I am being asked to design a gadget that has some special features, but 
also includes a guitar tuner.  I have looked at the web a bit, but not 
found any good references that show exactly how a tuner works.  One 
paper I found talked about a rather complex "constant Q transform".  I 
just don't think the $10 tuner I have uses anything that complex.  I'm 
thinking they are doing a PLL sync to the input or something more like 
that.

One reference I found talks about using a peak detect to measure period 
rather than frequency like an FFT.  I would think the FFT has too little 
resolution unless it is very long.

Anyone know how the commercial low end gadgets really work?  Maybe I'll 
take mine apart, but my bet is they are using chip on board with the die 
under a dab of black goo.

Rick

On Mon, 13 Aug 2012 18:52:30 -0400, rickman <g...@gmail.com> wrote:

>I am being asked to design a gadget that has some special features, but 
>also includes a guitar tuner.  I have looked at the web a bit, but not 
>found any good references that show exactly how a tuner works.  One 
>paper I found talked about a rather complex "constant Q transform".  I 
>just don't think the $10 tuner I have uses anything that complex.  I'm 
>thinking they are doing a PLL sync to the input or something more like 
>that.
>
>One reference I found talks about using a peak detect to measure period 
>rather than frequency like an FFT.  I would think the FFT has too little 
>resolution unless it is very long.
>
>Anyone know how the commercial low end gadgets really work?  Maybe I'll 
>take mine apart, but my bet is they are using chip on board with the die 
>under a dab of black goo.
>
>Rick

I think you're generally right.   It has to be very simple, and since
the proper frequencies of the notes are deterministic and reasonably
spaced it allows some simplifying assumptions.

That said, by far my favorite type of guitar tuner is an LED optical
tuner:

http://www.amazon.com/Planet-Waves-PW-CT-06-S-O-S-Guitar/dp/B000FJEL9C

That's even simpler to build and has a number of advantages, like you
can use it in a noisy environment.   I've also found that I can tune
more accurately with one of these than a chromatic tuner.

If your application allows that sort of thing it might be worth
considering.


Eric Jacobsen
Anchor Hill Communications
www.anchorhill.com

On 8/13/2012 7:14 PM, Eric Jacobsen wrote:
> On Mon, 13 Aug 2012 18:52:30 -0400, rickman<g...@gmail.com>  wrote:
>
>> I am being asked to design a gadget that has some special features, but
>> also includes a guitar tuner.  I have looked at the web a bit, but not
>> found any good references that show exactly how a tuner works.  One
>> paper I found talked about a rather complex "constant Q transform".  I
>> just don't think the $10 tuner I have uses anything that complex.  I'm
>> thinking they are doing a PLL sync to the input or something more like
>> that.
>>
>> One reference I found talks about using a peak detect to measure period
>> rather than frequency like an FFT.  I would think the FFT has too little
>> resolution unless it is very long.
>>
>> Anyone know how the commercial low end gadgets really work?  Maybe I'll
>> take mine apart, but my bet is they are using chip on board with the die
>> under a dab of black goo.
>>
>> Rick
>
> I think you're generally right.   It has to be very simple, and since
> the proper frequencies of the notes are deterministic and reasonably
> spaced it allows some simplifying assumptions.
>
> That said, by far my favorite type of guitar tuner is an LED optical
> tuner:
>
> http://www.amazon.com/Planet-Waves-PW-CT-06-S-O-S-Guitar/dp/B000FJEL9C
>
> That's even simpler to build and has a number of advantages, like you
> can use it in a noisy environment.   I've also found that I can tune
> more accurately with one of these than a chromatic tuner.
>
> If your application allows that sort of thing it might be worth
> considering.
>
>
> Eric Jacobsen
> Anchor Hill Communications
> www.anchorhill.com


Interesting idea.  By optical I assume it means this is a stroboscope. 
The description talks about the "two out-of-phase LED light beams", but 
I assume that is just for brightness or do you think they are doing 
something fancy with timing?  Are the two LEDs the same color?  I guess 
if you pulse one LED at the fundamental and another at 1/3 the 
fundamental a 2x or 4x harmonic string will be fuzzy while just using 
the fundamental will also look right for any harmonic strings.  It also 
doesn't require picking just one string.  I may have to build this just 
for my own curiosity!

I don't think the customer will go for this, but I can't say until I 
talk to them about it.  It won't work in really bright light, but I 
don't know if this is a problem.

Thanks,

Rick

In comp.dsp rickman <g...@gmail.com> wrote:
> I am being asked to design a gadget that has some special features, but 
> also includes a guitar tuner.  I have looked at the web a bit, but not 
> found any good references that show exactly how a tuner works.  One 
> paper I found talked about a rather complex "constant Q transform".  I 
> just don't think the $10 tuner I have uses anything that complex.  I'm 
> thinking they are doing a PLL sync to the input or something more like 
> that.

