Craig Sawyers

Back a decade or three I was CTO of Wharfedale, and we acquired a bust company called Lynx for a tiny sum of money. Run by two New Zealanders; they made a really sweet range of products based around an FET power amplifier. Sounded very nice indeed (even if it was a bitch to manufacture). This is an example http://www.canuckaudiomart.com/details/649106536-super_rare_lynx_nebula_mosfet_integrated_amplifier/images/694258/ . Anyhow, we were sat one day when a return came in - with a letter saying from a guy in Hong Kong saying it had burst into flames and demanding some outrageous compensation. We unpacked it, and sure enough it was a charred mess inside. Smelling strongly of petrol. We got the Chemistry lab at Leeds University to do some forensics and write an expert report. We sent that to the guy in HK - and that was the last we heard from him.

RIP the 84 dead in Nice France when a truck drove through the crowds celebrating Bastille day, watching a firework display at 11pm local time. Bastard drove for over a mile swerving to kill the maximum number of people. More than ten children among the dead. Eventually shot dead by police.

Bloody hell - that sounds dreadful Chris. Fingers crossed it heals OK; what did the doc say?

You have truly surpassed yourself with that last collection, Knucks. Truly superb!

It is mains harmonics. You must be in the UK because they are at intervals of 50Hz. Nothing to do with signal distortion.

3200 people in Hull. Hull - how on earth that number of people in *Hull* were persuaded to strip, then be spray painted shades of the sea from head to feet is a matter of astonishment. All shapes, sizes and ages. It was the news coverage, where this mass of people walked through the city centre. Absolutely no passers by took the blindest interest - almost "Well - this is Hull on a Saturday morning - what can you expect?" In this world of woe, this all leaves me refreshed and makes me smile.

That is really rough. That is no age at all, and in such tragic circumstances. So sorry for your and Matt's friend Jake, RIP.

Have a great day Mike!

CHM must be loving all of this. It'll be interesting how the three NPC old blokes sitcom with cars thrown in works out.

Have a truly great one Birgir!

Two people who broke the UK in one picture - the privileged Oxford University (so-called dining) Bullingdon Club, Criterion for entry: rich. Cameron and Boris Johnson in the shot. Fills me with the urge to defecate.

Meanwhile, a hero's welcome for Trump to Scotland

Have a great one! Happy birthday

No way am I going to trust my machines to this POS. W7pro64bit is just fine thank you. There are all sorts of horror stories about corrupted hard drives, unrecoverable situations and dead machines out there. To kill off W10's pop up insisting I upgrade (which was installed against consent almost as a virus) I used this https://www.grc.com/never10.htm Ha Ha - double post was a result of installing W7 updates at the same time!

No way am I going to trust my machines to this POS. W7pro64bit is just fine thank you. There are all sorts of horror stories about corrupted hard drives, unrecoverable situations and dead machines out there. To kill off W10's pop up insisting I upgrade (which was installed against consent almost as a virus) I used this https://www.grc.com/never10.htm

Have great one, Justin!

Britain is entirely in shock, as is Westminster. First British politician to be murdered in 25 years, first woman politician ever. 40 years old, two young children, shot and stabbed to death in broad daylight around midday yesterday outside her political surgery (see below), which she was holding in the public library. The 50 year old perpetrator walked calmly away, and was arrested by police. He apparently shouted "Britain First" - which is an ultra-right murky organisation. It seems he has a long history of mental problems too. Flags at Westminster and Buckingham Palace are at half mast. Political surgery. Politicians are accountable to their electorate, and all (or most) hold regular events at which people can come and have a one-on-one meeting to discuss their concerns and issues that their MP can help with. Even the Prime Minister does them. Campaigning for the In/Out EU referendum has been halted.

Harpy eagle, the ultimate apex raptor. Claws second only to a grizzly. Crap quality vid though.

Agreed. I'd like to know the precautions that must have been taken in machining and polishing the Be mirror substrates for the JWST http://www.nasa.gov/feature/goddard/2016/james-webb-space-telescopes-golden-mirror-unveiled . 6.5 metres diameter, 20kg per segment and 18 segments = 360kg of beryllium.

Very few audio products use beryllium, even though it is close to being the ideal material in terms of young modulus/density ratio. Used in the 1970's in the classic Yamaha NS1000M speakers for HF and midrange units. Surprisingly not particularly toxic in the metallic state - it is the soluble salts that are the killer. The mirrors in the James Webb Space Telescope are all of machined beryllium, gold coated.

For rating transformers I use a free simulation package from here http://www.duncanamps.com/psud2/ . For a capacitor input filter (the usual sort) the transformer VA rating is always significantly higher than the power delivered to the load. This is entirely a result of the pulse-like capacitor charging current. Just as a for instance, Tx with 100V, 1ohm secondary, bridge rectifier, 10,000u capacitor and 700mA load. Power to load = 0.7 x 135V = 94.5W. VA from Tx = 1.8 x 99 = 178W. This is typical - you need somewhere about 1.5 to 2 times the VA rating for the Tx than is delivered to the load. The other way to do this is to use the nomograms in a classic paper by Schade (Proc IRE, July 1943, 341-361, "Analysis of Rectifier Operation, O. H. Schade). There is an update with measurements in Linear Audio, V8, Sept 2014, 83-127 "The Otto Schade Method, A practical design method for Rectifier Circuits" by Rudolf Moers. All of this agrees with http://sound.westhost.com/power-supplies.htm which concludes with Transformer The voltage is determined by the power that you need from the amplifier. Calculate power from the formula ... P = Va² / R Where P is power in Watts, Va is RMS speaker voltage, and R is speaker nominal impedance The supply voltage (allowing only for basic losses) is calculated as follows VRMS = Va * 1.1 Where VRMS is the transformer secondary voltage (for each supply rail) VA Rating - Class-AB The minimum VA rating suggested is equal to the amplifier power. A 50W amp therefore needs a 50VA transformer, or 100VA for stereo 50W amps. Larger transformers (up to double the amp power rating) will provide a 'stiffer' power supply, and this may be beneficial. For continuous operation at full power (never needed for hi-fi but common for guitar amps), the transformer should have a VA rating of up to 4 times the amplifier power. It is suggested by some transformer manufacturers (and no doubt gleefully adhered to by many amplifier makers) that the VA rating needs only to be 0.7 of the maximum amplifier power. While this will work well enough in most cases, you will not have a 'stiff' power supply - a more appropriate term would be 'soggy'. The DC voltage will collapse as more current is drawn. VA Rating - Class-A The minimum VA rating suggested is at least 4 to 5 times the amplifier power. A 20W Class-A amp therefore needs a minimum of an 80-100VA transformer, or 160-200VA for stereo 20W Class-A amps. Transformer rating may need to be as much as 10 times output power, depending on amplifier topology and quiescent current [2]. The constructor needs to be able to work this out, or transformer failure is likely.

^This.