WAVEQUEST D/A CONVERTER
The Wavequest D/A Converter is currently the flagship of our products. It embeds knowledge and experience accumulated in over 10 years of work into audio electronics field and cutting-edge technology capable of making a product different almost in every way from the ordinary approach.
Again we have to thank and send our praises to Ross Freeman (1944-1989), the inventor of the FPGA and co-founder of Xilinx, Inc. for creating the premises for these wonderful chips. Into the good tradition of the Wavequest series, we built the DAC core, except the multibit d/a stage, into a powerful custom-designed piece of silicon. While in WQ Transport the design fitted into a 400K gates-equivalent device, the DAC uses a 3.4 million gates-equivalent device, about nine times the amount of the Transport.
Let's move again on the basic questions defining the philosophy behind the product. What do we want from a DAC and what is that WQ has to offer?
First, let's see what source of audio material is the most wide-spread. Despite the nice growth of high-resolution material, most of our music collection is based on regular audio cd's, either physically, or ripped at the classic sample rate of 44.1 KHz/16 bit. It makes sense to optimize the digital playback system for this kind of input, while harnessing all the advantages of currently available new formats.
The limitations of the classic 16 bit/44.1k are well known for some time now. Except for the NON-OS DACs, all other solutions tried to overcome the major disadvantage of the redbook format: the higher the frequency of the sound, the smaller becomes the number of samples which describes it. The notions of upsampling or oversampling came into place, with more or less successful implementation. Upsampling to 192K is trivial on the current level of technology. 384k is found from time to time, and barely you can find a machine to upsample to 768k. Inside WQ we are pushing the limit to a whopping 1,5 Mhz sample rate! You might ask, what kind of DAC supports this high sample rate? The fastest R2R chip to this day(PCM1704) accepts rates up to 16x(768k) - this is why after some consideration we choosed to use nothing less but discrete R2R DAC modules, which can work up to 3 Mhz. The interpolation engine we designed is quite flexible; you can select lower interpolation factors (8x, 4x) or it can by bypassed, transforming the dac into a non-os one.
So far so good, but what about jitter? How is this machine dealing with that? Well, let's remember the paradigm inside WQ trasport. The data was moved from the disc to a large RAM memory, which becomes the source, clocked by a very clean master clock. Instead of filling this memory from the disc, into the DAC, the memory inside is filled with the incoming data from the inputs - so there's a big similarity at a conceptual level. However there's a catch: the disc can be spinned or stopped at will to ensure that the RAM buffer will not overflow or underrun - but the exact frequency on the s/pdif input stream cannot be controlled and will more likely suffer variations, both in frequency and in time. Those interested in how we addressed this problem are invited to read the DAC's technology paper. Esentially, the Wavequest is a DAC with a built-in jitter cleaner, more advanced than the separately available dedicated solutions.
How about a volume control? Is it available as a feature? Of course. Made entirely in digital domain, the volume control is carefully engineered to achieve a 256 step accuracy. The WQ DAC low-impedance output can drive directly a power amplifier, skipping the preamp from the audio chain. The volume control can be bypassed by setting it's attenuation to 0 dB, and that's a valuable feature for anyone which intends to use a preamp in the system.
How about a direct connection to a computer? Is the WQ DAC equipped with such a link? The answer is yes. We have installed a convenient USB input for direct streaming your files into the dac. This transparent bit-perfect interface allows high-resolution files up to 192k/24 bit to be transmitted directly. To avoid computer's operation system tampering with the sound, special USB drivers are available.
TECHNICAL CHARACTERISTICS (for firmware 1.3 - subject of some changes in future versions):
- COAXIAL S/PDIF : 44.1-192K
- AES/EBU : 44.1-192K
- OPTICAL : 44.1-96K
- USB : 44.1-192K
- I2S : 44.1-384K
- I2S compatible devices: ROCKNA WQT, PS Audio PWT
DIGITAL PROCESSOR :
- MEMORY BASED ADPLL : 0.3 ps jitter (fixed mode setting)
- ADPLL loop corner frequency : 0.5 Hz
- DIGITAL FILTER : 2x-32x (max. 1.536 Mhz output rate), can be bypassed for NOS operation
- DIGITAL FILTE TYPE : polyphase sin x/x interpolation , 4000 taps
- DIGITAL FILTER STOPBAND ATT : -145 dB
- DIGITAL FILTER PASSBAND RIPPLE : 0.5 udB max.
- INTERNAL PRECISION : 63 bit
- DITHER : 4 bit, gaussian ultrasonic
- VOLUME CONTROL : custom multiplier array 256 steps
OUTPUT :
- THD+N, 0 dB : 0.006%
- DYNAMIC RANGE : 125 dB (A-weighted)
- S/N RATIO : 140 dB (A-weighted)
- IMPEDANCE : 5 ohm
- MAX. OUTPUT : +/- 5 Vpp
USER INTERFACE:
- APLHANUMERIC DISPLAY, 16 character (dimmer available)
- MENU ENTRIES : VOLUME, INPUT SELECT, PHASE, INTERPOLATION RATIO, ADPLL TYPE, DITHER
- REMOTE CONTROL WITH ALL FUNCTIONS
