Craig Sawyers

The horrors of Derna, with an estimated >20,000 dead as a result of two poorly maintained dams bursting, is alas a direct result of a state ruled over by two opposing political parties and inevitable lack of maintenance of infrastructure. That said, there have been apocalyptic storms battering central Europe and North Africa over the last month or so Madrid Spain https://www.reuters.com/world/europe/subway-train-lines-roads-closed-madrid-central-spain-after-heavy-rain-2023-09-04/ Greece https://floodlist.com/europe/greece-floods-september-2023 Bulgaria https://floodlist.com/europe/bulgaria-floods-september-2023-update Georgia https://floodlist.com/asia/georgia-floods-landslide-september-2023 Slovenia https://floodlist.com/europe/slovenia-floods-august-2023 Turkey https://floodlist.com/asia/turkey-black-sea-floods-july-2023 Russia https://floodlist.com/europe/russia-hundreds-evacuated-after-floods-damage-200-homes-in-sochi

I have a good friend who used to work on the security gate of a military airfield. They regularly would get some five star general, having waited in line, saying "Have you any idea who I am" to which the reply from the security team was to announce loudly "Excuse me everyone - this gentleman seems to be confused who he is. Can anyone help him?" At which point they would do a thorough security check on his vehicle "Can you take your luggage out of the boot sir. Can you open them" - you get the drift! Only the foolish fuck with security staff.

Oh yes he is. In an interview "I met my wife Jill at ESS — she was the Heil diaphragm tester — and she doesn’t have any problem with that. When I met her I had the Claw, a straight bass horn with a 50ft2 mouth and 9’ depth. Since then she has lived with the Kleinhorns (nearly as large, but stereo) and El Pipe-Os at 12’ high"

Nelson Pass's El Pipo transmission line speakers take some beating https://www.firstwatt.com/pdf/art_elpipeo.pdf The best quote from the article is "Funny things happen when your speakers are flat to 13Hz. You have to be careful about your tone arm, your windows, your neighbors, and your bowels"

Instability? Something in the circuit oscillating at beyond audio frequency?

That is a deep-pocket system for sure!

Reminds me of the Larkin poem They fuck you up, your mum and dad. They may not mean to, but they do. They fill you with the faults they had And add some extra, just for you. But they were fucked up in their turn By fools in old-style hats and coats, Who half the time were soppy-stern And half at one another’s throats. Man hands on misery to man. It deepens like a coastal shelf. Get out as early as you can, And don’t have any kids yourself.

I waged war with a family of rats that were under the garden shed. I bought a rat trap, put some chocolate on. Next morning trap snapped shut, chocolate gone, no rat. Tried cheese - same thing. So I bent the trigger so that if you sneezed it snapped. Chocolate on. Same damned thing. The darned things are really clever - must have been using a stick as a tool to trip the trap so they could eat the goodies. The neighbour bought a "humane" trap, and all he caught was a hedgehog. Then my cat got on the case, and worked here way through the lot. Came in each time looking a bit battered (rats fight back), tail high and proud. On the deck a half eaten rat. Repeat four times. Rat problem gone

Or theatres, or restaurants.

as a tool cabinet as you say it's going to have to survive quite a bit of weight. I'd use more than one cleat. I screwed mine to the wall with some fuck off screws

But straight grained is just not as attractive as cross grained (Krenov quirkily called such wood "rowed" - so the grain in interlocking rows). But it is a sod to finish properly, but definitely worth the effort. But that I had a helical head knife planer/thicknesser! I use Sapele as a substitute for mahogany. Because mahogany is CITES listed, many woodworkers buy old mahogany furniture and break it for the wood. I think that is a bad way of misusing old furniture, so I use sapele.

That is really neat. I'm a great fan of Sapele, but it can be a real bugger to get a good finish because of the cross grain nature of that wood. Because of that, putting it through a planer always produces tear out regardless of the direction of feed. I always end up using a scraper to get a good finish. With that in mind - how did you get such a great finish?

A belated very best wishes Antonio - happy birthday!

Lotus, like so many car manufacturers, is majority or entirely owned by China, the far East or India (Jaguar). Don't get me started on this soapbox....

