Where traditional DDL’s have only one or two taps, the Ursa Major Space Station has many–eight are used only for listening, and are called Audition Delay Taps, while others are used to synthesise reverberation and echo. The SST-282 can be compared to a special multi-head tape recorder, operating with a loop of tape 255ms long.
The tape corresponds to the SST-282’s digital memory, and the multiple playback heads to its multiple taps. The eight Audition Delay Taps are placed along this imaginary piece of tape to a resolution of one ms, and can be re-positioned at will to any of 16 pre-programmed patterns. You have continuous control over another tap, the Echo tap, which can be set from t to 255ms and fed back to the input to create the traditional effects of tape loops.
Two programs of Reverberation Tap delay times can be selected as well. Proprietary internal programming randomises these taps so that they can be stably fed back to produce reverberation. The equalised sum of these taps appears at a pot (Reverb/ Echo Feedback) where it can be adjusted to create any decay time from zero to about 3.5 sec.
An important part of the Space Station’s fundamental conceit is contained in the two groups of delay taps, one for auditioning and the other for reverberation. They operate independently of each other; that is, the Audition Delay Taps set up a way of hearing the contents of the memory, while the Reverberation or Echo Taps, when fed back determine the kind of reverberant sound existing in the memory.
Each act independently, so that endless varieties of sound can be created for example, a sound approximating normal room reverberation may be set up by feedback, and then auditioned with any one of the 16 programs to sound like rooms, like a slap, an echo, or even a reverberating comb filter. Or a comb-like reverberation effect can be set up by feedback, and then auditioned in a room, another comb, or as an echo, slap, etc.
Even more versatility derives from the built-in mixer, where Audition Taps may be mixed in any desired ratio to emphasise earlier reflections, to delay the onset of reverb, etc. The possibilities are many, yet the front panel layout is spacious, uncluttered, and intuitive, due in part to the flow chart screened on the panel above the controls.
The control functions were carefully chosen to balance adjustability, with its endless freedom, against pre-programming, with its convenience. For example, consider the advantage of not having to enter eight delay time values for each program, values you either guess or look up somewhere. Then realise that all the EQ, mixing, and feedback functions are self-contained–you don’t have to tie up large sections of a console, or untangle a patch-bay.
The Space Station is a new product, not rehash of old DDL ideas. Take the time to its differences – they result in a very powerful instrument, with room for a lot of creative discovery. Once you fully grasp the Ursa Major Space Station, you’ll be amazed it hasn’t been done before: it’s that sensible and exciting.
The Ursa Major Space Station was designed by an engineer with a broad knowledge of both analogue and digital technologies and the wisdom to choose and successfully use each to its best advantage. So, memory is digital, since with good A-D conversion, noise, distortion, and dynamic range will be excellent with no degradation as a function of delay time.
Also, with RAM memory, access is fast and to very fine resolution, permitting many taps and the randomising algorithm. A-D and D-A were a challenge: how to accomplish at a modest cost high speed A-D and the many D-As required each sampling period? A special set of converters had to be designed, proprietary to Ursa Major, that met the speed requirement and permitted a full 80+dB dynamic range and total distortion and noise better than 0.2% at maximum signal level – and with no analogue companding.
Perhaps the most arcane and interesting technology in the Ursa Major Space Station is hidden in the techniques used to randomise the reverberation delay taps. A patent disclosure has been filed for this, and we consider it highly proprietary, so little more will be said. But any worker in the field who has ever tried to create reverberation fed-back delays knows that this is no mean trick.
Input Controls
The Input Level control adjusts gain so that a wide range of source levels can be connected. Changes in this control don’t upset the mixing ratios. A four LED Peak Level indicator shows signal levels at O (overload), -6, -15, and -30dB in the digital domain, and is a true peak sense and hold circuit. It permits easy and secure setting of the proper operating level.
Mixer
The Ursa Major Space Station hag a 9 -input/stereo output mixer for the eight Audition Delay Taps and the Direct signal. Taps l, 3, 5, & 7 are fed to the left summing amplifier, Taps 2, 4, 6, to the right summer, and Direct to both left and right summers. Using the five mixing controls with reverberation, for example, gives control over the proportion of direct to reverberant sound in the output, and over the amount of early-arriving vs. later-arriving reverberation.
