Practice amps are all well and good, and many of them allow you to rehearse in silence by offering a headphone socket. But what about totally silent band rehearsals? It certainly seems like a good idea and Yamaha obviously think so as they've just introduced their 'Producer Series' which currently comprises a tiny battery or mains operated four channel mixer (the MM 10 which retails at £75.00), a headphone power amp (the MA 10 £79.00) and a set of small stereo headphones (MH 10 at £25). All interface with the excellent CS01 Mini Synthesiser.

In presentation terms the three units we were loaned to review (the mixer, headphone amp and cans) were very nice looking. Each is made of a grey metallic looking plastic and seems to be well constructed.

The MM 10 was the first unit we tried. It measures just under 9" by 5" by 2", weight is a negligible 1.1 lbs — just a shade smaller and you could slip it into your jacket pocket The four channels offered are each fed from a standard ¼" jack and offer a slider switch for mike or line level, a pan pot (the unit delivers pseudo stereo from a mono input) and a channel volume. In addition there are pots for aux level and master volume.

As well as the four jack 'ins' the MM 10 also provides you with two jack sockets marked 'pgm out', two phono sockets for aux in and a further two for line out.

Power for the unit derives from a single PP9 (which Yamaha claim will give 24 hrs. continuous use with an Alkaline type) or from an an accessory power adaptor for mains voltage operation (DC 9-12v).

The input functions are fairly obvious. You can plug in both low and high impedance mikes with the slider set on 'mic', or electronic instruments (guitar, bass, keyboard, cassette player etc etc) with it set to 'line'. Also on the input side, the 'aux in' sockets allow for connection of further MM 10 mixers, Hi-Fi tuners, cassette players and other such equipment.

The line out sockets are fed through to further mixers (to the 'aux in' sockets as we've seen), the aux in of an MA 10 headphone amp or a cassette deck. The two jack 'outs' marked 'pgm' out are fed into a power amp, if desired, to run through speakers.

The real attractions of this unit are the tremendous range of differing uses it can be put to. A player wishing to learn a song from a record can connect the mixer to a cassette player, radio or disc player, link through his instrument(s) and put the mixed output to either another cassette recorder or to the Yamaha headphone amp for private listening. Moreover, up to four players could share inputs and the mixed result be pushed through to a recorder, Hi-Fi system or an MA 10 (the latter of which allows two sets of headphones to be connected). In concept it's a very nice idea.

Our sample performed quite well. The overall adaptability of the input levels allowed for connection of a wide range of instruments and the device seemed physically well made. We've got some doubts, however, as to whether it's actually quite worth the £75 being asked for it. It's a bit noisy and on its own there is no provision for channel equalisation, so you're stuck with whatever sound you get from your instrument. True, some signal processor like an echo unit could be jacked into the aux circuit but that would change all the signals together rather than just, say, the lead vocal.

The MA 10 headphone amp (£79) does, on the other hand, provide equalisation. It shares a similar size format with the mixer but is powered by six AA penlight cells or another mains adaptor, if mains happens to be available, as opposed to a PP3.

"THEY'D BE VERY USEFUL FOR PLAYERS WHO SUFFER FROM NEIGHBOUR PROBLEMS...."

Facilities here include a single jack input, volume, master volume, treble and bass controls plus a headphone level pot and two stereo jack sockets for headphones.

The back panel of the MA 10 offers four phono sockets, two each for 'line out' and 'aux in' and a further four jack sockets — two for 'monitor out' and two for 'monitor in'. There are also three small pots on the back panel, one controlling the input level of 'aux in' and the other two which handle left and right monitor 'ins' respectively.

In some ways this unit is more useful than the mixer. Although only one instrument can be played through it at a time, the MA 10 does, at least, offer a wide range tone control system. Most unfortunately however our treble pot was producing crackling noises and induced a pronounced treble hiss when turned up full which was very noticeable indeed if the output was recorded. This control has to be used with some care if noise levels are not to become unbearable.

Part of the idea behind offering two volume controls on the input circuit are so that guitarists can overdrive the input if they wish and get a distorted sound. It seems unlikely to us that many guitarists would actually like the sound produced, however, which is very far from the sort of valve-sound overdrive which the majority of players we know seem to prefer. This is pure overdriven unashamed transistor distortion and didn't appeal to us at all.

One of the best aspects of the MA 10 is that it works a pseudo stereo effect on the input which sounds very pleasant on tape or through a Hi-Fi system. Again, as with the mixer, you can input a signal from a cassette recorder or tuner and play along with it, recording the result. But there are much more adaptable ideas for using the headphone amp than this, especially if it is linked with an MM10 mixer. One example which possibly illustrates its potential best is multichannel recording onto a two track cassette machine. Don't confuse multi channel with multi-track, however, as, of course, there is no possibility of overdubbing unless your tape machine is already capable of that role (something like the inexpensive, if limited, Teac A-108 would do that for you). What the MA 10 and MM 10 would allow you to do is record up to five instruments onto a stereo tape recorder in one pass, with a degree of mixing (at least in terms of volume) to hand. Only that instrument jacked into the headphone amp would have any Eq, though.

In fact a good way of using these devices would be for each player to have their own MA 10 so that they could individually use their tone systems and each have their own monitoring via headphones. They could be linked together via the Monitor out to Aux. in sockets.

The final component we were sent to try was a pair of the Yamaha headphones. These are priced at £25 and are of rather limited quality. They'll do the job, but better quality cans are currently on the market for similar money. We would find it hard to recommend these at this price.

Overall the Producer Series is a very good idea indeed. The units seem strongly made and enable owners to use them in quite a wide variety of ways. They'd be very useful for players who suffer from neighbour problems and who don't have access to a proper multi-track recorder, for bands who fancy silent rehearsals on coaches or in vans, on beaches, in hotel rooms or anywhere else, in fact. Our only serious quibbles relate to noise levels and prices. A complete set-up including amp, mixer, and cans would set you back £179 at recommended prices — frankly that's quite a lot of money. We also were not over-impressed by the noise levels inherent in the units. For this sort of money we'd have expected a somewhat quieter operation and, just possibly, some form of Eq on the mixer — or are we expecting too much?

Having said all that the Producer Series is unique and it's up to the individual whether he thinks these prices are too high for what's included, and whether he thinks the noise specs are acceptable. As yet there's no competition so if you want the idea, the Producer Series is what you'll have to buy. We certainly could see a lot of fun to be got from it — and maybe that's all one should ask?