Craig Sawyers

The notorious test of cartridge/arm, the pressing marked A11 is the real killer. My Zu/DL103, SMEIV (with damper) and Garrard 401 tracked it like a champ. And frightened the bejeezus out of me at the first cannon shot! This is what the grooves look like:

Looking at the TP schematic, the noise is limited by the input resistors of 2k2. The native noise of the OPA1632 is an equivalent noise resistance of 100 ohms (ignoring 1/f noise). Even so, with 2k2 input resistors the input circuit SNR should be ~ -120dBu, which is still pretty darned impressive.

Common mode rejection is critically dependent on resistor tolerance in a balanced amplifier like the OPA1632. I'd have to look it up but I think 0.1% resistors will mean a CMRR of -60dB. And at that level you need to make sure they thermally track too, and have very low voltage coefficient. All that hoohah with discrete component tolerance and CMRR is why THAT have adopted everything on a chip with laser trimmed resistors and bootstrapping to make the common mode impedance huge. The InGenius devices get to -90dB CMRR, the only real disadvantages are the pretty average SNR of -105dBu because the internal impedances are in the tens of k range and 5ppm distortion. That is where the OPA1632 with truly impressive low noise of 1.3nV/rootHz and ridiculously low harmonic distortion of 0.22ppm wins big time.

Doris Day - RIP. Always a joy to watch her classic movies. A long life, decidedly disastrous in her choice of men, and rather reclusive in later years. And RIP Brian Waldon, UK political journalist, MP and rottweiler interviewer. His political interviews and comment was a much watch on a Saturday morning in the 80's is he put politicians on the rack.

Good way to match to that accuracy is to make four of the resistors into Wheatstone bridge. Feed with a DC voltage that makes sense (say 10V), and check for a null between the arms. If the resistors are worst case 0.1% all the wrong way, you'll get a voltage of 0.2% of 10V across the arms, or 20mV. So you now mess with your resistors until you get a voltage of less than 20mV. Then you know they are matched to better than 0.1% In an odd quirk of history, Wheatstone also designed musical instruments, the most famous of which is the concertina.

It is very difficult to find any explicit data on asymmetrical JFETs, other than that they are rare and used mainly in high RF work or similar specialised applications. I think is is almost certain that the ones we typically use in audio are symmetrical.

Happy birthday Shelly!

The horror, the horror....

70's was the era of, well quite a bit. It was definitely the decade that fashion forgot. Flared trousers got so outrageous I used to wear bicycle clip when driving to stop my feet getting tangled up with my trousers, and them dangling in the dirt on the floor.. Oh and shirt collars with rounded ends. And I was so proud of my centre parted hair. At least I never got into platform shoes. I looked in hindsight such a dork.

Definitely not a mash up. Now I've seen Paul Simon perform this live (with Sting singing backing vocals). But this is better. In fact the best IMO

The whole capacitor thing is interesting. Back in the day I developed a supermarket security gate to detect product tags and hence shoplifting, which for a few years was in use globally. This used two audio frequencies superimposed on a 20Hz triangle wave. The amp was class D (quite something for thirty-odd years ago) and hence needed an output filter. Designed one, and bought the bits - chunky inductor, and polypropylene capacitors. First thing was that the inductor melted, and that was when I found out about proximity effect. The second thing was that the capacitors howled like a banshee being tortured with a hot poker. Anyway the capacitor thing was really interesting. I tried a variety of manufacturers, and found that acoustic output was determined by tight winding of the foils. Second that axial tubular ones were quieter than radials. That was down to the manufacturing process for the radials. First the foil is wound on a cylindrical former. The former is pulled out and what remains is squashed flat. The voids that are inevitably left cause the noise through electrostatic forces. The quietest were cylindrical audio capacitors - a design now made by Kimber. Far too expensive for the product of course. But I found Roderstein axial ones that were also silent and cost much less. Roderstein is now owned by Vishay. Anyway, it was an interesting exercise. As far as I know no-one tests audio grade caps by passing an audio band signal through them (of an amp or so) and listening to them. Any acoustic output is (a) frequency dependent and associated with mechanical resonance in the capacitor structure and (b) is clearly associated with a loss mechanism. Aha - found a few left over - they were MKP1845, and Vishay still make them https://www.vishay.com/docs/26023/mkp1845.pdf . Just E6 values, which is a pain.

