- Written by John E. Johnson, Jr.
- Published on 23 November 2009
On the Bench
All distortion measurements were made with two channels driven and within an 80 kHz bandwidth. Although the 3310 is rated into 6 ohms and not into 4 ohms, I ran tests at 8 ohms and 4 ohms to be consistent with previous reviews. I used the Pure Direct mode, as that bypasses signal processing (no DSP). The tests represent preamplifier and power amplifier performance by themselves.
At 1 kHz and 20 volts output into 8 ohms, THD+N was 0.016%, while at 4 ohms, it was 0.025%. The harmonic peaks are primarily odd-ordered.
Using 19 kHz and 20 kHz sine waves, the 1 kHz B-A peak was 97 dB below the fundamentals at 8 ohms and 93 dB below at 4 ohms. The A+B peak at 39 kHz was 83 dB below the fundamentals at 8 ohms and 79 dB below at 4 ohms.
IMD using the standard SMPTE 60 Hz, 7 kHz sine wave combination yielded 0.024% at 8 ohms and 0.034% at 4 ohms. However, it should be noted that the measurement only takes into account the peaks within 250 Hz on either side of the 7 kHz fundamental. There are also distortion peaks at 14 kHz and in the out of audio band (above the limits of hearing) that are not included in the measurement. All those extra peaks look a little scary, but other amplifiers costing a great deal more do the same thing. It is a matter of how high the peaks are.
THD+N vs. Frequency shows why you should use 8 ohm speaker with this receiver. Even the 8 ohm load resulted in distortion at 0.2% near the upper limit of hearing. Using 4 ohm load caused the receiver to go into fault above 1 kHz. Note that the 8 ohm measurements are using 50 watts output, which is above the average listening level. Most of the time, even in action movies, the output is about 5 watts or less. It is only during intense action that high power is required.
The THD+N vs. Power Output measurement indicated that the 3310, with two channels driven, will deliver 140 watts per channel RMS at the knee, then rises rapidly to clip (1% THD+N) at 160 watts. The 4 ohm measurement is only for comparison and interest. Don't be trying to drive your old 4 ohm speakers to high volume with this receiver.
The measured frequency response was flat between 20 Hz and 20 kHz regardless of the voltage and load (the slight separation of the graph lines near 200 kHz represents 8 ohms vs. 4 ohms. At 20 volts, the response is attenuated on purpose above 50 kHz to maintain amplifier stability.