I am always tweaking this blog. Unfortunately I tend to edit existing posts, so it is worth re-checking pages you are interested in, if you have visited before.
Changelog 2/3/17 Minimalist compact crossover page added 17/3/17 Matt Monro songs added to Mysteries page 19/3/17 Memphis soul stew added to Renaissance to rock page
- Minimalist compact crossover
- Darlington Part 4, more thoughts
- Some History of technology
- Shakespeare Scrapbook
- 80 years of BBC TV
- TTL & Microprocessors
- Sallen & Key slope
- Rare pigs
- Flying Scotsman
- Ancient civilisations mystery
- Mystery of the Princes in the Tower
- Aviation mysteries
- The Maks
- Renaissance to Rock
- Raspberry Pi Part 2
- Simple Twin T oscillator
- MR16 Led bulb problem
- Darlington Pt 3 Serendipity
- Hi fi humour
- Cost effective darlington amp Part 2
- Raspberry Pi
- Metal dome tweeters
- Orwell festival
- My new amplifier
- active and passive elliptic crossover
- Car & plane concepts
- Warnock’s dilemma
- simple cost effective darlington amplifier
- overclocking the 555 timer
- Rhythm of the rails
- Mission Freedom & AR48LS
- 741 and inventions
- Fixing the 42PF7520D
- Pioneer Powerbass
- 3rd order low pass filter table
- X-max problems?
- Tweaking the DAP D3109
- LS3/5A Inspiration
- Homage to Tannoy
- W6-1139 & TM1A compact 3 way design
- Tweaking the Mission 762
- Loudspeaker projects
A remarkably cost effective 3 way active circuit is due to Egerton in WW Circuit ideas, Jan 1988. A subsequent analysis by Brian Pollard in WW Feedback July 1988 showed a slight error in Egerton’s analysis but despite that the circuit is adequate. As given the crossover frequencies are 363 Hz and 1.456 kHz. Egerton found he needed a 200pF capacitor across R5 to suppress high frequency oscillation. The midrange filter is a maximally flat type. I haven’t tried this circuit myself as I have only just found it. Such an elegant circuit demands a decent implementation. However the mid-range driver needs to be high quality and ATC domes do not come cheap! A 2 way design could be made by eliminating the woofer components.
The resistor values given are exact presumably so you can see the relationships. Putting the nearest E24 series values slightly changes the results. I scaled the resistor values to the highest I would be comfortable with. That also gives the lowest capacitor value.
Try R1,2,3,4 &6 as27k, R5 &13 as 16k, R12 10k, R8 68k, R10 39k all Cs 8.2n. If the Cs are made 4.7n the crossover frequencies are 655 and 2.675kHz, which is suitable for the Faital pro 3FE22 I want to try.
The circuit appears to be a minimalist form of the State variable filter. The tweeter circuit unusually uses differentiators and an op amp is saved by combining the summing functions. Rod Elliots adjustable version of the filter (an analogue DCX2496!) is explained here:
The circuit seems pretty close to a Duelund crossover. John K has an analysis of the Duelund here:
There is also a good analysis by Linkwitz on his site. The other John K used a Dayton RS52 in one of his designs, which might be an appropriate mid-range unit. However it would need a notch filter to get rid of the breakup spike.
I summed the outputs in simulation by using a simple mixer circuit. That showed that the polarity of the mid had to be inverted as Pollard had noticed, also that the mid out was 3db more than normal which could be compensated by the mid amplifier of course.
With R1,2,3,4 & 6 as 13k, R5 9.1k R12 3.6k R13 6.2k R8 47k and R10 27k also all Cs 10n you get crossover frequencies at 447 and 3.57k suitable for the venerated ATC mid dome
I developed the amp a few years ago and was surprised how good the transient performance of such a simple design was. I think that performance is partly due to the current drive of the output stage.
The concept makes a virtue of a potential problem. Baxandall pointed out that Transistor Cbc would slow the response. In this case it acts as a free Cdom stabilising the Vas, which is the output stage.
I needed 800 ohm base stopper resistors to make the simulated design work, but they were not needed for the real world (except for the anomalous ST TIP142). I suspect that this is why the real world high frequency distortion was better than 0.1%, whereas the simulated distortion was 0.5%. More work needed to match the simulated to the real results but I leave that to the experts.
It was revealing to look at the op-amp output when the amplifier was giving a full output 20kHz triangle wave. There is a dead band which transitions in 1 to 2uS so you will be blissfully unaware of any problem. The ramps show that the darlingtons have good linearity.
