Nationalism is a curse ... but there are a couple of waving flags above anyway ... purely as a clue to the nationality of your "hosts".

Our site's name - Highlands Cottage Computer Center (HCCC) - harks back to a time when computers were so expensive and comparatively rare that organizations tended to gather them together in one place, which served as a central resource for everyone who needed computing facilities. There were a lot of bad things about this, but also some good things. Since HCCC has many computers from the very new to the fairly ancient, used for both work and play, and since most of them are gathered in one small room, its not an entirely inappropriate name. Although, since we no longer live at Highlands Cottage, it is nowhere near as appropriate as it once was! Once you have a domain name, you are sort of stuck with it ...

คา สิ โน ฟรี เครดิต 1000 ถอน ได้

June 2018

For eleven years -- between 2007 and 2018 -- this website was served up by a Digital MicroVAX 3100-95 running VAX/VMS with the WASD web server. It never skipped a beat and still works perfectly. However, the server was at the end of an ADSL line and that inevitably made it quite slow. There is also now a need for more geographic flexibility -- mostly accessing e-mail from a web client, which I didn't want to set up on the VAX. So as of June 2018, this site and associated e-mail services are hosted at Vision Internet. It was a painless transition.

I have also divested myself of all the "big iron" test equipment for which I wrote the GPIB based control software described in some of the pages here. This includes the Z3801A GPS DO, so the pages related to that ("precision timekeeping") have been removed.

The equally "big iron" Studer and Revox audio equipment has all departed too. I occasionally regret that, but time marches on, and they are probably better off with their new owners.

Dom's stuff

Nick's stuff

(Last updated: 23rd August 2019)

• Electronics

  • Repairing a Sony ICF-SW100 Radio

    Pre 1997 ones will die of broken ribbon cables. It is inevitable. Repair kits seem to be no longer available. Desperate times call for desperate measures...

  • ReVox A78 Amplifier renovation

    A fine amplifier. My E-Bay purchased example needed some TLC, though. It is (er, was) used heavily on an almost daily basis. Hopefully it is now used daily by its new owner...

  • The Recorder-Reproducer Interface

    A totally over-the-top specialized sort of pre-amp for use with recording devices (especially professional analog tape machines). It took 5 years to complete... But I learnt a lot! I haven't finished writing a full description of this, but maybe one day I will.

  • Circuit Diagram Symbols Library for Inkscape

    A Python program that writes an SVG symbol library for use in Inkscape is here. The result of running that is here (save the linked file to disk as something.svg -- just clicking on it will show a blank page). Nothing wonderful, but at least it works as a proper symbol library in the latest version of Inkscape (V0.91). The SVG file needs to go in
    ~/.config/inkscape/symbols

  • The S-2020 Audio System

    A DIY audio project that replaces the source components and the pre-amplifier/controller that I had been using up to Spring 2016. There is nothing new here, but it might be another example for people thinking of going down the DIY audio route.
    A (large, 33MB) PDF version of this is here

• Electronics? Computers? A bit of both.

  • Controlling GPIB Instruments from Ubuntu Linux

    A way of keeping that unruly test and measurement gear under control using your Ubuntu Linux laptop and an Agilent USB/GPIB interface. Maybe of some use to people who want to do that sort of thing.

  • Controlling a Rigol DS1052E Oscilloscope from Ubuntu Linux

    Some software to control and read waveforms back from a Rigol DS1052E oscilloscope. It would probably work with other DS1000 scopes and may be a starting point for interfacing with other Rigol devices. This is an example of using the USB Test and Measurement Class support built in to Ubuntu Linux.

  • Using a Measurement Computing PMD-1608FS with Ubuntu Linux

    Some software to control a USB data acquisition (and digital i/o) device. This is pretty specific to this particular device! Since this code uses some third party GPL 2 licensed material, it too is GPL 2 licensed (unlike my other code here, which is MIT licensed or public domain).

• Computers (Modern)

  • Negatives in to Positives: Fun with a cheap transparency scanner

    A Python program that can convert raw orange scans of negatives to decent looking positives. On a good day, anyway.

  • Simple Dust Busting: Cleaning up white dirt on scanned negatives

    Describes one simple way of removing dirt (hairs and other grot) that appears white on scanned negatives after they have been made in to positives. Includes a mixed Python and C program that implements the method.

