Energy-efficient DSP powers acoustic effects

Fishman uses the Blackfin ADSP-BF532 running at a power-conserving 169MHz to perform 32bit audio effects processing in its AFX pedals.

Playing unplugged is the essence of making music with an acoustic guitar - one big reason acoustic musicians have had relatively few choices in effects processors, whereas electric guitarists have so many.

With the help of Analog Devices' Blackfin processor, Fishman Transducers has designed its AFX pedals to play right to what acoustic musicians want: tonal nuances, rich natural sound and many hours of unplugged operation on stage and in studio.

Recognised as a premier designer and manufacturer of acoustic amplification products for more than 25 years, Fishman needed highly energy-efficient performance for the AFX pedals because they would be powered by the 9V battery that musicians prefer.

(Wall-mount adapter operation is optional).

Fishman uses the Blackfin ADSP-BF532 running at a power-conserving 169MHz (well below the processor's 400MHz maximum) to perform 32bit audio effects processing in its AFX pedals.

Because Blackfin integrates microcontroller functionality as well as digital signal processing (DSP), there was no need to add a separate microcontroller unit (MCU) that would have subtracted from battery life.

With a standard alkaline 9V battery, a guitarist can look forward to some 20-25 hours of operation.

Using a 9V lithium cell approximately doubles that time, according to Fishman.

That allows the AFX line to operate significantly longer between battery changes than the six or seven hours that players have come to expect from other digital effects pedals.

Available in three models - Chorus, Delay and Reverb - the AFX pedals premiered on the market in October 2007.

They build on a module initially developed for Fishman's digital Aura Acoustic Imaging guitar preamp: a compact PCB known inside the company as the "sugar pack", because it is about the size of a sweetener packet.

The flexible Blackfin-based module provides Fishman with a foundation for introducing other digital products.

Having created the "sugar pack", the company is able to focus on developing new features and delivering high quality products, while benefiting from the economies of scale that result from starting with a standard base.

"Our AFX pedals preserve the sound of the acoustic instrument while giving the player choices for different effects to add to the music", says David Fournier, Director of Development, Fishman.

"Their 32bit audio processing is a cut above in digital acoustic effects pedals, but you can be that sure players wouldn't be excited if they had to change batteries every performance".

"That's why now, when Fishman has a digital product, we are using Blackfin".

"No other processor we compared could match the power efficiency".

"Fishman is designing for innovation with its Blackfin-based module", says Jerry McGuire, Vice President, General Purpose DSP, Analog Devices.

"The results have made themselves heard in their digital acoustic imaging, and once again in these effects processors".

"And with my background as an engineer and a guitar player, it's gratifying to know that digital products can add to the music while letting you play unplugged for many hours at a time".

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