DACport development blog

The reason DACport works with Windows, Mac and Linux without needing to install any custom drivers is because it supports the USB class-compliant audio standard. All major operating systems ship with built-in standard audio drivers, which is the reason that most USB headsets are plug-and-play. Typically, however, these built-in drivers only support 16-bit/44kHz soundcards.  Most 24/96 products ship with custom drivers and require the user to go through a cumbersome installation procedure.

But not DACport, a true CEntrance innovation. We spent years of intense R&D effort learning how to make a 24-bit/96kHz USB DAC compatible with the existing OS drivers. The good news is that now you can reap the benefit of that effort. DACport is true 24/96 and plug-and-play. It works works right out of the box, with any computer. How’s that for convenience.

With DACport CEntrance set out to create the smallest portable audiophile USB DAC. Not a simple USB sound card with a compromised set of parameters, but the best, yet portable headphone amp with USB input. You can’t always be near your expensive home audio setup. With DACPort, you could use it on a plane, in a coffee shop or in a hotel room to relax and listen to high quality music away from home.

A high quality DAC needs to have descrete parts for everything. It can’t use an all-in-one chip, which is typically consumer quality, but has to have separate power supply, DAC and amplifier circuits. Normally this level of miniaturization would be impossible because of physical constraints. But CEntrance also designed the MicPort and AxePort, the recording interfaces used by musicians and broadcasters all over the world. So we had some minaturization experience. We also developed dozens of pro audio products for the largest brands in the industry, such as Mackie, Alesis, Harman Pro, and Gibson. CEntrance started out as a design firm back in 2000 and since then built up our “chops” in designing miniature electronics.

Here is a picture of the two circuit boards inside the chasis, actual size (depending on your monitor, of course). We are stil counting the total number of parts, but it’s a couple of hundred, mounted on the top and bottom of both circuit boards. There is no space left – it’s a tight squeese. The first prototypes are built manually, so a steady hand, good light and magnifciation are key. You can’t assemble these if you were partying the night before…

One of the benefits of DACport’s design is the small size of its PCBs. The advantage is in the layout of the ground wiring. When ground paths are short, there is less chance for ground loops forming inside.  Fewer ground loops means less noise and higher quality sound.

But the flip side of a small space is a limited number of power supply caps, which are needed to filter out the supply ripple and create a smooth, clean power for the amplifier circuitry. The design quickly becomes a study of compromises.  How do you maintain the best audio quality while conserving USB power, and fitting everything in the smallest possible space?

Higher power supply voltage provides several benefits. Firstly, there is more power available to drive any kind of headphones. Secondly, the signal-to-noise ratio is higher. Thirdly, ClassA amplifiers running at higher supply voltages typically produce lower distortion,  so all in all more votlage is a good thing.  It’s easy to raise the supply “rails” in a wall-powered product, but how do you do that in a portable device that takes its power entirely from USB?  Well, we recently made the decision to upgrade the internal power supply to 18 V to gain the last couple of dB of THD out of the circuit. Inside of the tiny aluminum tube there is a switching power supply that makes +/-9V out of the 5 V that is provided by USB.

It took several weeks of optimization, but the end result is simply astounding—we have achieved unprecedented -97dB of THD+N at the output! This means that DACport’s distortion spec is now at the theoretical imit of its Digital to Analog converter. This is miles ahead compared to a standard CD player! We simply couldn’t improve it any further. And so, on to new challenges.

We returned to the lab knowing that a lot of work was still ahead of us. For example – we are using the chassis from our award winning MicPort Pro and AxePort Pro products, but we need to make some changes to adapt this chassis for DACport.

Micport uses two control knobs and so there are two holes drilled at the top of the aluminum tube. DACport has only one knob for volume, so we were joking that between now and production time we will need to “learn how to not drill an extra whole”. Manufacturing is not always smooth, so we will see how that goes… Meantime, on the right is the picture of what it will look like once the hole is undrilled… If you said “photoshop”, you guessed it right. The engineer’s quickest tool….