Craig Sawyers

Only on Head Case

That, Kevin, looks outstanding!

Studying engineering *and* practicing for a major international musician competetion? I'd say the two are mutually exclusive if you plan on sleeping at all. Either that or you will do both badly and end up extremely fed up with yourself.

Spent the weekend loading a van with daughter's stuff, driving to Woodford (E. London), cleaning the capets in her flat, and moving everything in. Thus starts the next phase as a 1 year MA in Acting for TV, Film and Radio.

The 2SC3381's are used as current mirrors. For these to work properly there needs to be good matching and thermal tracking between Vbe drops. The best chance of that is to use a dual device with both transistors on a single piece of silicon.

Sounds like a pretty good day to me

Depends on what your budget is. I've recently gone to using a TentLabs CD player, which sounds completely stunning - a real giant killer. It is nominally a DIY player (!) but is actually supplied as completed electronics modules, requiring screwing together into the casework and wiring up. Link is here Tentlabs DIY CD player . I actually got mine in a known not-working condition as payment in lieu for some business advice. Turned out to be a weakness in a power supply regulator, and current production now incorporates my fix. In any case, Tent repaired the unit free of charge without quibble (5 year warranty). If you don't feel comfortable building the unit, you can pay more and take delivery of a built one. The caveat is that if your budget is the sort of price for a used CDP-2, the Tent is going to be a very expensive option.

Been there, done that, with a Georgian front (ca 1760)/Victorian extension (ca 1870) around 20 years ago. It was a helluva job, but worthwhile. Fortunately we did not have a foundation problem. But the wall could be bowing for several reasons - it either may not be structurally well connected to the rest of the building, or the foundation might be poor. The first is relatively cheap, because the wall can be pinned back onto the rest of the structure. The foundation is much more of a biggy, and it depends on why it is sagging. If the ground is poor (boggy etc), there is not much you can do. but if it is just that the building was not properly founded it can be underpinned, but think major expense. Here in the UK you see lots of old properties in which bowing walls have been corrected by bolting them back together. Basically a spreader plate on opposite walls, and a very long metal rod with threaded ends that passes through the space under the floorboards at first floor level. Repeat as necessary along the wall. Also used in the US - there is a thread about it here a bulging brick wall & star-shaped bolts! - Old House Forum - GardenWeb

Think of it as a completely floating (ie not necessarily ground referenced) zenerless ideal voltage source. So very low noise, because high voltage zeners (in fact anything >6.2V) operates in avalanche mode, not pure zener, and is an excellent wide-band noise generator. Basic idea shown in the T2 schematic, which can be found with a bit of searching on the T2 thread. 6.2V mentioned above actually has a relevance to zener calibration standard voltage sources. Because this voltage is the transition between zener action and avalanche, and they have opposite temp coeffs. So 6.2-ish volts is exceptionally temperature insensitive over a narrow range. So such sources have zeners which are designed with the insensitivity at room temperature (20C), or at an elevated oven temperature (30C or so). All of which is completely irrelevant to any high voltage design useful for electrostatic phones.

Bitter sweet - I recognise that feeling. Bloody well done!

Jeez. Looks dreadful. Glad you and yours are safe.

That, sir, has left me totally helpless with laughter!

Looks great Kevin - it is a bugger to work being so tough. But real Lignum Vitae has a wonderful perfume, doesn't it? Really looking forward to seeing the final thing. You definitely need pilot holes for the screws though, or drill and tap - just as you would for metal. As you know I tried 1/4UNC and M6 with perfect results.

That is my stock phrase to team members when things aren't happening quick enough: "C'mon guys - this isn't rocket science. Wait a minuite....". This instrument is a real pushing-the-envelope thing. There are two X-ray imaging spectrometers (to look at the chemical makeup of Mercury's crust) mounted on a 1 meter long optical bench. There is also an electronics box with a multi-output switched mode supply and a data processing unit on a 14-layer circuit board. Total weight is 8kg (17lbs). It has to be seriously radiation hard too. In order to do the science, the sun has to be spitting out x-rays, which only happen when the sun is in an active phase - when it also throws out massive amounts of radiation. One consequence is that FPGA chips, which are normally around $10, cost $19,000 each in the space qualified grade necessary.

The single large ground pin is specced at #16

Deliver the units to on time and to cost target. International team of around 80 involved and a budget of Euro14m. Stuctural and Thermal model delivered on schedule, Electrical Model due for delivery end November, Qualification Model due around Spring 2011, and Flight Model Jan 2012. Overall buck stops with me.

Due to start on Monday in a half-time employed role at Leicester University. I was actually doing the same thing for 2 1/2 years as an external consultant, but they could not cope with even longer as an external bod. So - and heaven knows why on earth I agreed to this - I said I'd take a huge pay cut to continue doing the job as an employee - and (UK) academic salaries suck big time. I'm not really salary-constrained in a major way, and I kind of have a good rapport with the team, and a sense of responsibility to see the thing through - and that swayed the decision. This is as Project Manager for a deep space instrument called MIXS (the Mercury Imaging X-ray Spectrometer) due for launch by ESA in late 2014. NASA have the second only spacecraft (Messenger) visiting Mercury about now; it is not in Mercury orbit yet, but doing fly-bys as it slows down enough to get into orbit. Ours will be the third mission (BepiColumbo), getting into polar orbit around the planet in 2020. All sorts of planetary gymnastics on its 6 year travel to catch up with Mercury - as has been the case with Messenger.

Oof.

The amazing thing is that the active, signal-route part of the circuit, is four tubes and four FETs. Everything else is either current sources or voltage sources. Plus the servo, of course.

Bored and twiddling my thumbs waiting for semiconductors to arrive to fix the zapped T2, I thought I'd try to get a grip on what the actual signal level circuit was doing. I've replaced all the current sources and 740V battery with ideal symbols. I've also left out compensation components, and some of the details of one or two current sources which I think are error handling, to prevent the thing blowing up if a tube goes down badly. I think the result shows the rather neat symmetry of the design, and the clever way in which DC voltage shifts are generated using the FETs and batteries to move the ground referenced input signal to -500V. File is here http://www.tech-enterprise.com/tekstuff/T2deconstruct.pdf

Interesting. I've just measured where my ESL57's are - 56" from the rear wall and a ceiling height of 90" - so a ratio of 0.62! I seem to have iterated to GC's golden ratio just based on moving them around and listening.

George Cardas is one of the audio business good guys. Fixated on golden ratios for sure, but that fixation has led to some exceptional results. His golden trapagon stuff is aimed at distributing the room resonances at the listening position in an acoustically acceptible way. But it seems to be suited to monopole speakers (ie ones in boxes) that are omnidirectional at low frequencies, and excite resonances in all three room dimensions. I'd be interested in learning what his thinking is on placement of dipole speakers (such as electrostatics, or Magneplanar panels) which excite resonances only in one room dimension.

I guess you were lucky you were only dressed as a wolfman - could've been a whole lot worse.

Reminds me of someone I met at a strange party long ago.

I vaguely recall slowing down some of the scenes to see the detail of what happened to the crew. Not pleasant. But you're right, a load of tosh.