  • GTerm: A dumb Telnet terminal with colour graphics and APL support (Updated: August 2019)

    All written in Python (with PyQt, Cairo and lots of other stuff). I did this mostly so I could do interactive graph plotting and use APL on an emulated CDC mainframe computer, but it was an interesting exercise in many ways. I doubt anyone else will find it useful as such, but some not very well documented features of various technologies (such as option negotiation for usable Telnet sessions with the Python Telnet module) are explained (somewhat) in the code, so it might help someone. It works on Ubuntu Linux and MacOS. Porting it to Windows would not be totally straightforward (due to how it uses select()).

• Computers (Retro)

  • CDC Mainframes

    Control Data Corporation is, perhaps, largely forgotten these days. It built the fastest computers on the planet for the best part of two decades, however.

  • Innovations in CDC Mainframes

    Control Data Corporation computers introduced a lot of important innovations way back when. Some highlights are described here.

  • A Ray Tracer for CDC Mainframes

    A newly written (well, 2005) application to run under CDC NOS. For the very few people running CDC NOS ... Not recommended for general purpose ray tracing on today's machines!

  • U.L.C.C. in the 1970s

    The University of London Computer Centre (U.L.C.C.) was established in 1968 to provide a central computer service for the University of London based on CDC mainframes. Here is some information about U.L.C.C. in its "CDC Era" which ended around 1982. There is almost no record of the history of U.L.C.C. on the internet AFAICS. As of 2019, the old U.L.C.C. website redirects to CoSector Digital. This, it seems, is what U.L.C.C. has become. I believe the purpose built U.L.C.C. building has now also been demolished.

• Photography (2019)

  I have no pretensions to being a photographer. This is a link to a one-off project which documents a walk around London's Soho area in February 2018. The page it links to tries to implement a zoomable map using SVG with links to other pages. It works on Safari, but whether it will work on anything else I really don't know.

  • Project Soho

• Audio

  • My Audio Systems Through the Ages

    An illustrated trip down memory lane, eventually coming almost --- well, not very --- up to date. There were major changes starting in Spring 2016 which are not in here.

  • Open Reel Analog Tape Machines

    Why I find these dinosaurs interesting. Very interesting ...

  • Analog Audio Tape Performance

    Some thoughts on the objective and subjective performance of analog audio tape recorders.

  • Audible and Inaudible Problems with Digital Audio

    Things that are "wrong" with digital audio, including many things you can't hear. Summary: there is nothing fundamentally wrong with digital audio. Digital recording, in particular, is superior in every way to analog recording, although analog recording can be excellent and has its own "character". Recording to analog tape may force working practices that lead to a better overall musical outcome on occasion.

  • A Funny Thing Happened on the Way From the D/A Converter ...

    Large amplitude ultrasonic signals from a consumer soundcard ... most curious.

  • How AC Bias Really Works (Maybe)

    An attempt to explain the process that transformed magnetic sound recording quality from pretty dreadful to excellent. It isn't simple. A straightforward computer simulation helps explain it ... up to a point. A PDF version of this is available here (this is part of the unfinished Recorder-Reproducer Interface documentation). The equations are more readable in the PDF document, but you miss out on the animated GIFs!

  • An Audio Slide Rule

    Build your own slide rule to show the relationships between some audio quantities. Sticky backed plastic and cardboard may come in useful ...

  • Servicing a Revox A77 (Dolby) Tape Machine

    Information on repairing and lining up one of these beasts. They are still capable of really good results and there is no shortage of spare parts to maintain them. The "Dolby" version has some additional complications, though ...

  • Revox A77 - 41 Years Young

    Seven years on from the repairs described in the above link, another problem surfaced. Once that was fixed (not too hard) measurements show that the machine is pretty much as good as new. Wow!

  • Audio links

    The inevitable collection of links to other audio related sites, somewhat skewed towards Studer/Revox enthusiasts. Many sites are in German, so Google Translate may be your friend (well, sort of).

• Vintage Technical Articles

  • Studio Sound June 1977 - The Centenary of Recording Sound (73MB PDF file)

    A set of (perhaps surprisingly) erudite articles on the history of recorded sound. The coverage is both broad and deep, with some material I haven't seen anywhere else.

