AVR-2308CI Measurements & Analysis

Amplifier Efficiency & Power Output

Amplifier Efficiency Measurements for linear a/b amps such as the ones employed in this receiver typically range from 40-50% depending on the load the power supply of the amplifier sees. The closer you get to full load, the higher the efficiency usually becomes (assuming you aren’t overtaxing the power supply and power devices of the amp causing excessive thermal losses). The AVR-2308CI achieved above 50% efficiency when driven at near full power into low impedance loads which was quite impressive for a receiver employing a conventional linear amp design. This receiver runs relatively cool dissipating around 54 watts in idle but be sure to give it plenty of ventilation for situations of heavy usage.

Note: All power output figures in this table are continuous and referenced to 1kHz but were also checked at full bandwidth to ensure the power figures reported were within 10% reported and at or below 0.1% THD + N.

The AVR-2308CI delivered a whopping 150wpc into 8-ohms and 211 watts into 4-ohms at 0.1% THD + N using my APC S-15 and SBATT to ensure the line stayed at 120V +- 2V. With 2 channels driven, it measured around 130wpc into 8 ohms and 190wpc into 5 ohms. Keep in mind most review publications test at clipping and don’t do continuous power measurements so our power numbers are usually a lot more conservative than what you typically find from other reviewers yet this receiver was delivering FAR more power than its rated specification of 100wpc.

For more info, see: The All Channels Driven (ACD) Test

Power Bandwidth

Figure 1. Denon AVR-2308CI Frequency Response vs Regulated Power

Using input regulation where I set the Audio Precision SYS 2722 to regulate the output distortion to less than 0.1% THD + N, the AVR-2308CI belted out around 150wpc across the entire audio spectrum (20Hz to 20kHz).

Frequency Response Uniformity

Figure 2. Denon AVR-2308CI Frequency Response vs Power

Whether I was driving the AVR-2308CI at 1 watt or full power, the amplifier section exhibited excellent frequency response uniformity with a -3dB point of around 147kHz.

FFT Distortion Analysis

Figure 3. Denon AVR-2308CI FFT Analysis @ Full Power

At full measured power AVR-2308CI again exhibited excellent distortion measurements (30.352 + 45.265)dBv =75.6dBv or 100*alog^-1(-75.6/20) = .0166 THD + N which is a respectable measurement.

Amplifier Output Impedance & Damping Factor

Figure 4. Denon AVR-2308CI Amplifier Output Impedance vs Frequency

The amplifier output impedance was a good margin higher than our 100 mohm or less mark I’d like to see on uncompromising designs, but it was still very linear and under a few hundred milliohms which would make it quite capable of driving a wide diversity of loudspeakers with consistently good performance.

Figure 5. Denon AVR-2308CI Damping Factor vs Frequency

The amplifier damping factor is about what I expected based on the measured output impedance. It is uniformly good across the entire audio frequency range but does fall shy of our 100 mark for uncompromised designs. The good news however is the amplifier doesn’t fall apart when driving low impedance loads like I’ve seen on some models in this price range in the past.

Signal to Noise Ratio (SNR)

With 200mV input and driving an 8 ohm load at 1 watt, I measured a 77dB SNR un-weighted which is quite excellent and explains why I found this receiver to exhibit a very low noise floor.