Empirical Audio Overdrive Diamond ODSX with Duelund Caps and Ethernet User Manual
- June 17, 2024
- Empirical Audio
Table of Contents
Empirical Audio Overdrive Diamond ODSX with Duelund Caps and Ethernet
Specifications
- Low-jitter USB interface module
- Ultra-Simple pure Class-A analog Path
- D/A Volume Control
- Ultra-Linear low-noise Output Stage
- Fully Balanced Analog Path
- Selectable digital filters
Performance
The performance of the Overdrive DAC is a result of several innovative
design breakthroughs:
- Low jitter Asynchronous USB interface module: This asynchronous USB module enables bit-perfect playback from Mac and PC, supporting sample rates up to 24/192.
- Ultra-Simple Analog Path: The analog path consists of an I/V stage (ultra-low noise op-amp) driving a single output transistor through a coupling cap. All stages are run Class-A, minimizing noise.
- 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, and 2 of the 4 are used for the Single-Ended outputs. The output drive is sufficient for all preamps and amps, and even high-impedance headphones like Sennheiser.
Design Choices
A number of design decisions were made to optimize performance and sound
quality:
- Separate Substation AC chassis: This key element contributes to the performance of the Overdrive SE by enabling more densely packed energy storage for each voltage and creating space between the magnetics in the supplies and the Overdrive Chassis to eliminate coupling.
Technology/Design
The Overdrive DAC incorporates our excellent low-jitter USB interface technology and breaks new ground for D/A converter technology. The Overdrive design philosophy is “less is more”, with one of the simplest analog paths ever devised. The Overdrive provides solutions for the three most important issues with digital sources:
- Jitter
- D/A noise/distortion
- Volume control noise/distortion
This high-performance triple solution is unprecedented and delivers a new sound quality level. The Overdrive is a non-upsampling DAC (no ASRC) that has an ultra-simple analog signal path, reducing background noise and harmonic distortion to unprecedented levels. It incorporates a preamp function that has never been tried in ANY audio product before. This preamp function adds no devices whatsoever to the signal path, leaving it simple and ultra-low noise. It has selectable digital filters that allow one to tailor the sound to your taste. You can effectively eliminate them if you want.
The sound of the Overdrive is simply indescribable and utterly magical. The clarity is unlike anything you have heard before, particularly when 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 the vocals right. The Overdrive USB DAC resets the bar for the term “accuracy” in digital to analog-conversion.
Performance
The performance of the Overdrive DAC is a result of several innovative
design breakthroughs:
- Low-jitter USB interface module
- Ultra-Simple pure Class-A analog Path
- D/A Volume Control
- Ultra-Linear low-noise Output Stage
- Fully Balanced Analog Path
- Selectable digital filters
Low jitter Asynchronous USB interface module:
This asynchronous USB module is the same device that we use in our popular
Off-Ramp 5 USB converter. This is a 5th generation USB converter and rates #1
against all other converters on the market. The USB interface enables bit-
perfect playback from Mac and PC, supporting sample rates up to 24/192.
Ultra-Simple Analog Path:
The analog path consists of an I/V stage (ultra-low noise op-amp) driving a
single output transistor through a coupling cap. All stages are run Class-A,
so it gets a bit warm. There are no resistors at all in the analog signal
paths, except for very small necessary damping resistors on the output.
Resistors add noise, so they are best avoided.
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. The volume is adjusted by changing the
reference voltage of the D/A conversion. It does NOT adjust the 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 reduces the S/N ratio with lower volume.
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. 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.
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.
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 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 users may find that some ultrasonics are audible.
- For these, the medium or low settings can be used. The settings do not engage until the track is stopped and restarted.
Design Choices:
Several design decisions were made to optimize performance and sound quality
over all other criteria:
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.
Op-Amp I/V conversion
This was necessary to optimize the loading of the D/A converter. Some D/A
chips require certain loading and voltage on their outputs to guarantee the
best linearity and low distortion.
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.
Separate Substation AC chassis
This is a key element contributing to the performance of the Overdrive SE. A
separate Substation enables more densely packed energy storage for each
voltage, a more optimized layout, and creates space between the magnetics in
the supplies and the Overdrive Chassis to eliminate coupling.
Break-in
All electronics need a period of break-in. New capacitors and dielectric insulators must stabilize with voltage and current applied. The Overdrive SE is broken in by Empirical Audio for approximately 5 days before shipping. An additional 25 days of 24/7 break-in is required for full break-in, with all inputs driven. Each input breaks in independently, so all should be driven with a signal. Outputs do not have to be connected to break in.
Volume settings
Volume Control
The volume control mode can be selected by using the right-most recessed
toggle switch on the front 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.
Optimum Manual Control
Manual control can be optimized for performance if the volume knob is near
maximum. The internal gain jumpers behind the front panel should be selected
so that the volume knob is rotated 50% at normal listening levels. The default
setting for these jumpers is medium.
