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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 7th Jan 2018, 11:46 pm   #1
Edward Huggins
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Default 79 Strand Speaker Cable.

Back in early 1980 John Catchpole, the well respected Head of Audio Design at Pye of Cambridge and author of "The Pye Book of Audo" and I were not happy over the limitations of the the then Philips imposed European DIN connectors for Hi Fi/Audio use. We conducted a series of experiments in the St. Andrews Road Labs using the increasingly popular 42 and 79 copper stranded cables. We used those from QED. We based the work on the most popular lengths of 1.5, 3, 5 and 7 metres. Given we were testing on DIN terminated kit, we tightly wound together the strands and tinned them to a c. 2mm solid strand soldered on to the DIN plugs. In those days there were no screw connected DIN plugs available to use. Tests were carried out on line resistance and inter-conductor capacitance and the results were faxed over to Eindhoven - no Internet then! There were clear improvements in both sonic and measured performance. The very co-operative Philips team could not disagee and, let's face it, really knew all of this anyway. Within 18 months (and co-incident with audio product manufacturing being moved from Eindhoven and Vienna to the Far East) Banana and Spring connector termination became the norm. Now at nearly 40 years ago, this seems almost lost in time, but I thought Members might be interested in this very "hands on" case.......
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Old 8th Jan 2018, 10:06 am   #2
Craig Sawyers
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Default Re: 79 Strand Speaker Cable.

That was very interesting Edward! The feeble DIN speaker connectors were not good, even pigtailed in the way you did at Pye. If you used hefty cable like 79-strand, the weight of the cable itself could cause the connector to pull out.

Back in the 70's I used to use a needle to push the feeble spring contacts in the receptacle inwards a bit to increase the retention.

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Old 8th Jan 2018, 10:44 am   #3
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Default Re: 79 Strand Speaker Cable.

Yes, the DIN speaker plug was grotty, but the mating socket was far worse.

I remember QED introducing their '79 strand' speaker cable. It was around the time the cable silliness took off. QED offered good quality copper with a sensible cross sectional area for low loss with typical speaker impedances and run lengths, and it was sufficiently flexible. The price was sensible as well.

I've been amused at how '79 strand' has become an icon, without mention of cross-sectional area. I started making jokes about 'factorisation distortion' when the silly people started saying single strand was better for something or another.

The Japanese iconised 'oxygen free copper'

I preferred simple good purity copper, no special attributes needed other than it had to be fairy-dust-free, and that can be assured simply by checking the price per weight of copper versus the London market price.

I've never counted the strands in what connects my hifi speakers, but 79 wouldn't surprise me. It's short, anyway with the amp right by them.

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Old 8th Jan 2018, 11:09 am   #4
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Default Re: 79 Strand Speaker Cable.

Quote:
Originally Posted by Craig Sawyers View Post
If you used hefty cable like 79-strand, the weight of the cable itself could cause the connector to pull out.
Rather like the dreaded SCART cables. In both cases, using a cable tie to strap the cable to a suitable point on the item's case to provide some strain relief, is often worthwhile.
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Old 8th Jan 2018, 11:40 am   #5
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Default Re: 79 Strand Speaker Cable.

DIN connectors are almost a worked exercise in how nice ideas go wrong in practice- and the sockets quickly got caught up in a race to the bottom. Some folk made DIN signal connectors with grippy, reliable rolled and formed plated brass leaf socket contacts and locking screw collar options that got used on stuff as swanky as Kudelski portable tape recorders and were very trustworthy- but mass market consumer stuff got cursed with sockets that had been made as cheaply as possible with stamped "tuning fork" contacts like the much-cursed McMurdo valve socket contacts, and with similar outcome.

I'm old enough to recall the QED 79 strand getting known- it was a perfectly sensible and unpretentious development with at least a grounding (!) in rationalism- but as so often in human endeavour, a degree of obsession sets in and proportion and scale are pushed into the background in the urge to be more conspicuously consumptive than the next man (and it probably largely is men....) and cable-hugging became a syndrome. I must have been about 15 when I acquired a Rotel RX802 (a fairly typical huge '70s receiver) with an intermittent PSU fault that was quickly fixed. About the first subsequent thing I did was to remove the hateful iffy DIN speaker sockets, fitting a small diecast box with 8x 4mm binding posts onto the original threaded panel holes for o-z plugs and QED 79 strand- (even then, I'd felt revulsion at the amount of professional surplus I'd seen messed up by bodging clowns. 28V kit fitted with unsuitable mains transformers- maybe secured by a single woodscrew, bargain basement all-plastic so-called "S meters" gouged into dignified old sets... Ooops, OT.)
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Old 8th Jan 2018, 1:21 pm   #6
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Default Re: 79 Strand Speaker Cable.

I've been using 79 strand cable since it's inception and find it works very well, there is no need for anything better unless you are using a very long run. It's good stuff and very sensibly priced in electrical factors like TLC.
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Old 8th Jan 2018, 2:38 pm   #7
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Default Re: 79 Strand Speaker Cable.

DIN connectors *can* be made properly: the cast-metal-bodied type with a locking ring were the standard for two-way-radio microphones for over three decades. Vehicle installations in taxis and emergency-service applications are a pretty unforgiving environment and the DIN mic-connectors never were a problem.

There were some truly horrid DIN plugs around though - worst in my opinion were the ubiquitous kind wich used the soft plastic barrel of the outer cover to hold two cheap, thin stamped metal half-shells round the plug proper.

For speaker connectors I much prefer the likes of neutrik "Speakons"; as to speaker cable I find 4mm or 6mm T&E house-wiring cable works just fine for domestic installs, though it doesn't well handle repeated coiling-and-uncoiling in gig/stage PA applications. Cheap though!
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Old 8th Jan 2018, 7:16 pm   #8
G8HQP Dave
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Default Re: 79 Strand Speaker Cable.

Am I right in guessing that 79 and 42 happen to be good numbers for arranging twisted layers of cable strands? The lowest such number would be 7? Does this sequence of numbers have a name?
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Old 8th Jan 2018, 7:19 pm   #9
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Default Re: 79 Strand Speaker Cable.

I suspect you're thinking of what now seem to be called 'centred hexagonal numbers' and which were just 'hexagonal numbers' when I first came across them.

Alas 42 and 79 are not members of that set of numbers.
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Old 8th Feb 2018, 12:30 pm   #10
dave cox
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Default Re: 79 Strand Speaker Cable.

Here are some 'circular packings' for 42 and 79 (you may need to scroll to find them)

42 strand here
79 strand here

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Old 8th Feb 2018, 12:58 pm   #11
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Default Re: 79 Strand Speaker Cable.

Very interesting: I had wondered why the spring-type speaker conectors were introduced.

The last equipment I bought that used DIN speaker connectors was some sets of outdoor Christmas tree lights that used them as power connectors for 24VAC. I must have got them around 20 years ago.
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Old 9th Feb 2018, 12:02 pm   #12
G8HQP Dave
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Default Re: 79 Strand Speaker Cable.

Quote:
Here are some 'circular packings' for 42 and 79 (you may need to scroll to find them)
Interesting. 79 has some loose strands, but at least they are arranged symmetrically. 37 would be better than 42.
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