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Power Technology DSP-FX

Digital Effects Processor
Published January 1997

The DSP‑FX is the world's first 32‑bit floating point digital effects processing system with a visual interface. It also comes on a standard ISA card for installation in a desktop PC. Dominic Hawken plugs 'n' plays.

The humble PC has come of age in recent years. Previously scorned by the creative Apple Macintosh types, and generally assumed to be a complex, unfriendly dinosaur of a machine suited only for use in an accountant's office, the system has continued to thrive despite the opposition. The release of Windows '95 (or Mac '89, for the cynical), coupled with the wide availability of cheap expansion hardware and peripherals, has finally begun to establish the PC as a major force within the entertainment industry. Many machines are now beginning to appear in recording studios, running automation systems and sequencer packages.

Multitasking operating systems like Windows offer the user the ability to run many different programs concurrently. The processor time is effectively shared equally between the running applications, dependent on their demands. Network and industrially‑orientated operating systems like UNIX and QNX actually take this principle one stage further, by automatically sharing the processors on multiple machines to complete the given tasks — after all, why use up all the available power on a single machine, when there is another at the other end of the room which is currently unused? This particular concept has yet to filter down to the software currently available to us common musicians, but the principle remains the same. It is perfectly possible to dedicate the power of a single PC to a number of tasks — sequencer, patch editor, mix automation, electronic diary, and now, with the latest release from Power Technology — effects processor.

Your immediate fear may be that this will be yet another amateur‑orientated soundcard dedicated to providing average‑quality sound effects for the latest Doom software clone. But the DSP‑FX is not just any old processor. This particular one has a technical specification to rival some of the best stand‑alone effects boxes on the market. Moreover, if you have the available space and processing power, up to eight individual units can be fitted into a single PC. Also, as the system is computer‑driven, you don't have to battle with a tiny LCD when adjusting parameters. Full‑screen mouse control is now a reality, without the need to delve into the MIDI specification and program your own custom mixer‑maps.

The DSP‑FX is a well‑thought‑out product.

Computer‑based processing also offers another distinct advantage over the hardware alternatives. It is possible to re‑program the custom DSPs — onboard, chip‑based signal processors that handle all the heavy number‑crunching — directly from the control software. This means that new effects can be added or modified at any time, with the card effectively functioning as a programmable workhorse, rather than a preset playback machine. It is also possible to distribute these new algorithms via the Internet for instant worldwide access, in much the same way as any registered user can download the latest version of Notator Logic from Emagic's website.

But let's stop for one moment. Whilst all of this is obviously very cool, and may be of intense interest to every musical tech‑head with a Demon account, it all rather disintegrates if the sonic results do not live up to expectations. After spending two weeks, on behalf of Sound on Sound, prising the only unit in the country out of the hands of the distributor, it was therefore with some trepidation that I finally slotted the card into my PC and had a close listen to the results.


The DSP‑FX is designed to run on any PC with a 386 processor, though a 486 or above is recommended. The ubiquitous Windows operating system (3.x or 95) is also required, and remote MIDI configuration is available as standard. The comprehensive manual describes the installation process in detail, as well as the various hardware add‑ons that Power Technology have released onto the market, most of which are geared towards the processing of 20‑bit audio signals, and their interaction with the FX card. The card itself is designed to fit into any 16‑bit ISA slot within a PC, and bears a remarkable similarity to a standard soundcard, although full‑size jack sockets have been fitted rather than mini ones, for analogue signal input/output. A standard D‑type socket is also supplied, together with an interface cable for connection to any AES/EBU digital signals, all of which are processed by an on‑board 20‑bit balanced converter.


The card itself is driven entirely by a series of 'FX‑Plug‑ins' — software utilities that provide the processing algorithms and on‑screen graphics for a wide variety of acoustic effects. These plug‑ins are small enough to be distributed via the Internet, or on floppy disks, and Power Technology have already produced a large selection that covers everything from reverb to pitch shifting — see the 'Power Tools: DSP‑FX Plug‑ins' box for more details. Purchasers of the card are given free access to any single plug‑in of their choice, with most users initially opting for the graphic reverb, and further effects can be purchased at a later date. One useful facility that is built into the system is a demonstration mode, where samples of any effect can be loaded and tested at any time. A 'demo' session typically allows the user a total of five minutes to hear how the plug‑in sounds. All the available controls remain active throughout the session, although it is impossible to save new presets to disk, and the actual effect shuts down once every 25 seconds until a button is clicked to resume the test. Once finished, a demo session can be restarted at any time.