RIP a legend whose face we never saw.

Apparently only 100 made in around 1979 https://www.theanalogdept.com/reference.htm

Thorens Reference. Rare as hen's teeth. So rare I've never seen one for sale - and probably could not afford it even if I did.

I put Pearl tube coolers on mine. The idea is that the glass envelope runs at a lower temperature, which is reckoned to be a good thing. The jury is out whether it does what it says on the tin, but none of my output tubes have failed. So far. That was a bit of a fatal statement thinking about it ? For clarity that is on my Gilmore T2, not the Stax hot plate.

I think the word is "thermally challenged", and just a very basic unregulated power supply.

Alas they did not do Echoes. At 20-odd minutes it would have used up a lot of the concert. That original 1972 pompeii gig was superb. Two of the best of Mason's comments last night were "We're not the Australian Roger Waters!" and "I toured with Roger Waters, and he was jealous about using the gong. But tonight I get to use the gong myself!" (For Set the Controls for the Heart of the Sun) The very best recent version of Echoes was also at Pompeii in 2006 with Gilmore and Wright. The bass guitarist is the same guy that played last night.

Back to the earlier topic. Life expectancy skewed because the average included child mortality, which was exceptionally high. However, although Mozart and Schubert died young, JS Bach was 65, JC Bach 53, Thomas Tallis 80, Beethoven 56, Hildegard of Bingen 81, Wagner 70 etc etc And back even further to the topic of the thread - last night went to see Nick Mason in concert doing early Floyd - nothing post Meddle. So Piper at the Gates of Dawn, Saucerful of Secrets, Meddle, Atom Heart Mother and a few that I did not know at all. Despite being 74 now he had lost absolutely none of his drumming ability and played for two hours solid.

What a great looking cat, Jacob. He might well have a very long life still ahead of him. Our (remaining) cat Cleo is 16, nearly 17 and is still going strong. Eats like a horse. Because she is so old she is not so spry and cannot get out of the garden now. Which is a good thing given current circumstances with poor Cheese. My daughter says that cats leave paw prints on your soul. So true.

If it is white grease it is basically thermally conductive oxides in silicone grease. Providing it is still paste-like and not really thick and goopy you should be OK.

Great quote Jose. Could equally applied to Mozart, who produced this lot of 600-odd pieces and died age 34 https://en.wikipedia.org/wiki/List_of_compositions_by_Wolfgang_Amadeus_Mozart Many of them are somewhat formulaic, but the majority are sheer genius. He basically wrote to live - so he did weird things like write for the glass harmonium. He apparently worked out a complete piece of music in his head, and then just wrote it down on manuscript in perfect neat notation, no crossing out, no corrections. His widow Constanze lived by selling his manuscripts and performance rights, before she married the Danish Ambassador, and lived to the ripe old age of 80. I believe Schubert died from syphillis - the same thing that drove Beethoven deaf.

They can't airbrush Pears out of history - he was too much part of Britten's life, and a fine (if slightly quirky voiced) tenor. I picked up the vinyl of War Requiem that was recorded a couple of months after the premier at the new Coventry Cathedral. Same orchestra and soloists (including Pears) and conducted by Britten. From an estate sale - I swear it was never played, it is perfect. Cost the equivalent of $3 - a real find! Schubert left such a splendid canon of work. And died at age 31. He crammed a whole lot of superb music into such a short life.

Schubert's Winterreise in Dorchester Abbey https://en.wikipedia.org/wiki/Dorchester_Abbey last night. Awesome setting. Tenor was this guy http://www.markpadmore.com/ and very good he was too.