Technical

What transport should I use? / What cabling should I use?

What is non-oversampling design? / What does digital filterless mean?

Why batteries?

Why do you use sealed lead acid rather than other rechargeable technologies?

Should I buy extra batteries?

What transport should I use? / What cabling should I use?

We suggest that you use the best quality transport you can afford with the dAck!. The dAck! was voiced with C.E.C. transports and Ack! Industries cabling. C.E.C.’s belt drive systems have consistently offered a fantastic synergy with the dAck!. Other transports that reportedly work very well are machines in Sony’s ES line, boxes by Meridian, Wadia, Esoteric, and Vecteur. De-jitter devices may help improve performance of sub-optimal transports or personal computers with jittery datastreams, however the output from anti-jitter devices can be poorer than the best transports so please experiment. Many of our customers have reported very good luck with the DIP classic from Monarchy Audio.

Digital cabling is more critical than analog cabling (analog we leave to user preference). The cable should be a consistent 75Ω throughout and have high bandwidth terminations to prevent appreciable reflection of data edges which can poison subsequent data upon back-reflection. We use impedance-matched adapters for use with RCA terminations/jacks but recommend the use of BNC connectors - which are designed for RF signal transmission - for high end setups. RCA cable length should be ~1.5m. BNC applications do not have a length constraint.

What is non-oversampling design? / What does digital filterless mean?

The Ack! Industries dAck! does not perform conversion like the vast majority of D-to-A converters. Almost all current-day DACs perform oversampling on the signal in an effort to remove ultrasonic square-wave components that arise due to time-discretization. This archaic technique was used to flatten the frequency response, but more importantly, to limit the ultrasonics that would cause some amplifiers of the era to become unstable. Through oversampling, engineers were able to remove the non-audio band ultrasonic images using brickwall filters that were gentler and less expensive than the ones used in the earliest generation of CD players.

Oversampling is done by increasing the sample rate of the signal before it reaches the DAC. Extra samples are placed between every real sample to fill in the blanks in the higher out-sampling rate system. These fake in-between samples are constructed using filters in the digital domain. However, the fact that there are more samples does not mean that there is more resolution in the output; you cannot recover more information than what was encoded on the disc. Furthermore, there are psychoacoustical problems associated with use of digital filters that damage the sound, and phase inconsistencies due to the continued use of steep analog filters.

The Ack! Industries dAck! forgoes the oversampling scheme completely. It can do this because the ear is perhaps the best brickwall filter there is. For the listener, non-oversampling gains major advantages such as improved tonality, glitch reduction, decreased system complexity, phase purity, and more accurate impulse response. All of these contribute to the dAck!'s unique, ultra-listenable sound.

Why batteries?

The dAck! is designed for cost-effective ultra-high performance. To approach the performance level of the battery supply, one would require a highly-regulated power supply that is both bulky and expensive. This would dramatically raise the price of the system while decreasing performance. The battery supply improves portability of the unit and improves its performance.

The power consumption of the circuit and size of the cells have been optimized to achieve a friendly medium: interactivity, bulk, lifespan, and play time have been carefully balanced for the end user. We do not sacrifice dynamics for the ultra-quiet background of the battery supply.

Why do you use sealed lead acid rather than other rechargeable technologies?

Part of the reason why the dAck! is so affordable is because its battery type has a large capacity at low cost. They are designed to be slow charge devices; the typical usage cycle for audio makes sealed lead acid the best type for this application.

Should I buy extra batteries?

Sealed lead acid batteries like to be kept full and trickle-charged continuously. Unfortunately, they lose charge over time if left unused on the shelf. We recommend that you purchase extra battery packs only when your current pack is fully depleted and no longer holds charge. If you decide you want an extra battery pack "just in case," it is recommended that you rotate the battery pack into your dAck! every 3 months to keep it conditioned. The batteries last 3-5 years if nicely conditioned so one could a rotate pair of cells in this manner for a rather long time.