Thirty‑two‑bit processing is implemented throughout the system, and the card automatically compensates for low‑level input signals to produce the highest sonic quality (see the '32‑bit' box for further details). MIDI control also comes as standard, with Power Technology recommending the JL Cooper MIDI controller to automate any parameter in real‑time, with tactile control or sequencer automation. Other options include the AES converter, a 20‑bit AD/DA system for high‑bandwidth master recordings, and the DSP‑FX PowerPack — effectively a complete computer, packaged in a rackmount case with an audio card pre‑configured.

In Use

Installing the system was surprisingly simple. After I plugged the board into an available expansion slot and ran the setup routine, the hardware was immediately recognised and the program ran correctly. The benefit of having a graphical interface was immediately apparent, with delay times and panning positions represented on‑screen by coloured circles, which vary in size, position and shade according to the effect settings. Editing the effect parameters is easily achieved, using either the mouse or via an external MIDI controller. Utilising the MIDI interface offers the added advantage of allowing current effect settings to be stored with sequence data, and there's also the potential for automating the editing process. The program itself was quick to operate and simple to configure, and the various plug‑ins are easily selected from an on‑screen menu. The review system was tested on a Pentium‑based PC, with 32Mb of memory.

Sonically, the DSP‑FX is extremely impressive, especially if you're able to take advantage of the digital interface. The 32‑bit processing really does seem to make a difference, with all of the effects sounding clean and smooth. The reverb, in particular, is very realistic, with a depth and natural‑sounding character that compares well with other systems costing many times the price. The graphical interface offers a much friendlier way of adjusting parameters, rather than the small LCD normally associated with processors of this type, and I found the control software easy and responsive to use. Even using the DSP‑FX with the analogue input only, it performs well, providing perfectly adequate effects, but if you use the DSP‑FX without the digital interface, you're really not making the most of the card. With the digital interface, the algorithms developed by Power Technology really come into their own, handling even the quietest of input signals.


The DSP‑FX is a well‑thought‑out product. The usual computer‑based problems associated with crosstalk and signal degradation appear to have been cured, and the degree of visual control offered is exceptional. The method that Power Technology have adopted for graphically representing their plug‑ins offers the user a quick and easy way to picture current settings, and effect editing is a simple process. The sonic quality is extremely high, especially when processing a digital source, and certainly comparable to some of the more expensive alternatives from Lexicon and tc electronic. The reverb plug‑in has a remarkable depth and clarity, is extremely realistic and really has to be heard to be believed. Even users unable to take advantage of the digital inputs will not be disappointed with the results obtainable with the DSP‑FX. Highly recommended for any digital studio, and well worth a listen for anyone with a spare slot in their PC.



  • Frequency response 20Hz‑20kHz, +/‑ 0.5dB
  • Dynamic range Greater than 90dB
  • Crosstalk between channels Better than 80dB
  • Total Harmonic Distortion Less than 0.01%
  • Analogue inputs/outputs ‑10dB nominal level; unbalanced quarter‑inch connectors
  • Maximum input level +5dB
  • Maximum analogue level +5dB
  • A/D & D/A converters Crystal 16‑bit Delta‑Sigma
  • Sampling frequencies 48kHz, 44.1kHz, 32kHz, 24kHz, 8kHz


  • Digital Inputs and Outputs AES/EBU, S/PDIF, FX‑Link
  • FX‑Link connector Proprietary multipin
  • AES/EBU connector 3‑pin, large XLR using supplied breakout box
  • S/PDIF connector RCA type
  • Sampling frequencies 48kHz (see text), 44.1kHz, 44.056kHz


  • 386, 486 or Pentium Processor.
  • Windows 3.11 (4Mb) or Windows 95 (8Mb).
  • ISA bus, VGA graphics.
  • 10Mb free hard drive space.
  • Standard MIDI interface required for external MIDI controls (not required for PC sequencer control).

