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August 7, 2018 / consort3


I was fascinated by the Dynaco A25 loudspeaker, not sure if any made it to UK shores but a huge sales success in the US. Designed in 1969 by Seas Norway, it had a 10in woofer with Aperiodic bass loading and a 35mm dome tweeter There was no crossover filter on the woofer, a characteristic it shares with the EPOS ES14. If the woofer has enough frequency response to meet the tweeter yet has a smooth roll-off why bother with filters? It would meet my requirements of the time (early 1970s), reasonable quality for a reasonable price. Good article here:

Interesting Diyaudio thread on the A25

I was not aware of these firms until recently. They seem worthy of a mention in that they are one man bands in British Hifi.
Audiomods make tonearms,
LFD amplifiers
Monopulse loudspeakers.
Another speaker maker
Kralk audio

I have no connection with the above firms.

I came across this article for removing the bias setup in amplifiers

Interesting website “Reg on audio”, different Reg to the UK one though
Here is one from the UK guru’%20williamson’s%20-%20twin%20twenty%20-%20part%201.jpg
Navigate the above site using this:,%20diy%20projects.htm

I was interested in the inverse Chebychev filter for sub woofer excursion reduction purposes. This little known filter has the ripple in the stop band.  However the zeros needed make implementation tricky. The Filterwiz program gave possible circuits as the Boctor filter for low pass and the single op-amp Friend filter for the high pass. A free version of the program is available. However I came across these implementations of elliptic filters:



They look like a combination of Sallen /Key and Bridged T filters. They were designed on the Nuhertz program which is not free. I wonder if these would make a crossover filter. It should keep me quiet for a year finding out!

US embassy workers noises in the head:

RF cafes Kirt confirmation of the Frey effect:

There is a myth that the British invented Radar. The Nazis had been developing Radar since 1934 and entered WW2 with the Freya 2.5 metre early warning system, the Wurtzburg 50cm system, a naval radar on 80cm and airborne radar on 60cm. The US, UK, France, Germany, Holland, Hungary, Italy, Japan and Russia had early efforts in the field. Okabe of Japan had invented the split anode magnetron in 1927. The US really got going when Taffy Bowen  went to the US to demonstrate the cavity magnetron  as part of the Tizard commission in 1940. The basic technology needed for Radar was the same as for television and there was a concurrence.

Jerry Lee Lewis famously influenced a lot of Rock & Roll pianists, but who influenced Jerry Lee? A little known Country & Western pianist called Moon Mullican.

Moon is rumoured to have co-written Jambalaya with Hank Williams.

Here is a Zydeco version:

I havent seen an objective review of a turntable since the days of Gordon J. King but here is a review of a Rega 6:

Difficulty finding components? Try this site:

Multiplexing Christmas light displays by Charlieplexing

Interesting blog from New Zealand:

Steve Conners new blog I used to follow it when he was Scopeboy

This is an interesting page from the  blog:

The cost of quality

WM61 microphone to 48V interface

I got this from an interesting site:

How to get really directional speakers using ultrasonics

An article in the Nov 18 IET house magazine concerned a new book on Dudley Buck, The Cryotron Files. This computer pioneer had invented various computing devices and the book posits his murder by the KGB. However his early death may be more prosaic:

There is consistency in the London Marathon times. The average male time is typically 4 hours 14 mins and the average female time is 4 hours 48. The top 2% male runners will do better than 2 hours 26 and  the top 16% will do better than 3 hours 20. The top 2% female runners will do better than 2 hours 56 and the top 16 % will do better than 3 hours 52.

It looks like the Marathon organisers need to look at the statistics. The average time for female runners is 4 hours 48 with a sigma of 56 mins so the slowest runners will be coming in at 3sigma i.e. 7 hours 36, which is borne out by this story:

How to repair your Linn LP12 Valhalla:

There is a sub-culture with LP12 power supplies. Naim produced one called the Armageddon and there is a DIY version nicknamed the Geddon.

The first speech synthesiser in 1939 by Homer Dudley:

The first vocal encryption system from 1943:

A baffling quiz, test your speaker expertise.

Live London tube map

The Magnum Opus or the  Horn speaker Bible is about to be published

The legendary Kettering grammar school space ops
Which led to this:

Power Semiconductors

Article about tape hiss

Impulse H6 Horn speaker clone details (post1331)

I had tried the Myers Briggs personality test, but recently found about the big five personality traits. This article compares the 2 systems.

It is the 90th anniversary of Decca Records, who famously rejected the Beatles, guitar groups are on the way out Mr Epstein! How Decca got into the US record business:

How to remove clutter from your links

The lightning empiricist was a magazine published by Philbrick between June 1952 and 1969. It covered op-amps and analog computers.

Micro-cap is a analog design simulator. Back when Pontius was a Pilot, it was better than the industry standard Pspice for certain applications. The owner has retired and made a nice leaving present by making it free! I saw that it had a filter designer with an active inverse Chebyshev facility so downloaded it. I hope to do a poor mans Hardman crossover filter using it.

Exploring electronic junkshops or how I started my interest in electronics

The Sonos problem

Barrie Gilbert RIP

Gilbert is famous for the gilbert cell:

Douglas Adams and 42

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