Product Roundup

One of the most useful things any audio engineer can carry around is a test disc to check the alignment of equipment, and to evaluate unfamiliar monitoring loudspeakers. There are many such discs around already of course, but a new one from Canford Audio is a little different to the rest.

The twelve-track Quick Check Test Disc has been specifically intended for line-up and subjective quality assessment of audio equipment and is available in three formats -- CD, MiniDisc, and DAT. In common with most test discs, there is a full set of test signals; all are at practical levels, and with usable durations. The sleeve notes are very comprehensive, not only stating what the tones should read on a variety of common meter types, but also what an AC Voltmeter should read when connected to 0dBu, 0dBV, or -10dBV outputs!

The test tones include a 440Hz Concert A tone which can also be used to check replay speed, and a swept frequency track which usefully starts with a reference level 1kHz tone and then switches directly to 20Hz, sweeping up to 20kHz before switching straight back to 1kHz. If you hear any gaps then either the replay system cannot reproduce, or your ears cannot hear, the signal!

In contrast to most test discs, however, Quick Check does not contain impressive music tracks -- just superbly recorded spoken (male) voice. This might be unusual, but it is what makes the Quick Check disc so useful. If you think about it, virtually everyone spends much of the day listening to the spoken voice, and our hearing is very highly tuned to spotting deficiencies or problems with its reproduction. Try it and you will quickly discover that, compared to music, the spoken voice is far more revealing of all manner of subtle flaws in loudspeakers, room acoustics, processing equipment and recording faults. The speech tracks include a channel and phase check, followed by five minutes of a prose passage by Washington Irving, followed by a further five minutes of a hypothetical shipping forecast. The recorded prose has not been limited or compressed at all, whereas the shipping forecast has been gently limited.

All in all, Quick Check is a very useful reference and test tool, and certainly a disc which I shall be using a lot from now on. The attention to detail is superb, the sleeve notes provide good advice and useful information, and the quality and accuracy of the test tones and voice recordings are excellent. In my opinion, the provision of voice tracks rather than superficially impressive music makes this disc worth every penny of its asking price!

CD, MiniDisc and DAT £21.15 each, or £57.58 for all three. Prices include VAT.
Canford Audio, Crowther Road, Washington, Tyne & Wear NE38 0BW, UK.
+44 (0)191 415 0205.
+44 (0)191 416 0392.
sales@canford.co.uk
www.canford.co.uk

If you need to add a MIDI interface to a Mac, it has to be external -- there is no Mac equivalent of a Soundblaster 16 with on-board MIDI port. MIDI interfaces invariably connect to Macs via either the printer or modem ports. The 32midiworks model under review is a 'standard' Mac MIDI interface, which means it can be used with most music software (running on System 7 or above) without the need to install any drivers. It includes both modem and printer connectors, so that two 16 channel MIDI ports (32 MIDI channels) are available, and switched thru connectors are used so that the Mac may also be used to drive a modem or printer without the need to unplug cables. When the switches are set to their Printer or Modem positions, the MIDI inputs are passed directly to the outputs, which provides a simple means to play live MIDI parts when the sequencer is switched off. Each port has one MIDI In and two MIDI Outs. Power, SMPTE Stripe and MIDI In/Out activity LEDs for both ports provide visual feedback to show what the unit is doing.

The 32midiworks has no power supply of its own, instead drawing its power directly from the Mac's ADB buss. This works by connecting the 32midiworks in series with the Mac keyboard via two ADB sockets on the box, for which the necessary cables are provided including those needed to hook up to the modem and printer sockets. In addition to its basic MIDI interface function, the 32midiworks can generate SMPTE in 30-, 30 drop frame, 25- and 24-frame formats. Code can only be generated from time zero, but another useful trick is the box's ability to covert incoming SMPTE into MTC, enabling it to double as a tape sync unit.

Physically, the 32midiworks is a simple steel box painted in a glossy grey spatter finish with sockets on all four edges. The SMPTE In and Out connections are on jacks, there are conventional MIDI In and Out DIN connectors, and there are further sockets for connection to the computer and to a modem and printer if you have them.

I'd spent most of the day struggling with some rather intransigent software that seemed determined to thwart all my efforts to review it, so it came as a welcome relief when I unpacked the 32midiworks, plugged it in, booted up Logic and it worked. The SMPTE striping starts and stops at the push of a button, and if SMPTE is fed back into the unit, the computer is fed with MTC. And that's it. It says midiworks on the tin and it's true, MIDI works! Paul White

32midiworks Dual Port Macintosh MIDI Interface £99.99 including VAT.
CIMPLE Solutions, Units 2-17, Wembley Commercial Centre, 80 East Lane, North Wembley,
Middlesex HA9 7UR, UK.
+44 (0)181 904 4141.
+44 (0)181 904 1200.
service@cimplesolutions.demon.co.uk
www.cimplesolutions.demon.co.uk

