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Appendix C: An Introduction to Digital Recording 

 

 

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Appendix C: An Introduction to Digital Recording 

The above nominal levels represent typical or average levels that are often 
exceeded when recording loud signals such as drum beats. The difference between 
the nominal level and the loudest signal that can be recorded without clipping is 
called “headroom”. Your Echo product provides approximately 14dB of headroom 
allowing an 18dBu signal to be recorded. 
 

Unbalanced and Balanced Inputs and Outputs 
 

An unbalanced signal, commonly used for guitars and consumer electronics, 
contains two components, a ground signal and a “hot” or active signal. The ground 
is the barrel of a ¼” connector and the shell of an “RCA” style connector. 
 
A balanced signal contains two active signals instead of one in addition to the 
ground. These are referred to as the “plus” and “minus” signals. A balanced input 
amplifier amplifies the difference between these two signals. Any extraneous noise 
picked up from power lines or other sources will appear equally on both the plus 
and minus inputs. This is called “common mode” noise since it is common to both 
signals and the input amplifier will subtract the noise on the minus input from the 
noise on the plus input.   
 
If the input amplifier is perfectly balanced and the noise on both plus and minus is 
precisely equal, the noise will completely cancel out. In the real world this is not 
the case and some of the common mode noise will still make it through, although 
at a much reduced level. How well an input amplifier rejects this common mode 
noise is called the “common mode rejection ratio” (abbreviated as CMRR) and is 
expressed in dB. 
 
Balanced outputs typically drive the plus and minus components of a balanced 
signal in one of two ways. A “differentially” balanced output signal is one where 
the minus output is the mirror image of the plus output. That is, if the “plus” output 
is at +1 volt, then the “minus” output is at –1 volt. 
 
An “impedance” balanced output provides most of the benefits of a differentially 
balanced output at a lower cost. In this case only the plus component actually 
carries the signal. The minus component is tied to ground through a resistor so that 
the output impedance matches that of the plus component. Since the impedances 

Summary of Contents for AudioFire2

Page 1: ...AUDIOFIRE2 TM AUDIOFIRE4 TM AUDIOFIRE8 TM AUDIOFIREPre8 TM AUDIOFIRE12 TM...

Page 2: ...Owner s Manual Version 2 2 for Windows...

Page 3: ...If you are unsure about the type of power at your location contact your local power company 8 Grounding Precautions should be taken so that the grounding capabilities of the unit are not undermined T...

Page 4: ...ician when any of the following occur a Objects have fallen or liquid has spilled into the unit b The product has been exposed to rain or water c The product does not operate normally or when a marked...

Page 5: ...by the Echo Service Department Unauthorized service repair or modification will void this warranty To obtain factory service Contact Echo Digital Audio Corporation at 805 684 4593 9AM to 4PM Monday t...

Page 6: ...6450 Via Real Carpinteria CA 93013 Echo and AudioFire are trademarks of Echo Digital Audio Corporation FireWire is a trademark of Apple Computer Inc Windows Windows XP Windows Vista and Windows 7 are...

Page 7: ...ANALOG INPUTS 28 DIGITAL INPUTS AUDIOFIRE 2 AUDIOFIRE 4 AUDIOFIRE 8 AND AUDIOFIRE PRE8 30 Adjusting Playback Volume 31 Nominal Levels 32 SETTINGS TAB 32 Sample Rate in XP 33 Core Audio Sample Rate Win...

Page 8: ...ion 42 MULTI CLIENT AUDIO 43 FIREWIRE ANALYZER 44 Status 44 Playback 44 Record 44 ASIO wakeup 45 ASIO host 45 Firmware 45 Buffer offset 46 Things to watch for 46 Saving a report 46 CONTACTING ECHO CUS...

Page 9: ...ned the box you should have found the following An audio interface box Four mounting screws with collars AudioFire 8 AudioFire Pre8 and AudioFire 12 only Two removable rack mount brackets AudioFire 8...

Page 10: ...u ll need the following A desktop or laptop computer with Windows XP Service Pack 3 or newer operating system An unused FireWire port A minimum 256Mb of RAM 512Mb highly recommended A fast high capaci...

Page 11: ...er account that has administrative privileges Otherwise you will not be able to install the hardware and drivers Important Check the Echo Website for Software Updates You should always check our websi...

Page 12: ...If you are installing an AudioFire 8 AudioFire Pre8 or AudioFire 12 securely mount the interface into your equipment rack If you will not be mounting the box in a rack then be sure to place the interf...

