd need a further two circuit poles to carry these signals, making the switch an impressive 9P12T. The standard shaft assembly takes up to 10 standard wafers (spec; actually looks designed for 20), so we're still squeezing in. But the closer the physical speaker placement is to symmetric octagonal, the less appropriate would be such an enhancement.

8-way switch

Prototype Wiring: Two Flavours

On the right is is the wiring diagram for the basic 8-way switch. The seven ganged 8-way wafers are represented by the green rectangles, and the "comb" of wipers is shown horizontally along the top, in default position 1.

In fact, the prototype eventually constructed for this design included the four extended "Mode 5" patterns described earlier. To show the generality and versatility of the rotary wafer implementation of a commutator, I decided arbitrarily to interleave these with their corresponding 7.x counterparts. So, if you're sitting on one of the four main compass point orientations, switching one step clockwise takes you to that same orientation in Mode 5, while one more click takes you to the next vanilla 7.x point, 45° further on. Hopefully the following 12-step cycle notation is self explanatory:

N → N₅ → NE → E → E₅ → SE → S → S₅ → SW → W → W₅ → NW

If you remove the end stop from the shaft assembly, one more click takes you full circle back to N. But I retained the stop on the prototype. It lets you rewind to a fixed known position; useful when you don't intend to add any switch state indication, beyond a couple of scrawled crayon marks.

12-way switch

The 8-way wiring was pretty clear: just eight adjacent helices, appearing as diagonal lines on the flat drawing. The schedule for the 12-way is a little more complex. For clarity, label the seven wafers abcdefg, left to right in the diagram, and number the output terminals on each wafer 1-12, top to bottom. Then the wiring schedule for our eight output circuits, in order of speaker number 1-8, comprises these chains:

1 --- b₂ - a₁ - b₁₂ - c₁₁ - c₁₀ - d₉ - e₈ - e₇ - f₆ - f₅ - g₄
2 --- a₃ - b₁ - c₁₂ - d₁₁ - d₁₀ - e₉ - f₇ - g₆
3 --- b₅ - a₄ - b₃ - c₂ - c₁ - d₁₂ - e₁₁ - e₁₀ - f₉ - f₈ - g₇
4 --- a₆ - b₄ - c₃ - d₂ - d₁ - e₁₂ - f₁₀ - g₉
5 --- b₈ - a₇ - b₆ - c₅ - c₄ - d₃ - e₂ - e₁ - f₁₂ - f₁₁ - g₁₀
6 --- a₉ - b₇ - c₆ - d₅ - d₄ - e₃ - f₁ - g₁₂
7 --- b₁₁ - a₁₀ - b₉ - c₈ - c₇ - d₆ - e₅ - e₄ - f₃ - f₂ - g₁
8 --- a₁₂ - b₁₀ - c₉ - d₈ - d₇ - e₆ - f₄ - g₃

There are four physical wire crossovers between wafers a and b. Despite being at different "heights" above the surface of the switch drum, these need insulation. The other six big diagonal crossovers that are apparent in both 8-way and 12-way diagrams are artefacts of the mapping from cylindrical switch body to flat plane drawing; in reality they connect physically adjacent terminals. Still, they probably need insulation too, because they're so near the wiper connections. The rest of the wiring can just use tinned copper 0.6 mm² link.

Seven wafers shafted and
ready for octuple helixing

Pro / Con

As mentioned before, the rotary wafer switch approach preserves the commutator property of having just one point of dry metal-to-metal contact per channel on the switch. However, it also preserves the property that selecting between settings involves each wiper crossing a variable number of contacts, and this causes wear. A possible mitigation to minimize this sliding contact is to scramble the wiring diagram, such that the most popular settings become adjacent, reducing total wiper travel over time. Obviously, this might make future rewiring desirable, whenever a new setting (compass direction) gains popularity.

Bulgin PX0551, PX0956/S, PX0957/S
and PX0959/P. Not shown: PX0552.

Choosing the Connectors

This is the first in a series of interchangeable concrete prototypes, which I'll be wanting to swap in and out of use in the context of a live home cinema setup. The system I'll be using to facilitate quick swaps is based on this range of Bulgin 8-way plugs and sockets. These are rated 6A at mains voltage (250Vac), which is a little hefty for this application, but they're just what I have available.

