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SPL compressor technology

In the compressor/limiter section of the Channel One the parameters for the time constants 
(attack and release) are set automatically and adapt themselves to the changing conditions 
of the input signal, far better than can ever be achieved by manual adjustments. The transient 
and final oscillation behavior of voices and instruments are constantly changing and at times 
are so erratic that a manual control will only achieve good average values, which at critical 
moments can produce disadvantageous effects (e. g. distorted sounds, “pumping”, etc).

If for example the compressor has to react very quickly to harsh P or T noises it must also 
be capable of reacting slowly to softer tones – otherwise distortion occurs. Accordingly the 
Channel One compressor regulates the level of large fluctuations faster than smaller ones; 
tones of longer duration are automatically processed with a longer attack time to prevent 
distortions.

The automatic setting of the release times is dependent on the input signal, too. Fast and 
large  level  fluctuations  are  correspondingly  processed  with  shorter  time  constants  than 
minor fluctuations in order to limit the distortion of the audio signal as far as possible. Overall 
this technique provides the optimal solution between fast, unobtrusive control response and 
the least distortion of the audio signal. The result is a natural and transparent sound impres-
sion.

A  further  technical  specialty  of  the  circuitry  contributes  to  the  high  audio  quality  of  the 
compressor  in  the  Channel  One:  SPL’s  double  VCA  drive.  One  VCA  receives  the  in-phase, 
the other the out-of-phase signal. Subsequently the signal is passed through a differential 
amplifier. The effect of this circuitry is that distortion products and offset fluctuations can be 
removed – the product of the differential of both signals means that possible interference is 
canceled out. The original information is however further amplified by 6 dB. In addition the 
VCAs provide relief to each other because they share their loads. They do not even run the 
danger of operating in the saturation range, which ensures to avoid offset noises, audible as 
clicks or pops.

SPL’s double VCA drive circuitry overall displays vastly improved distortion values so that a 
distinctly clearer and more transparent sound impression is achieved than with conventional 
circuitry. Voices and instruments are given a considerably more natural and dynamic timbre 
whereas ”muffled” tones are not audible.

The compressor characteristics are portrayed on page 26.

16

Channel One

Compressor 

Control Elements

Содержание Channel One 2950

Страница 1: ...Manual Channel Strip Channel One Model 2950...

Страница 2: ...40 Fax 49 0 2163 983 420 E Mail info spl info Internet www spl info The construction of the Channel One Model 2950 is in compliance with the stan dards and regulations of the European Community Notes...

Страница 3: ...UCTION SPL De Esser technology 13 Insert 14 Compressor Limiter ON LIMIT 14 COMPRESSION MAKE UP GAIN NOISE GATE 15 SPL compressor technology 16 Equalizer ON EQ PRE COMP 17 LMF LMF MHF MHF Recommendatio...

Страница 4: ...ample near a wash basin or bath in a damp cellar near swimming pools or the like In such cases there is an extremely high risk of fatal electrical shocks Insertion of foreign objects or fluids Never a...

Страница 5: ...s Be sure that any service technician uses original replacement parts or those with identical specifications as the originals Incorrectly substituted parts can lead to fire electrical shock or other d...

Страница 6: ...upported And more time remains for the creative tasks From the outset great value was placed on high flexibility An example are the three separate inputs for microphone line signals or instruments eac...

Страница 7: ...OPTIONS GND LIFT GND LIFT GND GND LIFT VOLTAGE FUSE VOLTAGE FUSE X L R W I R I N G PIN 1 GND PIN 2 HOT PIN 3 COLD T R S J A C K W I R I N G TIP LEFT RING RIGHT SLEEVE GND CONNECTOR WIRING Sound Perfo...

Страница 8: ...in ground potentials between driver and receiver would produce disturbances In balanced connections a reference signal with reversed polarity is transmitted additionally to the audio signal through a...

