This small project is to make a guitar tuner cord suitable to use with any guitar that has a pickup and the Tuner application (which now works with Diablo)

Here are the details of the cord I have made up.

I started with a 6ft A/V cable (4 conductor mini jack each end) from the same supplier as the 3ft one described in a previous post:

http://cgi.ebay.com/6-ft-Mini-AV-3-5...QQcmdZViewItem

$5.99 inc shipping.

Thanks st5150.

I cut off one end with plug (about 4") and saved for later use. I used the long piece to start with for most flexibility.

After checking for continuity I discovered that the red cable was all I needed. The cord has three individually screened wires. However note that the screen (ground) is not connected to the conventional position - ie: the fourth 'pin'. It is in fact connected to the THIRD 'pin'. The fourth 'pin' is signal in this case.

I soldered the screen and signal to a 1/4" with a 100k resistor in line on the siganl side to avoid distortion. However, this prooved to be too much reduction in my case. And actually, removing it completey gave the best result.

I prooved this by auditioning the feed through skype on another computer and determining the cleanest signal. No in line resistor was best.

Your pickup may be different and so you may or may not require a resistor. (Just make a temporary connection and try it out before finishing everything off)

So from there it was just a matter of carefully cutting back the other two screened wires (I checked all possible permutatiosn to ensure no other continuity), clamping the cable with the plug's grip and screwing the barrel onto the plug.

The shots below are during the process and the end result.

One disadvantage is that the N810 speakers are disabled when the plug is in the tablet so if you want to hear the reference tones from the keyboard, you have to unplug the cable.

While working with the setup I discovered a couple of things. I set my Ovation (which has an active pickup) to about mid volume for best results. You probably want to bypass any eq if you have that ability (mine doesn't)

Also, I found the tuner more reliable reading 12th fret harmonics. If your guitar has good intonation you can safely rely on this method but if not you should avoid harmonics and simply pick the open strings:

The following are the base frequencies (rounded to whole Hz) for each string but you may well get an even multiple as you tune. This is fine.

E2 = 82 Hz
A2 = 110 Hz
D3 = 147 Hz
G3 = 196 Hz
B3 = 247 Hz
E4 = 330 Hz

With care, I was able to tune to within 1hz for each string.

Hope this helps someone! Cheers!