Digital conversion is one of the least understood components of the modern professional recording set-up. In short, analog to digital conversion is what takes your analog signal and turns it in to a number there by making it possible to let a computer do complex math equations to among other things, record, manipulate, mix and render the audio.  Conversely the D/A does the opposite and converts the number back to an analog signal. This subject alone could fill a large book.

When explaining this conversion process, I often site the following analogy. Picture if you will, a light that is blinking on and off at a rate of 100 times per minute. Let’s pretend your goal was to film the light so that upon play back you would have a time accurate reproduction of the event. Now let us say that you are trying to film the light with an old fashioned camera that is running, for the sake of this discussion, at 100 “frames” per minute. That is to say that the camera is taking 100 “snapshot” photographs per minute. With a bit of thought, it is easy to surmise that upon play back (at 100 frames per minute) in this scenario, the light would appear as either always on or always off depending on the state captured by the first frame of the filmstrip in the camera. It is also easily deduced that to accurately reproduce the light’s frequency of 100 times per minute, you would effectively have to at least double the frame rate of capture.

This is the fundamental basis of sampling theory or “Nyquist” theory (named after Bell Laboratories engineer Harry Nyquist). Nyquist theory states that the rate of capture (Sampling frequency) has to be at least double that of the highest frequency that one wants to accurately reproduce. Since the upper range of human hearing is roughly 22.5 KHZ it is easy to guess why the folks at Sony-Phillips arrived at 44.1KHZ when deciding upon the standard for compact discs.  Now let’s say you were to capture the light at 150 times per minute as opposed to 200 times per minute. Keeping in mind that the light is still flashing at 100 times per minute. You would have a seemingly random pattern upon play back. This is a good analogy to what we in the audio world call aliasing. When you are recording for example a grand piano, at a sampling rate of 44.1 KHZ, there are most likely frequencies much higher than 22.5 KHZ present in the signal path. If these frequencies were recorded at the sampling rate of 44.1KHZ, upon play back there would be seemingly random blips and beeps or “aliasing.” To deal with this phenomenon, most analog to digital converters employ an “anti-aliasing filter” which filters out anything below the “Nyquist” frequency, in this case 22.5 KHZ.  This filter is in the analog stage not the digital, and is one of the most important parts of the converter as far as dictating sound quality.  In fact, the analog stage of the converter is the sound of the converter. The clock that dictates when to take the “snapshot” is a huge factor as well for obvious reasons. This, again, is a subject that could fill a book. If you have any further inquiries on the subject feel free to give us a call. For now let’s get to what makes the Burl Audio converters so special!!

Enter Burl

Too often the A to D and D to A converter is thought of as a digital only component.  This is unfortunate because much of what dictates the character of the sound, as stated above, is in the analog stage of the converter. Designer and Burl Audio founder Rich Williams recognized this when he designed the 2192 for Universal Audio.  Rich started Burl so that he could freely design what he believes to be the best audio path without the restrictions of a corporate manufacturer. We think he really hit it out of the park with the Burl family of products.  

By focusing on the analog side of the conversion process, Rich designed a transformer based, class A, and discrete circuit path much like that which is found in the most coveted analog tape machines of yesteryear (think Studer). This has resulted in a converter that produces harmonic detail that is just not present in the often cold and sterile analog path of the self proclaimed “transparent” converter.  The Burl family of converters just needs to be heard to fully grasp.  At conventional levels (typically -18 dbfs peaking ) the Burl is quite clean with a subtle warmth throughout the frequency spectrum.  We find that if you push it a bit, as you may do in tracking drums or electric guitar, it gets a bit warmer and enhances the harmonic detail. Most A to D converters just don’t work this way!! The D to A is a class A discrete signal path as well that is very clean and accurate.  The D to A does not include transformers as to provide the most accurate audio reproduction path.  In addition to the amazing analog section, Burl has incorporated an extremely low jitter clock that results in exceptionally accurate reproduction of audio. The Burl clock rivals some of the most expensive stand-alone clocks on the market!!

The Mothership is a modular multi-channel interface. It is comprised of a 4RU Chassis and a separate 1 RU power supply (this eliminates any worry of internal power supplies causing noise issues). Please note that the recommended racking specifications will have it taking up 7RU total.  The Mothership Chassis has 11 slots one of which will be occupied perpetually by a “Motherboard”. The remaining 10 slots can be occupied by several combinations of either a 4ch XLR input card (BAD4) or an 8 channel DB25 output card (BDA 8).  The Burl B80 Mothership lives up to its name in that it can be configured for a whopping 64 outputs for those who just mix, 40 inputs for those who want to focus on tracking, and any other combination of channels with in the 4 in/8 out/10 space capacity!!! You may also use multiple Motherships for a gargantuan sized rig!

The B2 ADC is a 1RU space 2-channel analog to digital converter. The B2 ADC has an input level select switch (stepped attenuator), which allows you to take full advantage of the transformers. By selecting a lower input level, you can drive the transformers a bit harder for a little extra flavor. By selecting a higher input level you can really have quite a clean and pristine signal path!

The meters are high-resolution RMS and peak style with 30-segment LEDs. The B2 is great to use for mix down as well as stereo tracking.  

The B2 DAC is the perfect companion to the B2 ADC. The significance of the B2 DAC, as with the entirety of the Burl line, is its analog signal path. This path consists of discrete, class A op amps with passive filters (no cheap capacitors, in fact, no capacitors at all!). This allows for an extremely accurate and wide stereo field and an all around accurate reproduction throughout the frequency spectrum.  The B2 DAC employs the same high-resolution precision meters as the ADC. This DAC really allows you to hear your mix and/or recordings with stunning detail exposing the subtle nuances that make all the difference!! Call us to set up a demo at our facility or yours!!