If you've ever read a hi-fi magazine, you'll have seen advertisements for cables that cost more than the gear they are connected to, which make extravagant claims about performance improvement. The Ripcord guitar cable doesn't (quite) cost as much as most guitars, but its makers certainly make extravagant claims for it. Those who've researched the subject, however, know that guitar cables do make a difference, as the cable capacitance forms a tuned circuit with the inductance of the pickups, adding a coloration to the sound. If you put a DI box at the guitar end of the cable, you lose this effect and the tone changes, usually for the worse. MIT, however, have done a lot more than produce a cable with the right capacitance to match the guitar; they've made a cable with a passive filter network at each end which, they claim, produces a richer tone, lower noise and greater clarity.

The passive networks are contained in small plastic 'lumps' at either end of the cable. Because each is different, the cable has to be used the right way around, so the ends are obligingly marked Amp and Guitar. Obviously the company don't tell you what's in the boxes, but there exist a number of passive, reactive components that could make a difference, including capacitors, coils and ferrite bead RF filters. Ultimately, I don't suppose it matters what's in the boxes as long as it works -- so does it?

Oddly enough, the Ripcord makes more than a subtle difference, most apparent when using my Strat Plus guitar with a valve Fender Champ amplifier. With a moderately overdriven blues sound, the Ripcord seemed to reduce the gritty components of the sound in such a way that the pleasurable parts of the distortion remained while the intermodulation products and general high frequency grot were significantly reduced. The guitar also 'felt' smoother to play, a well known phenomenon when using different sounding guitar setups. The sound was audibly smoother and more even, almost like adding the mildest tube compression, with more of a ringing, singing quality to the tone.

Other tests with my Line 6 amplifier also showed a noticeable improvement, but perhaps not as great as with the Champ. Similarly, my Yamaha Pacifica guitar didn't improve as much as the Strat Plus through either amp, so it's down to trying the lead with your own gear and making up your own mind. At over £60 for the lead, the Ripcord must be considered more as a passive signal processor than as a simple connector, but the improvement it made was great enough to make me feel I have to have one. Suspend disbelief for a while and try one yourself -- the difference is quite evident and very worthwhile in the studio. Paul White

10ft Ripcord £66.99, 15ft £76.99 and 20ft £87.99. Prices include VAT.
Class A Distribution, 39c New Bridge Street, Rackclose Lane, Exeter, Devon EX4 3AH, UK.
+44 (0)1392 494 988.
+44 (0)1392 496 335.

Volume Seven in the Twiddly Bits series is a real mixed bag of performance data, loops, grooves and riffs that come under the natty title of a Programmer's Toolkit. Whilst more up to date drum & bass and jungle styles are briefly touched upon, the main focus of the programming seems to be firmly on a retro-seventies dance floor feel. There are a number of keyboard arpeggios, riffs and licks that all fit neatly into the dance genre and are expertly programmed, with interesting use of pitch bend and rhythm. There are 15 or so four-bar bass riffs, and the drum patterns and fills also work well.

Moving on to the other main part of the release, we find a host of complex control templates to impose over your existing keyboard parts. These come in the form of large numbers of Pan, Pitch, Portamento and Gate effects. Again, these are mostly four bars long and are designed to be simply dropped over a pre-programmed keyboard part in your sequencer. On the whole they work well and should encourage us all to think more about the host of effective control features available to even the humblest of sound modules!

The last part of the release has a large number of resonant filter sweeps designed to 'analogue-up' a MIDI performance and make it whizz and swoop with a strong retro analogue dance feel. These have largely been programmed using Non Registered Parameter Numbers (NRPNs) and are specifically created for use with Roland's GS (Sound Canvas) family and Yamaha XG format instruments (MU series and beyond). NRPNs are generally control messages that different manufacturers often like to assign to different control functions (such as LFO, envelope or filter frequency cut-off points), and this means that other, perhaps older synth modules could well run into problems triggering these effects via MIDI.

In addition to these there are a few other oddments including some useful synth control panels in the form of Cubase Mixer Maps, and some wonderful wah-wah template effects.

All in all this is an interesting, and if you have the appropriate compatible sound modules, rewarding collection of programming oddments. I felt that the actual recorded MIDI parts (drum patterns, synth riffs, and bass lines) were perhaps not as exciting or devastatingly original as I would have liked, and with so much disk space taken up with the filter and control templates you aren't exactly spoilt for choice either. Having said that, as a collection of tools to integrate into your sequenced song data, or as an indication of the clever things you can do with even the most basic sound modules, Programmer's Toolkit works well, and like the other Twiddly Bits offerings, is too inexpensive to consider not buying! Paul Farrer

£24.95 including VAT.
Keyfax Software, PO Box 4408, Henley-on-Thames, Oxon RG9 1FS, UK.
+44 (0)1491 413938.
+44 (0)1491 413938.
mail@keyfax.com
www.keyfax.com

Over the last fifteen years or so, we have probably all gathered some awareness of the workings of digital audio systems through books and articles -- indeed, SOS has carried numerous features on the subject in its time. The problem with the written word on audio-related subjects, however, is that you can not hear the effects being described and, just as a picture says a thousand words, a good audible example can easily be worth as much.

