Software based tuners

ed packard · From: Show Low AZ

Tuners, in general, all share the same issues … accuracy, and stability.

Tuning forks and reeds will have frequency variation as a function of temperature.

Crystal oscillator controlled tuners will be only as accurate and stable as the oscillator … usually a function of voltage and temperature.

Software based tuner accuracy and stability is usually linked to the accuracy and stability of the frequency reference source used … usually the sound card contains the frequency reference source. All sound cards are not created equal, nor do they usually give accuracy and stability specs.

I have three software based tuners (perhaps only two), the BIAB, POWERTRACKS, and PETERSON STROBOSOFT. All (both?) of these indicate that their accuracy is sound card related. PETERSON suggests using an externally generated reference tone for the calibration of its software tuner; indeed, they recommend that one of their hardware tuners be used as the reference. I have not investigated the BIAB/PT issues yet.

Several questions come to mind:

1. What is an acceptable tolerance for accuracy?
2. What is an acceptable tolerance for stability?
3. What are the accuracy/stability vs. temperature for the various sound cards?
4. How stable are the thermal environments in which the sound cards reside (laptop vs. desktop etc.)

There are several methods by which to make these problems minimal:

1. Have an “online” frequency standard to which one can calibrate.
2. Record calibration tones on your hard drive.
3. Let your computer/external tuner get “up to operating temperature” before calibrating.
4. Recalibrate the tuner each time you turn it on UNLESS the tuner remembers the last calibration, and the operating environment has not changed.

I do like having the software tuner in my “virtual” preamp/effects rack.

Mark Herrick · From: Bakersfield, CA

Does anyone make a clamp so I can attach my Macintosh G4 tower to the leg of my steel guitar...

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ed packard · From: Show Low AZ

Bob L: I am not aware of WWV's freq refs being available online ... via radio, yes.

Mark H: I hope that your steel has large legs! I suspect that it could mount between the end legs if you are serious????

I use a software function generator, but have not checked it's accuracy yet re 440 Hz and cents.

Another little mental excercise: suppose that I record the A = 440 Hz reference onto my hard drive ... when I play it back, what variation might I expect?

Time and usage pressure upon the sound card makers should force the consistency/accuracy function to be compatible with the tuner usage without the calibration ritual. It may already be the case with the better designed cards.

John Daugherty · From: Rolla, Missouri, USA

My thoughts on xtal oscillator accuracy are: IF the xtal runs at 1 mhz and is divided down to,say,1000 hz,the change in the 1000hz signal is 1/1000 (.001) of the xtal frequency. This says to me that a change in xtal frequency of 10 hz would cause a change in the 1000 hz signal of only .01 hz.
I think I can live with that.

ed packard · From: Show Low AZ

John D: If such is the case then "no problemo"! The issue is perhaps a bit deeper. The concern is triggered by the warnings given by the makers of software tuners that calibration is needed per each installation. They point to the sound card as the problem. This indicates (to the degree that they are correct)that one needs a second tuner to calibrate a software tuner each time and place where it is installed (assuming that it remembers its calibration when the machine is turned off.

Then there is the issue that the hard drive RPM is not absolute either. So the experiment (per machine for the moment) is to record a known calibration 440 Hz signal (or similar) and compare the readback to that of the inputted signal for pitch shift ... over a period of time. I will get to that experiment, perhaps today.

Dick Wood · From: Springtown Texas, USA

Could somebody just give me a high Western E and I'll taker from there.

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Cops aren't paid much so I steel at night.

David Doggett · Posted 18 Jul 2005 6:44 am

I'm not sure how well various software tuners display their readout. Maybe some of the better softwares have very fine and stable readouts, so accuracy better than about 1 hz at A=440 (4 cents) can be observed and measured. The tuner in my POD XT, as well as the handheld tuners less than $100 that I have seen cannot be read with more accuracy than about 1 hz, or 4 cents. That is, their needles or blinking lights, or arrows, etc. do not respond to or indicate pitch differences less than that. With low notes it is much worse than that, and there is wild visual drift on every POD I have seen. The better handheld meters with needles, like the Boss TU12, are pretty stable, even with bass notes, but it is difficult to read their displays accurately within about 1 hz (4 cents) or less of the pitch. Those little guitar tuners that attach to the head and have blinking lights and arrows are much worse. You can hear the pitch change without seeing the lights or arrows change. They are just very coarse. I suspect that kind of limitation is much more of a problem than actual deviations of the tuners' internal reference pitch. If the lead guitar looks fine by one of these coarse tuners, but is sharp 0.5 Hz (2 cents), and the rythm guitar looks fine by the meter, but is flat 0.5 Hz (2 cents), then they are 1 Hz (4 cents) off from each other. If the bass player tunes by ear to the lead guitar, but gets it another 0.5 Hz (2 cents) sharp of him, then the bass is 1.5 Hz (6 cents) sharp of the rythm guitar, and that is very noticable to the ears. This same kind of drift can occur if you are tuning various strings to a coarse meter. To me, this kind of coareness of the display is more a problem in practice than I would expect tuner internal pitch variation to be.

