These precision instruments select from several analogue and digital inputs to provide simultaneously both analogue and digital monitor outputs as well as displaying level on bar-graph meters with multiple scale modes, indicating phase and providing audible monitoring on inbuilt loudspeakers and headphones. Intended for use in broadcast or similar environments they have input connectors on the front panel for use when mounted in racks with adjacent patch panels. One model includes a digital signal generator, with both analogue and digital audio outputs, offering line-up tones at 800Hz and 1000Hz.
Level is displayed by two horizontal bar-graphs. As delivered, these are marked using Nordic/ DIN 45406 scales. Two scaling strips are supplied to attach over the DIN scaling, for BBC IIa and 'Digital' scaling. The meters can show VU level and peak level simultaneously; a single LED showing the peak level in addition to the multiple LEDs showing VU level in a bar. Switches on the rear provide the following scales and modes: DIN, Nordic, BBC, 'Digital' scales; 'Peak, fast mode' shows each sample, 'peak only' shows the peak value in 'hold' mode, 'level only' shows just the level, 'peak and level' shows the level as well as the peak value.
The front panel has two grilles for the inbuilt monitoring speakers, and, otherwise, is split into two areas of connectors and controls. On the right, seven illuminated, interlocked switches select the inputs to be monitored; three analogue and four AES digital. Four similar buttons select between the display of the selected stereo signal, left on both channels, right on both channels and the mono sum on both channels. The remaining two illuminated switches here select the muting of loudspeakers and headphones and 'off', which switches off all inputs. The switches have removable lens-caps, which make it possible to re-label the functions of the switches if desired, using appropriate film. There are two horizontal bar-graph meters, each having 53 LEDs, for left and right level indication. Three LEDs indicate the phase of the selected signal; in or out of phase and conditionally mono compatible. A vertical row of LEDs indicate the sample rate of the digital output signals. Four rotary controls set the volume and balance each for the speakers and headphones, which connect by an adjacent 6.35mm jack socket. Insertion of a jack mutes the internal loudspeakers.
The third analogue and fourth digital inputs are positioned to the left of the input selector using the proprietary Ghielmetti GP3 connectors, for use with Ghielmetti patchcords or patchcord plugs. Two 3-pin (with additional polarising pin) sockets are positioned so that either two mono plugs or one stereo plug may be connected to the analogue inputs. A single socket is provided for the AES/EBU digital input.
The left hand area is concerned with the integrated signal generator and power. On the GMS2100 only, there are four illuminated switches to select either 800Hz or 1000Hz individually to the left and right outputs of the signal generator. Two rotary controls set the output level of the oscillator and the sample rate of the digital outputs. Each control has an associated column of LEDs to show the selected value. The outputs of the signal generator are provided on two Ghielmetti GP3 connectors for analogue and a single socket for digital AES/EBU, in a similar layout to that used for the inputs, described previously.
The rear panel has two pairs of 3-pin female XLR connectors for analogue inputs one and two. A further pair provide the analogue outputs. Each pair has two 3-pin, 6.35mm, stereo jack sockets wired in parallel with the XLRs. All are balanced connections, but may be wired unbalanced, with the expected reduction in level. Three 3-pin female XLR connectors provide the AES/EBU balanced 110 ohm inputs; each has an associated BNC connector for unbalanced 75 ohm connections. Similarly, the AES/EBU output is provided on a 3-pin male XLR, together with an associated BNC connector. Four miniature 'DIP' switches set the audio level meter scale. Power is supplied to the unit by an IEC inlet; separate technical and chassis earthing terminals are supplied as might be expected from this calibre of equipment. On both the GMS 2100 and GMS 2110 there is a toggle switch for power.
Analogue inputs: +27dBu maximum. Input impedance: 20k ohms balanced, 10k ohms wired unbalanced.
Analogue outputs: Output impedance: 60 ohms balanced, 30 ohms wired unbalanced.
Loudspeaker amplifier: 10W RMS per channel. Acoustic response: 80Hz-16kHz +/- 5dB, 600mm.
Headphone output: 0.2W RMS per channel, 8 ohms, 20Hz-20kHz +/-3db, less than 0.5% THD at 1kHz.
Digital inputs: 110 ohms balanced, XLR and G3P, 75 ohms unbalanced, BNC, galvanically isolated.
Digital outputs: 3V pp, 110 ohms balanced, XLR and G3P, 2.5V pp, 75 ohms unbalanced, BNC, re-clocked.
A to D converter: 24 bits, 96 or 192kHz. Analogue input: +15dBu maximum for distortion-free conversion.
D to A converter: 24 bits, sample rate automatically detected for 32, 44.1, 48, 88.2, 96, 176.4, 192kHz +/-3%.
Analogue input to analogue output: Gain: 0dB +/- 0.1dB, 10Hz-20kHz. At 1kHz, 0dBu input: Noise: -80dB. Crosstalk: -80dB. Switch-off attenuation: -90dB. Distortion: better than 0.1%.
Analogue input to digital output: Gain: 0dB +/- 0.3dB, 20Hz-20kHz. The following at 1kHz, 0dBu input - Noise: -90dB. Crosstalk: -90dB. Distortion: better than 0.1%.
Digital input to analogue output: Gain: 0dB +/- 0.3dB, 50Hz-20kHz. All at -15dBFS input, 1kHz - Noise: -75dB. Crosstalk: -90dB. Switch-off attenuation: -100dB. Distortion: better than 0.1%.
Digital input to digital output: Gain: 0dB, 10Hz-20kHz. All at -15dBFS input, 1kHz - Noise: -100dB. Crosstalk: -100dB. Distortion: better than 0.1%. Sample rates: 32 to 192kS/s. Output jitter: Better than 2ns.
Signal generator outputs: 800Hz, 1000Hz. Analogue: -50dBu to +10dBu, steps of 10dB. Digital: 3V pp, sampling rates of 32, 44.1, 48, 88.2, 96, 176.4, 192kHz. (GMS2100 only).
Power source: 90-267V AC, 47-63Hz, 60W maximum. Dimensions: 2U rack mounting, 250mm deep. Weight: 5.8kg.
Included accessories: 3x 600mm Ghielmetti patchcords with G3P connectors; 1x adapter cable, 300mm, G3P to male 3-pin XLR connector; 1x adapter cable, 300mm, G3P to female 3-pin XLR connector. Power cable.
Optional accessories: For additional patchcords and patchcord plugs, see Ghielmetti Digital/Analogue Patch Panels.