Equalisation
A simple shelving equaliser is placed in the circuit so that the high and/or low frequencies applied to the processor from the source, or from feedback, can be attenuated to simulate rooms with more absorbent walls, or smaller volumes. It changes the relative decay time at high and low frequencies. Reverb Program a Medium program provides for normal build-up and smooth decay of reverberation, while the long program gives a slower build-up and a longer decay time, as in a larger acoustic space. that the Reverb/ Echo Feedback control provides continuous, fine adjustment of the decay time down to zero with either Reverb Program.
Audition Delay Programs
An Audition Delay Program is a set of eight-time delay values set into the operating registers from PROM memory to produce the eight Audition Delays needed to create each effect. There are 16 Audition Delay Programs, grouped in four families, with names screened on the panel to aid in their recall.
The Effects
Rooms 1, 2, 3, & 4
These four programs use semi-randomly chosen delays spaced to sound like the early reflections of rooms. The maximum delay time in each program appears at the last taps, 7&8, and ranges from about 70ms in Room I to 255ms in Room 4. The smaller rooms are appropriate for auditioning with the Medium Reverb Program and shorter decay times, while the two larger rooms provide a more spacious sound and would normally be used with the Long Reverb Program and greater feedback.
In the smaller Rooms, the taps are closely spaced so that when all are auditioned equally, the gaps are filled in well and no disturbing echo is heard as would occur with a single tap at the longest delay time. Like all the Audition Delay programs, the Rooms can also be used without feedback to modify sounds by simply adding pure delay, or multiple delays. This is a good set of programs for general purpose doubling and loudness enhancement, or for creating multiple, abrupt-ending echoes.
Combs 6, 10, 22 & 38
The four Comb programs are for special-effect signal modification by comb filtering. Comb filters are created when a signal and one or more delayed versions of itself are combined. The result is called a comb because there are periodic nulls and peaks spread across the spectrum, placed at frequencies related to the reciprocal of the delay time. Because the delay times and tap gains are precise in the Ursa Major Space Station, the nulls produced are very deep; and, because there are four taps plus the Direct signal to combine for each output channel, the complexity of the resultant sound is much greater than with traditional DDL’s.
Furthermore, the left and right delays are interlaced so that they may be externally summed to yield combs of closer spacing and still more complex and varied sound. As if this wasn’t enough, when the Echo mode is used to create fed-back comb effects also, they can be auditioned through one of the Comb programs to make things even more interesting. Comb filters make good sci-fi machine-like voices, or tune percussive sounds, or place a sharp bite and edge on instruments like guitar or harp.
Delay Clusters – Fatty, Cloud, Slap 1, Slap 2 & Echo
As with some other aspects of the Ursa Major Space Station, these are so new we had to invent names for them. This family of programs uses delay taps spaced close together, in clusters on the time axis. The clusters occur at progressively later times as you move from Fatty to Echo. Fatty, with all its taps placed under about 40ms, has no audible separation from the source, but is an excellent loudness-enhancing effect that’s great with almost any source.
Comb filtering isn’t a problem with these programs due to randomised choice of times, plus the 7kHz delay response reduces any tendency to comb at higher frequencies. In Cloud, the cluster is later, almost with a gap, while Slap 1 and Slap 2 are delayed enough to be heard as a real slap echo, except, of course, with eight delay taps for greater fatness and loudness intensification. Echo produces a single repeat of the source at about 250ms, again with eight delays for more punch.
Space Repeats 2, 3 & 4
These three programs provide for 2,3, or repetitions of a sound, with even spacing in time from O to 255ms, and with L -R, L-centre-R, or L-R-L-R motion, respectively. All eight taps are used, even with the two-repeat program, to provide extra punch at each hit. Space Repeats are dynamite with percussive sound, or sharp transients, since these tend to reveal the spatial movement and time syncopation best. Of course, Space Repeats may be used with any echo or reverberant effect to cause the decaying signal to ricochet in stereo space as it dies out.
Echo Mode
This mode connects just one delay tap through the Reverb/Echo Feedback control to produce a decaying, repeating echo, as is done with tape. As the Echo Delay Time is reduced, the effect eventually becomes a frequency domain one, a recursive comb filter, whose sharp nulls and peaks vary with the delay setting. The complexity of these echo or fed-back comb effects can be increased by auditioning them with more than one Audition Delay. For example, if a 255ms echo is decaying in memory and is auditioned with the Space Repeat 4 program, the single echo will be heard beginning and continuing four times, for a higher echo density.
