current source

Use an external accurate resistor ?:-)

...Jim Thompson

impossible... :-))

For the moment I'm oriented toward something weird and not usual like CCII, differential transconductors or very nice stuff like that... But I guess I can find something simpler, (I highly hope).

Does it all have to be on-chip? Can you make accurate capacitors?

-f

How can you make an accurate absolute value?

I _have_ done systems that periodically re-calibrate themselves, but you have to feed it a reference during the re-calibration.

...Jim Thompson

Speaking of self-calibration, I wonder what ever happened to that self-tuning piano?

Thanks! Rich

Pianos are enormously difficult to tune because the overtones are NON harmonic! The keyboard needs "stretched" to compensate for this effect.

Apparently the lateral stiffness of the strings moves the seventh ovretone up to where the eighth harmonic is supposed to be.

The lowest notes are lowered by as much as thirty cents. The highest notes are raised by as much as twelve cents.

A piano tuned with a frequency meter will sound awful.

And Opporknockity tunes but once.

I don't see how that would help, unless you have a rather special situation we don't see.

As for an accurate voltage-controlled current source, your MOS IC can be calibrated during test, with any of several special features you add to the design: laser-trimmed or zener-zapped resistor segments, EEPROM DAC-style calibration, EEPROM uP self-cal, etc.

These days, we are told, such enhancements take very little silicon real estate, and may even be plunked-in from IP libraries. The EEPROM approach may be more attractive because it's practical for more fab lines.

Alternately you could design your IC so the current- calibration feature works in conjunction with a uP, which would determine and store the cal coefficients itself under software control, and feed them to your chip at powerup. :-) In this way you can avoid a large painful expensive external precision resistor.

Jim can fill you in.

One of Archie Campbell's spoonerisms and a story he told a number of times on the "Grand Ole Opry", but he said, "Opporknockity only tunes once!". ;-)

yes, that's the problem

yes/no. Process is an unexpensive standard CMOS with no options (another big constraint). The only capa available is a MOS capacitor, not really the best capacitor in the world, but we can survive with...

Are you thinking to something like "switched capacitors (active) current sources"?

Not bad, though I need at least an oscillator. I was looking for simpler solutions, (I know, It's not easy...)

Thanks anyway.

maitre Aliboron

The harmonics must follow the fundamental. If a piano string is tuned aurally by ear to its perfect "in tune" pitch, the fundamental will have a specific, measurable, repeatable frequency.

The Self-Tuning Piano simply measures and stores the fundamental frequency (period, actually) of each string after it has been tuned by a master technician. These values are repeated in the field. No theoretical or calculated values are used. It simply replicates an actual human tuning.

I am currently switching companies to produce the device. QRS kept putting the project on the back burner. I'm meeting with an executive of a major piano company (I guarantee you have heard of them) in two weeks. Hopefully the product will come out by the end of this year.

Don A. Gilmore Kansas City

You are in for a VERY rude surprise when your results will inevitably sound TOTALLY AWFUL.

Piano overtones on the lower notes are definitely and empnatically NOT harmonics. But, yes, they do follow the fundamental.

Talk to any piano tuner for the secrets of keyboard stretching. Low notes should be as much as 30 cents low; highest notes should be 11 to 12 cents high.

Sounds like you do not have the faintest clue what you are attempting to do.

...And it sounds like you don't have the faintest clue who you're talking to. I have worked on this device for over fourteen years and have had the help of many, many piano technicians, college professors and international experts in the piano manufacturing industry. I belong to the Piano Technicians Guild (look it up) and I'm a degreed mechanical engineer with twenty years' experience (UMR 1986). I also studied piano at the Conservatory of Music at UMKC for sixteen years.

This device has been covered extensively in the media, like the New York Times:

NPR Radio:

New Scientist Magazine:

And many other publications including the Nikkei Marketing Journal (Japan), Der Spiegel (Germany), Intermediar (Holland) and radio programs in Australia, South Africa, India, South America and Canada and even on Paul Harvey's afternoon broadcast.

It is also patented (US #6,559,369); look it up. The working model sits right here beside me and tunes a piano absolutely beautifully in nineteen seconds and uses no moving parts. It will be endorsed by famous concert pianists from around the world.

Thanks for the laugh.

Don A. Gilmore Kansas City

Overtones and harmonics are different. Overtones are higher-order resonances of the mechanical system, which need not be anywhere near harmonically related. Drumheads and gongs have nice sharp resonances, but because the overtones are not spaced in nearly-harmonic order the way piano string and organ pipe resonances are, you get "thump" or "clang" instead of "Deeerrrrrrrrrrrr".

Cheers,

Phil Hobbs

You're splitting semantic hairs. Just because overtones don't exactly match the theoretical "harmonic series" doesn't mean that they don't follow the fundamental.

If I tune a string until I get just the right overtones at just the right pitches that I am looking for in my aural tuning, the fundamental will end up at a specific frequency. If I push the string way down flat, the partials all go flat too. If I then pull it back up until the fundamental is at the same frequency it was at before, all the overtones will also return to exactly where they were before. So the fundamental of a string tells you more than just the fundamental frequency its vibration; it also duplicates the entire overtone series since the partials will retain their same relative positions to it.

Don A. Gilmore Kansas City

Thanks for the update! I've been chomping at the bit to hear what it sounds like while it's tuning itself ever since you first mentioned it. :-)

Thanks! Rich

Sounds to me like he has more than just a faint clue, which you seem to have overlooked. Do you ever read, or just write? Go back to the top of this post, and reread what Don A. Gilmore wrote. Once it is tuned by a master technician, each particular string will have its own fundamental frequency. Record that. Now, when the piano goes out of tune, what difference does it make by which method that string is re-tuned to its own, known, fundamental?

Thanks, Rich

So, when do we get to hear it in action? Like the cat that ate the cheese, I'm waiting with baited breath... ;-)

Thanks, Rich

This in NO MANNER negates the fact that a properly tuned piano keyboard totally sucks.

The keyboard MUST be stretched to sound anywhere near decent.

They WILL be stretched, just like the factory tuning. Everything about the manual tuning is duplicated exactly. The system does NOT use the theoretical frequencies of equal temperament at all. (Damn, now you've got ME using kooky kapitals).

Don Kansas City