Optimum Remote Control|
Remote volume control capability can be achieved quite easily by using a
combination of manual volume control, digital volume control (such as iTunes,
Amarra, or Pure Music volume), and the USB interface. If one adjusts the
volume to a comfortable listening level with the manual control with the
software digital control at max, then only small reductions of the digital
control from maximum are necessary to adjust the track-to-track amplitude
variation. Up to –9dB of reduction is possible without degradation in sound
quality with a high-quality digital volume. This is even better than having
yet another remote control. Most of us already have too many of those. It
allows you to use an iPod Touch or iPad for everything: song selection,
muting, and volume control, without any loss of resolution. This is the best
possible scenario.
Gain Switch
A two-position gain switch is recessed into the front panel. It is the left-
most of the two switches. The upper position is low-gain, which is typically
used for volume control direct to amps. The lower position is high-gain,
typically used with volume driving amps directly to low-efficiency speakers,
or line-level to a preamp. This can be switched at any time, but will only
take effect after powering down the Substation and back up again using the
front-panel power switch. For driving most amplifiers directly with 1V
sensitivity for full power, the switch should be in the “L” position. If you
have low-sensitivity speakers, you may need the “H” setting.
Range Jumpers
Two jumpers are provided to set the volume range. The range jumpers are
located just inside the front panel to the right of the volume control as you
look at the front panel. 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 have the least range, so
the lowest volume will still be loud. If the range jumpers are set for “Max”,
the volume control when at the minimum will be very quiet. This allows the
volume to be tailored so that a fairly wide arc can be used in adjustment for
track-to-track amplitude variation.
The default factory setting is “Medium”. Make sure the Overdrive is powered
off for this adjustment. The front panel and knob must be removed to access
these.
Substation AC
The Substation provides three DC voltages to the Overdrive, +12VDC, +18VDC and
–18VDC. In standby mode, all voltages are powered in the Substation AC, but
there is 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.
Substation Front Panel
The red LED indicators are:
- top + 12VDC
- Middle –1 8VDC
- Bottom + 18VDC
Substation Back Panel
AC service tips
Make sure that you use the same circuit from the AC panel for the computer and the Overdrive SE. Different circuits will potentially originate from different phases and may cause ground reference 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 this conditioner. Conditioners with filters generally limit the transient current flow, so we advise against using them in general.
Overdrive Panel
Overdrive Back Panel Connectors
Digital Inputs
I2S input
The Overdrive I2S input is compatible with the Empirical Audio I2S standard.
It can be driven with a Pace Car or an Off-Ramp. It supports up to 24/192.
S/PDIF coax input
The S/PDIF coax digital input can be driven from any audio device with digital
output conforming to the S/PDIF standard IEC-60958. The input impedance 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 to
minimize the jitter caused by reflections. Devices manufactured by Empirical
Audio can use a 1m 75-ohm digital cable length.
USB input
The USB input can be driven with a 5m (16-foot) USB cable from any USB 2.0
port on a computer. The USB port supports up to 24/192 sample rate and uses a
custom software driver for each OS version of Windows or Mac.
Analog Outputs
RCA – Single-ended outputs
The RCA outputs are designed to drive a preamp, amplifier or high-impedance headphones. These are AC-coupled, so there is a delay in the power output from them on power-on for the DC voltage to settle out. The line output level from these is 2.3VRMS in high-gain mode and 1.0VRMS 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 the ground. When active, the outputs can withstand short to the ground without damage to the Overdrive.
Headphone adapter
A headphone adapter is provided. The red plug on the adapter goes into the
left channel RCA output. Never use standard Headphones and the balanced
outputs to the speaker system at the same time without selecting the RCA out
Buffer – this may cause system or speaker damage. Also, avoid a high static
charge on the headphone cable when plugging it in. Ground yourself and the
cable contacts first.
XLR – Balanced outputs
The balanced outputs are designed to drive a preamp, amplifier, or high-
impedance balanced headphones. These are AC-coupled, so there is a delay in
the power output from them on power-on so 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
the ground. When active, the outputs can withstand short to the ground without
damage to the Overdrive.
Using both RCA and XLR outputs simultaneously
For best performance, this is best avoided, however, this is sometimes
necessary to drive a subwoofer or other ancillary electronics. Each of the 4
output drivers is shared between the balanced XLR and single-ended RCA
outputs. However, there is some isolation with small resistance between the
XLR and RCA outputs. If one uses all outputs simultaneously to a system, it is
recommended that either the XLR cables or the RCA cables be short and low-
capacitance and drive a high impedance buffer or preamp. If this is not
possible, then switch the recessed “Normal/Bypass” switch to the Bypass
position. This causes the RCA outs to be driven from a separate Op-amp,
isolating them from the XLR outputs.
DC Power Connector
The DC power connector is a professional 5-pin high-current locking connector.
The power inputs are:
- +12VDC Digital Power
- Digital Ground/Return
- -18VDC Analog Power
- Analog Ground/Return
- +18VDC Analog Power
Overdrive Front Panel Switches and Indicators
Input select toggle switch
- Select between USB, I2S, and S/PDIF coax digital inputs. The down position selects S/
- PDIF coax, middle position selects I2S and up position selects USB.
Digital Filter Select toggle switch
- Select between Low, Medium, and High-frequency roll-offs. High is the down position,
- Low is the center position and up is the medium position. It is recommended to use the down position always. The function does not take effect until a new track is started.