Slightly more appropriate might have been the Neutrik Speakon, shown below right. This range is actually designed for multi-speaker connections, and does feature a subset of 8-pole connectors, both cable and panel mounting. On the other hand, these are designed specifically to handle four channels, and to take two wires per channel in a standard pin connection pattern. I'm using eight channels, one wire per channel, and ignoring the common connections. All the '-' outputs are joined together, and to all the speaker '-'s in the wall plate, by a single uninterrupted wire. These are already connected in common inside my AV receiver - I've obtained the circuit diagrams from Yamaha to confirm this. I'm reluctant to use the Speakon solution with nonstandard wiring, but using it correctly would double the number of plugs and sockets involved. It's a first world hard choice.

Neutrik Speakon connectors.

That reminds me, did I tell you not to use any of my prototypes in your car surround sound system? Yeah, those amps tend not to have a speaker common, but drive both ends of the coil in opposition to get the max oomph out of your 12V battery. Don't go commoning up them speakers Cletus, it'll go badly for you.

I'm not going to worry about scare stories of induced currents on unbalanced wires - electrical suppression is of high quality nowadays, and anyway these are relatively high current, low impedance connections.

Making the Connections

Whatever connector family is used, we just need to interrupt the positive amplifier output feeds and insert a cable mount plug/socket pair, with the socket on the amplifier end and the plug going to the speakers. The cable mount adapters are the upper pair in the Bulgin picture. I'm connecting audio outputs 1 through 7 to the corresponding pin numbers on the socket, and the audio amplifier common output to pin 8, just in case the particular switch prototype needs a reference to that voltage level.

If there's no prototype switch in situ, we just connect plug to socket, and everything's as it was last week. But then, each prototype will be built into an ABS project box, fitted with panel mount equivalents of the plug and socket. The panel mount adapters are the lower pair in the Bulgin picture. Take care to connect the panel mount plug to the input (amplifier) side of the prototype switch, and the panel mount socket to the output (loudspeaker) side. Now to use a particular switch prototype, just separate the continuity plug/socket pair, and connect them to the switch box. These adapter polarities will ensure the connections always go the right way.

Lumberg KV81, SV81, SFV80, KFV80.

Once the prototyping's done and I've settled on a final design for the switch, I might convert to 8-pin DIN EN 60529 IP40 connectors (left). These have brass contacts plated gold over silver, resistance < 5mΩ, rated 5A at 60Vac. They should scrub up nicely, albeit fiddly to solder given the girth of my speaker wires. At least the cable mounted plug & socket are available with a 6mm entry option (standard is 3mm), which should help a bit.

I say might convert to these, because I've a doubt about their mutual compatibility. As seen in this illustration from Wikipedia (right), there are two different pin geometries for 8-pin DIN plugs and sockets. And while RS Components assures that these four Lumbergs play nicely together, close inspection of the photos fails to convince. Update: I bought a set of four from RS Components, and it turns out that the cable mount plug and socket use the left pattern, while the panel mount ones use the right. So, yeah, no; they need to be either all 80s, or all 81s, a fact which had been 404'd out of their web catalog.

Post Script

While installing the Bulgin connectors, it occurs to me - not for the first time! - that a similar plug and socket, but with eight poles arranged in a circle (instead of seven with a central one), and with all of its keying Dremeled away, could obviate the switch requirement entirely. Just pull them apart, twist, and rejoin for a new sound stage orientation. But where's the fun in that?

Next time we'll start examining an alternative approach, using toggle switches, relays, and permutation group theory.

Surround Sound Switch #2: Commutators

Previously:

Mother Of all Relay Boxes

Colouring In

We're on the trail of a switch to rotate the sound stage in a room with eight satellite speakers. I've modified the previous diagram to include this component, labelled "7P8T Switch" - it has 7 Poles or circuits to switch, and 8 Throws or settings to accommodate our target of eight compass point orientations. Notice that one of the eight outputs of this switch has now been attached to the previously orphaned speaker number 8.

