The Septar Board – in collaboration with John Harding (Technician, University of Ulster).
The “Septar” board functions as a break out box for polyphonic audio pick-up systems for electric guitar (including those designed solely for MIDI application) to allow audio for each string. The following prototype has been developed with a newly designed circuit to improve audio output of piezo-based pickup systems (notably, the Hexpander by Graphtech Guitar Labs).
The kits will be made available for purchase as a DIY kit, without housing, at a very affordable price. You can source housing on Ebay. Polyphonic audio software is under development in PureData and will be made available for free.
The software is a work in progress. Any suggestions or contributions welcome. Drop me an email at info at rickygraham dot net.
Technical Specification by John Harding (j.harding at ulster.ac.uk)
The board features 7 independent channels, each channel consists of an independent circuit, based on vintage vacuum tube topology, which provides impedance matching by employing low noise and spectrally accurate Junction Field Effect Transistors (JFet’s).
JFets are well renowned in audiophile circles for their sonic qualities, low noise and graceful overload characteristics, similar in many respects to the more well known vacuum tubes. JFets provide solid bass reproduction whilst maintaining extremely high resolution, bringing out more details, sounding cleaner, clearer, and more natural than the best bipolar transistors, and even the best Telefunken tubes. Passive High Pass filtering and ac coupling is present and individual to each channel and the JFets are Biased as Class A devices to achieve maximum performance figures. It produces high impedance input of 2MegOhm allowing us to boost even the weakest signal. The result is a very clean, no gain, low noise output, with very low output impedance, essentially maintaining the low frequency content of Piezo Pickups, even when driving the signal over long cable lengths:
Each of the seven channels achieves a flat frequency response (+/-0.05dB) from 10Hz to 20kHz and minimal phase shift over approximately 10Hz to 30kHz.
Since the entire circuit draws approx. 7 mA of current it can easily run on a single battery. Therefore you can expect two things: long battery life, and very low noise.
Price will vary with user specification. If you are interested in our proposed polyphonic audio break out kits, please send your name and email address to: info at rickygraham dot net and we will add you to our mailing list. You will receive notification when the kits become available.