However I was not 100% happy with the voltage regulators as a band-aid fix for the quiescent current with supply voltage variation problem. Hence the design never made it to a dedicated PCB layout from the Veroboard prototype. Nor did I formally post it to Diyaudio. I developed it until it was good enough for my own domestic use, but would not regard it as a “production” design. However the prototype has been happily working for several years so I offer the following ideas which I have not tried for you to experiment with.
The main issue was the quiescent current variation with supply volts. A way around this is to have 2 current setting pots, one for each of the upper and lower halves of the output stage. The current defining resistor is eliminated. Also the voltage regulators are removed. When setting the currents a resistive load is required. R13,14,30 and 31 to be 250 ohm preset pots. R10 and R28 are removed as well as the regulator components.
The current stability would also be improved by defining the op amp voltages with zeners. To lower the self heating effects of the NE5534, the voltage of these would be 12 rather than 15V. R2,3,21 and 22 are now 12V zeners. Also R4,9 ,23,and 27 are 330 ohm.
The thermal feedback would be more consistent if the Thermistors were bonded to solder tags and the tags used as the power transistor mounting washers. Nelson Pass uses tagged thermistors in his designs which gave me the idea.
Lastly a R-C filter at the input to limit the bandwidth both for TIM and radio interference reasons would be worth fitting. Put 470pF caps across R1 and R20
Where it began, for our purposes, little known Elizabethan physician Gilbert
Thought Morse invented the Telegraph? Francis Ronalds invented it in 1816. Unfortunately no-one wanted it.
It has been 150 years since Maxwell presented his equations:
The history of Maxwells equations
My friend has summarised them here:
Heaviside’s conflict with Preece “Theory versus practice”
A worthy biography of Heaviside is “Oliver Heaviside” by Paul Nahin
Another 150th anniversary George Boole. Boole like Heaviside was self -taught.
There is more to Boole than Boolean
Interesting article about a contemporary of Maxwell and Boole, namely Babbage
More detail on the invention
Article about Babbages friend, the first programmer, Ada
Great piece on Ada and Babbage by Wolfram
Impressive comic book of the Ada/Babbage story
Another contemporary British invention, the Bessemer process
A quartet of Victorian engineers beginning with B
I had to make it a quintet of people beginning with B. Thomas Bayes came up with Bayes’ Theorem, a basic law of probability governing how to modify one’s beliefs when new evidence arrives. Are you Bayesian or Boolean?
In the Boolean worldview, the world is organised into basic situations such as Sydney being north of Melbourne. Such situations are facts. Truth is correspondence to facts. That is, if a belief matches a fact, it is objectively true; if not, it is objectively false. If you and I disagree, one of us must be right, the other wrong; and if I know I’m right, then I know you’re wrong. Totally wrong.
In the Bayesian worldview, beliefs are not simply true or false, but more or less probable. That is, we can be more or less confident that they are true, given how they relate to our other beliefs and how confident we are in them. If you and I disagree about the cause of climate change, it is not a matter of me being wholly right and you being wholly wrong, but about the differing levels of confidence we have in a range of hypotheses. Dare I say it, shades of grey!
Good explantion of Bayes Theorem
Another question, are you Babylonian or Balkan in your Philosophy? Feynman used to say that there were two kinds of Physicists, the Babylonians and the Greeks. He was referring to the opposing philosophies of those ancient civilizations. The Babylonians made western civilization’s first great strides in understanding numbers and equations, and in geometry.
Yet it was the later Greeks – in particular Thales, Pythagoras, and Euclid – whom we credit with inventing Mathematics. This is because the Babylonians cared only whether or not a method of calculation worked – that is, adequately described a real physical situation – and not whether it was exact, or fitted into any greater logical system. Thales and his Greek followers, on the other hand, invented the idea of theorem and proof – and required that for a statement to be considered thorough, it had to be an exact logical consequence of a system of explicitly stated axioms or assumptions. To put it simply, the Babylonians focused on phenomena, the Greeks on the underlying order.”
Nevertheless, the existence of Babylonian method has actually a deep sense: axiomatic approach can be formulated only if satisfactory number of facts, needed for the generalization, is accumulated.
