Testing & Results
The testing was performed with computer audio hardware and software that is available to the average computer user.
The EB03 amplifier was first tested using a 48 kHz sampled white noise waveform as the input. This input contains energy at all frequencies up to about 20 kHz, so it is a convenient way to quickly measure the frequency response of an amplifier.
A digital audio recorder was used to capture the audio output of the DAC, and then the output of the SilverStone EB03 with the DAC as the input. The input impedance of the digital audio recorder is 10k ohms, so a 600 ohm audio transformer was used between the EB03 and the digital recorder to simulate a headphone load.
In order to measure the signal-to-noise ratio, a 4 kHz digitally generated sine wave was used. By comparing the frequency spectrum of this signal before and after the EB03 headphone amplifier, it is easy to determine if the amplifier has introduced any noise or distortion.
The EB03 was tested with two pairs of headphones ranging in impedance from 32 ohms to 150 ohms. Subjective listening tests consisted of a variety of acoustic and electronic material from an iTunes library.
Audio DAC: MBOX DAC (24 bits, 48kHz sampling)
PC Platform: :Windows 8.1 PC 64 bit
Audio Program: Adobe Audition CS6
- Audio Recorder: Tascam DR60D
- Tamura MET-46 600 ohm audio transformer (Mouser)
- Low impedance headphones: BeyerDynamic T5p (32 ohms)
- High impedance headphones: Sennheiser PC350 (150 ohms)
- Audio Test Material 1: White noise 24 bits, 48kHz
- Audio Test Material 2: 4 kHz sine wave 24 bits, 48kHz
- Audio Test Material 3: iTunes AAC encoded
In order to see how the SilverStone EB03 performs, the performance of the test system itself has to be measured. The frequency sweep shown below is what the white noise spectrum looks like without the EB03 in the signal path.
Likewise, the signal-to-noise ratio and harmonic distortion of the system is shown in the spectrum plot below.
When the EB03 is placed in the system, the resulting spectrum shows that the frequency response is flat out to 20 kHz.
Looking at how the EB03 behaves with a 4 kHz sine wave shows the expected low noise output with all harmonic distortion 86 dB below the level of the 4 kHz sine wave. Note that there was originally some second harmonic noise in the test signal that needs to be subtracted from the measured harmonic distortion.
So it turns out that the performance of the SilverStone EB03 is almost exactly what would be expected from an amplifier built using the THAT ICs.
Subjective Listening Tests
It’s good to know that the SilverStone EB03 performs well in the above measurements, but of course it’s necessary to listen to the amplifier with a few different headphones to determine the subjective quality of the device.
A pair of 150 ohm headphones from Sennheiser was used to listen to a wide range of audio material. In order to drive these relatively high impedance headphones, the volume control was set to about 50% of its maximum level. With plenty of room left for more volume, the audio was clear and more than loud enough to reproduce solid bass and high frequency response.
At the low end of the impedance spectrum, a 32 ohm pair of headphones from Beyerdynamic was used. These phones don’t require nearly as much voltage to drive, and the headphones were very loud at about the 25% volume setting on the EB03 headphone amplifier. Again, the headphones produced a solid bass and crisp high frequency response.