De-emphasis Enable toggle switch
- When enabled by switching up, it applies an equalization at the high-frequencies that eliminates harshness due to high-frequency pre-emphasis in some recordings. Down or
- A “Normal” position is recommended. The function does not take effect until a new track is started.
High/Low Gain switch – left recessed
- This selects between high and low gain. Low gain is an up position and high gain is a down position. The function only changes on power-up.
Volume/Line-Out toggle switch – right recessed
- This selects between volume control and line-out. Volume control is up position and
- Line Out is down position. The function only changes on power-up.
USB Fault Indicator
- USB fault is illuminated when the USB cable is unplugged at either end, or the +5V in the cable is not present. The 5V cable voltage is not used, except to light the LED.
Data Error Indicator
- I lluminated indicates that no valid data is coming in on the selected digital input.
DC Power Indicator
- Indicates that DC power is applied to the DC input connector.
Software
Software drivers must be loaded to support the USB interface for both PC and Mac before connecting the USB cable. For operation on a PC, Kernel Streaming is recommended to bypass Kmixer on XP machines and WASAPI on Vista and Win7 machines.
USB Drivers
Drivers are located on the included CDROM disk. Load the appropriate driver
for your machine and OS and execute it on the computer before powering the
Off-Ramp 4 or connecting the USB cable to the computer for the first time.
Player Software
For PC, the latest version of Foobar2000 is recommended as a player. Install
this first.
For XP, a Kernel Streaming plug-in is included on the CDROM. Copy this plug-in
to the “components” folder under C:\Program Files\Foobar2000. Then start
Foobar2000 and select the File pull-down. Then select Preferences. In the
Preferences window, go to Playback – Output – select HiFace Kernel Streaming
or Empirical Audio async 192.
With XP, the sample rate will be selected automatically. With Vista and Win7, you must change the sample rate manually on the computer in the control panel/sounds and audio devices/advanced, unless you are using Amarra, Pure Music or Ayrewave. For Mac, we recommend iTunes with software add-ons such as Amarra, Pure Music, or Ayrewave to improve audio quality and eliminate manual intervention to select samplers.
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.
Quick Start-up
Mac
- Put the supplied CDROM into your Mac and find the Mac driver folder.
- Open the folder and copy the driver software to your Mac hard disk for your OS.
- Execute the file and then execute the container (cardboard box ICON)
- The installation will start and one of the steps will ask you for your password
- Power on the Off-Ramp and connect the USB cable to the Mac and S/PDIF digital coax cable to the DAC.
- Power on the DAC.
- Check in the Preferences/Sounds that you have Empirical Audio async 192 selected for output
- Start your music player application
- Check that both the red and yellow LEDs are off on the Off-Ramp
- Play a track or playlist using your player application
PC
- Put the supplied CDROM into your PC and find the PC driver folder.
- Open the folder and copy all of the files for your OS to your C: hard disk.
- Execute the .exe file and follow the instructions.
- Power-on the Off-Ramp and connect the USB cable to a USB 2.0 port on your PC and S/PDIF digital coax cable to the DAC.
- Power on the DAC.
- Check in the Control Panel/Sounds and audio devices that you have HiFace or Empirical Audio async 192 selected for output
- Install Kernel Streaming in your player application
- Start your music player application
- Select HiFace Kernel Streaming or Empirical Audio 192 async Kernel Streaming for output
- Check that both the red and yellow LEDs are off on the Off-Ramp
- Play a track or playlist using your player application
Specifications
Inputs
- USB 2.0 or 3.0, Mac or PC, up to 5 meter USB cable – up to 24/192 supported
- S/PDIF coax – Canare 75 ohm BNC – up to 24/192 supported
- I2S (Empirical standard RJ-45) – up to 24/192 supported
- DC power (+12VDC, -18VDC, +18VDC) from included Substation
Outputs
- RCA’s left and right channels
- XLR left and right channels
Controls
- Input Select
- De-emphasis Select
- Digital Filter Select – High, Medium, Low
- Line/Volume Select
- Volume knob
- Internal jumpers for 3 volume ranges and two gain settings
Electrical
- RCA output Level – 1VRMS or 2.3VRMS, XLR output level – 2VRMS or 4.6VRMS
- Frequency response – 20-20kHz +/-0.5dB
- Output impedance – each channel 40 ohms
Included
- Overdrive DAC
- Substation DC power supply – over 60,000uFd of energy storage
- DC power supply umbilical cable
- 5-meter USB cable
- 3 AC adapter power supplies
- CDROM with PC and Mac installation software
- RCA to Phone-jack Headphone adapter – only high-impedance headphones supported
FAQ
- Q: How can I optimize the performance of the Empirical Audio Overdrive SE DAC?
- A: To optimize performance, make sure to follow the break-in period by driving all inputs with a signal for an additional 25 days of 24/7 usage. Additionally, for manual control, set the volume knob near maximum and adjust the internal gain jumpers behind the front panel accordingly.
Specifications are subject to change without notice.
© 2012 Empirical Audio all rights reserved.
References
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