Review, Modern Recording PDF 368kB
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1. The lower central portion of the front panel is occu pied by a set of nine pushbuttons for selecting one of the sixteen audition delay programs The first switch is an alternate action pushbutton which selects alter nate groups of programs for the remaining eight inter locking pushbuttons When the first switch is depres sed the eight switches select any of the rooms or combs programs as indicated by the labels above the pushbuttons When the first switch is not depressed the delay clusters or space repeats programs can be selected as indicated by a second set of labels below the pushbuttons At the right of the program selector switches is another alternate action pushbutton which when depressed selects a long reverb program as opposed to a medium reverb program when not depressed The medium program is said to provide for a normal build up and smooth decay of reverberation as compared to a slower build up and longer decay time for the long reverb program Continuing to the right there is a pair of controls for setting the echo delay time when the processor is in the echo mode A rotary control is labeled O to 255 milliseconds and is first set to the desired echo time The echo delay time is not affected until the associated set button is pushed at which time the echo delay time is updated to the value selected Finally a power on off pushbutton is located in the lower right corner of the front panel along with a pilot LE2. reference when in use see photo of front panel This diagram INPUT LEVEL Tem aan H j F i r i e i a oa a P URSA MAKYF a SPACE STATION SST 282 ECLA A Teh 1 F 7 i AUDITION DELAY PAH RAS provides a good starting point for learning about the station As you can see the heart of the processor is a multi tap digital delay line The delay line provides a maximum of 255 milliseconds about 4 second of time delay with a signal bandwidth of 7 kHz It has one input and two distinct groups of outputs as wellasa separate echo output The first group of delay line taps shown at the top of the delay line in the diagram are summed together and fed back to the input to generate reverberation when the unit is used in the reverb mode Reverb decay time is determined by the setting of the feedback control greater feedback providing longer decay times The unit is programmed internally to randomize the placement of the reverberation taps and avoid the harsh electronic sound of simple fed back delay line reverberators The other group of taps shown at the bottom of the delay line in the photo are used to audition the signal content of the delay line There are a total of eight audition delay taps which are mixed in pairs through FEVERRECHO FEEDAACE REWERS PROGRAM Laii lt i Fue to NI i R LA T MODERN RECORDING AEYERB ECHO O DIRECT p AUDITION DEA ee Jid 3A DIRECT E F fou
3. 80 Ursa Major Space Station By John Murphy and Jim Ford The Space Station SST 282 from Ursa Major isa highly sophisticated audio signal processing unit which employs a digital delay line with multiple taps outputs to produce a wide variety of reverb echo and comb filter effects There are sixteen Audition Delay Programs which provide four basic families of effects Rooms Combs Delay Clusters and Space Repeats There is also a switch for selecting either reverb or echo mode of operation The Space Station provides the user with front panel control over a wide variety of operating parameters with the result that many totally unique sound effects can be generated in addi tion to the more familiar sounding reverb and echo effects Because of its solid state electronic construction the unit is insensitive to both high sound pressure levels and mechanical shock this combined with the standard 19 inch rack mount packaging helps make the Space Station at home both in the studio and on stage The Space Station is currently priced at approx imately 1 995 General Description As is true of most complex signal processing equipment it is necessary for the user to have some understanding of the unit s oper ation in order to employ it to maximum advantage So before going over the front panel controls let s first consider how the Space Station works Ursa Major has provided a block diagram on the front panel of the Space Station for quick
4. D Input output connections to the Space Station are by way of 3 pin XLR type connectors on the rear panel The units accept either a balanced or unbal anced input signal and provides unbalanced stereo outputs The pin connections for the input and output connectors are provided for easy reference on the rear panel The only other item at the rear is a connector for the detachable line cord Field Test The Space Station was field tested ata local 24 track studio where we had the freedom to hear it on a variety of tracks from multi track master tapes The Station was interfaced through the console patch bay so that its reverb quality could be readily compared with that of several other reverberation systems on hand We compared the quality of the various reverb systems on a variety of program material including solo vocal tracks solo acoustic piano and solo drum tracks We heard some pretty good reverb from the Space Station but it was not quite as natural sounding as either of the two spring reverbs studio quality types or the standard plate reverb with which it was compared However the Space Station provided reverberation clearly superior to that of another digital reverb unit to which we compared it In contrast the Station seemed more diffuse and less colored than the other digital unit Reverb was most natural with the moderately long decay times that result from moderate amounts of feedback Higher feedback levels seemed t
