AESDA
PORTABLE AES TO ANALOG CONVERTER
The Whirlwind AESDA is a portable device for converting AES-3 and S/PDIF digital audio signals into analog audio signals. Digital input to the AESDA is through the female XLR or BNC. There are level meters that display the level of the incoming digital signal or they can be switched to display the analog output signal level. Each of the two decoded analog audio outputs has an independent level control, from which the signal is sent to the analog metering circuits and male XLR outputs. Another unbalanced analog output is provided on a 3.5 mm TRS jack, with its own level control, for use with headphones or as an unbalanced line level driver. Both professional and consumer versions of AES-3 can be decoded by the AESDA.
Additionally, the AESDA provides diagnostic analysis of the incoming AES-3 and S/PDIF digital signals for help in troubleshooting signal faults. The digital monitor section identifies the sample rate and characteristics of the incoming digital signal, and if there is a problem in the digital audio stream several different fault types can be identified.
99 Ling Road . Rochester, NY 14612
Phone 585 663-8820 . Fax 585 865-8930
Email: sales@whirlwindusa.com
http://www.whirlwindusa.com
Theory of Operation
The AESDA was designed to provide a portable means of converting an AES-3 or S/PDIF digital audio stream into a professional high-quality two-channel analog audio output. The digital input is extensively screened at receiving, with faults in the data or transport annunciated by type. A dual 11-segment VU meter monitors the audio level from the DAC or the level at the output. In the interest of conserving battery power, two display modes are available on the VU meter. One is a bar graph of the signal level, the other is a single LED which indicates the peak instantaneous signal level, with the single LED consuming less power than the bar graph. A ten-segment red LED bar serves to indicate the various operating modes and detected faults, if any. A switch selects the function of this LED bar, either to indicate operating mode, detected sample rate, etc., or to display any detected fault. The analog output has separate level controls for the left (A) and right (B) side. Output level may be set by selecting the analog output on the VU meters, and setting the controls to the desired value. A headphone monitor jack with separate level control is also provided for checking the analog audio signal. Recommended headphone impedance is between 16 and 100 Ohms. This jack can also be used as an unbalanced line level output. Primary power for the unit can be sourced from four “AA” cells (Alkaline, Lithium-Ion or Nickel-Metal-Hydride cells are recommended). An external coaxial power jack (5.5mm x 2.1mm) is provided for situations where battery power may not provide an adequate length of operation. The external power source should be able to provide 12 Watts of power at a Voltage range from 3.5VDC to 15VDC. This allows the AESDA to operate on a wide variety of power sources including car batteries, portable camera batteries, or a “wall wart” type of power supply.
Digital Monitor LED Function Details
Digital Info Indicators
Sample Rate
There are six sample rate indicators that show the closest standard sample rate to the signal as received: 44.1kHz, 48kHz, 88.2kHz, 96kHz, 176.4kHz, and 192kHz. Signals that have sample rates lower than 44.1kHz may be locked to and decoded by the AESDA, but their sample rate will not be displayed. Only one sample rate LED should be illuminated at one time in normal operation. With no input signal, the Fault LED and the No Lock LED (in Fault Type mode) will be illuminated instead.
Audio
The Audio LED indicator illuminates when the input digital data stream has been determined to be Pulse-Code Modulated (or PCM) digital audio. For other digital inputs that are not PCM audio, such as TDM data to DTS-CD, this indicator will be off.
Consumer
The Consumer LED indicator illuminates when the Pro/Consumer mode bit in the digital audio stream's Status bit indicates Consumer mode, and is off in Professional mode. Note that this indicator only presents validly when the AESDA is locked to a valid PCM audio data stream.
Pre-Emph(asis)
The Pre-Emph(asis) LED Indicator illuminates when the digital audio stream's Status bit field for this condition indicates that it is present. Typically, pre-emphasis is only used for sample rates of 32kHz, 44.1kHz, and 48kHz. When the indicator is off, it indicates that the audio signal embedded in the digital stream has not been pre-emphasized.
Fault
The Fault LED indicator illuminates when a detected fault, either in the hardware or the digital input signal has been detected. The user then can switch the unit over to the Fault Type display to further identify the fault.
Fault Type indicators
Hardware Fault
The Hardware Fault LED Indicator is illuminated if anything in the power-on diagnostic tests did not pass, or if the information presented by the control switches is invalid or cannot be interpreted. The unit may not operate properly with this LED illuminated.
No Lock
The No Lock LED Indicator illuminates if no signal is present on either of the two digital input connectors, or if the signal cannot be interpreted. Application of a valid digital audio stream to either digital input will cause this indicator to extinguish.
Parity Error
The Parity Error LED Indicator illuminates when the incoming data did not have an even number of ones and zeros, or if the number of bits was not 32. Typically, parity and bit-length errors are indicative of weak or noisy signals. Parity and bit errors are also typically not consistent between fields of data, so flickering of this LED is not uncommon in the presence of these types of errors.
CRC Error
The CRC Error LED Indicator illuminates when an AES Professional Data Block Cyclical Redundancy Check did not pass. When generated, the data is passed through a CRC generator, which calculates and embeds an 8-bit check word at the end of each frame. The digital receiver in the AESDA recalculates this CRC number from the received data and compares its result to the CRC number received. If the two do not match, then the data was not received the same way that it was transmitted, i.e., there may be one or more data bits that are in error. Note that Consumer Mode AES-3 and S/PDIF do not use CRC checking, so this LED will be off when receiving audio data of this type.
Confidence Flag
The Confidence Flag LED Indicator illuminates if excessive distortion is detected in the digital signal received. The distortion may be from low signal level, excess or incorrect cable impedance, or asymmetry in the signal (the “1” part and the “0” part of the signal not of equal length within a specific percentage). If only this error exists, without Parity, CRC, or No Lock errors, it is indicative of a signal that is marginally useable, and probably not reliable in the long run. When other signal-type errors are present, this is indicative of a bad cable, too long of a cable run, a bad transmitter, or an excessively noisy environment.
Validity Bit
The Validity Bit LED Indicator illuminates when the Left or Right or both of the Validity Bits indicate invalid data. These bits are embedded in the audio data, and there is one validity bit in each subframe. When one channel is invalid, the Validity Bit LED will flicker; if both channels indicate invalid, the LED will be steadily on.
No Error
The No Error LED Indicator is illuminated when no detected error is present. This provision allows at least one LED to be illuminated when Fault Type mode is entered and there are no faults.
Over Temp
The Over Temp LED Indicator illuminates if the detected temperature inside the unit exceeds 85°C. This temperature is the upper limit for reliable operation of the various internal components, and if exceeded for a long period of time, could cause permanent damage to the AESDA. No shutdown action is instigated by the AESDA, it just serves as a warning to the user.
Warranty
This product is guaranteed for one year from the date of purchase against manufacturing defects. For warranty service, return the unit, along with the original sales receipt, to: whirlwind, 99 Ling Road, Rochester, NY 14612, postage prepaid. We will repair or replace the unit at our option and pay the return postage.
