Dear friends, with special pride I present to you my latest model USB AUDIO DAC, called "VARNA IV". In the next few lines I will try to describe it as detailed as possible to see what is really new and valuable in this evolutionary model.
First, I must start with the idea that lay at the heart of this USB DAC. For quite some time I wanted to make such a device which combines the absolutely trouble-free operation and the software/hardware compatibility when using IC from the series PCM270x of "BURR BROWN", wonderful audiophile sound of my previous series USB DAC-s, but also have high output signal level to can be used successfully for professional use by DJ's and sound engineers. This USB DAC combines two unique properties-super ease of use in professional work, but also has an unique full-blooded, rich, natural and detailed sound. After all, for whom is this model targeted - for sound engineers and DJ's or for audiophiles? In fact, the device is very convenient for the DJ's and sound engineers, but it's high-quality sound directly qualify the DAC as an audiophile product.
Now I will point out the main design advantages of the device:
1.Using as USB receiver, the IC with proven software/hardware compatibility and absolutely smooth/reliable performance - PCM2706/07 BURR BROWN. This provides an invaluable advantage of the device to work with any operating system, without the need for special drivers-Windows XP, Vista, 7, 8; Linux; MacOS; Android 4.0 and above; even with microcomputer "Raspberry Pi" + software "Volumio". This is a very important feature - just plug the device in the USB socket of the computer and it starts to operate immediately. No need for any additional software drivers.
2.Using full galvanic insulation of the USB DAC "VARNA IV" from the computer to which it is connected. The separation was done on all four USB transfer lines D +, D-, Vbus and GND. Galvanic insulation of the digital part is made by using proven galvanic insulation IC ANALOG DEVICES aDUM4160. The power line from the USB port is insulated by galvanic pulse scheme DC-DC converter. In both realized topology, all the noises, disturbances and ground loops are going into the oblivion. The annoying requirement to plug the computer and amplifier in the same wall power socket is eliminated. "VARNA IV" breaks galvanicaly all electrical connections with the PC and thus achieves two very important advantages, resistance to interference, and greatly facilitated the use of the device.
3.Although we have galvanic barrier to the computer, "VARNA IV" requires no additional external power supply. This USB DAC is powered from the USB port to which the DAC is connected. This solution provides the next very important advantage, saving additional PSU. Saving the additional PSU means ease of use, less size and weight to carry, lower price.
4.Using entirely external, discrete, ultra low noise voltage regulators and filter solutions for maximum purity of the PSU. "VARNA IV" incorporates just 7 pieces independent discrete voltage regulators with ultra low noise levels made by MICROCHIP. All integrated power regulators in the IC's are switched off and are not used. Each individual function of each of the three IC's in the scheme is powered by its own ultra low noise voltage regulator and RC-filter. This is where lies the secret of the sound of this model. The low noise PSU is the main factor that allows the creation of a true audiophile device.
5.Separation of digital and analog ground planes and linking them only at one point. This approach ensures minimal penetration of high-frequency noise from digital part in the analog circuit. This is an another condition which builds the audiophile sound quality of "VARNA IV".
6.The linear outputs of "VARNA IV" receives signal from WM8524. This DAC IC incorporates a built-in charge pump in it's topology. The IC is powered by 3,3V of unipolar voltage, but the charge pump generates the mirror negative supply voltage. This allows the output of the IC to be theoretically free of DC-offset, which automatically ejected the decoupling capacitors. The linear outputs are feeded directly from the terminals of the chip. This simplifies a lot the analog circuit of WM8524 and reduces it only to a simple RC-filter. You will not believe what is growth of the sound quality only because of the removing of the decoupling capacitors in the signal path! This is another design success on the road to the audiophile sound.
7.Using a two-layer PCB with solid ground plane's. Typicaly for the models of the series "VARNA" and the new "VARNA IV" is based on the two-layer PCB with large low-resistance ground planes. The base components are carefully selected not only by it's parameters, but also by the most important-by it's sounding. There is no one component that is positioned accidentally. All power pins of chips are filtered locally with high capacity SMD capacitors.
8.Using a massive anti-resonant box of 12mm MDF, upholstered in hard-wearing black leather for car upholstery.
9.High output level from the linear outputs. The new model IC WM8524 has an excellent high output level-2,1V RMS. About 3 times higher than PCM270x series.
What are the differences between the older model "VARNA III" and the newer "VARNA IV" ?
1. Linear output signal is obtained from WM8524 of WOLFSON (in "VARNA III" that was PCM5100 of BURR BROWN). WOLFSON's DAC's were always known with it's great musicality. This model WM8524 is no exception. It is heard immediately, from the very first sounds of music playing from this IC.
2. "VARNA IV" uses only brand electrolytic capacitors of the Japanese company "NICHICON". For analog part are used audio-grade FW Series and KA. For the digital part are used ultra low ESR series HD. Everything is supplied directly from the official distributor of NICHICON - the company MOUSER. No any Chinese fake capacitors from E-Bay for pennies. Used capacitors have serious prices, but ensure high quality.
3.Entirely new topology of the ground-plane. It now consists of three independent clones, which bind at one point only to the chip. How exactly is realized, it's design secret. But the result is clearly audible.
4. The output RC-filter is already realized with proper quality components-resistors of the Japanese company "KOA SPEER" (which produces audiophile brand resistors KIWAME) and KEMET film capacitors series MMC (former RIFA).
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SPECIFICATIONS:
Word Lenght - 16bit
Sampling Rate - 32kHz/44.1kHz/48kHz
Processor Type - BurrBrown, Texas Instruments, PCM2706/7CDB for the headphone outputs and WOLFSON WM8524 for the linear outputs
Output Signal Level for the linear outputs - 2,1V (RMS)
THD+N for the linear outputs - 89dB at -1dBFS
SNR for the linear outputs - 106dB
THD+N with load 32Ohm for the headpnone outputs - 0,025%
Output power at 32Ohm load for the headphone otputs- 12mW
SNR for the headphone outputs - 98dB
Input Interface - USB 1.1 type B (printer type)
Output Interfaces - line out type RCA; 3,5mm headphone jack. All outputs can operate simultaneously.
Power options - feeded by USB
Dimensions: H-55mm; W-90mm; L (with plugs)-117mm
Weight: 320g
Designed and handcrafted in Bulgaria by eng.Ivelin Yovchev
Attention! The USB DAC may have output DC offset about 1-2mV. These are minor values and are practically negligible, but I have to mention this fact.
How to purchase USB DAC model "VARNA IV" ?
If you want to buy this product, please, contact me to the following e-mail:
[email protected]The price is 129 Euro. Packing and worldwide shipping - FREE. I use only registered, priority mail, with tracking number. This is the fastest and the most safe shipping method. I prefer PAYPAL transactions.