Past meetings of the Society
November 2014

Boston Audio Society
Amplifier Test Clinic
Saturday November 22, 12:00 Noon to 6:00 PM
Wayland, MA

The BAS Amplifier Test Clinic Standards

The BAS is known for high-quality test clinics. During our 42 years, we have set standards at our clinics for testing amplifiers, preamplifiers, CD players, recording tape, headphones, microphones, and more. Some have been adopted industrywide.

On November 22 we will hold another pace setting series of tests in an effort to help consumers choose the best amplifier for audio playback or to uncover a reference amplifier with standards that lead the industry. Our primary test tool will be the AudioGraph, a Swedish company, home of the PowerCube. The PowerCube is a unique piece of test equipment that measures an amplifier's output voltage across 20 loads. The loads have impedance magnitudes of 8, 4, 2, and 1 ohm, and phase angles, capacitive to inductive, of -60°, -30°, 0°, +30°, and +60°. The PowerCube adheres strictly to IHF 202 signal standard to create informative three-dimensional (3D) graphs of voltage versus impedance and phase at a single frequency, typically 1 kHz.

Audio Critic (opens a PDF in a new page) was the first magazine to use the new method for assessing dynamic power output. The PowerCube, a software-driven automated instrument with a PC front end, measures the maximum voltage the amplifier can deliver into the load at 1% distortion for a duration of 20 ms at 1 kHz. The graphic output of the instrument shows the 20 data points connected to form a more or less cubelike polyhedron, which illustrates at a glance the true dynamic performance of the amplifier. The test takes only a few minutes per channel. Under ideal conditions the voltage sourced by the amplifier should be a constant. Amplifiers, in PowerCube, will look like the Figures below.

Our literature search revealed that amplifier testing is spotty, some consider it a black art, and some manufacturers are reluctant to give you all the known specifications for their amplifier into ‘real world’ loads/conditions. There are numerous standards but wide disagreement on how and what measurements correlate to a quality playback experience in a listening room.

In addition to the PowerCube results, our tests will include: (1) frequency response into an IHF load, and (2) distortion at a moderate playback level.

How Do I Signup / Participate?

The clinic will be held in Wayland, MA. At the clinic, you will be charged $5.00 for each amplifier. After completing the form below, email it or snail mail it to the Boston Audio Society, POB 260211, Boston, MA, 02126. You will be notified of the exact time to arrive with your amplifier.

Please bring your amplifier’s accessories if it is unique and required to test your unit. We will have on hand standard XLRs, phone, and phono input/output connectors. You will receive a printed copy of your tests results. We will notify you in advance of the actual time to arrive at the Clinic and the address. If you do not have an amplifier to test, you are invited to attend the clinic to observe. However, you must return this form including only your name and e-mail address. We will forward the address of the clinic’s location.

Click HERE for the form. (opens into a new page)


The Boston Audio Society
PO BOX 260211
Boston MA 02126

problems? email Barry:

updated 1/11/15