Overdrive® SE USB DAC/Pre
USB digital to analog converter, Pre and Head amp
The Overdrive DAC enables you to play music from your computer delivering unparalleled sound quality to your preamp or better yet directly to your amp. All you need is the Overdrive and a PC or Mac. The Overdrive will also improve the playback from your CD transport. Once you start using the computer, however you will never go back to spinning CDs. Playback using the computer will be superior to the best CD transport you have heard, even playing low-res CD rips.
The Overdrive DAC is a breakthrough audio product. It incorporates our excellent low-jitter 192 asynchronous USB interface technology* and breaks new ground for D/A converter technology. It it not just a USB DAC. It also has S/PDIF coax input and I2S input. The Overdrive design philosophy is “less is more”, with one of the simplest analog paths ever devised. The Overdrive provides innovative solutions for the three most important aspects of digital sources:
- D/A noise/distortion
- Volume control noise/distortion
This high-performance triple solution is unprecedented and delivers a totally new sound quality level.
“…regardless of how I employed the Overdrive DAC I was aware that I was listening to the best USB DAC I had ever reviewed.”
Steven Stone, The Absolute Sound, Feb. 2010
The Overdrive DAC has received The Absolute Sound ‘Golden Ear’ Award 2010
The Overdrive SE has three digital inputs, USB, S/PDIF Coax and I2S. It has no analog inputs. We put the I2S input on the Overdrive so that it could be driven from the I2S output on our Off-Ramps or Pace-Car USB reclockers. The I2S interface allows the master clock to be closer to the D/A chip inside the Overdrive DAC, reducing clock jitter even more.
The Overdrive SE has a multi-pin high-current DC input connector only, so it requires a separate umbilical cable and power supply chassis, the Substation AC. The DAC must be powered from the included Substation AC chassis, which has an IEC AC inlet. The Substation AC stores a LOT of energy for the DAC, as well as providing power sequencing and protections.
The Substation AC is a high-performance power subsystem with three high-current switching supplies followed by three linear analog Hynes voltages regulators. We have found this combination to yield the lowest noise while providing the fastest reaction time for regulation. This delivers the ultimate in slam in the music playback with unsurpassed bass control. At trade shows, including RMAF and Newport Beach, we routinely ask attendees to put their ears into the tweeters of the speakers because they are dead silent, just like the system is powered off. This is how good this power system is.
“…my independent impressions of the Overdrive DAC were confirmed when I made direct comparisons to other highly-regarded DACs. The Overdrive emerged as my preferred DAC.”
Ed Momkus, Dagogo, Mar. 2011
The performance of the Overdrive DAC is a result of several innovative design breakthroughs
- Low jitter Clocks
- Low jitter 192 Async USB interface module
- Ultra-Simple pure Class-A analog Path
- D/A Volume Control
- Ultra-Linear Output Stage
- Fully Balanced Analog Path
- A large number of Black-Gate electrolytic capacitors
- Point-to-Point silver wiring for the analog output stages — Signature version
- High quality output coupling caps — V-Caps and Sonicap Platinums
Low jitter Clocks
The Overdrive SE requires 2 clocks in the USB module section because of the asynchronous USB protocol. The other inputs (S/PDIF and I2S) are clocked by the incoming stream. The two clocks provide for the two sample rate ranges on USB: 44.1/88.2/176.4 and 48/96/192. The Overdrive SE includes a dual Turboclock, which is an extremely low jitter dual clock with 2 Hynes voltage regulators. Feedback from customers indicates that this clock enables the Overdrive SE to beat good vinyl systems.
Low jitter 192 Async USB interface module
This USB module is the same device that we use in our outstanding Off-Ramp 5 USB converter. This is a 5th generation USB converter and rates number one against all other converters on the market.
Ultra-Simple Analog Path
The analog path consists of an I/V stage (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 damping resistors on the output. Resistors add noise, so they are best avoided. There are no switches in the signal path, but there are output relays for muting.
D/A Volume Control
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 changed by adjusting the reference voltage of the D/A. 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 technique is unique in the industry. Unlike other volume control methods it has the characteristic of reducing the S/N ratio as the volume is decreased - an ideal situation.
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.
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.
A number of design decisions were made in order 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 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.
- AC-coupled output – This was chosen because the alternative of DC-coupling would not allow a pure Class-A operation throughout, which delivers improved performance by eliminating crossover distortion. The coupling capacitors available now are very close to a copper wire in performance.
Hynes Voltage Regulator technology is a key component in the Overdrive SE design. Paul Hynes is internationally known for his high-performance regulator. These regulators add more dynamics, clarity and make it more analog-like. Hynes regulators are unique and provide not only high-speed accurate regulation, they reject input noise as well. Four Hynes Voltage regulators are included in the Overdrive SE, one for the USB module, one for the analog D/A voltage and two for the Turboclock module.
Measurements (Measured at 24/96):
- THD+N (1kHz @ 0dBFS): -100dB
- THD+N (1kHz @ -20dBFS): -105dB
- Crosstalk (typical @0dBFS): -118dB
- Crosstalk (@ 20kHz 0dBFS): -110dB
- Frequency Response (-10Hz to 20kHz): -0.6dB
- IMD (with 100K ohm load): -106dB
- Dynamic Range (A-weighted 1kHz): 106dB
- RCA Output Level: 1VRMS or 2.3VRMS
- XLR Output Level: 2VRMS or 4.5VRMS
These links show the impulse response of the Overdrive DAC at 24/96 and 24/192. Hardly any pre-ring and the pulse gets almost to 1.5V (the input level). Pulse on the 24/96 reaches 1.233V. Other DACs have more pre-ring and never get anywhere near the amplitude of the input signal. This demonstrates the fast slew-rate of this DAC and the grip that it has on transients.
- USB 2.0, Mac or PC, up to 5 meter USB cable – up to 24/192 supported
- S/PDIF coax – BNC (RCA adapter included) – 44.1, 88.2, 96 and 192 supported at 16 and 24-bits
- I2S (Empirical standard RJ-45) – 44.1, 88.2, 96 and 192 supported at 16 and 24-bits
- DC power (+12VDC, -18VDC, +18VDC) from included Substation AC"
- RCA left and right channels
- XLR left and right channels
- Input Select
- De-emphasis Select
- Digital Filter Select – High, Medium, Low
- Line/Volume Select – recessed
- High/Low gain Select – recessed
- Volume knob
- Internal jumpers for 3 volume ranges
- Overdrive SE DAC
- Substation AC power supply
- DC power supply umbilical cable
- 5 meter USB cable
- BNC to RCA adapter
- CDROM with PC/Mac installation software
- RCA to Phone-jack Headphone adapter – only high-impedance headphones supported
- Windows 7 / Vista
- Windows XP / 2003
- Mac OSX 10.6 Snow Leopard
- Mac OSX 10.5 Leopard
- Mac OSX 10.4 Tiger
*USB Software/Firmware licensed from M2Tech