Interesting reflections on Feynman:
Comments on the Feynman minority report of the shuttle disaster, interesting blog BTW
How ARM happened
More on the history of ARM
Arm 25th anniversary
350 years of scientific publishing. The Royal Society
Contemporary work showing interest in Science from the nobility
A good summary of the basics of electronics:
Germanium is making a comeback:
The hacker hacked
The history of spreadsheets or the first killer app:
Unsung computing hero Douglas Englebart
The engineering approach to innovation in science
Review of TRIZ for dummies
How to engineer serendipity
Divisions of time
Talking astronomy, where Jocelyn Bell discovered the Quasar. She, Lise Meitner and Rosalind Franklin are more famous female scientists than if they were Nobel Laureates:
Talking of Rosalind Franklin here is the story of the how the structure of DNA was discovered:
Lest I be accused of eurocentrism in the history of science
Sorry its creeping back in. Horrocks
Restoring the balance, Martin Bernal and Black Athena
More balance, Sanskrit and the periodic table
Erdos and the Egyptian fraction problem:
Computers can lead to experiments not being repeatable:
The future of the professions
Philosophy and work/life balance
Lord Nuffields philanthropy
Babylonian maths more advanced than we previously thought:
On the other hand:
The clock on most computers started theoretically on 1st Jan 1970. Someone has worked out when the clock on the Anti-Kythera mechanism started, for solar eclipses it is 12 May 205BC.
The age of enlightenment has become the age of entanglement
Newtons recipe for the Philosophers stone
The extraordinary career of William Dampier
Richard Hakluyt and his early travel book
The silicon revolution started at Shockley Semiconductor in April 1956 at Santa Clara which was the year Shockley got the Nobel prize for Physics for inventing the transistor. However by 1957 a number of staff he had recruited left to join Fairchild. More here:
How Silicon Valley got the name in 1971:
Unfortunately, all those manufacturing plants in Silicon Valley have left a toxic legacy in the groundwater.
The is/ ought problem
The above was written by Enlightenment philosopher David Hume who may have got some of his ideas from Buddism
Salvation by algorithm!
A scientific look at religon
Smartphones and social media are supposed to connect us. What happens when we are so constantly connected that forget how to be alone?
How information technology affects capitalism:
Maths lessons 4000 years ago in Babylon:
Another alliterative professor (see 741) was Ephraim Everitt who came up with the radical idea that Shakespeare had written more plays and suggested some. His idea was pooh-poohed at the time but these days there is more of an academic consensus that the bard wrote Edward III. Everitt also reckoned that the manuscript of Edmund Ironside was in Shakespeare’s own hand.
Well this is interesting. Kims FFP technique produced the following table:
Which shows Edward III to be more like Marlowe than Shakespeare. Also interesting is that the Henry VI part 2 and 3 plays are grouped with Marlowe, possible collaboration when they were both working for Stanley, but part 1 is elsewhere, possibly Nashe had some involvement. Dido, Queen of Carthage is also in the same area, might Shakespeare be the collaborator with Marlowe back in 1587. So keen is Shakespeare on the story of Dido, the Queen of Carthage, that he mentions her four times in The Tempest, twice in Titus Andronicus, and once each in The Merchant of Venice, 2 Henry VI, Antony and Cleopatra, Hamlet, and Romeo and Juliet.
One issue I have with Kims FFP technique is the spelling or lack of consistency in Shakespeares time:
Co-author with Marlowe of Henry VI ?
Another play to add to the canon?
Amazing what people can derive from a few lines of Shakespeare
Shakespeare as it would have been pronounced in 1600
Translate your text to Shakespearean dialogue!
Cumberbatch does Hamlet
Not a lot of people know that Shakespeare translated Hamlet from the original Klingon. For too long, readers throughout the Federation have been exposed to The Tragedy of Khamlet, Son of the Emperor of Qo’nos, that classic work of Klingon™ literature, only through inadequate and misleading English translations. Now at last, thanks to the tireless efforts of the Klingon Language Institute, this powerful drama by the legendary Klingon playwright, Wil’yam Shex’pir, can be appreciated in the elegance and glory of its original tongue.
Talking Sci-Fi I realised I had just missed towel day:
I have an obscure connection with Douglas Adams and it’s not that I once drove a Ford Prefect! There is a related obscure connection between Adams and the renaissance in that Douglas lived in the same small village as William Byrd, the medieval composer.
Consorts conjectures The absence of information about the ‘lost years’ of the Bard has led me to make some informed guesses about those lost years.
1578 Shakespeare leaves school early due to his father’s financial downfall and becomes teaching assistant at a noble house. He develops playwriting and acting skills teaching children. The noble house could have been the Stanley family place at Lathom. I think he could have developed into Stanleys Poet as it was fashionable then for noble people to have your own tame poet. When Stanley formed his own acting troupe in 1587 Shakespeare would have been in a good position to join the troupe. Stanley was a lawyer and he might have doubled as Stanleys scrivener..
