PAO-A1HDCI Set-Up & Design Overview

Somebody forgot to tell the engineers at Denon that just because you can build a thing, doesn’t necessarily follow that you must build that thing. The more familiar I become with Denon flagship products, the more I realize two things: Denon is always the first to implement new technologies without consideration if the end result is a box that weighs and costs more than most mere mortals can swing. Enter the new POA-A1HDCI 10 channel amplifier whose name may be forgettable but its momentous stature isn’t. When I first saw the prototype at CES two years ago, I remember thinking I can’t believe they actually produced a multi-channel amplifier that makes their AVR-5805 flagship receiver feel envious. Standing in at a hefty 132 lbs, it’s the largest and heaviest amplifier I’ve ever tested. When Denon shipped it to me with their matching AVPA1-HDCI pre/pro on a large palette, my wife was concerned where the shipper was going to place it while I was trying to figure out how I would hoist these monsters up my flight of steps. The Denon separates actually took priority in my garage over my Acura TL, at least until I managed to get them installed into my theater room. I was more than a little excited to test out the new Denon gear which I pegged as being the hottest items to review in 2008. Now that they had finally arrived, I wanted to be sure they would live up to all the hype and deliver true high end performance one would expect from the very best “separates” components.

Set-Up

“It’s got handles,” Jeff Talmadge, Product Manager of Denon told me. “It should be a breeze to carry…” what he didn’t tell me was that the handles were on the back panel of the unit and that I’d have to upright row it up my flight of steps into my theater room. I instead opted to carry it up the old fashion way – bribing my neighbor with a cold beer to help me carry it and install into my Audiav Crystal A/V rack. The handles did come in handy when pulling it into my rack while my friend pushed from the front. Make no mistake this amplifier is a two man install job unless of course you’re a competitor on the Strong Man show.

With an almost endless array of configuration options, I had to really think which options best suited my needs. Thus I listed some of the most common configuration choices highlighting the one I used for my application.

Common Connection options:

• 5.1 Main Zone all channels bi-amplified
• 5.1 Main Zone all channels bridged for up to 4x power to each channel
• 5.1 Main Zone, Zone 2 and Zone 3 stereo, with Zone 4 mono
• 7.1 Main Zone, Zone 2 stereo and Zone 3 mono
• 7.1 Main Zone with Front left, right and center speakers bi-amplified
• 7.1 Main Zone with Front speakers bridged and Zone 2 mono
• 9.1 Main Zone and Zone 2 Mono

Editorial Note on Amplifier Connection Type Definitions

Bi-Wire: When using speakers that have independent input terminals for the woofer and tweeter drivers, this type of connection allows you to connect both terminals to the same channel of the amplifier via the Spk A and Spk B WBT connections. The main advantage to bi-wiring is lowering the effective wire gauge. There are minimal benefits to this connection scheme and we usually recommend going with lower gauge single wired solutions instead.

Bi-Amp: When using speakers that have independent input terminals for the woofer and tweeter drivers, this connection outputs one input signal from two amplifiers to each woofer and tweeter connection. During this mode, the ten channel amplifier becomes a 5-channel amplifier. This allows for a greater degree of isolation between the drivers and better amplifier control. Ultimate bi-amplified installations involved active crossover solutions but we’ve seen and heard benefits of passive bi-amplifying assuming the amplifiers power supply is capable of such an installation.

Bridge Mode: This connection allows you to use two amplifier channels to output opposite phase signals generated from one input signal. When you bridge an amplifier, you effectively double the output voltage with can yield up to 4 times the rated output power assuming the power supply can deliver that much current. This is a good idea for applications that require lots of power to reach high SPL’s but its important to note that each amplifier effectively sees ½ the rated impedance of the loudspeaker so if your speaker system is rated nominally at 4-ohms, be sure the amplifier is stable for two ohm loads before bridging it. Never bridge an amplifier that isn’t designed to do so!

Though I didn’t make use of the 10th channel for Zone 2 mono, I did get a chance to really punish this amp by bridging it for my reference speakers which dip dangerously low into the 2-ohm region while at the same time had it powering the rest of my surround speakers for a full 7.1, or in my case 7.4, spectacle. Unless otherwise noted, all of my listening tests were conducted via this loading scheme on the amplifier.

All of the connections I made between the POA-A1HDCI and the AVP-A1HDCI were via balanced cables furnished by Blue Jeans Cable. My reference gear consisted of all RBH Signature Special Edition speakers, two Velodyne DD-15 subwoofers, a Denon DVD-5910CI Universal DVD player and Toshiba HD-A2 HD DVD player and an XBOX 360.

POA-A1HDCI back panel view

If there was an award to be given for the most complex amplifier back panel, Denon would surely win it with the POA-A1HDCI. At first glance, it appeared to have as many connections as a flagship A/V receiver and was initially about as intimidating, but it’s important to break it down into sections and realize that it’s mostly just one amp module repeated 9 extra times. The POA-A1HDCI accommodates both balanced and unbalanced input connections. Each channel may be configured as “normal”, “bi-amp” or bridged as well be completely defeated. Each channel is labeled for a particular speaker but the channel assignment is ultimately dictated by the AVP-A1HDCI processor. The amp can be configured via switches for each channel on the back panel, or if you have the matching AVP-A1HDCI processor via the Link control which bypasses all back panel switches once you make the link connection and flip the control switch to AVP. It took me a few minutes to understand how to properly bridge two-channels.

