Empirical Audio

About Empirical Audio

Recommended Hardware Configurations

Starting at highest performance

  1. Overdrive SE DAC using USB input and Final Drive transformer buffers on the outputs
  2. Off-Ramp 5 (with HDMI Hynes reg and Turboclock) driving PS Audio PWD with 1.25-1.5m HDMI I2S cable
  3. Off-Ramp 5 (with HDMI Hynes reg and Turboclock) driving Wired for Sound DAC2 with 1.25-1.5m HDMI I2S cable
  4. Off-Ramp 5 (with S/PDIF Hynes reg and Turboclock) driving Metrum Octave DAC, Rega DAC or Berkeley Alpha DAC using 1.5m S/PDIF coax cable
  5. Synchro-Mesh reclocking virtually any 2-channel digital device (Sonos, Squeezebox, Servers, Apple TV etc..) using 1.5m S/PDIF coax cable to drive the DAC of your choice

USB enhancements

All of the USB interfaces above will benefit from the Short-Block USB filter and an upgraded USB cable in 1.5m length or longer.

Best Computer Source

The best USB source currently is the late 2009 Mac Mini with SSD and at least 4GB DRAM. Use USB port next to the center one. Better than newer Minis. The SSD can be purchased from Other World Computing. 120GB is recommended. This is a 30-minute task to replace the hard disk yourself:


You can get it with a USB-ATA adapter so the drive can be plugged into a USB port for formatting prior to swapping the hard drive and installing in the computer (recommended). They do not come formatted:


Power Supplies

The Mac Mini, Off-Ramp 5 and Synchro-Mesh can be further improved be replacing the wall-wart AC adapter with a fast-reacting linear supply such as those from Paul Hynes Design, or LI battery supplies that have ultracapacitors in parallel with the batteries:


DAC enhancements

1) plug the DAC and the Mac computer always into the same AC circuit, same ground.

2) install the following tweaks from iTunes iBooks to help the Mac OS:
The Audio Optimization Guide For Apple For Apple OS X - Mountain Lion
The Audio Optimization Guide For Apple For Apple OS X - Snow Leopard

3) Use an Empirical Audio Short-Block USB cable filter

4) Drive your Amps direct using balanced from the Overdrive or Final Drive.

5) Use Final Drive between the DAC and the amps

System Equalization

I know, EQ was a dirty word to audiophiles in the past, but trust me, no more. The parametric EQ that comes standard with Amarra is truly transparent and can take your speakers to the next level. If you have speakers that cost $15K and want them to sound like $100K, this will get you there.

The EQ in Amarra is easy to use. For each correction, you have these parameters to adjust: Amplitude, Frequency and Q. Q is the spread of the effect, so a high Q like 25 will be a very narrow correction. Q of 2 will be wide, covering a wide range of frequencies on both sides of the Frequency selected.

EQ is not something that you want to be adjusting by ear, because this is very tricky and error-prone. Instead, one needs a Spectrum Analyzer to show you the response from 20Hz to 20kHz in your specific room. You play a pink noise file in repeat mode from the computer to give you the flat signal and then a microphone and analyzer will show you where in the frequency range the suckouts and bumps are. You can then adjust the Frequency, Amplitude and Q in real-time to eliminate these suckouts and bumps. Typical EQ will have one or two corrections for the crossover in the speaker (they are never perfect) and one or two for room resonances. Amarra standard EQ has 3 corrections, but you can call-up the advanced version in the Amarra preferences to get 4 corrections if you need more than 3.

With the advent of the iPad, the spectrum analyzer software is much easier to use and less expensive. This can be purchased on iTunes as "Audiotools". Once you have Audiotools installed on your iPad, start it up and inside select "FFT". It will prompt you to pay for the internal FFT tool, which it will download to your iPad. This is the spectrum analyzer that you will use the most.


Audiotools can use the built-in mic in the iPad or by adding a mic preamp, the iAudiointerface2, it can use a professional mic. The mic in the iPad is not really sufficient to do accurate spectrum analysis, so we recommend you purchase the iAudiointerface2 and a good mic with calibration file. The mic calibration file eliminates any non-linearities in the mic response, making its response virtually perfect.


To purchase:


We recommend either the CM125 mic:


or if you want a pro mic, the Earthworks M30:


An additional $50.00 gets you the calibration file for the M30. This is loaded from your computer into the iPad, so it must be stored in the computer first. The iPad and computer must connect and communicate. Studio Six Digital has instructions for this.

You will also need a XLR mic cable if you get the M30 mic. The CM125 mic can plug directly into the iAudiointerface2 preamp, so no cable is necessary.

Call Empirical Audio today to discuss your needs.
(541) 595-1001 - 10:00am to 6:00pm Pacific Time