David Mellor tries out three new effects units from ADA - a MIDI programmable stereo equaliser, MIDI valve preamp, and a pitch transposer - and finds one that gives his secret studio weapon a run for its money.

It's not really a secret. It's just not the sort of thing that gets talked about very often. Maybe I'm just old fashioned, but it seems to me that the cleaner and more realistic-sounding studio equipment becomes, the more I want to 'mess up' those ultra clear vibrations that I'm hearing.

What I'm after is - dare I say it? - distortion! But I want to have the choice. 'Clean' when I want clean, and 'dirty' when I want dirty. Most times I want at least a moderate veneer of dirt.

I have been refining my dirt-adding techniques over the years, and now I reckon I have the perfect solution. It's a small, valve driven, guitar amp called the Fender Champ. I bought it secondhand for just under a ton and it does all the right things for me. As I said, it runs on valves, giving me that nice rounded 'valve sound', but the best thing is that it is only six watts in power. I don't deafen myself or the neighbours when I crank it up to full level.

Don't get the idea that the Champ is good only for guitars, synth sounds too can benefit from having their faces rubbed in it. Especially DX-type sounds, which are known for their high degree of clarity. Sometimes that clarity is great, other times it needs the 'dirt' treatment...

The three ADA effects units that I have for review are the MQ1 MIDI Programmable Stereo Equaliser, the Pitchtraq pitch transposer, and the MP1 MIDI Programmable Tube Preamp ('tube' being American slang for 'valve'). I intend to concentrate on the MP1 Tube Preamp because it is the most unusual of the units, although many of the things I say will apply to all three.

VALVES - THE REAL THING

The active glassware of the MP1 consists of two 12AX7A valves (the wonderful 12AX7A - sigh!). These are the devices that generate the distortion, but there is associated solid state circuitry that helps the 'bottles' create a wide variety of sounds.

As you probably know, valve distortion is different in quality to transistor distortion. It is certainly preferred by many people - me included. There have been many attempts to simulate the valve sound using various transistors, FETs, integrated circuits and black magic. The ones I have heard mostly sound like glorified fuzz boxes. Some are better than others, but there is nothing like having the real thing. And with the ADA MP1, we have it.

MP1 TUBE PREAMP

Let's consider first the basics of the unit. It is a 1U rack-mounting box which accepts a mono input and produces a stereo output. The input can be either line level or guitar level. Similarly, the output can be line level or a lower level more suited to feeding a guitar amp. The front panel input is meant for guitars, and has a sensibly high input impedance. This means that it doesn't try to suck too much current out of the pickups, dulling the tone. Other instruments will be better off plugged into the rear input, which is balanced, lessening the possibility of interference. Whichever way it gets in, the input signal then comes upon a variety of treatments:

The first choice you have is among Clean Tube, Distortion Tube or Solid State. The Clean Tube setting basically means that the valves are working at their correct voltage levels to give the best performance they are able. The Distortion Tube setting alters the valve bias so that there is a much stronger effect. Solid State, as you can probably guess, removes the valves from the circuit completely.

There are two Overdrive settings, one for each valve. The 12AX7A is like two valves in a single glass envelope, so there are in fact four gain stages. Overdrive 1 sets the level of signal going into the first valve, Overdrive 2 sets the level into the second. Turn these both full up and you will indeed create plenty of graunch.

After the Overdrive sections comes the EQ, which lets you filter out some of the nastiness produced by the distortion - or emphasise it if you want. This is a useful four-section EQ with Bass, Mid, Treble and Presence controls. Bass and Treble are adjustable in 2dB steps from -16dB to +16dB, Mid and Presence are slightly less wide ranging at +/-12dB. An added bonus is the Chorus section, which produces the effect you expect, with adjustment of depth and modulation rate.

FEEDBACK

Now the time has come to take out the vintage Stratocaster and give the MP1 a real test.

I started by plugging my Sennheiser headphones into the headphone socket at the back of the unit. It's a good job they were high impedance 'cans', because the MP1, according to the manual, can only cope if they are 600 ohms or more. Most headphones are low impedance.

Selecting a virgin program, I plugged the Strat in and started playing. I was admiring the subtle delicacy and nuance of my playing, when I realised that I couldn't hear anything. Aha!

You have to turn something up. Setting the gain to 10 (still couldn't hear anything) and Overdrive 1 to 10 gave me what I wanted - a clean, but typically valve sound, slightly distorting on chords. Bringing up the level of Overdrive 2 to 5 gave a thoroughly distorted guitar sound on single notes. Upping it to 10 (and lowering the master gain) gave a sound more like a square wave than a guitar, but exactly what you would expect.

