Maxim MDD-1500H Digital Delay
In recent years, the production of echo and related time delay effects has benefitted greatly from advances in the field of microelectronics.
Echoes can be produced using anything from a cave to a mainframe computer but until now, the most common methods used were magnetic tape loops or analogue delay lines.
Both these methods have their limitations and it is probably fair to say that the latest breed of digital delay units offer the best combination of quality, versatility, and value for money.
It is only recently that the price of digital delays has dropped from thousands of pounds to only a few hundred, and the Japanese-built Maxim delay under review here, is one of the most inexpensive units currently available.
To many people, the word digital has a certain mystique and is often assured to be synonymous with perfection. Sadly, this is not entirely true, as anyone who has listened to the effect of quantisation noise on a low frequency musical signal must appreciate. When a signal is digitised, it is resolved into a finite number of steps.
An eight bit analogue to digital converter, for example, would resolve 256 discrete levels only. It is the difference between the original waveform and the stepped reconstruction that is heard as noise and it is particularly noticeable when there is little or no high frequency content present to mask it. In general terms, the more bits used when digitising a signal, the lower the quantisation noise, although other factors also contribute, such as whether the device is companding or linear. The E&MM digital delay uses a companding converter to produce very acceptable results from only 8 bits.
The Maxim delay uses 14 bits, which is theoretically capable of producing exceptionally good results.
The Maximum(!) delay time depends on the amount of memory used and in this case, there is a choice of 400ms with a 15kHz bandwidth or 1024ms with a 7kHz bandwidth. This is selected by means of a pushbutton switch on the front panel, the status of which is indicated by an LED.
The Sub Delay time can be set independently of the Main Delay and its level may be adjusted by means of a pot mounted on the back panel. Hi and Lo EQ is provided for the pre-delay signal so that, used in conjunction with a mixing desk, a degree of high frequency could be added and the mixer's own EQ used to compensate, resulting in a possible further improvement in signal to noise ratio. Alternatively, these controls may be used creatively by imparting a different EQ to the delayed sound.
Delay time setting is achieved by means of pushbuttons. First, select Delay or Sub Delay and then use the up or down buttons to respectively increase or decrease the delay time which is displayed on the LED numeric display. There is a further button labelled fast, which, when used in conjunction with the up or down button, speeds up the process of changing the delay times, which then may be changed from minimum (1 ms) to maximum, in a couple of seconds.
Main Delay, Sub Delay and the effect of the feedback control can be switched in or out by means of three pushbuttons or by footswitches (not provided) which may be plugged into the rear panel. A useful application of the footswitch facility would be to switch between Sub Delay and Main Delay to select different echo effects, in a live situation.
A Hold facility is provided which continuously loops around whatever sound is currently in the memory and interesting sequencer-like effects can be built up in this way.
Unfortunately, the delay time controls are inoperative when 'Hold' is being used which prevents pitch manipulation of the stored sound by this means.
Another regrettable omission, in common with many other machines, is the lack of a 'one shot' function which would be useful for storing, say a drum beat, and then playing it on demand by means of a sync input or even pushbutton. This type of facility appears only to be available on the more upmarket machines, yet the extra electronics required would be both cheap and simple, adding very little to the retail price, (cf. Boss DE200).
Facilities are provided to select 0dB or -20dB levels for both input and output which should preclude any compatibility problems for live or studio usage and five-step LED meters are provided to monitor input and output levels.
One area in which cost cutting has taken place is in the omission of a modulation oscillator which would normally be used to provide chorus, vibrato or flanging effects, however, an external input is provided for connection of a suitable low frequency oscillator. A maximum modulation amplitude of 10 volts is specified and it would be a simple matter to find a suitable LFO circuit to meet this requirement. The range of pitch modulation available is more than adequate for the production of convincing flanging and chorus effects and this modulation also operates on any stored sound in the 'Hold' mode.
The unit is tastefully styled and takes up only one unit of rack space and rubber feet are provided for those of us too poor to afford racks.
Looking at the front panel, one is reminded very much of the Cutec unit and I have been informed, rightly or wrongly, that both units are manufactured by the same company. There is also an identical unit with the same model number marketed under the name Evans, which like the Maxim unit, is distributed by Blue Suede Music.
Internal construction is of a suitably high standard and typically Japanese, in that it contains more components than you would expect to see in a comparable British device.
One minor design blunder is that the folded rear edges of the case obscure most of the rear panel legends, but you can still make out enough to know what socket does what.
In terms of performance, the delay sounds are clean, as would be expected from the wide bandwidth, with no noticeable aliasing on a variety of inputs including guitar, synth, and voice, but some quantisation noise was evident on the lower strings of the guitar. Although this was not serious for most purposes, a 14 bit design is capable of much better performance.
The lack of any instructions or even spec sheet is a little remiss but to be fair, operation is quite straightforward.
In terms of value for money, the delay time and bandwidth are very good and a better noise figure could probably not be produced at this sort of price. One little gripe is that the Sub Delay level pot is mounted on the rear panel which would render it quite inaccessible if rack-mounted.
Although the recommended retail price is £390, I have yet to see one of these units offered at much over £300, so you should have no trouble tracking down a good deal. A similar model is offered but without Sub Delay at a slightly reduced price but I think that the extra flexibility offered by this is a worthwhile addition.
Review by Paul White
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