nonsense

To quote Queen Victoria, we are not amused.

Toroidal air coils don't have an external field and shouldn't pick up anything. Machines for winding toroidal coils do exist (though I've never seen one).

There are lot of different non-polar capacitors. Which one do you have in mind? A colleague who had built a calibrator for six digit DVM mentioned teflon film capacitors in his job interview. I never had to go beyond polypropylene film. It was a great job interview, and our principle engineer who also interviewed him, had much the same reaction.

A high electric field will compress the insulating film (in the same way that high current will stretch the wires in an inductor. But at high audio frequences neither the wire nor the dielectric has got time to more far enough to introduce much of a non-linearity.

She got extremely fat by the time she'd got to John Larkin's age. He has merely gotten fat-headed.

John Larkin experiences well-informed critism as a lame insult.

Why would anybody bother?

Because the MC1496 was John Thomson's cheap and dirty version of the four quadrant multiplier, and nobody is going to spend serious money on buying it.

Analog Devices have much better parts, laser trimmed for good performance, and they can get legacy part prices for small quantities of them.

If you were going to go to the trouble of actually building a low distortion oscillator - creating a complete scehematic, and a printed circuit layout and getting the printed circuit made, anybody sane would spend the extra money to get the high performance legacy part, rather than letting Jim Thompson's cheap-skate part mess up the performance

Who'd design for a 9V battery power supply? Or pay any attention to Edward Rawde's idea of a specification? There are already some LTSpice simulations in earlier threads here that ought to meet that specification. +/-9V might be a bit tight. +/-18V should be fine.

John Larkin experiences well-informed critism as a lame insult.

Why would anybody bother?

Because the MC1496 was John Thomson's cheap and dirty version of the four quadrant multiplier, and nobody is going to spend serious money on buying it.

Analog Devices have much better parts, laser trimmed for good performance, and they can get legacy part prices for small quantities of them.

If you were going to go to the trouble of actually building a low distortion oscillator - creating a complete scehematic, and a printed circuit layout and getting the printed circuit made, anybody sane would spend the extra money to get the high performance legacy part, rather than letting Jim Thompson's cheap-skate part mess up the performance

Who'd design for a 9V battery power supply? Or pay any attention to Edward Rawde's idea of a specification? There are already some LTSpice simulations in earlier threads here that ought to meet that specification. +/-9V might be a bit tight. +/-18V should be fine.

An ancient ic, and hard work to make it do anything with long term stability. Burr Brown made some very good multipliers in the past, but they did get swallowed up by Analog devices.

I might take a different approach, in that a single quadrant sine table readout, enough resolution, d to a, followed by a tunable low pass filter, might be an interesting approach.

We had the old Radford ldo and dms at one place, all analog and quite impressive for its time.

Chris

And Analog Devices had Barry Gilbert, who knew a lot more about four quadrant analog multipliers than anybody else, and quite a lot about quite a few other complicated chips. He started his career as a technical college lecturer in the UK, and really did know what he was talking about.

There won't be anything much wrong with the long term stability of the MC1496 - it will stay the same loose tolerance mess forever.

It isn't, unless you spend a fortune on a high resolution D/A. A tunable low pass filter isn't all that practical either.

A conventional toroidal inductor still has a single turn about the central axis. And an air-core toroid will still generate noise from a non-uniform mag field.

My first employer had a toroid winder, a little thing about the size of a sewing machine. It could handle small wire. The things that do heavy wire are totally different.

Lots on Youtube.

Depends on what you mean by "much."

It would be interesting to test caps for linearity at the sub-PPM level. Somehow.

A vacuum cap should be pretty good at audio frequencies, if it's rigid enough. One could build a differentiator to magnify harmonics.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

That was a recursive lame insult. Clever.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Yes. You can get a fast 20-bit DAC that's good to 1 PPM.

Drive that from a DDS core with a big 360-degree lookup table in RAM. Now one can tweak the table to null harmonics to deep-sub-PPM levels.

The problem, again, is how to measure the distortion.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

So post a circuit using one. I've yet to see anything from you do better than 60dB.

Yes I recall how high an opinion of JT you had.

Or generate insults just because they can?

How much noise do 9v batteries make?

Certainly low freq noise from chemistry tempco.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

If it's a chemistry problem then perhaps Bill can enlighten us about what effect 9V batteries may have and what filtering may be suitable.

Even 24 bit now, though that might limit output frequency.

You could perhaps use one of the older HP 35xx series analysers, to get started, and there are some quite excellent pro grade audio analysers that might be good enough.

Another way, since you know what the value should be, as it's in the lookup table, is to compare that with with the output, and as you say, autotune the output for optimum accuracy. Complicated to implement, but might be possible. Settling time applies though, as the servo loop adjusts.

Chris

I would never consider using raw battery power to drive any sensitive circuit, when a cheap fixed or variable voltage regulator could clean up the noise, and provide better stability as the batteries age.

Chris

I would never design a low distortion sinewave oscillator without allowing for easy change of power supply. Then I can decide what batteries/power supply/filtering is most appropriate at a later time. Using batteries for initial testing removes any potential ground loop issues which can arise.

There’s a paper from the LIGO folks about 1/f noise from batteries. IIRC alkalines were the pits, especially 9-volts. The best were NiCd and lead acid.

I’m not at my computer or I’d pull up the reference, but it isn’t hard to find.

They were all better than bandgaps, for sure.

Cheers

Phil Hobbs

Flabby ideas are worse.

You do seem to be getting less an less tolerant of critical observations. Try thinking a bit harder before you post - but that kind of intellectual exercise does seem to be beyond you.

I spent about an hour yesterday hiking around Central Station. An old friend from Melbourne was in Sydney and wanted to get together with me there at the point that is maximally distant from the point where my train gets into Central Station. She's also a old friend of my late wife, and somewhat bonkers, if extremely intelligent, so I got the exercise, tedious though it was.

Flabby ideas are worse.

You do seem to be getting less an less tolerant of critical observations. Try thinking a bit harder before you post - but that kind of intellectual exercise does seem to be beyond you.

I spent about an hour yesterday hiking around Central Station. An old friend from Melbourne was in Sydney and wanted to get together with me there at the point that is maximally distant from the point where my train gets into Central Station. She's also a old friend of my late wife, and somewhat bonkers, if extremely intelligent, so I got the exercise, tedious though it was.