Born out of Necessity

My day is spent at the computer. I come in with a cup of coffee, tune in to a web radio station or select some music from the server and start working. My desktop speakers are connected to the line out jack of the PC, which is not ideal, because the onboard audio sound is mediocre and has a lot of noise, so I soon get tired of listening. That's so frustrating... Sounds familiar? I've personally wanted for a long time a product like DACmini PX - a compact, high-quality USB DAC with a power amplifier, which sits by the computer monitor, letting me adjust volume, select inputs and choose between headphones and speakers. A product, whose time has come! And so we have it -- with DACmini PX you can listen to music the entire day without feeling tired!

Below are some notes about the design, and also some frequently asked questions. These notes apply to both DACmini CX and DACmini PX, since they come from the same family.

DACmini vs. DACport

DACport and DACmini are two very different products. DACport is portable, while DACmini is compact, desktop unit. The two products are similar in that both share our proprietary 24-bit USB audio design (which we also licensed to Benchmark, Bel Canto, Emprical, Lavry and many other brands.) But that's where the similarities end.

- DACport is optimized to run on USB power. It does not need isolated grounds. It does not need additional inputs or outputs. It's a product that's designed to be very small and highly portable. It travels inside the laptop case and goes wherever you take your laptop.

- DACmini is an externally-powered product for use in a home, or an office. Using external power allows us to increase internal analog voltages to +/-15V, achieving higher output level, lower noise, lower distortion, and robust immunity from ground loops and interference. Overall, DACmini sounds better and louder than DACport, especially on those headphones, which are notoriously hard to drive. DACmini has another important advantage - it can be powered from the wall outlet, or from an external DC source, such as car, boat, or DC battery. This makes DACmini a highly versatile audio product.

Which Headphones?

A lot of people ask if our headphone amplifier products can drive their headphones. The answer is "Yes, they Can!" (did you get the pun? Headphones are called "Cans"). At CAN JAM'10 we purposely showed both the DACport and DACmini with the 600 Ohm version of the Beyerdynamic 880 headphones, which sound great but are known to be quiet, demanding a louder driving level. Both DACport and DACmini drive these headphones with ease. People also brought in to test Audeze LCD2, Dennon 7000, Sennheiser 760, and Beyerdynamic Tesla T1. In general, in-ear monitors (Westone, JH, Etymotic, Shure) are more sensitive, so these are easy to drive. Large headphones are more of a challenge for small, battery powered units. Since DACport and DACmini both have sophisticated internal power supplies that ramp the 5V from USB up to +/-9V (DACport) and +/-15V (DACmini), both products are very loud with headphones from 32 to 600 Ohms. Rest assured, you will have plenty of volume, no matter what headphones you use. In case of doubt, pick DACmini - it is even louder than DACport.

Which Speakers?

DACmini PX will drive any speakers capable of handling 25W per channel and featuring 4...8 Ohm impedance. Of course, we wouldn't be CEntrance if we didn't create a fully integrated solution. Our new MasterClass™ 2504 coaxial nearfield speakers offer the perfect pairing for DACmini PX — we've matched the speakers to the amp and vice versa. A lot of care went into voicing the amp and the speakers to work together well and the result is very impressive indeed!

Galvanic Isolation

Most homes don't have perfect wiring, which is a common source of headaches in audio. We see this a lot in the professional sector, where music stages are seldom wired correctly and the sound engineer constantly fights ground loops. A ground loop forms when you plug your computer into one outlet and the audio system into another. Both work fine on their own, but when you short the two grounds together you hear buzz, rustle and other noises. DACmini is designed to protect you against ground loops. It features Galvanic Isolation between the computer ground and audio ground, eliminating cross-talk. No need to invest in re-wiring your house or installing gold-plated outlets. DACmini brings audiophile quality to real-world homes.

Left Brain/Right Brain

With DACmini we approached isolation seriously. To minimize interference, the DACmini audio PCBs are actually divided in two. The entire right side is digital and the entire left side is analog (this is done because most headphones have the cable coming out on the left side). Now you know why the USB jack is on the right -- it's because digital lives there. The DAC chip is the holy grail of good sound and it needs to operate in a "clean room" environment, with solid clocks, stable power and no external interference. Internally, near the DAC chip, signal crossing is not allowed, because nothing should affect your sound! The physical separation of the PCBs means that digital and analog signals never cross inside the unit. Analog signals run in balanced fashion, further improving noise immunity.

Silent Switching

DACmini makes your listening enjoyable in many ways. Internal signal switching is performed silently, so that you never hear loud pops or clicks when you turn on the unit or select inputs. We used expensive, audio-grade relays for internal switching. We only use gold-plated, four-layer PCBs, to minimize corrosion and increase the longevity of your sound investment. Of course, there are no capacitors in the audio path either, only gold-plated wiring, for the purest signal path.

Chip Choice

When asked about the chips we use in our products, our answer is simple: CEntrance only uses the finest components in its products, chosen after many hours of critical evaluation, to guarantee highest audio quality, professional-level reliability and longevity of your investment. As a well-known design firm, CEntrance is the official 3-rd party design provider for Texas Instruments, AKM Semiconductor, Analog Devices, Oxford Semiconductor, XMOS Semiconductor and many other IC vendors, so naturally we have early access to the best chips. But the chip is only half the answer — correct implementation is the other half. Not everyone is an experienced circuit designer. If someone tries to use a great chip and gets frustrated, they post on the Internet that the chip is bad and other people read that as true. We prefer to have our customers listen to our products and make their decision on the sound quality, not on what they read about chips on the Internet.

External Power

DACmini PX takes 19 VDC from an included adaptor and cleans it up inside to be virtually insensitive to power-line noise. DACmini PX makes full use of the external power, generating isolated +/-15V voltage rails inside the unit and feeding that to all internal analog circuitry. A full 30V of clean power offers a lot of room - it lowers the noise and reduces distortion for all critical internal components. This level of protection from external interference comes from our experience designing professional audio equipment. Our broadcast customers may not always work in ideal environments, yet the show must go on.

Happy Listening!

Michael Goodman, Chief Product Architect