I've also coloured the wires connecting the amplifier output stages to the switch inputs, and those connecting switch outputs to loudspeakers. When working with multi speaker systems, both ends of every wire should readily be identifiable at all times. I use the following colour scheme, which agrees with the applicable Consumer Electronics Association (CEA®) Standard where possible:

(-)	Common Negative	Black
FL	Front Left	White
FR	Front Right	Red
C	Centre	Green
SL	Surround Left	Blue
SR	Surround Right	Grey
SBL	Surround Back Left	Brown
SBR	Surround Back Right	Orange*
SB	Surround Back*	Yellow
SW	Sub-Woofer	Violet*

* CEA® uses "Tan" for SBR, "Purple" for SW, and has no SB channel distinct from SBL/SBR. ANSI/CEA-863-A uses "Khaki" for SBR. My wire stocks are limited to the palette of the electronic colour code.

Spot the error?

Looking back to the diagram, the wire colours indicate that when the switch is in its initial (default) position, the SBL output is connected to speaker 1 (brown wires), SL to speaker 2 (blue wires), and so on. There is still no connection to speaker 8 in this switch position, since there is no yellow wire coming out of the receiver. As the switch is operated, these default connections are broken and various others made.

If you use wire markers of the type shown here, you'll be painfully aware their numbers don't lend themselves to a logical speaker numbering. The electronic colour code doesn't correspond to the CEA® audio source colour scheme. Best to ignore these numbers and just concentrate on using the correct colour marker for each wire. And maybe that's just as well, given the manufacturing error evident in these French made markers. Noticed it yet? Hint: it's in the right hand set.

Rolling Commutators

Okay, so what form does this switch take? Well, it need not be a literal 7P8T switch. Such a thing would be able to connect any input to any output, for each given setting or position of the switch; whereas we have certain considerations of symmetry to satisfy. For example, wherever the Front Left & Right (FL/FR) signals go, we'll surely want the Centre signal (C) to end up between those two. And we want to assign every signal exclusively to its own, unique destination speaker: no two distinct signals should ever become connected together. Assuming that we're uninterested in "mirroring" left and right (maybe to watch an upside down TV while practising handstands?) the symmetry group we're aiming for is just the set of rotations - and not the reflections - of a regular octagon.

Electro-mechanically speaking, the simplest solution is a sliding contact arrangement known as a commutator. Picture a row (let's call it a comb) of seven or eight electrical fingers or brushes labelled abcdefgh, in sliding contact with a copper circuit board. Yes, a comb of brushes, a comb whose every tooth is a brush; stay with me here. We may take these to be the amplifier output signals, and may choose h to be either "no signal", or else the amplifier's central SB output, if such exists. On this board too is a pattern of contact pads, linked in chains to eight output pins, numbered 12345678 along the edge.

As recently as the first moon landing, an engineer in need of such a commutator might take a stroll down Glasgow's Stockwell Street on a Saturday afternoon, to a shop called Radio, Mechanical and Electrical (R.M.E.) Surplus Supplies Limited. Approaching one of the gentlemen serving behind the horseshoe shaped counter, he'd ask for a seven or eight pole switch. Momentarily sinking from view, that gentleman would presently resurface clutching a massive iron, copper and bakelite contraption which, he would explain, had just been ripped from a decommissioned submarine a few days earlier. It would weigh about two kilograms in new money. "One pound and five shillings", he'd venture, causing the hot ash to fall from his cigarette into the surrounding component trays. But it was always possible to make a deal.

This diagram illustrates such a linear switch, with its comb in the starting position (first row).

In the initial configuration shown here, it's easy to trace that input a is connected to output 1, b to 2, c to 3, and so on. Now, operate the switch once. That's to say, comb the inputs, by moving the row of brushes down by one step. Assuming your eyesight is much better than mine, you should see that input a now connects to output 2, b to 3, c to 4, and so on, up to input g, which now connects to (previously disconnected) output 8; and input h, which has now looped around to connect with output 1.

