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PPG Hard Disk Unit

Digital recording direct to hard disk, from the company that built its reputation with the Wave synthesisers. Paul Wiffen examines the new direction.

The distinction between digital tape recording (as typified by the Sony PCM system) and sound-sampling is becoming decidedly blurred. The PPG HDU, for instance, is a machine developed by a company renowned for devices in the latter category (like the Waveterm), yet if the circumstances suit, it could easily provide a solid-state substitute for a tape-based system.

The basic concept behind the HDU is to use an 85-Megabyte Winchester drive to store 12 minutes of 16-bit digital recording at 44.6kHz sample rate (which is exactly the same sampling format as the Compact Disc process). The total sample time is divided between 10 tracks, each of which is 72 seconds in length, and you can output four of these tracks simultaneously via the four output jacks.

In a 12-minute mono sample, the HDU uses all 10 tracks to make an uninterrupted recording. Alternatively, the sections recorded on each track can be triggered at the appropriate points during a piece of music programmed into a MIDI sequencer (the HDU recognises both MIDI Clock and Song Position pointers). This means that the acoustic sounds in a song (vocals, pianos, guitars, whatever) can now be sequenced via MIDI alongside synthesiser parts and digital drum sounds.

The HDU can also be played from a MIDI keyboard, and in this application, the fact that each track can hold 10 separate samples (sharing the 72 seconds between them) is especially exciting. In this way, 100 samples can be immediately accessed - and you can trigger any of these from a sequencer.

Onboard the HDU, any 64 of the 100 samples can be chained together into 'songs'. These allow you to order your samples as necessary, and then trigger events at the appropriate point in your visual moments.

Even more interesting for people who work in film and video is the Time Manipulation function, which allows you to match recorded audio with video when the two are of different length. For example, if you have an audio passage that is 35.2 seconds in length, but video that's only 30 seconds long, the Time Manipulation function matches the two together without any change in pitch. Listening to this function, it's considerably better than an average 'harmonised' signal, with no noticeable glitching in the signal. Frankly, I'm still wondering exactly how this is done.

The HDU's real-time processors are able to generate a wide range of signal-processing effects digitally (ie. without the degeneration you'd get from turning the signal back into analogue and the line noise that results from patching). These effects include echo, flanging, phasing, delay, distortion and harmonising. And if you use an external sound source, you can use two effects simultaneously.

Although using a sample from the Winchester means you can use only one effect at a time, you can resample the result to another part of the Hard Disk Unit, the signal going through the D-to-A and A-to-D converters.

Mixing tracks together (often referred to as bouncing or ping-ponging) is also possible in the digital domain, so again, there is no loss in signal or build-up in tape noise. You can also simulate different types of amplifiers (such as a tube or certain vintage brand of amplifier) in real time.

The HDU comes complete with a remote control, the PPG Commander. With it, you can call up all programs and data in the memory of the HDU, as well as all other functions. Every function has its own 'Page', where the controls and parameters are displayed numerically or in a graphic form. Everything is controlled via eight analogue controls: six knobs and two faders. On the rear of the Commander, there are four jacks in the remote control for connecting pedals and switches. And at any point, the display tells you what controllers are connected.

By the end of this year, PPG plan to offer options like a SMPTE card interface and a Streaming Tape back-up for downloading samples and setup information. These options will include both software and hardware in one package.

And even as you read this, the boffins at PPG are working on further software updates and features, and after their clever tricks with time and pitch correction, who knows what they will come up with next?

Price £10,000+ excluding VAT

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Casio CZ1 Polyphonic Synthesiser

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Boss Dr Pads

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Oct 1986

Donated & scanned by: Stewart Lawler

Gear in this article:

Hard Disk Recorder > PPG > HDU

Review by Paul Wiffen

Previous article in this issue:

> Casio CZ1 Polyphonic Synthes...

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> Boss Dr Pads

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