Pickup testing with the V5 integrator

[stratotarts]

Hi,

I am the designer of a circuit which provides an effective, extremely low cost method of testing guitar pickups. The project began in 2014 and has undergone many stages of improvement and evolution. You can read about the history of it here: link. I would like to thank Antigua for being the primary beta tester throughout the most recent development stages. The current version incorporates an integrator and a high impedance preamplifier. It is intended to be used with a computer sound interface and audio analysis software. The current version has been implemented in a PCB, which has been designated the V5.5. Here is a photo of a typical test setup:



A limited number of PCBs are available at low cost, until they are exhausted. At that point, I will decide whether to publish the Gerber files, or produce more boards. Here is the documentation:
Pickup Measurement Procedure

[JohnH]

Hello and welcome to GN2! I'm glad you are here!

[antigua]

Thanks for joining!

[stratotarts]

I finally paid to buy a "pro" or paid copy of RightMark. It has a feature that makes me wish I'd done that sooner. I can save the test results as wav files, and reload them into slots later. This means I can create charts combining fresh and previously measured data, for comparison. It also means that raw test results can be file shared between different people or posted online.

[antigua]

Just FYI, I just had a battery die using the V4 integrator, and I wasn't sure what symptoms would surface when the battery started to die, but what I saw was that the low end amplitude was very low, so rather than seeing a flat line between 100Hz and 1kHz, it was instead a steep upwards arch. The integrator apparently requires more juice to lift up the lower frequencies, so when the battery was dying, it was most obvious in those lowest frequencies. 

[stratotarts]

The circuit will perform reliably and for quite a while on a battery, but I recommend using a switching regulator based 9V adapter. We found out before that some adapters are too noisy, but I did find one cheap off-the-shelf 9V adapter that is absolutely quiet - I continue to use it for all my tests.

Having said that, a small difference in the power supply voltage should not affect the measurements significantly. So it is more a matter of convenience which supply you choose.

[antigua]

Aside from the clean power source, the more petty reason is that it means one less wire and power supply I have to deal with. Thanks to your inclusion of the LED light , I rarely leave it on.

[stratotarts]

Here is an update to the testing document, only because C1, C2 and D1 had to be updated in the schematic. I have also finally gotten around to including the slope calibration procedure.
link to Pickup_Measurement_Procedure