User manual RANE AD 13

[. . . ] WARRANTY EXPLANATION -- PLEASE READ CAREFULLY Rane offers a limited warranty, described in full on the Limited Warranty card included in the packing materials, which covers both parts and labor necessary to repair any defects in the manufacturing of your Rane product. The warranty period is two (2) years, starting from either(i) the date of retail purchase, as noted on either the sales slip from an authorized Rane dealer or on the warranty registration card sent, in to the factory or, (ii) in the event no proof of purchase date is available, from the date of manufacture, which is coded on the rear of the chassis. If you send in the registration card according to the instructions on the card, or retain your sales slip as proof of purchase, you will receive a full two (2) year warranty period from the date of purchase, regardless of the date of manufacture. If you do not send in the registration card ("I forgot. "), or you do not have a sales s1ip from an authorized Rane dealer ("My dog ate it. "), the warranty period will only extend two (2) years from the date of manufacture. [. . . ] So, you have read the previous page and you're ready to continue. Use the block diagram as a pictorial guide as we describe the signal path of the AD 13. It will help you a lot. AD 13 BLOCK DIAGRAM In the beginning, signal is applied at the input either through the 3-pin connector or the barrier strip. Whether the input is balanced or not, it will first pass through the Radio Interference Filter to strip it of local police matters and reruns of Falcon Crest. It will then be applied to the differential amplifier which unbalances a balanced input and rejects common mode noise on the input lines. For unbalanced inputs the differential input amp behaves like a piece of ordinary zip cord. The next stop on the tour is the input level control. From the input level control the signal is passed to the input gain adjustment amplifier which preconditions the audio signal for presentation to the nine pole elliptic anti-aliasing filter. The anti-aliasing filter prevents any frequencies above 20kHz from entering the audio to digital converter. If they were allowed to pass they would cause a great deal of difficulty with the meter reader and some severe distortion at the output of the system. The next stop in the signal path is the pre-emphasis block This circuit boosts high frequencies relative to the tower frequencies for two reasons: First, high frequencies are usually lower in level than low frequencies and can be processed with higher resolution when boosted and second, to reduce the output sensitivity of the unit when de-emphasis is applied at the output to compensate for the pre-emphasis and return the overall frequency response to flat. The lower high frequency sensitivity at the output results in a lower output noise level. 7 The branch in the road after the pre-emphasis leads to a dead end at the headroom meter, which must be attached after the pre-emphasis is applied to the input signal so that a visual indication of what is really being applied to the digital converter can be monitored. Up the other fork lies the sample and hold circuit. This clever trick provides the converter with a steady voltage during the conversion process. To do this, the sample and hold actually holds the input voltage steady during each sample cycle, releasing the input only after a digital reading is completed. Once the sample is complete, the sample and hold takes another look at the input and then freezes the voltage at a new level. At this point in the signal path lies the de-emphasis circuit which removes the frequency shaping that was applied to the signal before conversion to the digital domain. The aforementioned steps in the audio are then removed with another nine pole elliptical filter. All of the frequency components of these steps are higher in frequency than the cutoff frequency of the filter. At the output of the filters there is a buffer amplifier which scales the gain appropriately and drives the output level control pot. After this processing, the signal is subjected to a pair of amplifiers which either directly drives the outputs in an active balanced or unbalanced fashion or through a switch selectable output coupling transformer. The very last item of importance is the bypass relay. [. . . ] The INCREASE/DECREASE switches will always affect the delay time by 20 microsecond intervals on power up. This may be changed to the 1 millisecond step mode by pressing either INCREASE or DECREASE and then tapping the CHANNEL SELECT pushbutton. Tapping it again will toggle back to the short increment mode. SETTING TIME DELAYS Setting up the time delays for optimum effectiveness in the AD 13 or any other delay device can be something of an art. [. . . ]