Denon PMA-A100 Integrated Amplifier Review & Measurements

It's not often we get the chance to review an integrated amplifier from Denon. This is a high-end product from a company who we've determined in the past REALLY knows how to make good amps. So when they announced the PMA-A100 would be part of their 100th anniversary product line-up, we asked for it. And we had high expectations.

Turns out Denon met our expectations and even blew by them in some areas. The A100 is a stereo amp that weighs nearly 57 pounds and even has cast iron feet. There are also hardly any lights on the front of the unit, making it a truly audiophile product - with nothing wasted on unnecessary displays or LED status lights. A very dim orange input selection light sits atop the source knob and the green power light will flash red when you mute the amp or turn solid when you power down the unit into standby mode. You know it's a serious amp when the user manual is only 10 pages long. It's all power and no frills - just like it should be.

While we're on the topic of features, or lack of them, let's talk about what it does have. The PMA-A100 has 7 inputs including 2 recording devices, phono, CD, tuner, and 2 line inputs. What that means is that in a 2-channel system you're going to have all you need. The phono inputs also have the ability to switch between MM and MC-style cartridges. You also have Power Amplifier direct inputs - this is a direct feed into the amps and it will bypass all other electronics, relying on the source device's output levels for volume control. On the back, both the Phono and CD inputs are gold-plated high quality connectors and there is a preamp output in addition to the two recorder outputs. Even the non-programmable remote is audiophile, made from a brushed aluminum case and featuring metallic buttons and a narrow, elongated profile. Most of the remote is designed to control a CD source. It's every bit as simple as the front of the amp, though for us it wasn't much good for more than volume and power controls.

One absent feature is a line of power outlets on the back that can act to switch on devices when the PMA-A100 is turned on. As more and more audiophiles are turning to power conditioners, that's not entirely surprising. For speaker connections, the A100 has 4-pairs of high-end 5-way binding posts that can be used for bi-wiring a pair of speakers if desired. We've found bi-wiring to be mostly a waste of time, but some people have the cables lying around and enjoy it, so there you go - it's ready for you.

As for power, the A100 puts out 80 watts per channel into 8-ohms at .07% THD. Dynamic power is rated up to 160 watts into 4-ohms, but this is likely continuous given what we're seeing in the amp. We bench-tested this amp below and so check out how it performs when you halve the impedance. And the construction of the amp is beautiful inside as well as out. The power layout is symmetrical with dual transformers, giant 71V 12000 microfarad capacitors, and big heatsinks. It's a work of art.

Listening Tests

The stereo amps were put to good use, driving a pair of Salk Songtower speakers in our reference room. And honestly, the louder we played this amp, the better it sounded. I mean it, we had this thing cranking and we couldn't get any audio to distort. The speakers just asked for more and we could quickly tell that the contest between our ears and the power of the PMA-A100 was going to be won by the amp.

We ran a lot of music through this integrated amplifier, including one of our favorites from Jeff Wayne - the Musical Version of the War of the Worlds. We also played tracks from Seal, Blue Man Group and several albums from Steely Dan. The amps were extremely capable at pushing the low frequencies out of our Salk speakers to the point where it felt as if we had a small subwoofer in the room. On the high end, the tweeters retained all the detail of the tracks we played, never breaking up or sounding brittle. This amplifier just sounds refined and true.

Denon PMA-A100 Measurements & Analysis Report

By: Gene DellaSala

All measurements were conducted using our Audio Precision APx585 8 Channel HDMI Audio Analyzer. I did some quick spot-checking on the PMA-A100 amplifier gain structure and found it measured 29dB (into 8 ohms) as specified by Denon.

Signal to Noise Ratio

Denon PMA-A100 SNR @ 1 watt (unweighted)

The Denon PMA-A100 measured 78dB SNR at 1 watt with 100mV input signal.  This is a good measurement but not as stellar as we've seen on other high quality gear.  At rated power (80 watts), the SNR was 98dB.

Frequency Response

Denon PMA-A100 Frequency Response

The Denon PMA-A100 exhibited ruler flat frequency response for the full audio bandwidth even when driven at 100wpc into 8 ohms which is above its 80 watt power rating.  The -3dB point is around 80kHz which is the limit of the Audio Precision test equipment.

