Fusion Guitar

The challenge

The Fusion Guitar puts a speaker inches from a set of magnetic pickups. Past a certain volume the system feeds back, and without a fix for that, the whole idea of an integrated body, speaker and pickup arrangement was not a viable product.

The guitar was the passion project of David Auld, a guitarist and industrial designer at Outerspace Design. Outerspace had no electronics capability of its own, so it contracted Tekt to take the product from a crowdfunded proof of concept to something manufacturable. Tekt's deliverable was the audio electronics and the firmware: a compact, powerful printed circuit board and the code driving the connection between the player and the iPhone. Nine months separated the concept from a product that had passed Apple's MFi testing.

The work

Feedback cancellation

The core problem is acoustic. Tekt characterised the critical resonance modes and feedback characteristics of the instrument, then built a DSP feedback cancellation algorithm around what that measurement showed. It is the piece of engineering everything else on the product depends on.

Signal integrity without a shielded cavity

An electric guitar normally relies on a shielded cavity to keep environmental noise out of the signal path. This one is plastic-bodied, with no significant electromagnetic or electrostatic shielding — in an audio application where environmental noise is immediately audible. Signal integrity was therefore a design discipline in its own right rather than a late correction.

iPhone integration and audio transport

The main processor was a Cypress Semiconductor PSoC 3. Cypress's MFi solution was reasonably mature on USB audio transport and iOS handshaking, but it needed added error correction and resilience to make transport reliable, plus audio clock stabilisation so the stream decoded cleanly and without glitches. Tekt also built the soft controls that link audio transport to the user interface. Presented at ElectroneX in September 2017 alongside Outerspace Design, the guitar was broken down into three subsystems: a fully integrated iPhone dock, an amplifier, and a USB audio system with DSP.

Amplifier and power

Around the processor sat a high-power, compact and efficient class-D digital amplifier, with power management and analogue design to match. The product is specified at up to 12 hours of playing time from its internal lithium-ion pack.

Into manufacture

Tekt is an Apple MFi (Made for iPhone) certified design house, and the design for this project was approved by Apple's MFi testing, which includes extensive software and electrical stress tests. With electronics design and firmware development complete, Tekt worked with the client and a contract manufacturer in China, overseeing an initial production run of 2,000 units. 1,081 backers took delivery globally, worth roughly half a million dollars in initial sales. The company then raised further investment and took subsequent refinements in-house. The guitar went on to win an Australian Good Design Award and was featured in the anthill Smart 100.

About the client

Fusion MusicTech is the venture behind the Fusion Guitar, and its parent company is Outerspace Design, the industrial design consultancy where David Auld conceived the instrument. Fusion CEO Con Dekazos, on the engagement: "we look forward to working with you again in the future. Please pass on our sincere appreciation to the entire team."