On Thu, 05 Nov 2009 18:55:49 -0600, flipper wrote:

On Thu, 05 Nov 2009 17:11:31 -0700, Jim Thompson
wrote:

On Thu, 05 Nov 2009 17:59:36 -0600, John Fields
wrote:

On Thu, 5 Nov 2009 17:56:35 -0000, "ian field"
wrote:


"Jim Thompson" wrote in
message ...
On Thu, 05 Nov 2009 11:12:46 -0600, John Fields
wrote:

On Thu, 5 Nov 2009 16:20:21 -0000, "ian field"
wrote:


"John Fields" wrote in message
news:9n24f5tikm8h0aaq6m04sgf58b2mdfkagf@4ax .com...
On Wed, 4 Nov 2009 22:09:04 -0000, "ian field"
wrote:


"John Fields" wrote in message
news:14b3f59r96io1hnj8bmets5hnhs09tu0b3@4 ax.com...
On Wed, 4 Nov 2009 13:17:24 -0000, "ian field"
wrote:

What would be the minimalist circuit blocks for a frequency domain
sample
and hold?

What I envisage is the sampling triggered by a tone that exceeds a
pre-set
threshold and continues to generate a copy of the tone until reset.

---
I'm confused...

What do you mean by 'sampling' and what do you mean by 'threshold'?

Sample a frequency - the analogy with "sample and hold" is once the
frequency is recognised, something like a VCO continues to reproduce
the
frequency until a reset.

Threshold is when a tone exceeds a set amplitude it triggers the sample
action, so as to prevent background sounds confusing the circuit.

---
OK, that's doable.

Next, do you need the copy to be a sine wave, like the original, or can
it be a square wave

Also, what kind of frequency/phase accuracy are you looking for with
regard to the difference between the source and the copy?

What else can you tell us? Voltages, power, etc, etc.

You know, the details the devil's in.

Its for feeding a digital frequency counter, so it can be converted to a
square wave at any point in the process.

The objective is for a frequency range equal to all the keys on a piano,
it
needs to be fairly accurate.

---
There may be a much simpler way to solve whatever problem you need the
gadget for.

What's your application?

JF

Sounds like piano tuning... he hits a key, and wants "sustain" (while
he counts it ??)

He'd be better off starting a high speed counter when both amplitude
and "zero-crossing" conditions are and measure period. Then invert to
get frequency.

You've got part of it, the piano in question is electronic with PWM note
generation so selecting church organ voice, while giving a sustained note -
gives a DFC reading of about 12kHz for any note. To solve that problem a mic
is to be used instead of connecting to the output jack, I want to measure
the frequencies that different instrument voices assign to the keys - church
organ is the only voice that has sustain.

---
I'm not familiar with PWM note generation.

How does it work?

JF

Class-D or similar. I'm surprised the "carrier" is only 12kHz...
seems low.

Well, according to this page

http://www.electricdruid.net/index.p...e=info.hammond

the highest generated harmonic on a Hammond is 5924.62Hz so, in
theory, it's enough.


...Jim Thompson

That's certainly pushing Shannon to the test ;-)

...Jim Thompson
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