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1.1.3.  D/A Volume Control: 

The revolutionary volume control is accomplished without 

any added parts

 to 

the line-output signal path.  It is not an entirely digital or entirely analog volume 
control.  It is a little of each actually. The volume is adjusted by changing the 
reference voltage of the D/A conversion.  It does 

NOT

 adjust attenuation of a 

resistor divider, change the gain of an amplifier stage or truncate bits in the digital 
data.  All of these would add noise and/or distortion to the signal.  This volume 
technology actually reduces S/N ratio with lower volume. 

 

1.1.4.  Ultra-Linear Output Stage: 

The output stage is a single transistor in Class-A mode.  It is well known that this 
simple configuration results in some compression distortion, but also sounds 
most natural.  In order to effectively eliminate this compression distortion, we 
incorporated a compensation circuit in the Overdrive.  The output stage 
impedance is low enough and the power output high enough to drive most high-
impedance headphones easily, so we provide an adapter.  It can drive either 
normal or balanced headphones such as Sennheiser. 

 

1.1.5.  Fully Balanced Analog Path: 

There are 4 analog paths, all identical.  They connect from the D/A converter chip 
to the outputs.  All 4 are used for the balanced outputs, 2 of the 4 are used for 
the Single-Ended outputs.  Resistors provide some isolation, so all outputs may 
be used. We recommend low-capacitance interconnects if all 4 outputs are used, 
and shorter is better.  The output drive is sufficient for all preamps and amps, and 
even high-impedance headphones like Sennheiser. 

 

1.1.6.  Selectable Digital Filters: 

A front panel switch selects 3 digital filter responses, low, medium and high.  For 
most DACs these are automatically selected, low for 44.1, medium for 96 and 
high for 192.  However, the Overdrive allows these to be selected manually in 
order to improve audio quality.  This makes the Overdrive closer to a NOS DAC.  

For sample-rates of 176.4 and 192, the high position MUST BE SELECTED.

  

It is recommended that the high position be selected for all sample-rates, 
however some speakers with Supertweeters may render ultrasonics audible at 
44.1.  For these, the medium or low settings can be used.  The settings do not 
engage until the track is stopped and restarted. 

 

 

1.2.  Design Choices: 

A number of design decisions were made in order to optimize performance and sound 
quality over all other criteria: 

 

1.2.1.  Small Chassis size 

This was critical to reducing both digital and analog signal path lengths.  Long 
signal paths add distortion due to circuit-board dielectrics and also introduce 
more noise due to ground-plane coupling and crosstalk.

 

1.2.2.  Op-Amp I/V conversion 

This was necessary in order to optimize the loading of the D/A converter.  Some 
D/A chips require certain loading and voltage on their outputs in order to 
guarantee best linearity and low-distortion.

 

1.2.3.  AC-coupled output  

This was chosen because the alternative of DC-coupling would not allow a pure 
Class-A operation throughout, which delivers lower distortion.  The coupling 
capacitors available now are very close to a copper wire in performance. 
 

 

Summary of Contents for Overdrive SE

Page 1: ...Empirical Audio Overdrive SE SX DAC User Manual 2016 ...

Page 2: ... particularly driving amps directly Other DACs sound muddy in comparison The bass is tight and the detail and imaging is more than first rate it s breathtaking Drums are rendered with more realism than any other DAC is capable of The leading and trailing edges and harmonics of percussion strings and woodwinds are delivered with true realism Even with this level of detail and dynamics it still gets...

Page 3: ...d shorter is better The output drive is sufficient for all preamps and amps and even high impedance headphones like Sennheiser 1 1 6 Selectable Digital Filters A front panel switch selects 3 digital filter responses low medium and high For most DACs these are automatically selected low for 44 1 medium for 96 and high for 192 However the Overdrive allows these to be selected manually in order to im...

Page 4: ...ront panel Up position selects volume control The switch selects between volume or line out on power up only not on the fly To make a change you must power off the Substation and back on using the front panel power switch As with all systems at initial power on the volume should be rotated to its lowest setting before playing music 4 2 Optimum Remote Control Remote volume control capability can be...

Page 5: ...ition at normal listening levels If the volume is too loud when you have the volume knob at minimum set the internal gain jumpers to the next setting The settings are illustrated on the circuit board Three volume ranges are possible The range setting provides a lower volume extreme It does not affect the maximum volume only the minimum volume If the range jumpers are set for Min the volume will ha...

Page 6: ... no DC output The three red LEDs should be on when the power cord is attached The Substation AC provides power sequencing to the Overdrive SE so it should always be powered using the front panel switch Danger never connect the Umbilical to the Overdrive with the Substation power on 5 1 Substation Front Panel The red LED indicators are top 12VDC Middle 18VDC Bottom 18VDC ...

Page 7: ...ference voltage differences with resulting high currents in the ground This can potentially damage other components in your system Power conditioners can have high impedance in the ground connection to the AC service so if you use a conditioner it is best to plug both the computer and Overdrive SE into the same conditioner Conditioners with filters generally limit the transient current flow so we ...

Page 8: ...nce is 75 ohms It is recommended that stock transports and devices other than that manufactured by Empirical Audio use a 1 5m minimum 75 ohm digital cable in order to minimize the jitter caused by reflections Devices manufactured by Empirical Audio can use a 1m 75 ohm digital cable length 6 1 3 USB or Ethernet input The USB input can be driven with a 5m 16 foot USB cable from any USB2 0 port on a ...

Page 9: ...ere is a delay in the power output from them on power on in order that the DC voltage settle out The line output level from these is 4 6VRMS in high gain mode and 2 0VRMS in low gain mode The volume control reduces this On power down the outputs disconnect from the output drivers and short to ground When there is no valid signal the outputs are disconnected from the output drivers and shorted to g...

Page 10: ... applies an equalization at the high frequencies that eliminates harshness due to high frequency pre emphasis in some recordings Down or Normal position is recommended The function does not take effect until a new track is started 7 4 High Low Gain switch left recessed This selects between high and low gain Low gain is up position and high gain is down position The function only changes on power u...

Page 11: ...7 7 Data Error Indicator Illuminated indicates that there is no valid data coming in on the selected digital input 7 8 DC Power Indicator Indicates that DC power is applied to the DC input connector ...

Page 12: ...ality and eliminated manual intervention to select sample rates If you use iTunes alone then select HiFace or Empirical AudioAsync 192 in Preferences Audio and use Utilities Midi options to select the sample rate Using iTunes alone requires you to manually select the sample rate each time you change to playback of a different sample rate 9 Quick Start up 9 1 Mac Put the supplied CDROM into your Ma...

Page 13: ...C 18VDC 18VDC from included Substation Outputs 1 RCA left and right channels 2 XLR left and right channels Controls 1 Input Select 2 De emphasis Select 3 Digital Filter Select High Medium Low 4 Line Volume Select 5 Volume knob 6 Internal jumpers for 3 volume ranges and two gain settings Electrical 1 RCA output Level 1VRMS or 2 3VRMS XLR output level 2VRMS or 4 6VRMS 2 Frequency response 20 20kHz 0...

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