Page 13: ...sta Windows 7 6 You can now attach external audio devices to the connectors on the AudioFire interface box Information on attaching external devices to the audio interface box may be found in the foll...

Page 14: ...s two analog line inputs 1 2 an amber power indicator light and an 1 8 stereo headphone output jack with a corresponding volume knob which monitors analog outputs 3 and 4 labeled Headphones in the Aud...

Page 15: ...analog line outputs on the rear panel These analog inputs 3 4 operate with an input impedance of 10Kohms The input and output connections can be used with balanced or unbalanced cables via the connec...

Page 16: ...10Kohms The input and output connections can be used with balanced or unbalanced cables via the connectors By default the inputs and outputs are set to receive or send a 4dBu signal You can switch bet...

Page 17: ...1 2 with meters and trim knobs Inputs 1 2 also have Phase 80Hz Pad LoZ DI and phantom power buttons with corresponding LEDS In addition there are six meters and trim knobs on the front panel for unive...

Page 18: ...Useful for miking drums etc 80Hz Turns on an 80Hz high pass filter to reduce low frequency rumble and hum Pad Reduces the preamp gain by 20dB to accommodate large microphone or line level signals con...

Page 19: ...ill be provided to all microphone inputs On AudioFire 8 and AudioFire Pre8 to enable phantom power press the button labeled 48v on your audio interface box the LED next to it will light up and phantom...

Page 20: ...osts There is enough headroom so that you can be conservative in this area and there is no need to push the input levels right up to the edge of clipping Analog Inputs and Outputs AudioFire 12 AudioFi...

Page 21: ...reWire devices so other devices will require external power to function Caution Plugging the FireWire cable in rotated 180 degrees can cause permanent damage to your AudioFire FireWire adapter or both...

Page 22: ...Pre8 The 2009 AudioFire 8 and AudioFire Pre8 are equipped with Optical S PDIF and ADAT There is a digital mode switch in the Echo console which lets you choose the digital format that you prefer MIDI...

Page 23: ...are labeled IN and OUT on the dongle The S PDIF connectors are used to transmit digital audio data between digital audio devices via an electrical signal When connecting devices to the S PDIF jacks t...

Page 24: ...ice equipped with a Word Clock connector The Word Clock I O uses a BNC connector As with the S PDIF I O a shielded 75 ohm RG 59 coaxial video cable should be used BNC connectors have been widely used...

Page 25: ...e folder in the Echo Digital Audio group and click AudioFire Console Automatic Flash Update As the console starts up it checks the firmware that is loaded in each AudioFire If the AudioFire is running...

Page 26: ...Eight different output busses are shown here four analog busses and four digital busses Note The digital busses are collapsed in this view To view the digital busses click on the left facing arrow Thi...

Page 27: ...e channels correspond to the currently selected output bus tab Beneath the labels are two green label fields that can be changed by clicking in them and typing Below the green label fields are nominal...

Page 28: ...ically there is a different set of input monitor controls for each output bus but only one set is visible and changeable at a time In the example above the only set of input monitor controls that is v...

Page 29: ...trols for analog outputs 3 and 4 However you can still see the input signal on the input level meters for Analog input 1 2 At the top of each input channel below the channel number is a green label fi...

Page 30: ...input channel will prevent it from being monitored by the currently selected output bus Again this does not affect recording These are followed by the monitor fader which controls the input monitor l...

Page 31: ...ly decreasing the number of available bits thereby taking away from the potential dynamic range of the system Therefore we suggest that whenever possible you leave the output faders Playback Output Bu...

Page 32: ...you to connect either professional or consumer gear to each input and output Selecting the 10 level provides a digital boost after the converters For universal inputs with an analog trim knob you shou...

Page 33: ...For more information please refer to Appendix C An Introduction to Digital Recording The application or audio software you are using may change the sample rate The settings tab gives you an easy way t...

Page 34: ...dio hardware If a given synchronization source input clock is not detected that clock source will be grayed out You will only be allowed to select input clocks that are currently connected For more in...

Page 35: ...iate format for your DAT CD recorder or Mini Disc recorder if you don t know which one to use and are having difficulties simply try the one that is not currently checked Note No Echo hardware transmi...

Page 36: ...Note that when the About Dialogue Box is open you are frozen out of the console until you close this box Copy Version Information to Clipboard The About Dialogue Box also has a button labeled Copy to...

Page 37: ...oFire 2 and AudioFire 4 now support routing playback from the computer to different physical outputs Audio applications see the AudioFire s outputs listed as Playback 1 through Playback 6 Using the co...

