MORE FROM DK STABLE

As one of the oldest suppliers of add-ons for the Sinclair market, DK'tronics has built up a reputation for good, basic, hardware. The latest additions to its range for the Spectrum - two joystick interfaces, a printer interface and a sound generator - do not break any new ground but are well designed and constructed.

All use a new, restyled, case which can be used with the Spectrum Plus and should also fit most full-sized keyboards. In addition, three of the four items have through connectors - a welcome change.

The less expensive joystick interface is Kempston/Sinclair compatible. It has two standard joystick sockets on the top, the left Kempston and the right Sinclair - keys 6, 7, 8, 9 and 0 for fire. Priced at £13 it should prove popular with arcade fanatics. It does not have a through connector, and thus must be the last add-on attached.

For those who need a wider choice of keys the programmable interface at £22.95 could be the answer. It can be programmed using the tape provided or, when a game is running, via a switch on the top. The tape allows you to program any of the keys, including Shift and Enter, and to read two or more keys at once, so you can move diagonally and fire at the same time.

The printer interface is disappointing. It can drive any Centronics printer but it has disadvantages which make it a doubtful buy.

The software tape provided has two pieces of code on it, one for Epson compatibles and the other for the MCP 40. The Epson code is only 520 bytes long and redirects LPRINT and LLIST to the printer. A copy routine is included but only in one size and, when tested on an Epson printer, appeared to give a line feed which was out by 1/72in. The bottom two lines of the screen are not copied. The MCP code is 680 bytes long and includes a half-sized copy option as well as supporting the INK command.

For MCP 40 users the interface might well be a good buy at £39.95 but Epson or Seikosha users who want to use COPY should look carefully before buying.

The Sound Generator, priced £29.95, is based around the ever popular AY-3-8912 chip and includes a built-in amplifier and external speaker; it also amplifies the BEEP. The problem with this chip is that it is not one of the easiest to program, although thorough instructions are included that show you how to do this in Basic or code.

To overcome that, software is included on tape which allows you to write a tune in three-part harmony and replay it. You cannot alter the length of note - you have to enter two notes to double the length - nor edit a voice once it is entered; you are limited to 256 notes per voice.

The chip has 15 envelopes built in and a different one, and/or noise, can be assigned to each voice. That, again, is rather basic and reflects the age of the chip.

Although the chip is well known the problem has always been lack of support from software writers. DK'tronics is well placed to change this and some future releases will contain routines to drive the generator.

DK'Tronics
£29.95

These have a built-in sound generating chip, usually of the AY type and offer three channels of programmable sounds for music or effects.

Separate speaker and interface, AY-3-8912 chip. Good software program to use as a three track recorder supplied with the unit. Takes a bit of time to get used to but produces very effective sounds.

KEEPING UP WITH THE SIDSES

The Dk'Tronics three channel sound synthesiser is a fairly nifty little gadget which, for £30-odd, upgrades your standard BEEPing Spectrum to a machine with sound capabilities comparable to those on a BBC or Amstrad. Based on the AY-3-8912 programmable sound generator chip, the unit comes complete with a plug-in speaker and cassette based software to get you started.

The chip itself has fourteen registers, which may be accessed from the BASIC 'OUT' command, and sounds may be controlled on the three channels available. This direct approach is probably not for the beginner, and to avoid total despair on the part of the new user Dk'Tronics have thoughtfully written some software which allows you to interact with the chip by driving a cursor round the screen. Displayed options may be selected with a single key press - or by pressing 'fire' if you've added a Sinclair or Kempston joystick.

Adding a joystick is advisable, as it makes programming sound effects from the screen menu simplicity itself, as the software is really very slick, taking the pain out of experimentation and allowing the complete novice to start making a respectable racket very quickly!

Using the demo Music Designer software, you are able to program up to three tunes (or sequences of sounds), using all three voices simultaneously and 'record' them into memory. Once you've set up a voice with the associated parameters of waveform (either tone or noise), enveloping, attack and decay and shape, notes may be entered into memory by moving the cursor up and down a keyboard displayed at the base of the screen and pressing 'fire' to enter a given note. As each note is added to your growing composition, it is played back to you, and a simple editing function allows you to space back to the last note added to the stream and delete or change it.

The instruction booklet that comes with the unit is the tiniest bit impenetrable, but all the information you might require to program the unit directly is there. A little time spent experimenting with the demonstration software would certainly pay dividends if you wished to delve into programming the sound chip directly. Most people would probably be quite happy to stay with the software supplied.

One minor niggle with the program is the fact that you cannot immediately hear the effect of changes you make to the wave formations - it's necessary to keep scampering down to the screen keyboard with the cursor to play a note, which can get a bit frustrating.

The unit itself, quite naturally, fits onto the edge connector, and sound is output via a mini-jack socket on the top of the unit, which has a little volume knob for you to twiddle. Don't be surprised if you soon get disappointed with the effect of twiddling this knob when the speaker supplied is connected - the output level is little short of wimpy, and is better suited to headphones. Connecting the output to your stereo is also a viable option, especially if you want to hear the delicacies of the envelope shaper, but be careful. It would be fairly easy to damage your speakers if you don't watch the volume level.

From the musical point of view, the unit is definitely a lot of fun, but it is not really capable of generating the more complex sounds that a musician might expect. The attack and decay isn't quite true to form, altering the pitch of sounds rather than the amplitude (volume), which is a little naughty, and not the way a true music synthesiser works. Similarly, the manner in which the wave forms are manipulated by the envelope is interesting, but not really conducive to really first rate music synthesis.

To be perfectly fair, the unit is sold and described as a sound synthesiser, and for the purpose of experimenting and generating interesting sounds (which may be incorporated into your own software), the package represents good value and is well supported by the Music Designer software. If tuneful and more complex sounds are your goal, the Dk'Tronics package could prove a bit of a let down.

However, if you are thoroughly bored with the possibilities of BEEP, and want to go a stage further in computer sound generation, the facilities offered by the sound Synthesiser will allow you into the same league as BBC and Amstrad owners. If you really want to be a computer musician, then there's probably not much of an alternative to lashing out on a Commodore 64, which contains a very smart custom sound chip by the name of SID!