5. ct signal path of the unit we observed that the unit could be driven into slew limit ing by high level high frequency tones The observed slew rate limit was 0 4 volts per microsecond which implies a slew rate ratio slew rate limit divided by peak output voltage swing of 0 054 volts per microsec ond per peak volt out When compared to the recom mended minimum slew rate ratio for freedom from slewing induced distortion 0 5 it appears that slew ing headroom is marginal A quick calculation reveals that the slew rate ratio will be maintained above 0 5 for input signal levels up to 19 3 dB peak level How ever operating the unit with such a low input signal level would degrade its noise performance The best compromise might be to operate the unit with some what reduced input levels say by allowing the 6 dB LED to only rarely flash J G Jung M L Stephens C C Todd An Overview of SID and TIM Part II Audio July 1979 84 We noted that the unit is excellently constructed using modular printed circuit cards with all the inte grated circuits and there are lots of them in sockets for easy maintenance The user s manual for the Space Station provided sufficient discussion of the proces sor s operation to allow a new user to obtain good results Conclusion The Ursa Major Space Station is an audio signal processing unit which employs a multi tap digital delay line to generate a wide variety of special effects as we
6. e set as high as possible without flashing the O dB indicator as signal levels above this will cause digital overload To the right of the input level control are two smaller rotary controls labeled equalization These controls act on all signals entering the delay line including the feedback signal providing up to 10 dB of high or low frequency cut Since the feedback signal is affected these controls have the effect of reducing the 82 decay times of the highs and lows The next five rotary controls constitute the output signal mixer with the first control providing direct signal at the output The next four controls allow mixing of the signals from the eight audition taps Each control adjusts the level from a stereo pair of taps with longer delays on the higher numbered taps Continuing across the face of the unit next there is a pair of push buttons one for selecting either mixed or dry output signals and the other for selecting either the reverb or echo modes of operation With the first control in the Dry position the output consists only of direct signal still under control of the Direct level control In normal operation this switch would stay in the Mixed position except to bypass the effects The reverb echo feedback control is located at the far right of the front panel By varying the level of the reverb or echo signals fed back to the input of the delay line the rate of decay of either type signal can be controlled
7. ll as high quality reverberation The Space Station maintains a good level of audio quality But a sound effects unit like this has to be heard to be appreciated So if you re looking for a time delay effects unit we suggest you make sure to audition the Space Station LAB TEST SUMMARY Note 0 dBV is referenced to 775 Vrms nput Output Levels Minimum input level for 0 dB peak level indication 0 6 dBV Output level for O dB indication 7 0 dBV dry signal only with the direct level control at maximum Output clips at 16 6 dBV Noise Performance 20 kHz filter unweighted For a dry signal only noise 74 2 dBV R of the output is 67 9 dBV L With the four audition taps at maximum noise at the output is 66 8 dBV Distortion Performance THD plus noise at O dB peak level indication Frequency Dry Output Delayed Output 10 kHz 037 1 kHz 0036 12 1 00 kHz 0032 12 Bandwidth 3 dB points 6 Hz to 20 kHz 1 O Hz to 7 1 kHz Slewing Performance Dry signal path Delayed signal path Slew rate limit dry signal path 0 4 volts per microsecond Slew rate ratio at O dB peak level dry signal path 0 054 volts per microsecond per peak volt CIRCLE 30 ON READER SERVICE CARD 9 MODERN RECORDING
