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. 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 after 14 years.

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

Dolby Digital EX, Dolby Digital, Dolby Pro Logic IIx, DTS-ES, DTS 96/24, DTS Neo:6, DTS, Audyssey

Front 130 W + 130 W (8 ohms, 20Hz - 20kHz, 0.05 % THD)
Center 130 W (8 ohms, 20Hz - 20kHz, 0.05 % THD)
Surround 130 W + 130 W (8 ohms, 20Hz - 20kHz, 0.05 % THD)
Surround back 130 W + 130 W (8 ohms, 20Hz - 20kHz, 0.05 % THD)

BELOW: the rear has a complete jack panel with optical inputs. HDMI/1080p pass-thru and S-video inputs as well(!) It also has ethernet for connection to a home network which was very progressive for 2006.

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 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.

THE MICROPHONES
BELOW: Two microphones were available for Denon receivers during this period: the DM-S205 and 305. The 205 came with the AVR4306. The 305 came with the 5805, 3805, 2805 and 4806. Both look identical but the 305 has a metal shell while the 205 is all plastic. It has been said that both have the same specs. I'm not so sure.

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. I believe the 205 is the mic to use with the AVR-4306.

MICROPHONE EQ PROCESS
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.

The owners manual is misleading in that it implies you only need to sample multiple locations for the Audyssey surround effect. Yes you can save time by EQing a couple of locations and calculating the room. But in reality you should always sample a minimum of SIX locations to correctly setup the unit.

THE PREFERRED METHOD:
- I use a tripod with the mic on top. The first position should be with the mic in the center seating position. The 2nd and 3rd positions should flank it at both sides (ends of the sofa).
- Move the mic forward 2 feet for the next three samples. The 4th should be in the center and 5th/6th repeated on the end spots. When the 6th position is done it will read "Finished" on screen. For accuracy I use 6 small coins to mark each spot to position the tripod.

BELOW: The RC-1024 remote is complex and I didn't care for it. Its a Universal with several zone features and macros, and each input selection creates a different 'overlay' in the window. This means it can suddenly stop working until you find out what mode you've pressed. My family could never figure it out. A few months ago the power Off button stopped working so I replaced it with a Harmony remote.

BURR-BROWN DACS
Burr-Brown of Arizona manufactured a variety of DACs since the 1980s which are 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. Burr-Brown and Denon became synonymous during this period.

In 2000 Burr-Brown was sold to Texas Instruments (Dallas). By 2018 Denon appeared to have moved away from using Burr-Brown DACs. While the 4306 is said to use BB PCM1791A chips the modern-day Denons 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.

MODS and RESTORATION
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. Maybe the service center left it off when I had the firmware updated in 2008, weird. 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. While this wouldn't have caused any audible issues it looked sketchy. 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 were 14 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 couple of electrolytics on each pre-out wasn't worth the risk. If I were to damage it Denon would be little help as parts are doubtfully available in the 2020s. 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.

CONCLUSION
This 15 year old digital receiver (multi-channel digital preamp) is superior, quiet and musical. It has a wide variety of cinema and music effects that are valid in 2023. As one of the original Denon Burr-Brown units designed for the audiophile market its build quality and 24-bit/192-kHz DACS place its performance above many modern products. Well done Denon.

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