Ray Minich · From: Bradford, Pa. Frozen Tundra

Is CHU Canada still sending out time signals? I remember, as a kid, looking for WWV on the old Zenith (wish I still had THAT radio) and stumbling across CHU. Just wondering if it was still alive?

Jack Stoner · From: Kansas City, MO

One issue with a sound card would be the Analog to Digital conversion. The sample rate can be an issue (the higher the sample rate the more accurate the digital representation will be of the analog signal. Newer cards with 24 bit conversion would offer more accuracy than older 16 bit cards.

PC accuracy, like other computer components, have got a lot better over the years. We are now looking at CPU's with 3+ Ghz speeds (and any "clock" would require a much higher crystal oscillator speed). That would translate into a more accurate clock speed. Not as accurate as the cesium beam we had on the NASA tracking station I worked at, but more than acceptable for audio frequency measurement.

The other PC issue is what else is running. I'd close all other programs if I were running a software tuner, so the tuner has the main use of the CPU (there are programs/modules that are loaded at startup and are required by the Operating system and those must run in the background. There are other startup programs that are not really needed and just there for "convenience" (I remove all the "conveninence" programs as they are totally not needed in the startup or Sys Tray (displayed in the lower right of the task bar).

ed packard · From: Show Low AZ

Five tuners (two hardware and three software) are used in this experiment. The experiment is to determine the effects of the computer/soundcard/hard drive/software et al on the pitch of the inputted, recorded, and played back signal.

Tuner #1 is the Peterson VS-II.
Tuner #2 is the Peterson Strobosoft on a laptop.
Tuner #3 is a Korg DT-1.
Tuner #4 is the software tuner in BIAB.
Tuner # 5 is the software tuner in Power Tracks Pro Audio 10.

Re DD’s “blinking lights” observation:
By using the VS-II’s cents adjust feature, and monitoring the VS-II output with the Korg, it appears that the 440 Hz with 0 cents offset lights the center (0) led on the korg. -1 cent on the VS-II lights the first led to the left. -3 cents lights the second led to the left. -5 lights the third led to the left. – 20 cents on the VS-II lights the led marked -20 cents on the Korg. Same game going positive in cents, except that +1 cent still reads 0, and the first led to the right lights for either +2 or +3 cents offset.

Re the Korg DT-1, one led position off from 0 may be either 1 or 2 or 3 cents off from dead on. DD, your comments are definitely in the ballpark re at least this Korg LED tuner.

Now back to the software vs. hardware tuner issue. One issue with the Peterson Strobosoft seems to be that it is a download (no CD). This presents a problem re live performance usage. If the machine crashes, or the Strobosoft pgm screws up, recovery becomes an issue.

Unfortunately in this case, I had installed the Strobosoft download and performed the calibration prior to starting this experiment, and the calibration seems to be remembered after turning off and restarting the machine (reboot). Since there is no CD I can’t install it to my other computers and check the accuracy prior to calibration.

The highest resolution of the VS-II is stated at 0.001 cents. The highest resolution of
The Strobosoft is stated at 0.1 cent. Resolution is not the same as accuracy.

When using the VS-II as the source for A4 = 440 Hz into the mic jack on the laptop, the
BIAB and The Power Tracks tuners both read it as A5 but do show 440 Hz! ????
They both agree with the VS-II re cents offset (1 thru 20), but still read A5 instead of A4 … There must be an octave offset correction/control in the pgm(s) somewhere? Using the PSG as signal source, the BIAB & PT tuners are showing my G#4 as G#5 while the VS-II and Strobosoft show it as G#4.

