CanEVER Audio ZeroUno DAC-HPA!

The ZeroUno DAC-HPA is the latest member of the CanEVER Audio product family. It represents a top quality DAC based on the well accepted ZeroUno DAC, a strong headphone amplifier running in pure Class A and a remote controlled preamplifier able to drive any power amp or powered speaker – all in one box.

Those building blocks of the ZeroUno DAC-HPA are based on a set of high performance power supplies, giving each part of the machine a rock solid base to perform at top level. 

Looking at the boards inside the ZeroUno DAC, one can identify almost 70% of their space covered by the circuits for the individual power supplies. For more details about the design of the power supplies inside the products of the CanEVER Audio product line, please refer to the detailed technical descriptions of the ZeroUno DAC or the LaScala PowerAmp.

Special care inside the ZeroUno DAC-HPA has been taken as well to achieve as short as possible signal passes with a minimum amount of high grade components. Especially in the headphone amplifier, there are no coupling capacitors used in the signal path. All circuits are free of any feedback loops!

Input Connections: 1xUSB, 1x SPDIF via RCA, 1x AES/EBU via XLR and 1x OPTIC Output Connection: 2x Pair of unbalanced RCA-Connectors

Optional Output Configuration: 1x unbalanced RCA & 1x true balanced output via XLR-Connectors

Quick Overview:

The CanEVER Audio ZeroUno DAC-HPA is a:

- top quality DAC based on the circuit of the well respected ZeroUno DAC
- headphone amplifier with connections for unbalanced AND balanced connections to headphones
- digital preamplifier including remote control with functions for: volume, balance, absolute phase, input & mute

The analog output stage is based on a discrete topology without operational amplifiers and runs in pure Class A mode. It is designed as a current source with low output impedance able to drive power amps directly, if needed.

The headphone amplifier inside the ZeroUnoDAC-HPA is a dual mono design with a super-linear driver, delivering power of 2,5 Wrms even into 30 Ohm per channel in pure Class A.

The complete signal chain inside the ZeroUno DAC-HPA consists of only a very limited number of components. There are no capacitors, no integrated circuits and no feedback loops implemented.

Detailed Description

The ZeroUno DAC-HPA ́s DAC board is based on the same topology as that of the ZeroUno DAC. Different from that, the analog output stage of the DAC-HPA is a circuit based on discrete solid stage components instead of tubes. The headphone amplifier inside the ZeroUno DAC-HPA is based on the same concept as that of the CanEVER Audio LaScala PowerAmp. The headphone amp is designed as a small dual mono power amp running in pure Class A mode, which delivers an output power of 2,5 Wrms per channel.

All the design ideas, that made the ZeroUno DAC a very well respected DAC at the top level of performance in the market, are present inside the ZeroUno DAC-HPA as well. The heart of the DAC board is an ESS Sabre32 ES9018S chip, with its eight differential DACs used in a quad-sum configuration. The digital and analog filtering are a special design of CanEVER Audio and incorporate a dedicated output transformer topology inside the D/A interface.

The layout of the main board inside the ZeroUno DAC-HPA is exactly the same as that of the ZeroUno DAC to keep the “no noise” performances from that original circuit.

The massive use of several different ground planes, shields the unit from electric noise coming from outside and isolate the individual modules inside the ZeroUno DAC-HPA like “islands interconnected by bridges”.

All digital inputs of the ZeroUno DAC-HPA are the same as that of the ZeroUno DAC. The new USB receiver board incorporates full MQA functionality too. The USB board is powered in “battery mode” and comes with a galvanic isolation from the connected computer or streamer. This avoids any injection of noise by the external digital sources.

The output stage of the ZeroUno DAC-HPA is a pure Class A Single Ended Push Pull circuit very close to the design philosophy of the CanEVER Audio LaScala PowerAmp. It is is a high current audio line amplifier capable of driving even low impedance headphones or, in general, any heavy load.

The topology is N-NFB (No Negative Feedback) to reach the maximum “naturalness” of the sound reproduced.The topology is classic with a complementary JFET input stage followed by a transistor acting as driver and a transistor acting as power device. Special care has been taken to avoid the distortions created in a N-NFB solution using a JFET/transistors topology.

In the picture on the left, one channel is shown with the power transistors soldered at the backside of the mainboard.

A lot of effort was spent to setup a super-linear circuit that overcomes the non linearity problems of the above described circuit. The concept is based on the crossing of the driving signals, so that distortions will be naturally cancelled when summed at the push-pull driver in the output stage. In this manner, the non-linearity of the JFETs and BJYTs are absorbed by a reverse non-linearity mode. This technique is not new and implemented with success in very low noise application requiring high linearity.

The result reached is interesting because meanwhile in a classic push-pull configuration ONLY the even harmonics are cancelled leaving present the odd ones. With the crossed-driver topology (aka “reverse non-linearity mode”) the odd harmonics are cancelled as well. Finally, this leads to a “super linear” topology.

A similar result in terms of reducing distortions could be reached with the use of a feedback network. But, while “feedback” seems to be simple and cheap to implement, it comes to the price of lack in “natural sound”.

Extended listening tests have proven, that feedback loops tend to create certain “patterns” inside the reproduced music, which sound not pleasant to the ears (better: the brain) of the listeners.

Implementing the crossed drivers of the super linear topology, the stability and the linearity of the amp implemented inside the ZeroUno DAC-HPA are astonishing even. Deleting any feedback loops as well as capacitors from the signal path let the sound become more “real” and relaxing.

