Art PRO MPA II Guide de l'utilisateur télécharger pdf (Page 6)

Level Control.

VU Level Meter

Each channel of the PRO MPA has a backlit VU meter showing

its output level. The Ò0Ó level is calibrated to +4dBu. Use the VU

meter when adjusting the Output Level Control to aid in sending

the proper level to your next piece of equipment.

REAR PANEL CONNECTIONS

ItÕs easy to interface the PRO MPA with other equipment.

Balanced XLR and unbalanced 1/4Ó phone, input and output

connectors are located on the rear panel.

The PRO MPAÕs XLR connectors follow the AES standard of:

Pin 1 = Ground, Pin 2 = Hot (+), Pin 3 = Cold (-). The unbal-

anced 1/4Ó phone jacks are typical Tip - Hot (+), Sleeve -

Ground connections.

Input

Ideally, one input jack per channel should be used at a time.

However, because of its design, the PRO MPA can be hard-

wired into a rack without having to disconnect the XLR inputs

when using the 1/4Ó jacks. If no load is placed on the XLR input

(no instrument or microphone connected) the 1/4Ó jack will func-

tion as if there was nothing connected to the XLR input. Both

PRO MPA inputs may be used simultaneously. However, the

two signals will sum and the signal present at the XLR jack will

tend to attenuate the signal of the 1/4Ó input.

Output

Both balanced and unbalanced output connections may be

used simultaneously. This is particularly useful when using the

PRO MPA as a direct box for instruments or line level signals.

**Note: If you experience a grounding hum when using both

output connectors (one to the console, one to an instrument

amp) simultaneously, a ground loop may be the problem. To

remedy this problem, disconnect the ground wire (pin 1) from

the XLR cable plugged into the PRO MPAÕs output (or use a

ground-lifted cable). This interrupts the ground path and there-

fore breaks the loop.

power is present. However, if the mic doesnÕt need it, donÕt use

it. Some things are best left untested!

HPF (High Pass Filter) Control

The HPF is a low frequency roll-off intended for use to Òtune

outÓ unwanted rumbling or breath noises. A High Pass Filter

allows frequencies above its set point to pass unaffected while

gently rolling off frequencies below its set point. The range of

the PRO MPAÕs HPF is 7Hz to 150Hz with a slope of 6dB per

octave. This gentle slope allows unwanted low frequency infor-

mation to be rolled off while not affecting the tonality of the input

signal. In its fully counter-clockwise position, the filter has a set

frequency of 7Hz which can be considered ÒbypassedÓ or off.

The filter is located after the Input Level Contol and before the

tube circuitry.

Tube Character 10 Segment LED Array

Ten LEDs are provided on each channel which display how the

tube gain is affecting the input signal. These LEDs are calibrat-

ed with the tube circuitry to give you an accurate visual of its

output signal (**Note: these LEDs are pre-output level control).

Use this meter as a visual for setting the Input level to the PRO

MPA. The first four LEDs are labeled Clean. The tube is produc-

ing a clean output when this LED is lit.

The next four LEDs are labeled ÒwarmÓ. This is the optimal

operating range for the PRO MPA. At this level, the tube is pro-

ducing an output signal which most would term ÒwarmÓ.

Whatever you would like to call it is fine. YouÕll find the output

signal has an enhanced bottom to low mid quality with smooth

high frequency detail.

The last two LEDs are labeled ÒClipÓ. The first LED will light

approximately 6dB before audible distortion occurs. If this light

flickers, do not panic. The unique design of the PRO MPA

allows the tube to distort well before any other gain stage.

When a tube goes into distortion it is a gradual process and

tends to sound pleasing for a range before it turns into a distor-

tion box. After some use youÕll find the Òsweet spotÓ of the PRO

MPA is with this light flashing fairly regularly. You may find a

ÒclippedÓ level is suitable for some applications.

**Note: Use the Tube Character Array to aid in setting the Input

88 99

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Art PRO MPA II Guide de l'utilisateur Page 6

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