FIRST CONCLUSION … on the laptop being used (Gateway M680XL with conexant audio), the signal into the mic jack as read on the screen by the calibrated Strobosoft, the BIAB (no calibration ritual applied) , and the PT (no calibration ritual applied) tuners agree to less than a cent … just have the A4/A5 problem. If this is representative of what happens thru the sound card, It would appear that the sound card is not a point of concern; Why the warning by the software tuner manufacturers? CYA re older sound cards and slower systems? This one is about 2G with a 7200 RPM drive (drive speed does not enter into the above).

Would some of the readers that are into recording please record an A 440 fro their tuner using their recording program and then read the resulting readback frequency?

Jack Stoner · From: Kansas City, MO

Ed, have you checked to see if the install program (program) is on the hard drive somewhere. I've downloaded several programs that automatically install but the actual program is still on the hard drive.

If it's on the hard drive you can copy that to a CD and have a backup copy.

I just recently downloaded the Roxio Easy Media Creator V7.5 upgrade. It was 950 Mb and when the download was completed it automatically installed, but the downloaded program was on the hard drive. In this case I had to make a "data" DVD because of the large file size.

ed packard · From: Show Low AZ

Next experiment is to see if there is a pitch shift (in cents) by recording and playing back. The signal source is the VS-II, the pitch is 440 Hz. The record program is BIAB. The computer and sound card are as found in the last post.

The result is that there is less than 0.01 cents shift thru the loop = not an amount large enough to worry about.

And so end the hardware/software/record/playback experiments, unless someone finds that their system behaves drastically different.

Conclusion is that I do not have to worry about tuner performance accuracy, stability, resolution, etc. because of shifting from a hardware preamp/effects rack to a virtual one.

Question: Why should anyone with a computer buy a Strobosoft for US$80 when they can get either BIAB or PT, both of which have a good tuner built in, and each cost US$80 or less including the tuner?

Jack Stoner · From: Kansas City, MO

I can't really see how it will become a profitable product.

Most musician's are doing live, on stage, playing and wouldn't have a computer or take a computer to tune up.

(I have a VS-II, pricey, but a good tuner, that I have my own E9/C6 setting programmed as the factory programmed are useless for me.)

ed packard · From: Show Low AZ

Jack: re the Strobosoft pgm being on disk ... It might be but, as it is a download I believe that the "key" is machine specific ... not sure what degree of disaster it could recover from ... hope that I don't have to find out.

Yes, the VS-II is a fine tuner. The Strobosoft is "only" good to 0.1 cents they say. It also provides Hz readout along with Spectrum analyzer and o'scope on the screen. The SA has the freq axis marked, but the db axis is not ... no store, no freeze, no smoothing, etc.. The o'scope has no scaling included.

As far a product for profit goes, that is not my thing. Performers already have a ton of stuff on stage with them that is now available as software as opposed to "in rack", and all over the floor. I will send photos of the arrangement I have for the virtual rack I am using that prompted the experiments.

Russ Little · From: Hosston,Louisiana, USA

I use a small free program called eazy tuner
I downloaded from zdnet. Its slow because you have to dial in each note.
I have used it on my guitar , steel and the wifes Harpsacord and its worked well.
I have checked it against my portable tuner
Intellatouch and its right with it.
Im usually right on with the other guys in our group. of cource my ears are pretty old
Just my 2 cents
Russ

Jim Palenscar · From: Oceanside, Calif, USA

I have been using the Peterson Strobosoft and, while Ed "has me on the trailer" easily when it comes to technical issues, I have to say that the program is easily installed and readily calibrated at any time. I will e-mail John Norris from Peterson to see if he can join in this discussion to assist us in understanding more of the complex issues that surround tuners.

ed packard · From: Show Low AZ

Jim P: Having John’s input on the subject would be a good thing.
Some of the things Strobosoft that come to mind are:
1. Just how accurate/inaccurate are the sound card clocks for which “calibrate” compensates?
2. How about the rest of the system’s functions like variation in hard disk RPM?
3. If the rest of the system is stable, can a 440 Hz tone recorded on the hard drive be used as a “calibrate” tone instead of using (carrying around) a second tuner?
4. How can Strobosoft be transported to a “new” computer?
5. How about adding some scaling on the Spectrum Analyzer and O’scope presentations?
6. How about a peak hold mode on the SA for use in profiling the instruments response?

Just for openers.