Overdrive 1 and 2 need careful balancing. Increasing Overdrive 1 gives a dean distortion, if that's not a contradiction in terms. Increasing Overdrive 2 (with Overdrive 1 low) gives a much more 'horrible' sound. More hum and noise too, but you may want that.

Remembering that I was still on the Clean Tube setting, I decided to have a go at Distorted Tube. I slipped into my Iron Maiden T-shirt and took out my Gibson Flying-V (actually I don't have one, so I stuck to the Strat... and it was an Anthrax shirt). The Distorted Tube voicing is definitely for Heavy Metal usage only. This is where the guitar starts to scream. And I can swear that when I turned Overdrive 2 up to 5, I saw the ghost of Jimi Hendrix peer quizzically over my shoulder at the MP1!

One little problem I found when changing between the Clean, Distorted and Solid State voicings - the master gain is reset to zero each time. The manual states that this is 'necessary to suppress any loud surprises'. I can see the point, but surely this is only necessary when changing up from Solid State to Clean Tube, and from Clean Tube to Distorted Tube? Changing the other way cannot produce any aural surprises, so this should not be necessary. It would have been better too to only turn the gain down to halfway instead of zero, so there was at least some signal still coming through.

So far, I have encountered in the MP1 many of the different types of guitar sound that you hear live and on record. The onboard EQ extends the range possible. Thankfully, it's an EQ with guts, not the wishy-washy EQ that we often have to put up with on various types of equipment. I like trying out the extremes so I cut the Bass and Mid fully, and wound the Treble and Presence right up. The result sounded like a close approximation to a rattlesnake spitting in your ear, I would say.

Although the distortion generating circuitry and EQ are well up to standard, the built-in chorus isn't anything spectacular. It's OK, but don't rely on it as your only chorus unit. There are others much better. It's difficult to say why it falls down, but you only have to compare it with other effects units to appreciate the difference.

FACTORY PROGRAMS

Having had my fun, I examined the MP1's 29 factory preset programs. There are 128 MIDI selectable program locations, but doubles of the factory programs lurk deep in the MP1's memory, so if you erase them for any reason you can always get them back again. Although the MP1 doesn't let you name programs, the listing in the instruction manual gives an idea of what to expect. There are 'Notched Grind', 'Liquid Grind' and 'Mild Grind' - they sound a bit like floor cleaner. 'Classic Clean', 'Shimmering Clean' and 'Crystal Clean' are what the floor looks like afterwards. There are also several varieties of 'Metal', and other programs to keep the versatile guitarist happy.

I haven't yet mentioned the Solid State voicings, partly because I am not sure that these are what the MP1 is really about. Even so, there are some interesting compressed and chorused effects, but you can get the same things from conventional effects units. The variety of distortion sounds is what make the MP1 special.

EFFECTS LOOP

Another small item is the effects loop, which (hooray) uses separate jacks for send and receive. Much better than using a stereo jack in the tip = send, ring = return mode. It allows an external effects unit to be set in or out of the loop as part of a program. This is probably more useful for stage use than studio, but it's good to have it.

There is an interesting rear panel knob associated with this, which controls the level of the send to the external effects unit. It is a twin gang control which decreases the sensitivity of the return signal as it increases the level of the send. Using this, you can set the level to give the correct headroom in the effects unit, but the overall level of the effect remains the same. It's a concept which could find uses elsewhere, I am sure. And, by the way, thank you ADA for the multiple overload LEDs. It is easy to forget that overload can occur in different parts of the circuitry in any audio equipment. It's nice to have a guide to exactly where the problem exists so that appropriate action can be taken.

THE UNDISPUTED CHAMP?

What the MP1 does is brilliant, but whether it can surpass the trusty Fender Champ is a debatable point. I must admit that, until now, I had thought that the 'valve sound' was achieved purely by using a couple of bottles in the circuitry. But for all the amazing variety of sounds that are available here, it doesn't really and truly sound like a valve guitar amp. So what is the missing ingredient? My guess is that the 'valve sound' consists of the circuitry plus the distortion produced by a loudspeaker being driven a little harder than it wants to be. If that is so, then an authentic 'direct inject' valve sound will probably remain unobtainable.

In my view, the MP1 Tube Preamp doesn't replace the real thing. But what it gives is a tremendously wide range of other interesting sonic possibilities. A range that has been largely ignored since we all got into the habit of plugging our instruments straight into the mixing desk. I don't think the user interface of this machine (ie the DX7-like membrane switches) is as good as it could be, and the unit does look a bit cheap compared to the high standard of presentation of Japanese equipment. But internally, the MP1 has got plenty of what counts. It's not just for guitarists, it is for anyone who wants to put a bit of bite into their music.

FURTHER INFORMATION

MP1, MQ1, Pitchtrack £695 Inc VAT

Klondyke Trading Company, (Contact Details).