Craig Sawyers

^This

From a purely thermal management point of view - absolutely, 100%. But from the product safety perspective to CE or UL, the general rule is 25C above ambient (to max ambient of 40C and external part temperature of 65C) for touchable anodised casework - and an external heatsink counts as casework. So most manufacturers of power hungry audio gear now put the heatsinks inboard. Like Krell and Emotiva - but not interestingly Mark Levinson who still put their heatsinks on the outside and don't bother to certify for external temperatures.

I'd do it somewhat differently - release final Gerbers, BOM etc but only to those on the list who are (a) trustworthy (by some criterion like long term, regular contributors, no newbies etc (b) agree formally not to release to a third party. Something like that might be workable and prevent blatant commercial design duplication. Probably achieve nothing other than satisfaction, but why not send a letter to the Russians who are selling the BHSE. Also I know Brian Sowter - I am sure he would be devastated to know that he is supplying his attenuator transformers to someone ripping off the hard work of someone else.

If it isn't the Chinese plagiarizing products it is the Russians. In a business meeting a year ago or so, the visiting guy had been shown the inside of a unit in China where they had a team of 200 whose job was to decompile embedded code, FPGA code, ROM contents etc of Western products. We don't stand a chance in hell against that level of industrial scale ripping off.

I sure hope they are paying Kevin a royalty on sales. The Sowter (UK, Ipswich) attenuation transformers used are really good though, and very well thought of.

I've got a forward looking one that is not in the car at the moment - the micro-SD card died. New one on the way. But if I was doing this again, I would have the variety that looks both forward and backward so you can record rear end collisions, or car park damage.

Easy thing to check with a thermocouple for anyone with a carbon or kgsshv. The caps in the KG-T2 probably get pretty toasty, but that animal drags ~200W out of the mains, the transformers run hot, and there are two massive heatsinks along each side of the case that also get hot. So although I have not measured the temp of the reservoir caps I suspect that they get pretty hot through association with their surroundings. But noone is gong to leave the T2 on for much longer than you are listening; I let mine warm up for an hour (two max).

OK - I'll bite - what is KR, ( M ?

This was too good to be true. So famous that Wikipedia has an entry, with first sentence (wait for it) "Vera Coking was a retired homeowner in Atlantic City, New Jersey whose home was the focus of a prominent eminent domain case involving Donald Trump." https://en.wikipedia.org/wiki/Vera_Coking

All down to Arrhenius for semiconductors. And electrolytic capacitor life about halving for every 10C temperature increase. Not counting infant mortality. And thermal shock every time it is turned on. So in this context, what do you mean by MTBF?

I was wondering that too - I don't immediately recognize the glass envelope.

Well bugger me - I'm British through and through back as far as I've looked (late 1600's) and I knew absolutely none of that. Other than that there is a City of London, I had no idea of the inner machinery.

Happy birthday!

The other thing to work out is which end of the primary winding is next to the secondaries. You really want the hot or live input to be next to the core, and the neutral or low input next to the secondary. It will of course be perfectly OK the other way round, but makes-borne noise coupling via the interwinding capacitance much easier. As far as I know there is no straightforward way of figuring that out.

Somewhere I have a photo of some poor sod's old man after he peed against an electric fence. Imagine you took a blow torch to a sausage, for several minutes.

Yes - Dalbani were the outfit that supplied me with junk 2sc3675's. When I put one or two spares on the curvetracer they broke down at 400V or thereabouts instead of 900V minimum. Avoid Dalbani like the plague.

$6+ seems to be what 2sa1968 are going for now. And there is no guarantee that even they are genuine. A 20c part is almost certainly fake IMHO. I'd say you have some major problems.

^Every time - every damned time - you reduce me to gales of laughter

That indeed is a good point given that the main semiconductors are long obsolete. My T2 went together during the first builds with fake 3675's and actually produced sparks. Killed just about every bit of silicon as collateral damage.

Current world pi memory record 70,300 digits http://www.pi-world-ranking-list.com/index.php?page=lists&category=pi took more than 17 hours to recite it. I actually saw a guy back in 1976 who only had only 10,000 digits, but had it in random access - given any three or four digits at random from the number he could continue from that point immediately. Same event (at CERN) that Wim Klein extracted the 73rd root of a 500 digit number in a little under 3 minutes. Klein's party trick was going out for a beer, and walking though the car park would memorize all the number plates and make/colour of each car. People in the bar would test him - he never got it wrong. He was employed by CERN to debug computer code - he was capable of doing a mental dry run to find tricky errors. Good heaven - I found a photo of that event on the web. I'm five rows from the front, 3rd from the right, checked shirt. Klein is standing, and the guy sat next to the projector is the pi man - totally forget his name. http://www.symmetrymagazine.org/article/december-2012/%E2%80%98human-calculator%E2%80%99-wim-klein-advanced-physics-inspired-others

Are both channels the same in this regard? If so, have you checked that the LED's are the right way round, and the 100V zener is the correct way round?

That is where your active diff probe comes in handy. But interestingly the really old generation Tek probes, I guess because of their physical size, can handle much higher voltages. http://www.reprise.com/host/tektronix/reference/voltage_probes.asp Although CMRR would not be as good as the current product, using two P6000's say, inverting one channel on the scope and adding might skin that cat. There are two NOS P6007 on eBay at the moment for about $70 each BIN/ONO, x100 and handles 1.5kV AC and 2.4kV DC.

^That, old son is good natured

OK - decent scope, but be careful what and where you probe. My tendency would be not to probe with the T2 turned on - one slip with the ground lead, probe tip or your finger could spoil your day big time. I would turn the T2 off, attache probe connections and turn on again. But bear in mind that any complex feedback amplifier can oscillate - IIRC there are the odd single figure pF capacitors in there to stabilise the amp. Also probe impedance can modify the effect - either stopping the oscillation, making it worse, or changing the frequency.

Now you're hitting my buttons. A Quad-like array of Neoliths.......