Saturday, December 04, 2010

Changing climates

As I hardly ever write on my blog about my work I know that sometimes I meet people - when working - who take the trouble to "google" me, and think there's another Michael Saunby. Well, there probably is somewhere but the chap who was in South Africa in the last week of November was me.

It was great to meet like minded enthusiasts at the CTA Mobile Observatory 2010 and I'm confident that great things will happen as a result of our meeting. Thank you very much to everyone who made it happen, particularly Kevin and Pete.

Tuesday, September 21, 2010

Another distraction

Just acquired this bargain on eBay -

A 1940s Vortexion EG 20 electric guitar amplifier. Must be the big brother of the EG 10, as advertised in 1947.

Valves used are 4 x CL33 in parallel push-pull and 2 x EF40, no rectifier valve as metal rectifiers are used.

The amplifier is complete and very clean so my plans are to first do a minimal restoration to get it working in as close to original state as possible, then convert to safer AC use only with a modern mains transformer and 4 x EL33 to replace the CL33. Though I suppose that 2 x 6L6G would give similar performance.

I'll keep notes on the restoration here

Monday, July 19, 2010

KT44 push-pull valve "quality amplifier"

Here's the latest of my Wireless World Quality Amplifier builds. Again I've avoided the expense of vintage PX4 or PX25 triodes and used tetrodes. This time however they are strapped as triodes as in the classic Williamson and Leak TL/12. Those amplifiers used a pair of Marconi KT66 beam tetrodes as triodes. Williamson reckoned the characteristics of these valves when strapped as triodes was equivalent to the PX25. I've chosen to use the less common, but now far cheaper KT44 - actually Mazda 11E3, but they're the same valve. The KT44 is a rather different looking valve, it looks more like an 807 - itself a variant of the popular American 6L6G valve, much loved by electric guitar players.

From Quality Amplifier
The circuit is very simple. In essence it is the output valves and drivers from the Williamson, with the phase-splitter and feedback loop removed. So at present there is no negative-feedback, as in the original 1934 Wireless World Quality Amplifier.

Saturday, June 26, 2010

Back at the ranch

Last weekend I did something a bit different, a first for me. Indeed a first for the UK. The Vintage Computer Festival 2010 at the National Museum of Computing at Bletchley Park.

I took the uniselector clock with me and it was quite a hit, much photographed and now featured on several blogs, here are some -

But I'm at home this weekend enjoying the sunshine, so perhaps tonight I'll put my snapshots from Bletchley online. - Done. More 3D (anaglyphs) of the festival, museum and park on PicasaWeb.

Sunday, April 18, 2010

Stereoscopic Projection by Polarlised Light - demonstrated in 1936

The Wireless World - August 28th, 1936

Stereoscopic Projection by Polarlised Light

Experiments in Manfred von Ardenne's Laboratory

AT this year's Conference of the German Society for Photographic Research, in Berlin, a paper was read by Dr. Haase, of Jena, on new polarising filters and their applications. During the subsequent discussion it emerged that more exhaustive tests and measurements on stereoscopic projection, with the help of the new filters, had been carried on in the 'Manfred von Ardenne Laboratory. At a demonstration at the Lichterfelde laboratory an opportunity was given of seeing the almost startling results given by this solution of the "plastic film " problem. The optical quality of the pictures shown was so good that one felt oneself to be actually standing in the midst of the scene portrayed on the screen.
The idea of obtaining stereoscopic pro-jection by the use of polarised light was, as von Ardenne mentioned at the demonstration, suggested by Anderton a good many years ago. Practical application of the principle, however, failed because at that time there were no suitable polarisers available.

Polarisation Filters

It was not until the appearance of the new " polarisation filters " which have only been on the market a few months that it was possible to produce polarisers in the form of apparently ordinary spectacles, which, however, thanks to the correct orientation of the two "filters " forming the glasses, enable each of the two eyes to pick out only the appropriate image from a composite picture of two images thrown on the screen, each with its light polarised at right angles to the light of the other. Since the image visible to one eye vas photographed by a camera situated a little to the right or left of the camera photographing the image visible to the other eye, the effect on the observer is to give a stereoscopic picture. With the old-fashioned stereoscope, where the two pictures were side by side, the eves were inclined to strain themselves in bringing the two images together. With the present system there is no tiring effect on the eyes, because the two images are merged together on the screen by the projecting apparatus. On removal of the "spectacles," the naked eye sees only one picture (as the photograph shows). This is "flat," with its outlines double.
Completely satisfactory stereoscopic projection, such as was here seen, demands that the state of polarisation of the light should not be changed at the screen. Demonstrations and measurements have shown that this difficulty has been eliminated to such a degree that from all seats of an ordinary cinema the stereoscopic picture can be seen faultlessly.

Saturday, March 27, 2010

Bluetooth A2DP for the Quality Amplifier

In December 2008 I started building a variant of the 1934 Wireless World Quality Amplifier, and by the summer of 2009 I had a pair of these working with a valve preamp based on a Mullard design from the 1950s and a pair of the original Leak Sandwich speakers from the 1960s.
All very well, but this is 2010 and I seem to listen to music on Spotify more than any other source and radio programmes on iPlayer.
This week I added a Bluetooth A2DP stereo receiver to the amplifier, and I am very impressed by how well it works. Given that these things are almost being given away (mine cost £15) I cannot recommend it enough.

From gadgets
For anyone looking to do the same, here are my notes on getting it working with Windows 7 or Ubuntu.

Sunday, March 07, 2010


My latest "gadget hack".

From gadgets

Not sure what this 1940s telephone was originally used for, some sort of radio telephone link I guess. Anyway it seemed ideal for conversion to a bluetooth phone. With the handset down the original loudspeaker fitted in the dial aperture is loud enough to be heard clearly in a quiet room. I though some extra amplification might be needed, but I got lucky.

The clear glass bezel was in my junk box and works beautifully to allow the bluetooth earpiece blue/amber LED to be seen.

From gadgets

A simple project, but very pleasing.

Friday, February 12, 2010

Hiding a castle - no magician required

Update - 9th March. Since posting this Okehampton Castle and Okehampton Primary School have been given their correct locations on Google Maps. Well done Google! Oh and it's now easier to make corrections; see new-way-to-edit-places-on-google-maps.

Search for "Okehampton Castle" in Google Maps, and you'll see something like this -

Which looks so very plausible. There's no castle there though! Switch to satellite view and there's nothing to be seen.

Where is it hiding you ask?

Here it is (or yertiz as the locals say) -

Monday, February 08, 2010

Another thing computers will never be able to do...


This time from a BBC Radio 4 program.

Computers will never be able to simulate the "warrior ethos", the mindset and ethical outlook of the professional soldier.

Presumably it's vital to the proper conduct of war and only true soldiers have it.

Sunday, January 10, 2010

Will 3D save consumer tech?

Maybe, maybe not. Best experiment rather than go with guesswork.

Notes on my new Fuji FinePix REAL 3D W1 "on me wiki 'ere"