I always thought that they did zero-cross detection, but never
looked inside. For the price, it has to be a microprocessor with
very little analog circuitry. Maybe a digital version of a PLL,
but I doubt an analog one. 

$10 tuner, minus store markup, doesn't give much to buy
the parts with.

-- glen

On Mon, 13 Aug 2012 19:49:16 -0400, rickman <g...@gmail.com> wrote:

>On 8/13/2012 7:14 PM, Eric Jacobsen wrote:
>> On Mon, 13 Aug 2012 18:52:30 -0400, rickman<g...@gmail.com>  wrote:
>>
>>> I am being asked to design a gadget that has some special features, but
>>> also includes a guitar tuner.  I have looked at the web a bit, but not
>>> found any good references that show exactly how a tuner works.  One
>>> paper I found talked about a rather complex "constant Q transform".  I
>>> just don't think the $10 tuner I have uses anything that complex.  I'm
>>> thinking they are doing a PLL sync to the input or something more like
>>> that.
>>>
>>> One reference I found talks about using a peak detect to measure period
>>> rather than frequency like an FFT.  I would think the FFT has too little
>>> resolution unless it is very long.
>>>
>>> Anyone know how the commercial low end gadgets really work?  Maybe I'll
>>> take mine apart, but my bet is they are using chip on board with the die
>>> under a dab of black goo.
>>>
>>> Rick
>>
>> I think you're generally right.   It has to be very simple, and since
>> the proper frequencies of the notes are deterministic and reasonably
>> spaced it allows some simplifying assumptions.
>>
>> That said, by far my favorite type of guitar tuner is an LED optical
>> tuner:
>>
>> http://www.amazon.com/Planet-Waves-PW-CT-06-S-O-S-Guitar/dp/B000FJEL9C
>>
>> That's even simpler to build and has a number of advantages, like you
>> can use it in a noisy environment.   I've also found that I can tune
>> more accurately with one of these than a chromatic tuner.
>>
>> If your application allows that sort of thing it might be worth
>> considering.
>>
>>
>> Eric Jacobsen
>> Anchor Hill Communications
>> www.anchorhill.com
>
>
>Interesting idea.  By optical I assume it means this is a stroboscope. 
>The description talks about the "two out-of-phase LED light beams", but 
>I assume that is just for brightness or do you think they are doing 
>something fancy with timing?  Are the two LEDs the same color?  I guess 
>if you pulse one LED at the fundamental and another at 1/3 the 
>fundamental a 2x or 4x harmonic string will be fuzzy while just using 
>the fundamental will also look right for any harmonic strings.  It also 
>doesn't require picking just one string.  I may have to build this just 
>for my own curiosity!
>
>I don't think the customer will go for this, but I can't say until I 
>talk to them about it.  It won't work in really bright light, but I 
>don't know if this is a problem.
>
>Thanks,
>
>Rick


Two red LEDs, and I *think* they just strobe at the expected
fundamental freq.   They're separated in space over about 1/4" when
projected onto a string, so you see the beat motion of the string when
the rates don't match and the two illuminated parts of the string are
still when the rates match (i.e., it is in tune).

For six bucks you can buy one and play with it.

I bought a bunch of them on sale once, and haven't used any other type
of tuner since (for guitars, anyway).


Eric Jacobsen
Anchor Hill Communications
www.anchorhill.com

On Mon, 13 Aug 2012 19:49:16 -0400, rickman <g...@gmail.com> wrote:

>On 8/13/2012 7:14 PM, Eric Jacobsen wrote:
>> On Mon, 13 Aug 2012 18:52:30 -0400, rickman<g...@gmail.com>  wrote:
>>
>>> I am being asked to design a gadget that has some special features, but
>>> also includes a guitar tuner.  I have looked at the web a bit, but not
>>> found any good references that show exactly how a tuner works.  One
>>> paper I found talked about a rather complex "constant Q transform".  I
>>> just don't think the $10 tuner I have uses anything that complex.  I'm
>>> thinking they are doing a PLL sync to the input or something more like
>>> that.
>>>
>>> One reference I found talks about using a peak detect to measure period
>>> rather than frequency like an FFT.  I would think the FFT has too little
>>> resolution unless it is very long.
>>>
>>> Anyone know how the commercial low end gadgets really work?  Maybe I'll
>>> take mine apart, but my bet is they are using chip on board with the die
>>> under a dab of black goo.
>>>
>>> Rick
>>
>> I think you're generally right.   It has to be very simple, and since
>> the proper frequencies of the notes are deterministic and reasonably
>> spaced it allows some simplifying assumptions.
>>
>> That said, by far my favorite type of guitar tuner is an LED optical
>> tuner:
>>
>> http://www.amazon.com/Planet-Waves-PW-CT-06-S-O-S-Guitar/dp/B000FJEL9C
>>
>> That's even simpler to build and has a number of advantages, like you
>> can use it in a noisy environment.   I've also found that I can tune
>> more accurately with one of these than a chromatic tuner.
>>
>> If your application allows that sort of thing it might be worth
>> considering.
>>
>>
>> Eric Jacobsen
>> Anchor Hill Communications
>> www.anchorhill.com
>
>
>Interesting idea.  By optical I assume it means this is a stroboscope. 
>The description talks about the "two out-of-phase LED light beams", but 
>I assume that is just for brightness or do you think they are doing 
>something fancy with timing?  Are the two LEDs the same color?  I guess 
>if you pulse one LED at the fundamental and another at 1/3 the 
>fundamental a 2x or 4x harmonic string will be fuzzy while just using 
>the fundamental will also look right for any harmonic strings.  It also 
>doesn't require picking just one string.  I may have to build this just 
>for my own curiosity!
>
>I don't think the customer will go for this, but I can't say until I 
>talk to them about it.  It won't work in really bright light, but I 
>don't know if this is a problem.
>
>Thanks,
>
>Rick