ONSemi. Abandon all hope for the next production batches. Mouser says "758 Expected 12-Dec-23", but that alas for the hated semiconductor supplier, can usually be taken with sizeable a pinch of salt. Farnell says 249 will be delivered to them on 26th Jan 24. RS says 21st Feb 24 See what I mean about pinch of salt? Stock, when ONSemi finally supply a few thousand will disappear pretty darned quick as manufacturers hoover up stock for their production. Manufactured in China, like just about every semiconductor I've bought in recent times.

303's are stereo. I have a 33/303 + FM4 as my system in the kitchen feeding Mordaunt Short ceiling stpeakers. Fiber feed to a cheap D/A from the TV, and roof aerial to feed the FM4. The 303 is just about bullet proof. We used to use them in the mid 70's as disco amps. They had herbal smoke, beer and heaven knows what else ingested into them. Dented cases - and they just shrugged it off and just kept working.

The recommended torque for the AAVID shoulder washers is 5 to 6 inlb (0.565Nm to 0.678Nm) https://4donline.ihs.com/images/VipMasterIC/IC/AAVT/AAVTS01008/AAVTS01008-1.pdf?hkey=CECEF36DEECDED6468708AAF2E19C0C6 The TO220 specification for hole diameter is 0.139" to 0.161" - 3.53mm to 4.09mm. The spigot diameter on the 7721-10ppsg is 0.14" - so a potential clearance of 0.001" (25um) in diameter on the lower tolerance of the hole in the TO220 tab. Which is a push fit that needs careful alignment. But should be absolutely fine even in those circumstances. But it could be worth reducing the torque on reassembly to about 5.5inlb (0.62Nm) to meet the AAVID requirements. The torque could be with either dry threads or lubricated threads. Personally I'd go with lubricated threads, because any thread galling will really mess with transmitting torque to pressure between the semiconductor package and the heatsink.

You also need to be careful on tightening torque. For correct assembly, the torque is surprisingly low. I bought a torque screwdriver for exactly this purpose. What insulating bushes and washers have you used? Have a look at https://www.onsemi.com/pub/Collateral/AN1040-D.PDF Basically overtightening can distort the semiconductor package and compromise thermal transfer, and that you have split the insulating bush suggests you are massively overtightening the fixing screw. Craig

Even Madrigal/Mark Levinson (like the No33 spec) have performance data generated by muppets. RMS Power - there is no such thing. Well you could in principle calculate RMS Power - but it is a meaningless number. The only meaningful audio power is Average Power. See for example https://www.analog.com/en/analog-dialogue/raqs/raq-issue-177.html

Any idea what the amps are?

"Linn’s innovative Bedrok™ sidewall technology. This technology uses special beech plies that are compressed under high pressure, creating a solid and dense material that reduces unwanted vibrations." AKA Panzerholz from Delginit "Beech-based Delignit® materials feature special technical and mechanical properties (e.g. friction wear and resistance, dimensional stability, breaking load). Beech is one of the toughest and hardest types of wood. It is just 1/10 the weight of constructional steel but has 1/3 of its rigidity. Wood products also represent long-term storage for environmentally damaging CO2 (one cubic metre of wood absorbs almost one tonne of carbon dioxide)." "Panzerholz® A DIN 7707-compliant hardened panel material made of a combination of phenolic resin and hardwood with a hardened structure." https://www.delignit.de/en/brands.html . These guys also do bulletproof versions. In Panzerholz they apply high pressure to the ply makeup before the epoxy goes off, so it ends up much thinner and higher density that just regular plywood. It machines beautifully, can be epoxy bonded (white wood glue does not work), and can be polished to a fine finish. You have to hide the ply edges, (by a 45 degree mitre) or use them as a design feature. It is astonishingly well damped as a material, and stiff, which is why it has been used in audio products, including loudspeakers. I has actually been machined to make entire plinths, by epoxy bonding thinner plies and NC machining, or for my slate plinth as a simple 25mm thick support plate. There is alas little mystery regarding the "innovative Bedrok™ sidewall technology"

I have a few that almost never get used. My go to methods are ratchet straps and a selection of gizmos to protect the work, or Bessey clamps, like this https://www.besseytools.co.uk/bessey-die-cast-zinc-screw-clamp-lm20-10-200-100 which are not cheap, but are exceedingly good. I have quite a number in different sizes.

Happy birthday Birgir!

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