Having satisfied ourselves that the switching arrangement works as advertised, we can easily see how this design might be transformed into a rotary configuration, such as a flat disc or cylinder. Actually, there's one little niggle worth mentioning about that. Did you notice this switch was implemented using just a single layer of substrate? This is intimately connected to the fact that the underlying symmetry we're modelling (rotations of an octagon, remember?) contains no reflections or other crossovers. But if we want a commutator without an end stop, allowing the control dial to spin freely in all directions, then we'll have to introduce another topological layer to provide the multiple helical connections required between channels. Otherwise these will interfere with the comb wiper connection tracks.

The commutator design has one great advantage over most others: there is just a single point of sliding contact per channel, where the brush meets the copper. Most of the alternative designs we'll be examining later have multiple contact points along each constituent circuit, leading to increased contact resistance per channel, concomitant power loss, and more seriously, greatly increased non-linearity.

Nitpicker's Corner

"But isn't a commutator designed to keep electric flow direction constant under rotation?" - Okay, here's what to do. Dig up your house, cement it to the top of the switch rotor, and spin. Now whatever direction your house points, the music will always come from geographic North. You're welcome!

Next time: We travel to beautiful Bulgaria in the hunt for a 7P8T switch.

Surround Sound Switch #1: The MORB

Mono - Stereo - Quad - Octo!

An octagonal pattern is a good general purpose arrangement for the surround sound satellite loudspeakers in a room. Not because of the wealth of media available in 8.1 or 8.2 formats (there are none), nor because it follows faithfully the researchers' and manufacturers' recommendations about ideal speaker placement (it doesn't). It's a good pattern because it so readily accommodates various others. Everything from 1.0 up to 7.2 in fact, the only exceptions being formats incorporating so-called front presence speakers.

Note: the ".1" and occasional ".2" or ".x" always refer to the sub woofer(s). Low frequency effects (LFE) being non-directional, these components can be placed almost anywhere in the room that's convenient, although if you're trying to fill a larger auditorium space, it's quite handy being able to place two diagonally opposed LFE sources rather than just one. In this series, as in real life, LFE sources won't get many more mentions.

More interestingly, the availability of that eighth idler satellite (numbered 8 in the diagram) allows any of these patterns to be rotated into any of eight orientations - think of the major compass points. Here I've numbered the speakers clockwise as seen from above, and arbitrarily selected the normally idle one to be eight.

From an AV viewpoint, most rooms have one default purpose or usage, which might be watching TV or movies, and so there is a natural "front" wall to the sound stage. But there may also be a frequently used projector, mounted to use another wall or corner mounted screen, in which case it would be useful to be able to rotate the sound stage to become centred in that direction. Again, surround sound music might best be enjoyed by sitting at yet another wall, perhaps to take advantage of the better stereo separation afforded by the longer side of the room. And so on.

Corner Cases

Incidentally, if you think eight orientations separated by 45° constitute a bit of overkill, and that four or even two separated by 90° increments should be enough for anyone, remember that many rooms acquiring a new projector along a wall will already be equipped with a television mounted on a corner unit.

Given the sheer quantity of sophisticated audio signal processing performed every millisecond by a typical modern AV receiver, it comes as a surprise to find that many of even the most recent models do not support this simple mapping of amplifier outputs to particular speaker terminals. What about crafting your own custom firmware to do the job? Well, these embedded systems ain't Linux. When it comes to sound codecs and audio processing, the template was set by the original Dolby pioneers in this area, killing off a thriving hobbyist community as bycatch; and it reads, Thou shalt not.

Seriously, I've tried every variation of approaching the manufacturers directly, seeking any option whatsoever of letting me map the preamp outputs to loudspeaker amplifier inputs. I've tried shaking my European consumer legislation threateningly at them, demanding transparency and disclosure. And I do have to admit, their objections do make perfect sense.

The octoroom is a compromise. But then, so is almost every surround sound system installed today. People will always push their surround speakers back into room corners, no matter what generations of psychoacoustic researchers say about their ideal placement. We might as well try to get the most out of that.

MORB-1
© Audio Design Associates, Inc

Did I mention that we're dealing exclusively with wired speakers here? Well, we are. No Bluetooth, no WiFi, no Cat 6. Just big fat high-current, multi-stranded copper wires. So that leaves us with one remaining option: a speaker switch.