Power Tools: DSP FX Plug‑Ins

A wide variety of plug‑ins is available for purchase or testing, and the best place to check them out is Power Technology's web site ( The site is very comprehensive, with loads of data and detail on current products, as well as email addresses for technical support and further information. At the time of going to press, the following plug‑ins were available:

  • GRAPHIC REVERB: A full 32‑bit reverberation algorithm, equipped with a number of room types, including Hall, Spring, Plate and Small Room. The graphical control is geared towards natural parameters, and offers adjustment of room size, liveliness (or decay‑time diffusion), stereo spread, and high‑frequency absorption. A red box is displayed to represent the room, with its shade of colour denoting absorption characteristics.
  • MULTI‑ELEMENT CHORUS: This plug‑in offers control of four independent chorus elements, with each element displayed on‑screen as a coloured oval shape. Delay time, modulation depth, frequency and pan can all be defined, as well as the overall signal gain.
  • FULL STEREO PITCSHIFTER: Two pitch channels are available, each of which can be assigned separate settings. Gain, shift‑amount (in cents) and pan position are all adjustable, and graphically viewed as coloured circles on black background.
  • ANALOGUE TAPE FLANGER: As in the original method, where pressure was applied to the flange of a reel‑to‑reel tape recorder to vary the speed of one deck against another, this time it is the mouse that is used to adjust the effect. Depth, feedback, modulation frequency and gain are also available as programmable parameters.
  • MULTI‑TAP DELAY: Eight individually controlled channels, each with separate output level, feedback and delay. Once again, the multi‑coloured display offers a unique insight into the current sonic configuration.

32‑Bit Processing

There are two main buzzwords associated with digital recording: 'bandwidth' and 'frequency'. If you're not familiar with these terms, imagine a comparison between digital recording and making a film. The audio 'frequency' is comparable with the number of frames per second that you can capture with a camera, and the 'bandwidth' is analogous to the depth of colour that you can capture on each still picture. A dodgy black and white movie, which jumps from frame to frame, is analogous to an audio file which sounds dirty and unlike the original. The latest Spielberg epic is analogous to a high‑bandwidth, high‑frequency recording using the latest technology.

The DSP‑FX utilises 32‑bit internal signal‑processing throughout, whereas most other systems stop at 24‑bit. Whilst in the pro world a 24‑bit bandwidth has always been perfectly acceptable, and is certainly capable of producing extremely realistic effects, the sonic quality is ultimately limited by the signal level that is to be processed. If the input level is low, the available bandwidth will also be low and the process will suffer. With this in mind, the programming team at Power Technology have been working on the problem and appear to have developed a solution, evolving a system that automatically adjusts the signal headroom to match the incoming signal level. This is a unique approach, which effectively normalises any incoming sounds, and compensates for changes in output level within the software — a very processor‑intensive task. However, with the built‑in power of an on‑board DSP, and the capability of Power Technology's institute, timing problems appear to have been solved and the result is an extremely effective unit which sounds as good as the hype.

DSP‑FX Pricing

  • BASIC SYSTEM: £816.62 (includes choice of one FX plug‑in).
  • STUDIO SYSTEM: £1380.62 (includes Graphic Reverb, Analogue Tape Flange, Multi‑Element Chorus, Multi‑Tap Delay and Stereo Pitch Shifter FX plug‑ins).
  • STUDIO SYSTEM PLUS: £1674.37 (includes Studio System plug‑ins and digital I/O system).
  • INDIVIDUAL FX PLUG‑INS: £205.62 (Graphic Reverb, Analogue Tape Flange, Multi‑Element Chorus, Multi‑Tap Delay, Stereo Pitch‑Shifter and Parametric EQ).
  • FX Pack Modular System: £TBA (system can be configured with up to four DSP‑FX cards and PC interface cards).
  • 24‑bit AES/EBU‑S/PDIF interface: £316 (with interconnect cable).
  • AES/EBU‑S/PDIF interface 4X: £468.82 (with 4X expanded memory and interconnect cable).
  • DSP‑FX AES/EBU converter: £633.32 (stereo 20‑bit A/D‑D/A, includes AES and S/PDIF formats, and pro‑level balanced I/O).


  • Relatively inexpensive in comparison with the competition.
  • Excellent graphical interface.
  • Easy to install and configure.
  • New effects easily obtained.


  • Needs the digital interface for the best results.
  • PC only.


Extremely realistic digital effects at an affordable price.