With this in mind, Focal Press have recently published a new CD on the topic of digital audio, as the latest addition to their Music Technology Series (see box). The new release is available in two versions: you can either get a straight demonstration CD complete with comprehensive sleeve notes, or a 'Resource Pack' which combines around 40 pages of notes and overhead transparency masters with a copy of the CD.

The lecturers' notes are unlikely to be appropriate to the more casual reader, as a fairly high degree of prior knowledge is required to make sense of them. The stand-alone CD, however, is far more affordable, and the comprehensive sleeve notes act as a more than adequate guide to the demonstration tracks. The CD carries no fewer than 93 listening examples, which reveal the effects of different bit resolutions, truncation, dithering and noise-shaping; sampling clock jitter; word clock synchronisation errors; error correction and interpolation; pitch-shifting; and zipper noise from operational controls. The final nine tracks are configured as a "critical listening test" for the user to evaluate their ability to detect typical digital artefacts -- something which is far harder than might at first appear!

Many of the demonstrations on the disc are quite subtle and a good monitoring system (speakers or headphones) is sometimes required to hear the characteristic effects. The sleeve notes do not provide any advice on what to listen out for, but the choice of demonstration material is well suited to the relevant artefacts and the compilation has been produced to a very high standard by Markus Erne, chairman of the Swiss branch of the Audio Engineering Society.

If you are interested in developing your understanding of digital audio, want to be better able to recognise some of its quirks, or just like listening to the hi-fi in your anorak, this very reasonably priced CD would certainly be a worthwhile purchase. Hugh Robjohns

Digital Audio CD Students Edition £11.74 ISBN 0 240 51501 3
Digital Audio CD Resource Pack £58.74
ISBN 0 240 51502 1. Prices include VAT.
Focal Press Customer Services Department, Heinemann Publishers,
PO BOX 382, Halley Court, Jordan Hill, Oxford OX2 8RU, UK.
+44 (0)1865 314301.
+44 (0)1865 314029.
bhmarketing@bhein.rel.co.uk
www.butterworth.heinemann.co.uk

DI boxes are essential pieces of studio kit, but they don't all do the same job. For DI'ing an electric guitar or bass that doesn't have active circuitry, you'll need a DI box with a high input impedance, whereas for a line level signal (such as is produced by a guitar preamp), an impedance of around 47k(omega) is more common. What's more, if you're DI'ing a guitar amplifier, it's useful to be able to take a feed from the speaker output so as to retain the coloration of the amp's output stage, but because DI'ing bypasses the speaker, some form of speaker simulation filtering will be necessary to restore a natural amp tone. Valve amplifiers don't like running without a speaker, so you either have to provide a dummy load or fit a thru socket so that the original speaker can be left connected (BBE have taken the latter approach).

The BBE DI-10 is designed specifically for use with line or loudspeaker level signals, which suggests that it was designed with instrument amplifiers in mind -- there is no high impedance instrument input. Being an active DI box it needs a power source, and can run from either batteries, phantom power or an external mains adapter. A switchable speaker simulation filter is included, based on a 24dB/octave low-pass network with a 4kHz cutoff frequency. This may seem rather severe, but in practice most guitar speakers roll off quite steeply above 3kHz. If they didn't, the overdrive harmonics would sound raspy and unpleasant.

Packaged in a neat but tough steel box, the DI-10 has an unbalanced line input jack, speaker in and thru jacks and a balanced XLR output as well as an unbalanced jack output. A DC inlet accepts a 9V DC power supply and a slide switch brings in the speaker simulator.

The DI-10 works fine in both straight and filtered modes, and the speaker simulation provides a lively basic tone with a decent amount of bite and no nasty high end rasp. I did an A/B comparison with my passive Palmer Junction box using a Boogie V Twin preamp as the source, and though there was a notable difference in tone, I wouldn't say that either one was more or less authentic than the other -- it was more like the effect of using a different mic on the same amp. The Palmer had more low end punch, but I felt the BBE was better at putting over the top end ring and bite while at the same time keeping the tone smooth and natural.

In all, the DI-10 is a good instrument amp or preamp DI box, with a speaker simulator that sounds better than some dedicated units I've tried -- a very pleasant surprise! Paul White

Sound Technology plc, Letchworth Point, Letchworth, Hertfordshire. SG6 1ND, UK.
+44 (0)1462 480000.
+44 (0)1462 480800.
www.soundtech.co.uk