John Norris · From: Peterson Strobe Tuners, Illinois, USA

Hi,
This topic coincided with the NAMM show so I apologize for not being able to answer before now.
To answer Ed's questions

1. Just how accurate/inaccurate are the sound card clocks for which “calibrate” compensates?

I've not been able to find out specific information regarding absolute accuracy of sound card clocks, or their temperature dependance. The card manufacturers just don't seem to publish that, instead concentrating on things like total harmonic distortion.
So in the absence of such information one would have to be on the safe side, hence the calibrate function.

2. How about the rest of the system’s functions like variation in hard disk RPM?

Disk speed, RAM, etc won't affect the tuning results, only the sound card makes any difference. Visually, the display could be affected by not drawing fast/slowly enough, but this is all taken care of in StroboSoft so it works the same on fast or slow computers so you never need to worry about it.

3. If the rest of the system is stable, can a 440 Hz tone recorded on the hard drive be used as a “calibrate” tone instead of using (carrying around) a second tuner?

This should only be done to calibrate another sound card, not the same one being played because it'll always be "in tune with itself".

4. How can Strobosoft be transported to a “new” computer?

If the computer where you wish to run StroboSoft is not online, you will need to copy the machine code down and register it from a computer that is connected to the net. In this case you will need to visit our www.strobosoft.com website and click on the REGISTER link. Choose DELUXE REGISTRATION. Fill in the information requested and enter the machine code from the computer you wish to install StroboSoft onto. Do the same as above after you confirm your information to copy and paste the unlock code to the target machine.

My advice is to copy the unlock code to a text file or Word .doc and carry it to the new machine since it is lengthy.
Each download is capable of being installed on two machines.

5. How about adding some scaling on the Spectrum Analyzer and O’scope presentations?

There is some scaling on the oscilloscope, but StroboSoft is first and foremost a tuner, and features such as this will be added as time allows.

6. How about a peak hold mode on the SA for use in profiling the instruments response?

See above.

A few corrections:

The highest resolution of the VS-II is stated at 0.001 cents. The highest resolution of
The Strobosoft is stated at 0.1 cent. Resolution is not the same as accuracy.

The accuracy of all current Peterson tuners whether hardware or software is 0.1 cent over the entire range (where did you see 0.001 cent?).
The ability of a tuner to accurately detect tones is useless unless its display is of high enough resolution to convey that accuracy to the users eye.
That's the main problem with non-strobe tuners (hard or soft).

Conclusion is that I do not have to worry about tuner performance accuracy, stability, resolution, etc. because of shifting from a hardware preamp/effects rack to a virtual one.

With the same sound card, the same clock is used for playback and record, so there is zero difference in pitch between a signal recorded then played back. This has some interesting possibilities. If you have a sound card that is quite off-pitch (say +10 cents out), if you tune using an uncalibrated software tuner, you will also be +10 cents out. When this is recorded onto the same device, it will be played back at +10 cents. However, if this is burned to a CD for example and played on an accurate CD player, it will be perfectly in tune... whereas if you had calibrated your tuner to compensate for this, the CD would be 10 cents flat!!!

So, you need to be careful when to and when not to calibrate. A rule of thumb is if recording digitally into the same device as used by the tuner, then don't calibrate, otherwise calibrate.
I know of some customers who have noticed that their laptop sound cards can be 9 cents or more away from their good reference tone, or high-quality desktop sound card. Presumably this is because very cheap components are used (an inaccurate oscillator) rather than any temperature variations.

So, basically, this variation can be big or small, significant or insignificant, ... it just depends.

Some numbers....

1 cent is 0.059% or approx. 600ppm.

Why should anyone buy StroboSoft?
1. Its the only software tuner which is actually made by a tuner manufacturer.
2. Its the only software tuner which is configured for steel guitar.
3. It's a Peterson

! (we've been doing this since 1936 and a certain amount of experience has accrued)

Anyone looking for info or specs can visit: www.strobosoft.com
There is also a part of the Peterson Forum dedicated to StroboSoft:
StroboSoft Forum

Thanks for the interest!

John N.

ed packard · From: Show Low AZ

John: Thanks so much for the response; particularly the "transportability" between machines info.

I compared the Strobosoft, VS-II, BIAB, and Powertracks, and Korg DT-1 tuners on a Gateway 680XL laptop, ..all the software tuners agreed, hence the comment that it looks like the Virtual Rack useage on this machine is ok without calibration concerns.

Can't recall where the .001 cent value came from.

The scaling and peak hold functions would be nice ... at the moment I use a program called TRUE RTA for the sonic profiling of system, instruments, and components.

Thanks again.

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