Denon's surround-sound receivers have been highly regarded as far back as the 1980s when home theater and Dolby Pro-Logic came on the scene. In fact in 1990 Stereophile magazine even awarded a Class A rating to the Denon DRA-1025 receiver, a status only given to very expensive and exotic separates.

The Denon AVR-4306 came out in 2006. A robust 40 lb preamp/receiver it was rated at 130 watts x 7 and retailed for $1999. With dual rear surround jacks this allows the receiver to output 5.1, 6.1 and 7.1 surround. It also has two pairs of side surround speaker jacks: A and B. This extra pair of side speakers makes this in essence a 9.1 receiver. In 2008 I was lucky to stumble across a like-new open box at a great price. The first thing I did after buying it was to ship it under warranty to the Denon NJ service center. Along with a full checkup I asked them to upgrade its firmware to the latest version. My understanding is that the latest version had more to do with HDMI and FM functions and not audio performance. So if your 4306 is working properly I wouldn't stress about tracking down decade old firmware. Currently I use it as a digital preamp fed by an optical toslink from my home theater PC to push three individual power amps. I recently decided to open it up and see how its fared.

2006 SPECS
Sixteen Burr-Brown 24-bit/192-kHz D/A converters
High-performance 24-bit/192-kHz A/D converter
32-bit floating point DSP (digital signal processor)
Newly-developed large-current power transistors

DTS-ES Matrix and Discrete, DTS, DTS 96/24, DTS Neo:6, Dolby Digital EX, Dolby Digital, Dolby Pro Logic IIx, HDCD

BELOW: the rear has a complete jack panel with optical, HDMI/1080p pass-thru, and S-video inputs(!) It also has ethernet to allow a home network to access the menus from a PC which was very progressive for 2006. It doesn't support aRC HDMI but HDMI 1.1 is available for surround. Rather than mess with HDMI handshake issues I use only optical for 5.1 audio.

BELOW: The build quality is high with audio-grade capacitors throughout. The power supply makes up a left side of the interior with output transistors visible down the center. Note the factory metal tape at the bottom edge to reduce static. The audio boards on the far right are removable but are buried under several web cables and connectors.

Burr-Brown of Arizona and Denon were synonymous during this period. Burr-Brown had manufactured a variety of DACs since the 1980s which were legend in the audiophile community. Known for their high sound quality, low distortion and excellent specs they gave a stamp of quality to any digital equipment containing them.

In 2000 Burr-Brown was sold to Texas Instruments (Dallas). The 4306 is said to use BB PCM1791A chips while modern-day Denon receivers boast 24-bit/192-kHz D/A converters made by AKM (Asahi Kasei Microdevices, Tokyo). AKM products are high quality but their use reveals a shift away from the American DACS that Denon built their name on.

Two microphones were available for Denon receivers during this period: the DM-S205 and 305. Both look identical but the 305 has a metal shell while the 205 is all plastic. The 205 came with the AVR4306. The 305 came with the 5805, 3805, 2805 and 4806. It has been said that both have the same specs. But in a Denon white paper from 2006 called "Audyssey/Multiext" it states: "Denon offers 2 different models of microphones. The DM-S305 (AVR-5805/4806) and DM-S205 (all other AVRs featuring Auto Setup and/or Room EQ) microphones have different calibration curves and are NOT interchangeable."

CONCLUSION: Denon produced both mics from 2004 to 2006 and switched to a funnel-shaped DMA-409 in 2007. Its been suggested that Denon created the 205 to save money. However for Denon release both at the same time and state in print that they are not interchangable seems pretty clear cut. The 205 is the mic to use with the AVR-4306.

The first setup pass checks the background noise, connected speakers, and polarity. The next pass sets the speaker configuration, distance, channel Level, crossover frequency, & room EQ. The room should be as quiet as possible with no AC or other noise.

Optical is limited to 5.1 (6 digital channels) not because of the cable but the circuit at either end. When DVD players appeared in 1997 they included an optical output to transmit the 5.1 digital channels for home theater. When Blu-Ray players appeared in 2006 they came with optical outputs for the same purpose. In other words: standard DTS/DD 5.1 transmits perfectly over optical because it was designed to from the very beginning. So how do 6.1 and 7.1 work over optical? Here's the old-school explanation. I'm going to mention DTS because I prefer it for my home theater.

Imagine my surprise while taking these photos when I saw a loose ground wire near the front panel. I found the screw rolling around in the bottom of the chassis. Luckily it seems to not have caused any issues.

BELOW: The unit is filled with web cables of all sizes and shapes. Behind the main pair of "Elna for Audio" 18,000uf 71V caps one web had come loose. I glued it back in place.

BELOW: Every electrolytic on the audio boards is a brown Elna RA3. According to the 2004 Elna catalog the RA3 is a "miniature aluminum electrolytic capacitor for audio. With the same size as that for Series RE3 miniaturized standard capacitors, a high resolution sound quality grade has been realized. The newly developed audio use material makes clear sound a reality. All lead wires are copper clad steel".

Denon chose RA3s over standard types, so while the electrolytics in the 4306 are almost 20 years old I decided to trust the sound quality and leave them as is. The cable layout is complex and dismantling the unit just to replace a few electrolytics wasn't worth the risk. So the only thing I did was to line up all the caps. I find this adds a nice Feng-Shui feel. I also replaced the metal foil tape on the chassis edge and blew the dust out.