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ADA Signal Processors

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.

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.


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.


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.


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.


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.


MP1 MIDI Programmable Tube Preamp

  • Clean Tube, Distortion Tube, or Solid State voicings
  • Valve circuitry
  • Four band EQ
  • Stereo chorus
  • Effects loop
  • Headphone socket
  • Stereo output (line level or instrument level)
  • Compression (in Solid State mode)
  • MIDI In, Out, Thru
  • 128 Programs
  • Assignable MIDI Program Change
  • Optional MIDI foot controller for Program Change


  • 15kHz bandwidth
  • 84dB dynamic range
  • Transposition: +/— 1 octave (by cents, ratio, or standard interval)
  • Regeneration
  • Regeneration insert point
  • Modulation

NOTE: The MP1 and MQ1, according to the manual, will have level 2 and level 3 software updates. Level 2 will give upload and download of parameters via System Exclusive data, also real-time SysEx control. Level 3 will add MIDI Time Code functions.

MQ1 MIDI Programmable Stereo Equaliser

  • 14 frequency bands
  • 12dB boost/cut
  • Constant Q filters
  • LED brightness indicates degree of cut and boost on each band
  • Equivalent Input Noise: <102dB (do they mean dBu?)
  • MIDI In, Out, Thru
  • 99 programs
  • Assignable MIDI Program Change
  • Optional MIDI foot controller for Program Change

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.


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.


MP1, MQ1, Pitchtrack £695 Inc VAT

Klondyke Trading Company, (Contact Details).

ADA Pitchtraq

Perhaps it wasn't such a good idea to try out a modestly priced pitch changer so soon after reviewing the latest Eventide Harmonizer. But since most of us (me included) have to live in the real world, the Pitchtraq is definitely worth investigation.

The Pitchtraq is a single channel unit - no stereo output - which puts it one rung down from the Yamaha SPX90, which has single channel input but two channel output. The ADA unit does have other features to compensate though.

Like the other ADA units reviewed here, it adopts the membrane switch approach to programming, with knobs for Input and Output Level (Brownie point for the often absent Output Level control). There are three methods of setting the transposition interval:

Method 1 is by setting a transposition in cents, where 1 cent = 1/100th of a semitone. Method 2 is the ratio method, where you enter a number from 0.5 to 2.0 and the incoming frequency will be multiplied by that number. The third possibility is the Standard Interval. The Pitchtraq understands major and minor thirds, 4ths, 5ths, major and minor 6ths, and octaves - transposing up or down. If you are wondering where the 2nds and 7ths went, most users wouldn't consider them to be useful harmony intervals, and you can set them by cents or by ratio if you really want to.

Feedback, or regeneration, is provided here so you can create those sparkling arpeggio effects. Unfortunately there is no delay available, other than the slight delay necessitated by the pitch changing process. Variable delay is essential for getting the best out of regenerated pitch changing, and the lack of this facility means that you would have to supply it externally. There is a regeneration insert point, so it's no problem to add it if you have a spare digital delay (a minus Brownie point for putting the insert on a single stereo jack, not two mono jacks as used on the MP1).

What the Pitchtraq has that other units don't is a sweep oscillator for the pitch change, so you can go alternately up and down in pitch at a variable rate. Whether this sounds good or not depends on what type of sound you are using it on - it does generate the occasional click - but it's another string to the Pitchtraq's bow.

Programmability is rather more modest than the other two ADA units. There are a mere 16 memory locations available, plus unerasable locations for the 16 factory presets. It's probably just about adequate, but why not give people more? There's no MIDI on this unit by the way.

So how good is the Pitchtraq at its job? Well, it's not brilliant. It has a 'wobbly' effect which gets worse the higher you go in pitch. But used as a thickener together with the original signal, it can achieve some very useful sounds. Rather better than the SPX90's pitch change program was the octave down transposition. Doubling at the lower octave is a very useful thing to do, but you can't contemplate it with the SPX. You can do it fairly well with the Pitchtraq.

I have to say that I found the Pitchtraq to be the least satisfactory of the three ADA units. The MP1 Tube Preamp is excellent, the MQ1 Equaliser is very usable. The Pitchtraq is on the borderline of good value at the price offered. Hear before you buy.

ADA MQ1 MIDI Programmable Stereo Equaliser

When is a graphic equaliser not a graphic equaliser? Or to put it another way, when is something which is not a graphic equaliser, a graphic equaliser after all?

Confused? Yes me too, but the ADA MQ1 is in fact a graphic equaliser on the inside, but not in external appearance.

The essential feature of a graphic equaliser is a number of fixed frequency, fixed bandwidth filters. Many examples of the type have vertical sliders on the front panel which look as though they display a graph of the frequency response which has been set. Unfortunately, they don't. They roughly show boosted frequency regions and cut frequency regions, but they don't come close to showing the actual response. This is because the frequency bands interact with each other. Raising two adjacent sliders by 12dB means that intermediate frequencies will be boosted by an amount greater than 12dB.

So the MQ1, although it has no 'graphic' display, is still a graphic in intent. There are 14 frequency bands each with a +/-12dB range. Not as versatile as the 30 or 31-band units that are available, but still a useful tool. Like the Programmable Tube Preamp, all settings are made via membrane switches. Boosting a frequency band involves selecting Edit mode, then Gain, then the frequency you want to change, then using the increment/decrement buttons to make the change. It should be apparent that this is neither as simple nor as intuitive as the usual slider method. Particularly if you want to raise a region covering several bands, there is a lot of button clicking to do. Incidentally, the brightness of the LED on each frequency button gives an indication of the degree of cut or boost - but it is a very rough indication.

I was extremely disappointed to find that the eternal annoyance of conventional stereo graphic equalisers was not done away with on the MQ1 - and it so easily could have been. Equalising in stereo is a bother because you have to painstakingly set one channel to what your ears tell you is correct, then duplicate those settings on the other channel manually. Since the MQ1 works through software, it would have been straightforward to have the possibility of setting the EQ on both channels simultaneously. But you can't. (Maybe on the next software revision?)

The good thing about software programmability is that you can have all your favourite EQ curves stored in memory, with 99 programs possible. I very much liked the ability to step though different EQs very quickly and find one that suited the sound I was using. It's certainly a different way of working to twiddling knobs and trying to head in the direction of a good sound. I also liked the randomness of it, where you could find that an EQ that you wouldn't have thought suitable will suddenly spring up and be just what's needed.

Sound-wise, the MQ1 is a quality equaliser. It offers a subtly different type of EQ to the conventional graphic, as it has so-called 'constant Q' filters, as opposed to 'variable Q'. Variable Q means that the EQ curve gets sharper the greater the degree of boost or cut. With constant Q, it stays the same. As I said, it's a small difference to the ear.

An interesting professional feature of the MQ1 is the possibility-of locking out the front panel controls via software so that the EQ can only be changed by an authorised person. This is useful for fixed installations where you don't want anyone meddling with the controls. Unfortunately, the review unit I had forgot that it was supposed to be locked when it was switched off!

To sum up, the MQ1 is a useful little equaliser. I wouldn't have it as my only outboard EQ, but the possibility of storing settings makes it highly desirable.

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Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Nov 1988

Donated & scanned by: Mike Gorman

Gear in this article:

Studio FX > ADA > Pitchtraq

Preamp > ADA > MP1

Studio FX > ADA > MQ1

Gear Tags:

Graphic EQ
Pitch Shifter

Review by David Mellor

Previous article in this issue:

> Making the Most of 'M'

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