Page 38: ...Fire 2 Console Window on Vista Settings Tab selected System Tray Icon When you open the console you will see an icon added to the system tray Clicking the left mouse button on the tray icon will bring...

Page 39: ...ppropriate button To restore the device to its default state click the Reset button The Gang buttons the Phantom power button Clock source buttons the Sample rate buttons the Locked sample rate button...

Page 40: ...ontrol panel you can set the Core Audio sample rate from the Echo PCI console Be aware that setting the Core Audio sample rate from the console will cause the current playback and recording devices to...

Page 41: ...box is checked the ASIO driver will instruct Vista Windows 7 to prioritize audio over drawing windows on the screen Surround Sound Playback Stereo versus surround sound modes When you first install i...

Page 42: ...og outputs for your AudioFire Click the Advanced button you will be presented with the Advanced Audio Properties dialog Select the speaker configuration that best describes your setup Windows Vista Wi...

Page 43: ...t applications must use different audio outputs you will need to configure each individual audio application accordingly Troubleshooting tips Turn off system sounds Make sure all applications are set...

Page 44: ...displays your current sample rate and buffer size as selected in the AudioFire console or an audio application Immediately below that is the expected buffer time in milliseconds Playback The playback...

Page 45: ...ver is responsible Try going into Device Manager and disabling any hardware that you don t absolutely need For example one test machine had a USB camera hooked up With the camera hooked up and running...

Page 46: ...cord time The ASIO wakeup time is too long The ASIO host time is too long To get glitch free playback the wakeup time plus the host time must be less than the average buffer time If the wakeup time is...

Page 47: ...runs at the AudioFire product s selected sample rate Think of it as a kind of electronic metronome which clicks back and forth at the digital sample rate It is one of the most widely used forms of sy...

Page 48: ...an external device via S PDIF ADAT or Word Clock you must set the AudioFire to the correct base clock rate See the following table for the correct base clock rate setting AudioFire 12 Only External C...

Page 49: ...soles and Channel Names When you install additional AudioFires to your system a letter will be appended to the name of each AudioFire to give it a unique name For example when you install a second Aud...

Page 50: ...at can be copied and sent to our technical support staff and they will respond to you quickly Please fill in all the details completely The best way to get the help you need is by giving us plenty of...

Page 51: ...section of this manual for details Or you may have a ASIO application open in the background Close all audio applications and attempt to install the driver again Problem Your computer spontaneously r...

Page 52: ...2 AudioFire 4 or AudioFire 8 Solution Digital information is transmitted in either of two modes professional or consumer The professional mode is usually implemented in devices that are likely to be...

Page 53: ...synchronize with an external device it will play back at the rate generated by that device For example if the sound you are playing was sampled at 44 1kHz but you are synchronized with a device runni...

Page 54: ...elect the S PDIF clock as the input clock This can be done from the console Problem You re syncing to an external device and suddenly you ve lost sync Solution Whenever your AudioFire product is synci...

Page 55: ...most of them all you need to do is read the software manual to learn how to use them with your AudioFire product In general ASIO is preferred for your AudioFire product ASIO Software Here is a partial...

Page 56: ...he input that is read This number is called a sample The number of samples taken per second is called the sample rate On playback the process happens in reverse The series of numbers is played back th...

Page 57: ...ming signal can be represented by any of over 16 million possible values The output DACs are also 24 bit again over 16 million values are possible The S PDIF inputs and outputs also support signals wi...

Page 58: ...disks are capable of storing large amounts of data though the performance of hard drives can vary substantially The speed and size of your hard drive will be a major determining factor in how many tra...

Page 59: ...today s equipment uses impedances other than 600 ohms it is more useful to represent signals by voltages rather than power and the dBu unit was introduced A signal level of 0dBu is identical to a leve...

Page 60: ...oth the plus and minus inputs This is called common mode noise since it is common to both signals and the input amplifier will subtract the noise on the minus input from the noise on the plus input If...

Page 61: ...th no signal present A system with a high dynamic range will be quieter than one with a lower dynamic range Dynamic range is a very important specification and your echo product uses converters that h...

Page 62: ...pressed or amplified after it is recorded and that some headroom is necessary when recording to avoid clipping The only way that 96dB would be adequate is if all music were recorded so that the peaks...

Page 63: ...erter 56 dynamic range 61 E Echo Console 25 I input level meters 19 input trims 20 installation 11 12 M microphone preamp 19 MIDI 22 MIDI time code 22 23 MTC 22 23 P phantom power 19 professional mode...

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