Meet the MORB

Maybe what we need then is the Mother Of all Relay Boxes! This little beauty used a 12VDC trigger to switch up to eight amplified channel signals between two alternative sets of speakers. Originally designed to channel cinema sound into either one of two rooms, with a little bit of cross-wiring, the literature states:

MORB-1 can also be used to spin a room. Here we are talking about a room that has a stationary surround sound speaker array with a video display that spins to face two different directions. As the TV turns from one position to the other, the speaker array can be altered so that the proper speaker channels face the user at all times.

Were there only two out of the possible eight orientations of interest to us, which will usually be the case, then this might have been just the job. Unfortunately, the link to the MORB-1 cut sheet, while taking us to many alternative and very impressive modern systems, no longer leads to any specifications about the MORB itself. I get the impression from the Audio Design Associates website that the landing page for this old school piece of low tech is kept around for purely sentimental reasons. Last time I saw an original MORB-1 on ebay, it was going for about £400.

While we can only now guess what was contained within its 93 cubic inches (approx. 6½" x 5" x 3"), it seems safe to say it probably used substantial electromechanical relays, because: three inches tall! Also, any electronic solid state alternative would have carried the twin penalties of crossover distortion and non-linearity, disturbing both frequency response and the dynamic balance between soft and loud sounds.

Room Preparation

Already this promises to be a long journey, with multiple disruptive disturbances of the home cinema setup in prospect; better start defining some boundaries, and some interfaces.

The eight satellite speakers of the octoroom are permanently wired in place, using the thickest multi-strand copper wire available for the purpose. This turns the whole room into a single rigid component, which I'd like to be able to disconnect and reconnect with ease. Step up Euronetwork Ltd., suppliers of this 7.1 Speaker Wall Faceplate with 14 gold plated Binding Post Connectors, suitable for 4mm banana plugs. Of course the octoroom needs 16 sockets not 14, but luckily there's some space at the bottom - and the same company offers a single speaker version of the faceplate. I'll just drill a couple holes and transplant these... damn, they're different. Aw well, close enough.

While we're in the banana market, let's also make the AV receiver itself a little easier to slide out and into position. Following a YouTube breadcrumb trail from Big Clive, via Julian Ilett, and ending up at Techmoan's door, I discover this handy tip for making the unit's terminal posts compatible with banana plugs: pull the bungs out with a bent paperclip (I used a screw nail but the principle's the same, just debung'em). Then sling a load of gold plated banana cables between the seven AV receiver output terminal post pairs and the original seven post pairs on the wall plate, ignoring the extra eighth pair for the moment, and enjoy the new freedom of movement afforded by your Euronetwork hardware (any political irony detected in this sentence is entirely intentional).



Next time: Rolling your own Commutator.

Haken: Aquarius (2010)

Above: Celestial Elixir recorded at the twelfth ProgPower USA (PPUSA XII, September 17 2011, Center Stage Atlanta GA). This YouTube performance is taken from the official DVD, available from Lucid Lounge Studios.

After their self-produced Enter the 5th Dimension demo in 2008, the English progressive metal band Haken released their debut album Aquarius in 2010. Richard Henshall composed all of the music, and Ross Jennings wrote the words, for this concept album about a child born a mermaid.

Such a professional level of composition and arrangement has achieved recognition at the Guitar Pro format Tab site songsterr.com, where an extraordinarily detailed tab has been uploaded by prolific contributor (158 tabs at the last count) Chris. This instrumental version of the song is so well transcribed, it's a neat treat to listen to its realistic playback:

http://www.songsterr.com/a/wsa/haken-celestial-elixir-tab-s91733t3

Wizards and Warriors

What Could Possibly Go Wrong?

Players, such as wizards and warriors, have weapons; such as staffs and swords.

So innocuously begins Eric Lippert's latest forage into object-oriented design. Like all of his best work, this adventure soon takes us into various intuitive dead ends and surprising ambush back-alleys. You will nod sagely as he overcomes each successive objection, excises each fly from the ointment, with a new design principle or approach; THEN CURSE as your newest paradigm rears up and bites you in the assets. Finally, you will marvel at the astonishing and enlightened conclusion of it all, by which time you will have become a better human being in every sense that matters (to an object-oriented software designer).