Страница 9: ...tch on the front panel Please read the important notes in chapters 48V and Activating phantom power on page 11 The microphone input can also be equipped with an optional input transformer see page 29...

Страница 10: ...r is 12dBu 0 dBFS PLAYBACK INPUTS The playback signal is connected to the unbalanced PLAYBACK INPUTS to create a head phone moni toring mix If a mono playback signal is available only the LEFT connect...

Страница 11: ...PHANTOM POWER ALSO WHEN CHANGING MICROPHONES THE INPUT STAGE OF THE CHANNEL ONE CAN BE DAMAGED IF YOU IGNORE THESE PROCEDURES 1 Connect the microphone to the Channel One 2 Now activate phantom power...

Страница 12: ...n connected regardless of which input is selected You can choose the line input as source as long as the instrument input is not being used INSTRUMENT The INSTRUMENT input jack is placed on the front...

Страница 13: ...of operation has distinct advantages because it is unobtrusive and helps retain the original tonal quality Compressor typical side effects such as lisping or nasal tones do not occur Finally its opera...

Страница 14: ...shows the processing intensity see GAIN REDUCT on page 23 Usually the signal flow follows the design of the Channel One and for this reason the input signal normally arises from the de esser or when...

Страница 15: ...eration of the subsequent recording system MAKE UP GAIN With the MAKE UP GAIN control you can restore the overall level reduction caused by compression or limiting With assistance of the GAIN REDUCT d...

Страница 16: ...ignal as far as possible Overall this technique provides the optimal solution between fast unobtrusive control response and the least distortion of the audio signal The result is a natural and transpa...

Страница 17: ...n the switch is pressed the equalizer operates in front of the compressor limiter when not pressed the succession remains unchanged This function permits very flexible operation with the Channel One w...

Страница 18: ...f bass emphasized instru ments during recording or subsequently when mixing etc MHF The center frequency of the semi parametric mid high frequency filter is set with the MHF control The frequency rang...

Страница 19: ...the equalizer so that the newly created spectrums can also be processed with the EQ A more or less over driven field effect transistor forms a part of the distortion circuitry It s characteristic cur...

Страница 20: ...T display does not show any values An instance of a sensible application could possibly be when the output signal of the Channel One together with the playback signal are reproduced via the studio mon...

Страница 21: ...o that of the OUTPUT control or MUTE switch which means the volume in the headphones does not alter although the output value of a modula tion has changed TIP When working with hard disc systems or di...

Страница 22: ...e EQ and behind the output control All possible causes for overload can be directly checked overdriven microphone instrument line gain an excessive make up value in the compressor limiter too much boo...

Страница 23: ...f the AD converter and on page 29 Although the values of the PPM OUTPUT display only cover up to 12 dB sufficient headroom remains internally approximately 6 dB so that the output value can exceed thi...

Страница 24: ...kHz 80 dB 10 kHz 78dB 0dBu LINE IN only THD N Gain A weighted 5dB 99 4 dBu 20 dB 97 2 dBu 42 dB 79 4 dBu Input impedance Line 20 kOhm Instrument 1 MOhm Maximum input level Line 22 dBu Instrument 14dBu...

Страница 25: ...25 Channel One Block diagram...

Страница 26: ...and output Curve B shows the curve charac teristics of the compressor The soft knee characteristic is clearly visible Curve C portrays the limiter s curve characteristics Diagram2 shows various cut an...

Страница 27: ...r at 3kHz The proportional Q characteristic is distinctly visible Diagram 4 displays the curves of the LMF filter Various cut and boost settings at 150Hz Again the proportional Q char acteristic is cl...

Страница 28: ...Copy master recall settings Artist Album Gig Title Engineer Track s Groups Date...

Страница 29: ...synchronization The yellow Sync Lock LED illuminates when a valid sync signal is present at the SYNC INPUT and the converter is automatically synchronized to the external sample rate To prevent inter...

Страница 30: ...Manual Channel One Model 2950...

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