User manual ART DIGITAL MPA

[. . . ] ART Digital MPATM Microphone Preamplifier TABLE OF CONTENTS Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Front Panel Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] This mode brings out the harmonics in the input sources, particularly stringed instruments. The tube circuit runs extremely clean in the "high" (IN) position of the plate voltage switch. As signal levels rise distortion remains very low until within 6dB of clipping, where the overload characteristics smoothly limit the signal swing. There is increased bandwidth (>100KHz), and headroom in this mode as well. Meter Switch The analog meters can monitor either the output signal at the output jacks ("output" position) or the tube output level ("tube" position). VU on the meter measures +4dBu at the output jacks in "output" mode. When in "tube" mode there is 10 to 15dB of headroom above 0VU before the tube saturates (for "normal" and "high" plate voltage settings respectively). Digital Section Front Panel Controls Digital Level Control The levels driving the A/D converter are adjusted with this control. The topology of the DMPA lends itself to simultaneous use of the analog and digital outputs, as each has its' own level control. Located before the Digital level control is the insert jack, allowing processing to be added before digital conversion. As the Digital Level control is used refer to the Digital level LED meter which indicates both peak and average level present at the A/D converter input. This meter helps you get the perfect level adjustment and avoid clipping the A/D. Refer to the section titled "Obtaining the perfect digital level setting" for more detail on the operation and use of these features. When the output of the unit goes off to a system that can handle only 16 bit data, the 8 least significant bits of data are ignored (truncated). This leaves the sound with gritty "digital" sounding signals at very low levels. Depressing the Dither switch adds a dither component that when truncated replaces this with a more musical sound as the levels trail off into the noise floor. 6 ART Digital MPATM Microphone Preamplifier Generally, keep the unit in 24-bit mode (the out position of the switch) unless you are connected to a system that will truncate the signal to 16 bits. If the unit CANNOT sync to an external source (either out of range, not connected or a system failure), the optical Output select switch will blink. (You may see this switch flash once between changing sample rates, indicating the fraction of a second it takes to settle to the new rate. NOTE: When using the ADAT Input as a sync source, the maximum sample rate is limited to about 50KHz Sample Rate (selection being set to ADA - not wordclock or any other fixed sample rate). 7 ART Digital MPATM Microphone Preamplifier Optical Switch The optical output jack of the DMPA can have one of two formats. When this switch is depressed AND lit blue, this jack will output 8 channels of ADAT. (ADAT cannot be output if the sample rate exceeds 48KHZ - the Sample Rate selection being set to an internal rate). In this case the switch cap will NOT be illuminated, and the output format will revert to 2-channel mode (TOSLINK). When ADAT output is active, The left channel of the DMPA is output on CH1, the right channel of the DMPA is CH2, and the rest of the channels consist of data received from the ADAT Input jack. [. . . ] The transition between either setting is smooth and quiet and the gain variation is minimal. NOTE: It takes 15-30 seconds for the tube circuit to fully transition between either mode. During this time, the unit passes a signal and the only noticeable change is a slight increase in level in the "HIGH" setting. The "Warm" setting produces a smooth transition from very clean low levels up to a "round" saturated clipping on peaks. This setting is reminiscent of old tube gear, and used to get the most tube-like sound out of the unit. The "High" setting of the plate voltage switch has increased bandwidth and headroom, very low distortion and runs extremely clean until it reaches a point of saturated clipping. [. . . ]