1582 Aged 18, he marries Anne Hathaway and they have a child (this is known)
1585 After his twins are born moves to London. Possibly with Stanley at his London base (Cannon Row).
1587 He becomes so useful to acting company that he is invited to join, writing plays from scratch.
One more alliterative professor Hildegard Hammerschmidt-Hummel and Shakespeares portraits
A history channel documentary covered this (50 mins in)
Modern re-creation of Shakespeares portrait
The lack of evidence of Shakespeares life has led to some notorious forgeries:
These are extensively covered by yet another alliterative Professor, Samuel Schoenbaum’s in Shakespeares lives. Schoenbaum dominated Shakespeares studies and was intolerant of others views, yet with so little factual evidence there is only speculation. Ian Wilson in “Shakespeare the evidence” has a convincing argument that Shakespeare was under the patronage of Ferdinando Stanley.
The worldwide following of Shakespeare
Another attempt to rewrite the Bard
Where did Shakespearean Londoners go when they wanted a day out? To Brentford Staines or Ware according to Middleton and Dekkers Roaring girl of 1612. In Jacobean times the Thames was tidal up to Staines, so they would go up river on a flood tide and back downriver on an ebb tide. The journey to Ware was more difficult up the River Lea. Edmund Spenser described the river in his epic poem The Faerie Queene as “the wanton Lea that oft doth lose his way”. The Lea could confuse travellers with its twisting, splitting course.
Parody of “Shall I compare thee to a summers day”
Discussing memorable Shakespeare lines with a friend and he remembered “What news on the Rialto” from the Merchant of Venice. This had resonances with me as I am restoring a Reliant Rialto car! Another line from the same play he remembered was “Do cream and mantle like a standing pond”
The poisons, potions and charms of Shakespeare
On the 400th anniversary this seems apposite:
Which is Shakespeares most popular play:
Interesting that King Lear does not appear in the top ten in the US but is popular in the UK, perhaps we have more ageing thespians.
There is a link between the rythym of Rap music and iambic pentameter which I have only just realised, thanks to Lenny Henry.
Restoration of Religious paintings John Shakespeare supposedly whitewashed
Not alliterative but Oxford professors CS Lewis, Tolkien and Lewis Carroll turned Christianity, Anglo Saxon and mathematics into successful works of fiction.
Cornish influence on medieval Theatre:
On Nov 2 1936 the BBC started TV broadcasts from Alexandra Palace. There were 2 systems the Baird and the Marconi-EMI and both systems were tried, the Marconi system winning. That decision was made in March 1937. On May 12th 1937 the first British outside broadcast was made, the Coronation of George VI. You could buy these sets at launch:
By September 1938 KB and Philips sets were also available
These were household names back until the 1980’s, when Sony, Hitachi (GEC) Toshiba(Rank), Panasonic, Sanyo(Philips/Pye) and Tatung (Decca) took over. The bracketed make is the factory that the Japanese took over. Pedants will point out that Tatung was from Taiwan. Funny how the Japanese made a success of TV production in the UK when the Brits could not.
A BBC programme covers the start up:
The Baird work was not wasted as the flying spot Telecine became a useful piece of kit.
The 1953 coronation of the present Queen provided a major boost for TV. A lot of the population finding a place to view a TV set. My father in law built a DIY one for the occasion.
Here is the history straight from the horses mouth:
German experiments with early TV
Yet another great engineer beginning with B, Blumlein gets a posthumous Grammy award for inventing stereo, but his inventions helped establish Television.
TTL (that is transistor – transistor logic) is 50 years old
Good article on the history of TTL
A 4bit microprocessor built in TTL
An even simpler TTL processor
A more complex TTL microprocessor
See inside the 74181 ALU
A TTL processor that does not use the 74181 ALU also interesting web-ring
Not a lot of people remember the Signetics 8200 series and the AMD 9300 series TTL
While I am on a historical bent, this site is good on old microprocessors etc.
The z80 versus the 6502
Simple z80, 6502 and 6909 computer designs
The development of the 6502
and this on the 70s and 80s personal computer boom
Historical computer designs index
The modern way of designing a microprocessor using VHDL
People still use DOS
The 16 bit (2 byte) microprocessor came out in the mid seventies
I have not been paying attention to what can be squeezed into the humble 8 pin DIL package. How about the NXP LPC810M, a 32 bit ARM microcontroller or the Microchip 128K X 8 serial SRAM? Are they the most complex chips put in the package?