  • Some Articles by "Cathode Ray" from the early 1970s (13MB PDF file)

    "Cathode Ray" (M. G. Scroggie) wrote a long series of articles on fundamental topics in electronics, published in "Wireless World", starting in the late 1930's. In my opinion, his writing is extremely clear and entertaining. Quite exemplary, in fact.
    The link above is to a few random articles from copies of "Wireless World" I happen to have.
    For a more complete collection, his books: "Second Thoughts on Radio Theory" and "Essays in Electronics" are sometimes available second hand (e.g. via Abe Books). I cannot recommend these too highly --- most of the subjects he deals with remain very relevant (the laws of physics don't have an expiry date).
    A much better collection of his articles than the one at this site can be found at: www.vk6fh.com
    Douglas Self's always excellent site includes several "Cathode Ray" articles in his .
    Keith Snook's site has another excellent collection of "Wireless World" articles, many written by "Cathode Ray".

  • "Joules Watt"

    In the late 1980s another "Wireless World" author followed in the footsteps of "Cathode Ray". He (presumably "he" ... could be "she") went by the name of "Joules Watt"! They wrote a number of interesting pieces. Below you can find three of these articles, which are a pretty good read --- although maybe not as good as "Cathode Ray"'s (no offence intended!).
    • A fair introduction to Maxwell's equations. Some parts of the introduction may seem a little strange ... why is Maxwell's theory about to be replaced? Well, at this time there were several very vocal individuals bombarding "Wireless World" with letters expressing the opinion that conventional theories of electromagnetism were all bunk. They particularly disliked displacement current. It didn't end with Maxwell, by the way. They hated relativity even more ... in fact they hated all of modern physics! All very odd indeed ... This article was one of several aimed at responding to this nonsense.

    • All About Curls and Divs (9MB PDF file)

      A fair introduction to vector calculus, written as a follow up to the above article.

    • Logs Again (5MB PDF file)

      Sort of about logarithms. But also sort of about Bode plots. I'm not so sure about this one, to be honest...

  • "Pioneers" by Tony Atherton

    Also from the late 1980s "Wireless World" is this series of articles about people who made key discoveries or made real progress in understanding electricity and electronics. I don't have the full set, unfortunately. They are rather good, I think.

    • 1. Stephen Gray (1666-1736): discoverer of electrical conduction

    • 3. Andre Marie Ampere (1775-1836): father of electrodynamics

    • 4. Charles Wheatstone (1802-1875): master of telegraphy

    • 5. Samuel Morse (1791-1872): the American Leonardo

    • 6. William Thomson, Lord Kelvin (1824-1907): mathematician, scientist and engineer

    • 9. Guglielmo Marconi (1874-1937): father of radio

    • 10. Vladimir Kosma Zworykin (1889-1982): catalyst of television

    • 11. Edwin Howard Armstrong (1890-1954): genius of radio

    • 12. Jack St Clair Kilby (1923-): inventor of the integrated circuit

      
      (Dr. Kilby died in 2005, long after this article was written.)
  • คา สิ โน ฟรี เครดิต 1000 ถอน ได้ An excellent pamphlet from 1980 published by the Central Electricity Generating Board. It does what it says on the tin. I got this at a local boot fair in 2012 for 20 pence.

  • Fourth International Congress on Acoustics, August 1962 (6MB PDF file)

    The third paragraph of the section entitled "Psychological and Physiological Acoustics" describes an experiment by a Dr. D. L. Pimonow of the French "Centre National d'Etudes des Telecommunications" which is yet another that purports to show that the ear can detect the presence of filters in a signal path far beyond the known frequency of audible sine waves. In this case, a 45kHz low pass filter was detectable. The loudspeakers (ionophones!) and amplifiers had a "pass band of 100 kc/s", and the test signal was a train of 5us pulses at 2Hz, every second of which was filtered, with the other untouched. The subject adjusted the amplitude of the filtered signal until it sounded the same as the other signal to them. No doubt there are many factors that might be involved, but it is another example of these sorts of things that I came across quite by chance. There seem to be quite a lot of them, over many decades.