Update:  If you search YouTube for PlanetWaves SOS Tuner you'll find a
few vids, but this one seems to have the best view of how it looks on
a string:

http://www.youtube.com/watch?v=VLPghJtAxUk&feature=endscreen


Eric Jacobsen
Anchor Hill Communications
www.anchorhill.com

On Aug 13, 6:52 pm, rickman <gnu...@gmail.com> wrote:
> I am being asked to design a gadget that has some special features, but
> also includes a guitar tuner.  I have looked at the web a bit, but not
> found any good references that show exactly how a tuner works.  One
> paper I found talked about a rather complex "constant Q transform".  I
> just don't think the $10 tuner I have uses anything that complex.  I'm
> thinking they are doing a PLL sync to the input or something more like
> that.
>
> One reference I found talks about using a peak detect to measure period
> rather than frequency like an FFT.  I would think the FFT has too little
> resolution unless it is very long.
>
> Anyone know how the commercial low end gadgets really work?  Maybe I'll
> take mine apart, but my bet is they are using chip on board with the die
> under a dab of black goo.
>
> Rick

There's a whole sub-culture of there of DIY guitar players - making
their own stompboxes etc.
So using the almighty google and searching "DIY guitar tuner" gives
some useful results. You can take a look at the circuitry in some of
these links to see what they're using:

http://www.schickt.de/comments.php?y=08&m=06&entry=entry080606-004307

http://www.diystompboxes.com/smfforum/index.php?topic=88097.0

http://www.groupdiy.com/index.php?topic=4416.0

http://www.instructables.com/id/Visual--Aural-Guitar-Tuner-The-Tune-Trainer/?ALLSTEPS

Cheers,
Dave

"rickman" <g...@gmail.com> wrote in message 
news:k0c0fs$rhs$1...@dont-email.me...
>I am being asked to design a gadget that has some special features, but 
>also includes a guitar tuner.  I have looked at the web a bit, but not 
>found any good references that show exactly how a tuner works.  One paper I 
>found talked about a rather complex "constant Q transform".  I just don't 
>think the $10 tuner I have uses anything that complex.  I'm thinking they 
>are doing a PLL sync to the input or something more like that.
>
> One reference I found talks about using a peak detect to measure period 
> rather than frequency like an FFT.  I would think the FFT has too little 
> resolution unless it is very long.
>
> Anyone know how the commercial low end gadgets really work?  Maybe I'll 
> take mine apart, but my bet is they are using chip on board with the die 
> under a dab of black goo.
>
> Rick

AFAIAA, the algorithm generally works on cross correlation between the input 
and a reference frequency, which would be the intended frequency of the 
string. That's the way I'd do it.

The guitarists I know generally use phone apps nowadays. 

 rickman wrote:
>One reference I found talks about using a peak detect to measure period 
>rather than frequency like an FFT.

Since you are interested only on the fundamental frequency, not the
harmonic content, my first crude attempt would be to low-pass filter,
amplify, clip and measure the period.

No, I don't know how they do it either.
If I find it, I may vivisect the tuner I have *somwhere* at home.
--
Roberto Waltman

[ Please reply to the group,
  return address is invalid ]

On Tue, 14 Aug 2012 00:48:09 GMT, e...@ieee.org
(Eric Jacobsen) wrote:

>Update:  If you search YouTube for PlanetWaves SOS Tuner you'll find a
>few vids, but this one seems to have the best view of how it looks on
>a string:
>
>http://www.youtube.com/watch?v=VLPghJtAxUk&feature=endscreen

Thanks, Eric. That makes the whole thing dead-obvious as to
how it works. And it illustrates how to use electronics to
supplement and augment the human brain and anatomy to produce
something cheap and effective and appropriate all in one go.

I just love stuff like that.

Damn easy to do. I could punch one out in short order right
now, just seeing that. (Kind of like Galileo just hearing
about the invention of the telescope and from that and
nothing else knowing what needed to be done to make one.
hehe. Though I'm no where near as smart.)

Jon