Enjoy it here:

Part One
Part Two
Part Three
Part Four
Part Five

Note: the "DSLs" that emerge toward the end of Part Five are of course Domain Specific Languages.

The Uroboros and Other Quines

The 50-Language Uroboros

Eleven, Fifty, One Hundred Languages...

Something over five years ago, I described Yusuke Endoh's cycle of eleven programs - each of which, "written" in a particular computer programming language, prints out the source code - in a completely different language - for the next program in the cycle. Here, I have put the verb "written" into "so-called quotes", because in fact every program in such a cycle is auto-generated by the preceding one. So in fact, nothing at all need be "written", in the sense of "consciously composed" - half a dozen decent monkeys banging on a few old typewriters for a fortnight ought to suffice!

Just kidding, of course. Yusuke-san's achievement was and remains a very clever and unspeakably elegant construction. That its method of discovery can so readily be explained, and thence extended and generalised in various ways, detracts in no part from this.

The 100-Language Uroboros

Cyclic Cod Cosmologies

At the time, this extension of the Quine concept made me muse on the subject of Sims. The notion that our universe is "almost certainly" a simulation was trending highly at the time, and this cycle of languages seemed to lend the air of a Kekulé, benzene-ring "snake anecdote" to the previously hierarchical model of Sims creating Sims, creating Sims... and turtles all the way down.

For what if the laws of thermodynamics, working their random magic on the primordial "box of smoke" bestowed on us by an unstable vacuum, at some particular moment allowed the appearance of a configuration matching one of these Quines? Why then, wouldn't the subsequent evolution of the system be driven deterministically through the remaining phases, and eventually, back to that same starting configuration? In other words, the prime mover may be the ultimate effect, and we may well be products of creations we have authored.

Obviously this cosmology glosses over the fact that the laws of physics do not, in fact, appear to comprise a particular sequence of discrete, high-level computer language compilers and interpreters. Pah! Don't distract me with such trivial details!

Subsequent Developments

The original sequence of eleven languages went like this: Ruby, Python, Perl, Lua, OCaml, Haskell, C, Java, Brainfuck, Whitespace, Unlambda (and then back to Ruby). Then I missed a landmark in the development of this program cycle, because in 2012, Yusuke-san produced a 50-language variant demonstrating his complete mastery of the technique. Not so much by the sheer number of languages, as by the arbitrary character of his choice of "50" as a temporary stopping point, and the fact that all 50 languages are sequenced in alphanumeric order of language name!

Now there's a 100-language version, announced to the world on December 23rd, 2014 with the comment, "the 100th language: Lazy K. Merry Quine-mas!" This new dragon stretches all the way from A+ to Zoem and back, taking in all the Cs, sundry Lisps, Makefile, Visual Basic and LOLCODE among the many others along the way.

When you remember exactly what these programs do, the functionality disclaimer at the foot of the GitHub page is its own peculiar brand of comedy gold.

In Other News

Yusuke-san (@mametter) is also responsible - in collaboration with his wife Hiren (@hirekoke), whom he credits with teaching him Gingold, Monaghan and Lucy's SPH (smoothed-particle hydrodynamics) methods - for this almost-viral ASCII 2-D fluid mechanics simulator, currently doing the rounds:

Microsoft Achieves Privacy Standard

Microsoft has achieved the globally recognized ISO/IEC 27018 privacy standard for Azure, Office 365, and Dynamics CRM Online. And here is the BSI certificate to prove it! These services are now aligned with the standard’s code of practice for the protection of Personally Identifiable Information (PII) in the public cloud.

Further Information

Announcement last Monday by Microsoft's General Counsel & Executive Vice President, Legal and Corporate Affairs, Brad Smith:

http://blogs.microsoft.com/on-the-issues/2015/02/16/microsoft-adopts-first-international-cloud-privacy-standard/

"With the Microsoft Cloud, you’re in control", he concludes, and it's hard to deny that's a step in a good direction.