Digital Preamplifier & Headphone Amplifier ZeroUno DAC-HPA
The drawback is the need for carefully selcted JFET and BJT in pairs combined with high quality power supplies of laboratory standard.

The selection process starts from groups of 1000 BJT and FET, ending up at only 20 to 30 transistors suitable for the amplifier.

All the solid state devices are specific for audio use and not simple “industrial” components.

The power supply is completely dual-mono, with separated transformers for different power rails. In total 6 (!) toroidal transformers are used to power the unit.

The picture on the side shows the power supply of one channel only.

The output is protected against any DC current, that might flow at the output in case of a fault. A double contact relay opens and protects the circuit, if needed. The circuit is active as well, when the ZeroUno DAC-HPA is powered on or off to protect the attached headphone from the transient noise of the power supply. The circuit is not part of the signal path!

Sometimes some very basic points valid for implementing a high quality audio circuit without feedback loops get lost. Of great importance are the layout of the printed circuit boards, its topology, the way the components are grouped and last but not least the gounding!

The final implementation of the headphone amp and the analog output stage of the CanEVER Audio ZeroUno DAC-HPA is the result of many prototypes and associated listening sessions. It incorporates years of experience in the design of amplifiers of any kind, whether tube or transistor based, Push-pull or single ended etc.

Inside the cabinet of the ZeroUno DAC-HPA there are two boards stacked above each other. First there is the main DAC board, which is that out of the ZeroUno DAC minus the components necessary for the tube output stage including the heating system for the tubes itself. Stacked to this board the is that of the headphone amp including the discrete Class A analog output stage. In between both boards there is a massive sheet of aluminum. This plate on one hand acts as a heat sink for the four transistors of the Class A headphone amp and on the other hand it shields the analog amp from the digital noise radiated by the DAC board below.

Finally: How does it sound?

... pure Class A amplification with a super-linear driver, no capacitors or integrated circuits in the signal path and no negative-feedback with ability to drive loads even below 30ohms ... it really come close to his “brother” – CanEVER Audio ZeroUno DAC about which Art Dudley wrote in his  STEREOPHILE review:

“ But while more flexible choices abound, and while cheaper choices are also thick on the ground, I've heard no other digital product that succeeds quite so well as the ZeroUno at letting music sound like music! Strongly recommended”.

Technical data
  • The circuit of the ZeroUno DAC-HPA is based on the ESS SABRE32 ES9018S DAC chip with a proprietary hybrid filter design and encapsulation against external noises.
  • For optimum performance the SABRE chip runs on a proprietary implementation of special developed firmware
  • One motherboard based on a four-layer PCB with extra thick copper traces to achieve ultra-short signal paths with minimal wiring, to avoid electromagnetic induction of noise and to insure perfect grounding
  • Discrete built power supplies for the digital and the analogue section using SIX toroidal transformers, last generation of ultra-low noise rectifier diodes and high quality – low noise regulators
  • audio grade resistors and capacitors
  • Comprehensive noise regulation for all digital circuits
  • Jitter free operation by patented high performance algorithm
  • Integrated 32 bits volume control with a residual noise below -130dB for best performances even if at very
  • low output levels
  • On board output level setup to match different sensitivity of the direct connected power amplifiers
  • Voltage-compensated, ultra-low phase noise and low jitter crystal oscillators (clock) acts as master clock.
  • Two separated clocks for sampling families of 44.1, 88.2, 176.4, 352.8 kHz and 48, 96, 192, 384 kHz
  • DAC output stage with shortest possible signal path based on custom made amorphous audio transformers
  • produced by Lundahl with first order discrete analogue filter for best THD and digital noise suppression
  • True Class A discrete built analog output stage with zero negative global feedback.
  • Separately powered USB chip by a “quasi battery power supply” to avoid any distortion induced by the
  • connected computer (no connection to the +5V powerline of the USB cable)
  • USB input based on XMOS xCore audio chip with bit perfect transfer for 16bit, 24bit or 32bit data in PCM
  • format up to 384 kHz including support for native DSD/DoP and MQA.
  • 4 Digital-Inputs: 1x USB 2.0; 1x true S/PDIF 75 Ohm BNC or true AES/EBU 110Ohm XLR; 1x S/PDIF RCA; 1x
  • USB input compatible with following audio formats via PC and MAC:
  • - PCM: 44.1; 48; 88.2; 96; 176.4; 192; 352.8 and 384 kHz up to 32 bits
  • - DSD (DoP): 2.822 MHz / DSD64, 3.072 MHz, 5.644 MHz / DSD128
  • - MQA all formats
  • SPDIF inputs (AES/EBU, BNC, RCA) compatible with PCM signals from 44.1, 48, 88.2, 96, 176.4 and 192 kHz, up to 24 bits. The OPTICAL input accepts music files with a resolution up to 24/96 kHz
  • LCD Display with variable brightness, changing letter size for better reading from listening position
  • Infrared remote control with direct function keys for volume, balance, absolute polarity, mute and input
  • channel
  • No drivers required for LINUX or MAC OSX
  • USB Audio 2.0 driver available for Windows XP/Vista/7/8/10
  • Gain = 26dB (x20);
  • Zout < 1 ohm;
  • Vo max = +/-12V;
  • Pout = 2.5Wrms onto 30ohm
  • Distortion with 1KHz, 1Vrms, into 30ohm load

- 2nd harmonic below -102db
- 3rd harmonic below -100dB
- 4th harmonic below -125dB
- 5th harmonic below -120dB