User manual ART TUBEOPTO 8

[. . . ] Tubeopto 8TM 8-CHANNEL TUBE MICROPHONE PREAMPLIFIER / OPTICAL INTERFACE USER'S GUIDE IMPORTANT SAFETY INSTRUCTIONS ­ READ FIRST This symbol, wherever it appears, alerts you to the presence of uninsulated dangerous voltage inside the enclosure. Voltage that may be sufficient to constitute a risk of shock. This symbol, wherever it appears, alerts you to important operating and maintenance instructions in the accompanying literature. Please read manual. Read instructions: Retain these safety and operating instructions for future reference. Do not open: Aside from four vacuum tubes, there are no user serviceable parts inside. [. . . ] The gain sensitivity is identical for both the XLR and 1/4" TRS jacks, however the XLR input impedance is 6. 4K Ohms and the 1/4" TRS input impedance is 20K Ohms. The front panel Pad switch varies the sensitivity of both inputs. Balanced Output Jacks Eight low impedance 1/4" TRS balanced output jacks provide audio output from the D/A converters driven by the ADAT Lightpipe Input. Output Level Switch This switch optimizes the output level of the rear output jacks with your system operating level. In this case the maximum output is +20dBu when the digital level equals 0 VU. When the switch is in the "out" position, the output levels are optimized for ­10dBV systems. FIGURE 3 - Rear Panel 4 Wordclock Input and Thru Jacks The Wordclock input is used to externally sync the Tubeopto 8TM to a master clock source. The BNC Wordclock Input jack is connected directly to the BNC Wordclock Thru jack, providing the ability to loop through the Tubeopto 8TM and connect other devices to the wordclock sync source, saving the use of a BNC T­adapter. FIGURE 4 - Block Diagram The Wordclock input is high impedance thus leaving the wordclock connection unterminated. (A 75 Ohm BNC terminator should be used on the Wordclock Thru jack if the Wordclock Input jack is used only. ) ADAT Lightpipe Jacks Each ADAT Lightpipe jack supports eight channels of 24 bit digital audio data conforming to the ADAT Lightpipe protocol, which transfers eight tracks over a single fiber optic cable. The ADAT Lightpipe Output jack data is generated by the eight internal A/D converters that are directly driven by the outputs of the eight preamplifier channels. The A/D sample rate and sync source are selected by the front panel switch. The ADAT Lightpipe Input jack accepts eight channels of digital audio data at any sample rate between 40KHz and 52KHz. This data is directed thru the eight internal D/A converters to the eight rear balanced audio outputs. Since the D/A converters sample rate is derived from whatever is coming in the ADAT Input jack, this section can lock to non-standard sample rates as long as they are between 40KHz and 52KHz. FIGURE 4 - Block Diagram 5 HARDWARE OPERATION How to adjust the preamplifier controls for the lowest noise Start with the Gain and Output knobs centered, and the Pad switch in. Increase the Gain control until the Clip LED in the meter just barely comes on during the loudest peaks in level, and then back off the control slightly from that point. (The Clip LED should come on occasionally at most. ) If there is not enough level with the Gain control set fully clockwise, back off the gain to 12 o'clock and place the Pad switch in the out position. Adjust the Output control until the -10 LED is on most of the time during loud passages. Increasing the input gain and decreasing the Output level control adds more tube warmth. Remember, that the Clip LED looks at both the preamp input and output peaks, whereas the -10, -20, -30 LED indicators only look at the preamp output level which feeds to the A/D converter. How to set the Output Level switch (on the rear panel) Setting this switch correctly can lower the noise in the output signal chain by optimizing the operating levels between the Tubeopto 8TM and external gear. One way to determine how this switch should be set is to send audio to the Tubeopto 8TM from an ADAT digital interface and run the audio outputs into a line input on a mixer or signal processor. Check the meters on the mixer or signal processor to see if the level appears to be too high (clipping) or too low (barely showing any indication on the meters). Set the Output Level switch so that the level meters in the external gear do not indicate excessive clipping yet still provide good full-scale (or near full scale) deflection. Changing the sample rate The D/A converters always sync to the incoming ADAT data stream. The front panel display and switch apply to the A/D converter sample rate and sync source. Pushing the Sample Rate switch (or holding it down) cycles through the various settings. [. . . ] 7) When using the Tubeopto 8TM as a Preamp-to-ADAT only, if the red Wordclock LED is on solid or either of the green (44. 1KHz or 48KHz) LED's are on then the Preamp, A/D, and ADAT Output sections will be functioning normally. In this case if the yellow ADAT LED is flashing it just means that you are not using the ADAT Input section. 9 WARRANTY INFORMATION Limited Warranty: Applied Research and Technology will provide warranty and service for this unit in accordance with the following warrants: Applied Research and Technology, (A R T) warrants to the original purchaser that this product and the components thereof will be free from defects in workmanship and materials for a period of three years from the date of purchase. Applied Research and Technology will, without charge, repair or replace, at its option, defective product or component parts upon prepaid delivery to the factory service department or authorized service center, accompanied by proof of purchase date in the form of a valid sales receipt. Exclusions: This warranty does not apply in the event of misuse or abuse of the product or as a result of unauthorized alterations or repairs. This warranty is void if the serial number is altered, defaced, or removed. [. . . ]