8. next group of programs is referred to as Delay Clusters and includes five programs This family provides eight delays that are closely spaced in time with the cluster of repeats occurring at progressively later times going from the programs Fatty to Echo In the program labeled Fatty the delay of the echo cluster is less than 40 milliseconds These programs provide extra richness for slap echo type effects REVERB amp TRE Space Repeats is the name of the last group of programs Three programs provide 2 3 or 4 echoes evenly spaced over the 255 milliseconds of available delay They provide left right motion and are espec ially recommended for use with percussive sounds When the echo mode of operation is selected the reverb taps are disconnected from the feedback loop and the single echo tap is connected into the feed back control The Echo Delay Time control is then used to establish the location of the echo tap anywhere along the delay line Long delay times give rise to decaying repeating echoes whereas short delay times produce comb filter effects These effects can be further enhanced by auditioning them through more than one audition delay tap Now that we have some idea of how the Space Station works let s go over the front panel controls and rear panel connections At the far left is an input level control which is used in conjunction with the LED peak level indicator below The input signal level should b
9. o result in an electronic sounding hash towards the end of the decay We don t feel that this would be a serious problem in most applications however as the low level hash would typically be masked by program material As a special effects unit as opposed toa reverberation unit the Space Station truly excels We found the effect of the delay cluster programs especially appealing on percussive sounds fatty handclaps were great while the space repeats programs gave an interesting machine gun effect on Snare pops The operator s manual provides over twenty recipes of control settings for various effects most of which we auditioned Needless to say most of these have to be heard to be appreciated but they included such effects as doubling comb filtering thickening slap ricochet reflections resonance fattened echo and pure delay All in all we heard quite a wide variety of effects and especially combinations of effects reverb through a comb filter for example The unit s noise was not noticeable and there was no sub jective impression of limited high frequency band width We performed our usual listening test back at the shop by connecting the Space Station into a tape monitor loop of the preamp in our reference system Listening to high quality discs through the direct signal path of the processor we noticed only a slight softening in the high frequency range when the unit was switched into the listening chain Lab Te
10. r front panel level controls along with the direct signal on its own level control to make up the output signal Taps 1 3 5 and 7 are summed and sent to the unit s left output while taps 2 4 and 8 appear at the right output The position of the eight audition delay taps along the delay line determines the time delays and relative spacing of the initial echoes from the processor These eight time delay values are set by selecting one of sixteen Audition Delay Programs There are four groups of programs named Rooms Combs Delay Clusters and Space Repeats The first of these rooms uses semi randomly chosen delays spaced to sound like the early reflections in the natural reverberant field of real rooms The longer time delays are from the later taps so the user can readily adjust the signal level for the earlier or later taps to emphasize the earlier or later room reflections as desired Rooms 1 through 4 provide increasing amounts of delay to simulate increasingly larger rooms The four comb programs are intended for special effects Closely spaced delays are combined to produce the series of notches in frequency response commonly known as a comb filter thus named because the closely spaced notches resemble the teeth of a comb The comb programs provide good sci fi effects on voices and can be used to add a tonality to percussive sounds APRIL 1980 e MULTLTAP DIGITAL DELAY REVERBER ATION PROCESSOR ECHO The
11. st For specific results of the lab test see the accompanying Lab Test Summary The input of the Space Station was found to be relatively insensitive with no less than a 0 6 dBV input signal level required for a O dB peak level indication Thus an auxiliary line amp may be required for interfacing with systems standardized on 10 dBV signal levels Inter MODERN RECORDING hi eel Fig 1 Ursa Major Space Station Frequency response of dry and delayed signal paths facing with 4 dBV systems should present no problem Noise performance through the dry signal path was not quite as good as some professional audio equip ment we ve encountered and the noise level for the left output was about 6 dB higher than for the right channel The noise level increased when the four audi tion taps were set at maximum level but was stilla respectable 66 8 dBV THD through the direct signal path was quite low about 003 increasing about tenfold at 10 kHz to about 03 For O dB level signals through the delay line THD was about 0 12 Bandwidth through the dry path was 6 Hz to 20 kHz The high frequency bandwidth through the delay path was limited to 7 kHz by a very steep anti aliasing filter see Figure 1 Although more extended high frequency bandwidth would be desirable we observed that the highest octave wasn t really missed in the reverb and effects maybe because of the full bandwidth of the direct signal In testing the dire
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