Power Measurements

Using our Audio Precision APx585 8-channel HDMI analyzer, we conducted a full barrage of multi-channel amplifier tests on Denon PMA-A100. We tested power using three methods all of which were taken at < 0.1% THD + N:

• Continuous Full Power Bandwidth (CFP-BW) from 20Hz to 20Khz into 8 and 4-ohm loads (up to two-channels)

• 1kHz Power Sweep vs Distortion (1kHz PSweep) - popularized by the print magazines, this is an instantaneous power vs distortion test at 1kHz. The problem with this test is it often masks slew related and or frequency response problems some amplifiers exhibit at the frequency extremes, and thus inflates the measured power results. It does provide an instant gratification # for consumers to argue over on the forums so we are now incorporating this test to please the masses.
  

• Dynamic PWR - 1kHz CEA-2006 Burst Method testing. This is a dynamic power measurement adopted from the car industry similar to IHF method only a bit more difficult for an amplifier and more representative of real musical content.

Keep in mind most review publications don't do continuous power measurements and they usually publish power measurements into clipping at 1% THD + N. Our measurements are very conservative as we use a dedicated 20A line with no Variac to regulate line voltage.  We constantly monitor the line to ensure it never drops more than 2Vrms from nominal which in our case was 120Vrms. 

For more info on amplifier measurements, see The All Channels Driven (ACD) Test

Denon PMA-A100 Power Sweep Test (1kHz)
Left Pic: 2CH driven, 8 ohms;  Right Pic: 2CH driven, 4 ohms

Denon PMA-A100 Dynamic Power Test (1kHz)
Left Pic: 2CH driven, 8 ohms;  Right Pic: 2CH driven, 4 ohms

# of CH	Test Type	Power	Load	THD + N
1	CFP-BW	123 watts	8-ohms	0.1%
1	CFP-BW	195 watts	4-ohms	0.1%
2	1kHz Psweep	108 watts	8-ohms	0.1%
2	1kHz Psweep	115 watts	8-ohms	1%
2	1kHz Psweep	155 watts	4-ohms	0.1%
2	1kHz Psweep	165 watts	4-ohms	1%
2	Dynamic PWR	148 watts	8-ohms	1%
2	Dynamic PWR	245 watts	4-ohms	1%

Denon PMA-A100 Power Measurement Table

Denon rates the PMA-A100 as follows:

• 80 watts RMS @ 8-ohm from 20Hz to 20kHz  (0.07% THD)
• 160 watts dynamic @ 4-ohm @ 1kHz (0.7% THD)

Denon's amplifier ratings are a bit peculiar.  They could have very easily rated this a 120wpc amplifier and nobody would have argued it.  I assumed they derated the power as a marketing strategy so that reviewers like myself would praise them from being ultra conservative.  Let me just pause for a moment and throw some love and praise at Denon.....OK now that that's over, you would think Denon would have at least specified 4 ohm power as continuous and NOT dynamic since this amp can clearly deliver 165 watts continuously with both channels driven into 4 ohms.  At any rate, the PMA-A100 has a sturdy power supply and ample output current.  In fact, I'd say looking at the measurements, its clear Denon employed some current limiting when driving this amp into 4 ohms as it didn’t quite double down in power but still provided way above specified power.  The PMA-A100 should be right at home driving virtually any moderately efficient speaker to reference levels.

FFT Distortion Analysis

Denon PMA-A100 FFT Distortion Analysis
(left image @ 1 watt ; right image @ full rated power)

I ran FFT distortion plots at 1 watt (left pic) and full rated power (right pic) to determine how clean this amplifier really is.  At 1 watt, the spectral distortion was good that the harmonics were below measurable limits of my test gear!  At full rated power (80 watts) the 3rd order harmonic distortion product was higher than the 2nd which is usually undesirable but the levels are still exceedingly low (28.176 + 57.359)dBV being 85.5dB down from the fundamental or 100*alog^-1(-85.5/20) = .0053%  

Crosstalk

PMA-A100 All-to-One Crosstalk at Full Rated Power

I measured each idle channel one at a time while the other acted as the disturber to determine the worst case channel to channel crosstalk.  The PMA-A100 produced some of the lowest channel to channel crosstalk measurements I've ever taken on an amplifier!  This is no surprise given the immense real estate this amplifier has for only two channels.  Whether I measured at 1 watt or full rated power, channel to channel crosstalk was better than 100dB for the entire audio bandwidth.  Note how at even 80kHz this amplifier produced superb results.

Conclusion

Look, we know it's $2500 - but that's OK. Some people want to spend good money on a quality two channel system. With the PMA-A100 you'll spend a good deal of money. But you'll get a REALLY good two-channel system as a result. If you have the money, we're recommending this.

Unless otherwise indicated, this is a preview article for the featured product. A formal review may or may not follow in the future.