AVM Ovation SD 6.2 Preamplifier/DAC

Winning the Darwinian Struggle for Digital Sound

Equipment report
Solid-state preamplifiers,
Digital-to-analog converters
AVM Ovation SD 6.2
AVM Ovation SD 6.2 Preamplifier/DAC

The layout of digital and analog audio circuits puts the streaming engine on the far left; the digital audio circuits, USB receivers, and DAC in the middle (with all the inputs); and the analog output stage on the right. All the active circuits are built upon multilayer boards with gold-plated conductors. The circuit boards are also coated in black instead of the standard green for more efficient and even heat dissipation. (The boards serve as their own heat sinks.) This helps stabilize temperatures in the densely populated circuits, while warmer parts like the power supplies are kept away from the digital audio components, which need lower temperatures for best performance.

AVM uses as many surface-mount-devices (SMD) as possible to further shorten signal paths and decrease the effects of stray magnetic fields. SMD requires expensive automated robotic assemblies to stuff the circuit boards, but it ensures that all units are made exactly alike, eliminating the human factor and increasing accurate repeatability.

Like most high-end manufacturers, AVM pays a great deal of attention to power supplies, and the Ovation features three separate switching supplies with extensive voltage regulation. As noted earlier, changes in digital standards (i.e. USB) may require hardware upgrades in the future. This is one reason for a modular design that makes swapping existing circuit boards easy. The USB receiver is located on a module that can easily be exchanged. The same applies to the DAC.

The DAC section is built around two ESS 9018 K2M Sabre32 DACs per channel for truly balanced conversion to analog. As noted, the DAC accepts PCM up to 32 bits and 382kHz, as well as DSD128. DSD is converted to analog by the DAC natively without an intermediate conversion to PCM. The Ovation offers user-selectable upsampling rates, up to 384/32. Down-conversion is also possible, although I don’t envision a scenario in which this feature would be used.

The analog stage receives a balanced signal from the DAC, and the signal remains fully balanced throughout the audio circuits. The solid-state audio output stages are designed in a dual-mono configuration on completely separated and stacked PCBs. This design provides a channel separation of around 140dB. The circuit is DC-coupled, with a servo preventing DC from appearing at the output jacks.

The analog output stages use select, audio-grade op-amps. The volume control is located directly before the XLR and RCA analog output jacks to minimize signal path lengths.

The Ovation SD 6.2 also has a tone control, located directly before the output, which can be bypassed. A light touch on the bass control (100Hz corner frequency) can help in a given room and system. The same is true of the treble control, which affects the more audible portion of the upper octaves up to around 10kHz, but leaves response flat above this frequency.

Finally, the Ovation’s Class A headphone amp provides exceptional sound quality. The Ovation SD 6.2 offers a well-designed remote control, but is a $699 option. Making the remote control optional makes sense because most owners will use a smartphone to set up and operate the Ovation SD 6.2 as well as to manage music playback on a daily basis.

Key Features
The Ovation SD 6.2 does not have a lot of flashy displays, but it is extremely flexible and easy to use. Its key features include the ability to handle virtually any type of digital input; accept analog inputs; stream Tidal via AVM’s app; apply tone correction via the bass and treble controls; separately adjust and set input levels so each input has the same volume; adjust channel balance (this setting is not available using the remote control, a tablet, or an iPad); set several different levels of loudness control to compensate for the perceived reduction in bass and treble at lower listening levels; customize the remote-control operation; name the inputs; and set the analog inputs (one balanced and one unbalanced) to theater pass-through.

The full range of features are described in the operating instructions and AVM Network Guide available at avm-audio.com. As is the case with any new, complex digital product, both are essential reads.