Oscilloscope Piano Tuning 101

April 17, 2011 by Jason Komp 10 Comments

[Todd Harrison] recently wrote in to tip us off on his submission to the Tektronix oscilloscope contest – using a scope to tune a piano. In his video he demonstrates how a Fast Fourier Transform can be used to determine the fundamental frequency of the note being played. This is a quick and easy way to determine if that key is in tune, and if not, how far off it is from the desired frequency and in which direction.

He goes on to explain that a scope can only be used as a starting reference point since “mathematically correct” tuning on a piano doesn’t sound right to the human ear. It turns out that when struck, the stretched wires in the piano behave less than ideally. In the case of a piano, the overtones (the other peaks shown on the scope higher in frequency than the fundamental) are actually slightly sharper (higher in frequency) than the expected harmonic whole-number multiple of the fundamental frequency. As a result, the frequency ranges of each octave must be “stretched” in order to accommodate this and sound correct when multiple notes are played together across octaves.

Typically, only the A4 key is actually tuned to its correct frequency of 440Hz and all of the other keys are manually tuned off of this baseline. The amount of necessary stretch applied to each octave increases as you get further away from this initial reference point in either direction and is unique to each and every individual instrument – thus there is no universal device capable of perfect tuning. Although [Todd] admits that he won’t attempt to tune the entire piano himself using this technique, he finds it a convenient way to keep the most heavily played center sections of the piano closer to true between professional tunings.

If you have any interesting or unique uses for your Techtronix scope, you can enter the contest here. Just don’t forget to tip us off too! Thanks [Todd]!

RGB Stroboscopic Guitar Tuning

November 3, 2010 by Mike Szczys 15 Comments

This is [Michael Ossmann’s] RGB LED stroboscopic guitar tuner. If his name is familiar that’s because we mentioned he’d be giving a talk with [Travis Goodspeed] at ToorCon. But he went to DefCon as well and spent the weekend in his hotel room trying to win the badge hacking contest.

Despite adversity he did get his tuner working. It’s built into a toy guitar that he takes on road trips with him. By adding a row of RGB LEDs between two of the frets he can use the vibration frequency of an in-tune string to flash the three different colors. If the string is not in tune the three colors will dance around but matching it with the LED frequency produces a stable color. He then uses that big yellow button to advance to the next string. See his demonstration after the break.

This is basically a built-in plectrum tuner that uses one LED package instead of two.

Continue reading “RGB Stroboscopic Guitar Tuning” →

Intel: High-bandwidth Digital Content Protection Cracked

September 18, 2010 by Mike Szczys 54 Comments

Intel says that HDCP has been cracked, but they also say that it’s unlikely this information will be used to unlock the copying of anything. Their reasoning for the second statement is that for someone to make this work they would need to produce a computer chip, not something that is worth the effort.

We question that logic. Not so much for Blu-Ray, which is the commonly associated media format that uses HDCP, but for HD digital cable programming. There are folks out there who would like to have the option of recording their HD television shows without renting a DVR from the cable company. CableCard tuners have been mostly absent from the market, making this type of recording difficult or impossible. Now that there’s a proven way to get the encryption key for HDCP how hard would it really be to create a man-in-the-middle device that uses that key to authenticate, decrypt, and funnel the audio and video to another encoder card? We know next-to-nothing about the protocol but why couldn’t any powerful processor, like an ARM, or even an FPGA (both rather inexpensive and readily available) be programmed for this task?

Leave a comment to let us know what you think about HDCP, and what the availability of the master-key really means.

[Thanks Dave]

Audible Tuner For The Blind

June 27, 2010 by Mike Szczys 17 Comments

[Lain Sharp] modified this guitar tuner so it can be used by his blind friend. In the picture above you can make out a small white project box that houses the additional electronics. Inside is another battery and an ATmega168 providing a connection for an earphone. The AVR chip connects to each LED on the tuner and converts the visual tuning meter to an audio cue. Check out the demonstration clip after the break to see how it works.

Now if we could just figure out how to get our strings in tune with our built-in keyboard.

Continue reading “Audible Tuner For The Blind” →

Resurrecting ISA Hardware

June 9, 2010 by Mike Szczys 40 Comments

[Alex] had an old FM radio tuner card come his way. It used an ISA connector, a standard that went the way of the dodo in the mid-nineties. With the challenge of implementing an ISA-bus to configure the card he set out on his mission. What he came up with is a working radio using the ISA card and driven by a PIC 16F877. Join us after the break for schematic, code, and a few details. Continue reading “Resurrecting ISA Hardware” →

Electronic Guitar Pick Tunes The Strings For You

November 23, 2009 by Mike Szczys 25 Comments

The Stimmmopped is an electronic guitar tuner made to be used as a guitar pick. This uses two LEDs synchronized to blink at the exact frequency of the string you are tuning. Pluck the string with the corner of the PCB and then shine the light on the string you are tuning. As the vibrating string moves back and forth it will only pick up the spot of light when the frequency matches that of the blinking LED. Once in tune, both red lights will appear to be constantly illuminated and immobile on the string.

An Atmel ATmega8 is used to control the device, interfacing with two buttons and a seven-segment display to choose the pitch currently being tuned. Gibson has a robotic guitar that features an auto-tuning mode, but if you don’t want to shell that much this low cost and simple build is for you.

[Thanks Sören]

Digital Tuner Reverse Engineering

October 27, 2009 by Mike Szczys 32 Comments

hvr-1600-i2c-sniffing

Hackaday alum [Ian Lesnet] tipped us off about some reverse engineering of the HVR-1600, an analog and digital television encoder/tuner. The project was spawned when [Devin] noticed his Hauppauge HVR-1600 didn’t tune channels in Linux quite as well as it did in Windows. He had a hunch this was due to improper initialization settings for either the tuner chip or the demodulator.

To fix this he used two test points on the board to tap into the I2C bus. Using a logic analyzer he captured the command traffic from the bus while running Linux, then while running Windows. By filtering the results with a bit of Perl, and comparing them by using diff, he tracks down and finds the variation in the commands being sent by the two drivers. After a bit of poking around in the Linux source and making the necessary changes, he improved the tuning ability of the Linux package.

[Devin’s] work looks simple enough, and it is. The difficult part of this process is being smart enough to know what you’re looking for, and what you’ve got once you’ve found it.