Programmable Digital Delay
First of several new products from Dynacord is this rack-mounting digital delay line. Paul White managed to find time to review it.
As the recent Frankfurt Music Fair demonstrated, 1984 looks like being something of a vintage year for respected German manufacturer Dynacord, with a whole host of new, high-technology musical products about to be unleashed from their Straubing factory. First of these to hit the UK will be the PDD14 programmable delay line, and Paul White recently had the good fortune to cross its path.
If last year was the year of the affordable digital delay, this current one will probably be the year of the affordable programmable digital delay, and the Dynacord model under review here is as good an example as any of what the marketplace has to offer.
Dynacord have been producing quality audio equipment since the sixties, but their profile in this country has never been anything other than a fairly low one. Although the construction of their products has always been rugged, it's probably true to say that, in the past anyway, the styling of their models would not have looked out of place in an army testing range. The PDD14, on the other hand, is both smart and conventional in appearance, which is good to see. Housed in a black 19" rack-mounting case 2U high, the Dynacord is fitted with small handles on the front (after the fashion set by the Roland Rack models) and features a visually pleasing, clearly arranged front panel layout.
The inside of the unit differs noticeably in constructional syle to that of most Far Eastern units, and indeed is more reminiscent of the approach adopted by American designers of high-grade laboratory equipment. There are two PCBs, one carrying all the components related to the front panel and display, the other holding the main bulk of the circuitry, including the memory and EPROM operating system. The layout is well thought-out and makes good use of the available space, without resorting to cramming everything in for the sake of external appearance.
The circuitry generates delays of up to 760ms at a bandwidth of 15kHz for all delay times. Analogue-to-digital conversion is achieved by means of a quasi-14-bit non-companding system, and this results in a highly commendable 85dB signal-to-noise ratio.
The programs themselves are stored in non-volatile RAM, whilst the actual delay is produced by five 4164 dynamic RAM chips, giving a total of 320Kbits of available memory. Just how many bytes this represents depends on how many bits wide the memory bytes are, but I would guess that between 22Kbytes and 32Kbytes would be needed to produce a delay of this bandwith and resolution.
The block diagram supplied with the system points to a fairly conventional design philosophy, the only parts warranting further description being the programmable controls themselves. Being digital, the control range of each adjustable parameter must be resolved into a finite number of steps, and in the case of the PDD14, 64 of these steps are used. These are converted to a six-bit binary number which can be handled and stored by the internal processor system. Because of this digital control, all gain adjustments within the circuit such as 'level' and 'feedback' are handled by VCAs, which also receive their instructions from the microprocessor system.
The controls are typical of most digital delay units with the exception of the programming section. A modulation oscillator is provided so that, in conjunction with the feedback control, all the usual chorus, flanging and echo effects can be reproduced to a very high standard. Eight sets of useful parameter values can be stored for instant recall, there being six programmable parameters from which to choose. These are Duration (Feedback), Tone, LFO Speed, Modulation Depth, and Mix and Output levels.
The front panel has a numeric display which indicates the program currently operating and also shows the delay time in milliseconds. Programming is achieved simply by setting up a suitable sound, pressing the Store button, selecting the desired memory and then pressing Store again. A Manual switch is provided so that sounds may be set up without interfering with settings already in the memory.
Also available is the PFS14, an optional footswitch bank that can be connected to the PDD14 via a multicore cable and locking plug. It really is an essential purchase if the Dynacord's programming functions are to be made proper use of in a live situation, since it allows the user to change programs or bypass the effect completely, the program number being indicated by a single numeric LED display.
The footswitch unit is necessarily large to accomodate the eight selector switches plus the Bypass switch, but it is well made, easy to use, and has a fine non-slip base.
The signal connections are all made by means of standard jack sockets on the rear panel, and the input can be adjusted to accept any level between five millivolts and three volts. A hi-lo Gain switch is provided so that the input may be matched to microphones or instruments, and a ten-section LED meter is also incorporated to help optimise the input level. It's worth noting at this point that the only switch on the back panel is the ground-lift, so full marks to Dynacord's designers for a sensible layout, fairly rare in this field.
There are three separate outputs for direct, delayed, and mixed sounds, with a further socket being provided for an additional footswitch to activate the Repeat or Freeze mode, which causes the sound in memory to loop continuously every 760ms. The input and output sockets and the Repeat footswitch socket are thoughtfully duplicated on the front panel for convenient operation when the PDD14 is used as a freestanding unit.
The first thing I tried was to change the delay time using the increase-decrease buttons. The rate of change starts off very slowly and then accelerates until the switch is released. I found this procedure painfully slow and would much prefer an analogue rotary control or at the very least a 'fast' button of some sort.
Having set up and stored eight different effects, I tried the footswitch and keypad selector, both of which worked well without causing any switching noise. However, some odd effects were caused when switching from a short delay, modulation effect to a long, straight delay, as the contents of the PDD14's memory take a short while to flush out.
The sound quality of all the delay effects matched the high standard the written specification suggested, though flanging effects, as is so often the case, proved a little noisy due to the high levels of feedback involved.
All the common time delay effects were easily obtainable and a set of useful patches is provided in the handbook for those who want to set up a particular effect with the minimum of experimentation. The modulation range was particularly good, so flanging was not limited to the anaemic effect produced by some lesser units.
With the exception of the odd little annoying feature (such as the slow method of adjusting the delay time alluded to above) operation of the PDD14 should pose no problems and the sound quality is excellent. I'm quite surprised that there is no sampling facility on this unit, and even more surprised that in the Repeat mode, only 760ms loops are possible.
All in all, though, the PDD14 is a quality piece of equipment at a reasonable price, and as such is definitely worth checking out if you're in the market for a new delay unit, providing you can live without a sampling facility.
The PDD14 carries on RRP of £589 including VAT, while the PFS14 footswitch costs a further £118, also including VAT. Further details from Washburn, (Contact Details).
Review by Paul White
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