Power Amplifiers

Anthem P2 Two-Channel Power Amplifier

ARTICLE INDEX

 

Introduction

Anthem's statement multi-channel power amplifiers are called the P series. They come in two versions, a five-channel (P5) and a two-channel (P2). My home theater test lab has a Classé CA-5200 200 watt x 5 amplifier which works great for the majority of applications, but it is driving electrostatic speakers (ESLs), and for a handful of Blu-ray movies, the amplifier will go into protect mode when at high volume, because ESLs typically have a very low impedance (1 ohm) in the high frequency range. So, I figured I just need more power for the front two channels, since they are set at higher volume than the side and rear channels. My center channel speaker is a conventional cone design, so it does not have this problem. I turned to Anthem, and requested their P2 to see if it would solve my problem. It solved my problem, and I think now all the cockroaches that had been hiding in the walls have now left the building.

Specifications

  • Design: Two-channel Power Amplifier; Class AB
  • Power: 325 Watts RMS x 2 into 8 Ohms, 500 Watts RMS x 2 into 4 Ohms
  • FR: 10 Hz - 150 kHz, - 3 dB
  • THD+N: 0.008%
  • Input Impedance: 18 kOhms RCA, 22 kOhms XLR
  • Inputs: XLR and RCA
  • Dimensions: 9.4" H x 19.25" W x 22.5" D
  • Weight: 75 Pounds/each
  • MSRP: $4,299 USD
  • Anthem AV
  • SECRETS Tags: Anthem, Amplifiers, Power Amplifiers, Class AB

The Design of the Anthem P2 Power Amplifier

The Anthem P2 and P5 are modular power amplifiers, meaning that each amplifer has its own power supply circuitry except for the main transformer, which delivers rail voltage AC to each module.

The amplifier is biased as Class AB, single-ended. However, the XLR input is balanced. This means there is signal inversion on one conductor in the circuit immediately following the XLR input jack. The two signals, one inverted with respect to the other, are combined before being sent to the input stage, which is single-ended as is the remaining portions of the amplifier, e.g., the output stage. This provides for Common Mode Rejection (CMR) of any noise that is picked up along the way coming in from the cable feeding the XLR input.

The single-ended nature of the amplifier allows it to drive very low impedance loads, which is the principal reason I chose the P2 to try out with my ESLs (besides the fact that the P series is highly regarded). Each module has 14 output devices, which is another reason it can work with low-impedance loads.

The rear panel of the P2 is easy to deal with because the chassis is the same one as in the P5. So, the two sets of speaker binding posts are spread out nicely for big fingers like mine, and the switches for changing the input from XLR to RCA also have plenty of room. The AC recepticle is a two-prong non-grounded type. Even though there are only two modules in the chassis, it still weighs a hefty 75 pounds, and the two handles on the rear are useful for moving the amplifier.

 


The Anthem P2 Power Amplifier In Use

OK, so here was the setup for testing: OPPO BDP-95 universal player, Denon AVP-A1HDCI SSP, Classé CA-5200 multi-channel power amplifier (5 x 200 watts), Anthem P2 driving the front main left and right ESL speakers (Threshold ES-500), Paradigm Reference Signature C5 center channel speaker, and Final Sound ESLs for the surrounds. Cables were Emotiva.

First, let me say that the reason the Classé was shutting down when I played the system loud with the movie shown below, is that the CA-5200 is fully balanced, and this reduces the ability to play into unusually low impedance loads. Secondly, ESLs have low sensitivity, so you have to crank up the volume control more to have high volume than you would with high sensitivity speakers. So, the CA-5200 works for 99% of my listening (no problem with my music listening, just the movie sound tracks which have explosive sequences). Third, the CA-5200 is rated at 200 watts into 8 ohms. I also have a pair of Classé CA-M600 monoblocks, which are rated at 600 watts RMS output. Those have no problem with the sound tracks, but they are in use in another lab.

So, on with the movies.

The scene I was having trouble with is chapter 3 from House of Flying Daggers. It's the dance scene where the heroine responds to crystals being thrown against numerous drums that encircle her by flinging sashes from her silk robe against the same drums that the crystals struck. There are very intense, very high frequencies, and the Threshold speakers have very low impedance at high frequencies.

anthem-p2-amplifier-movie-daggers

Well, regardless of the volume, there was no shutdown of either the CA-5200 or the P2 (the rear channels are also ESLs, but surround channels have sound levels much lower than the mains). If I had turned the volume up any louder, my ears would have gone into shutdown, but not the amplfiiers. If you don't have this film on Blu-ray, get it, because it is great for demos with your friends. Not the entire movie, just chapter 3.

Here is another movie that is not all that great in storytelling, but chapter 22, the attack scene, is wonderful as a demo of your home theater, and it is also the best air attack war movie scene I have ever encountered. Again, when the machine guns were firing, bullets were ricocheting, and bombs were exploding, the P2 handled those Carver Mark IV's with a steel grip; no problemo, and this is a scene where it would be ridiculous to watch at low volume.

anthem-p2-amplifier-movie-pearl-harbor

I also listened to some surround sound SACDs, and the P2 fit right in with the beautiful sound of the CA-5200, which, by the way, like the P2, is made in Canada.

With that problem now out of the way, let's take a look at the performance on the bench.


The Anthem P2 Power Amplifier On the Bench

All distortion measurements were made within an 80 kHz bandwidth, and using the XLR inputs on the P2, into 100 kOhms, except where noted.

At 1 kHz and 10 volts into my Carver Mark IV ribbon speaker, distortion was only 0.002%. The fact that the second and third ordered harmonics were about the same size was reflected in a very musical sound quality, with no harshness.

anthem-p2-amplifier-1-khz

Using a combination of 19 kHz and 20 kHz sine waves, the B-A peak at 1 kHz was 82 dB below the fundamentals.

anthem-p2-amplifier-19-khz-20-khz

IMD, using 60 Hz and 7 kHz, was only 0.003%. This is very good performance, and means the sound will have plenty of detail, which is what I heard.

anthem-p2-amplifier-imd

THD+N vs. Frequency showed a flat spectrum of 0.002% out to 2.5 kHz, then a rise to about 0.05% at 20 kHz.

anthem-p2-amplifier-thd-plus-n-vs-fr

Here is the impedance/phase plot for the Carver speaker.

anthem-p2-carver-speaker-impedance-phase

The power output spectrum at 8 ohms load shows the soft knee at 20 watts, and the hard knee at 340 watts, with clipping (1% THD+N) at 380 watts.

anthem-p2-amplifier-thd-plus-n-vs-power-8-ohms

The 4 ohm spectrum has the soft knee again at 20 watts, but the hard knee is at 540 watts (the hard knee is the "practical" limits of the amplifier), and clipping at 600 watts.

anthem-p2-amplifier-thd-plus-n-vs-power-4-ohms

The measured frequency response was 10 Hz  -200 kHz, -2.5 dB.

anthem-p2-amplifier-fr


Conclusions About the Anthem P2 Power Amplifier

Well, the P2 certainly solved my problem with using ESLs at high volume. From what I have heard, the outputs can be shorted and it still won't shut down (one of my writers took the challenge, and it remained on and ready to rock & roll. The P2 also sounds very good, and of course, this is the most important thing about any amplifier. In any case, if you have speakers that dip into the low range of impedance and are not very sensitive, the P2 would be an excellent solution.