• L1 & L2 > L1 (hot)
• L3 & L4 > L3 (hot)
• R1 & R2 > R2 (hot)
• R3 & R4 > R4 (hot)

Where for example L1 is the hot for the L1/L2 bridged amps and the Red (+) A speaker terminal for L1 is positive while the Red (+) A speaker terminal for L2 is negative. You cannot use speaker terminals B for bridging. Speaker polarity for bridged mode was poorly documented in the manual and is shown via a crude black and white connection diagram of a speaker being connected to the amp. In my opinion, they should have circled the + side for the bridged channels on the back panel for greater clarity but if you remember that “hot” implies amplifier input connection and + speaker polarity, you will get the connections right. Also note that the switch to select “normal, bi-amp, bridged” always points to “bridged” on the “hot” amp of the pair grouping. Once you have a channel pair configured into “bridged” mode, you can confirm it by selecting the amp pair on the front power meter which will illuminate the two associated amplifiers. Bi-amp connections and channel grouping work similarly to bridging except you connect the high portion of one speaker to the +/- terminals of one amp while connecting the low portion of the speaker to the +/- terminals of the adjacent grouped amplifier.

Screenshots from the AVP-A1HDCI Power Amp Configuration Screen

The Link control connects directly to the AVP-A1HDCI and can also be connected in series with another POA-A1HDCI for a 20 channel application. Not even I could ever envision this, but I am sure someone with a deep enough wallet and passion for the hobby could make it a reality. This is accomplished via the mode switch which has three settings “option” for future use, “1” and “2” for master and slave operation, respectively. It’s pretty neat to have the ability to fully configure the amplifier from the processor and I am hopeful they can take better advantage of this feature perhaps by offering power monitoring via future firmware upgrades to the AVP-A1HDCI processor. There is also a 12V trigger for those not using the Link control feature found on the matching pre/pro. An RS-232C connection (first time I’ve ever seen this on a power amp) is available for external control as well.

The Denon multi-channel power amplifier features three channel level meters across its front-panel. I like the idea here but don’t particularly care too much for the white backlighting. Personally I’d rather they run across the street to McIntosh labs and replace them with blue ones and make the panels larger so they can be more easily seen from a distance. Regardless, I like the idea of monitoring power with old fashion VU meters and it gives the amplifier a nice high end appeal to it.

You can select the output level (dB indicator) of each power amp channel by using one of the channel level meters. The channel level meter to the left of the unit's front-panel displays the output level of Left 1, Left 2, Left 3, or Left 4 channel of the amplifier. The channel level meter to the right of the unit's front-panel displays the output level of the Right 1, Right 2, Right 3, or Right 4 channel of the amplifier. The channel level meter located in the center of the front-panel of the amplifier display the output level of the Left 5 or Right 5 channel of the amplifier. I monitored the front 3 channels, especially since my mains were configured in bridged mode to see if I ever drove the needles into red.

According to the manual, the front panel level indicators represent the following power levels which are more ideal than a reality for bridged amplifiers. Rarely have I come across an amplifier that can truly deliver 4x the power when bridged, especially into a 4-ohm load as you will see in the measurements portion of this review. I believe however that these power figures are more representative of dynamic rather than sustained at least for bridged modes of operation.

Design Overview & Build Quality

The Denon POA-A1HDCI is a no holds barred, no compromise multi-channel THX Ultra2 certified amplifier design that represents some of the best engineering I’ve seen to date in a traditional linear Class A/B amplifier. Each of the unit's ten amplifier channels feature a discrete power amplifier assembly and DC power supply to eliminate interference between channels. The POA-A1HDCI is equipped with eight individual transformers to supply power to each discrete circuit and uses 4 main power transformers to drive the ten channel power amplifiers with separated coil winding for pure audio playback. High current DC rectifiers and companion high current filter/storage capacitors (20 x 10,000uF 80V 105 deg C rated to yield a whopping 200,000uF total storage capacity) ensure stable performance with low impedance (4-ohms) speaker loads, even in bridged mode. In fact this is the industry's first 4-ohm UL rated amplifier I’ve come across. This is quite an engineering feat for a multi-channel amp which requires a helluva lot of heat sink area and high current devices to double down its power with halving load impedance while meeting the stringent heat dissipation requirements of UL. To do 150wpc into 8-ohms like this amp is rated, you need at least 55V rails so the 80V caps have more than enough design margin to ensure this amp can deliver more than rated power and not get wigged out during high line voltage conditions when plugged into a power conditioner that does voltage regulation. The POA-A1HDCI appears to be a very conservatively rated 150wpc x 10 amplifier with good headroom to help prevent clipping during high power demands.

Editorial Note on Amplifier Clipping

Once an amp runs out of headroom it enters a mode commonly referred to as “clipping”. When an amplifier clips it essentially sends a square wave response or DC voltage to the speaker which after only a few short cycles can fry a tweeter's voice coil or burn out series inductors in the crossover sections.