Review and Measurements of Denon PMA-50 Amplifier

[restorer-john]

Huh?

4ohm requires 2x the wattage [2.83^2 / 8 = 1W ; 2.83^2 / 4 = 2W] and since 54 = 2*27, an 85dB @2.83Vrms sensitive 8ohm speaker and an 85dB @2.83Vrms sensitive 4ohm speaker will get to identical loudness.

Except 4 ohm speakers are not sensitivity rated with 2.83V, they are rated at 2V...

Speakers are rated xxdBSPL/W- 8ohm speakers use 2.83V, 4 ohms use 2V.

 

[restorer-john]

There is a single spike at 840 kHz or so, which is likely the switching frequency.

Is that a new record for switching frequency? That's well into the AM band. How does am radio go near it?

 

[amirm]

Is that a new record for switching frequency? That's well into the AM band. How does am radio go near it?

Radio? What is that?

 

[Willem]

This is indeed not state of the art but much better than many other lifestyle units. I note that here in Europe it has been discontinued and my guess is that the lack of inbuilt streaming is responsible.
Another (lacking?) feature that is not mentioned is auto on/off. I have that on our little Ava Maestro 50 and it allows me to put the amp out of sight and turning it on and off by sending a signal from tbe CCA that is its only source.
My Maestro has a similar limited output. That was not enough to drive my inefficient Harbeth P3ESRs. It works fine with the more efficient QAcoustics 3010. So even for a small lifestyle unit power is an issue since many small high quality speakers are inevitably inefficient.

 

[BillG]

Bluetooth is not streaming. And it is lossy so not really the same thing.

Yes, it is, in that it's wireless transmission of digital data - I can go all over the Web and find references to "Bluetooth streaming".

I'm well aware of how it works in regards to compression and lossiness. If its lossiness would cause one to exclude it as a streaming method, other than a degradation in sound quality caused by certain codexes, that's a bit of weak argument in light of the various formats used to store digital media locally. Also, the newest Bluetooth codexes are rapidly approaching transparency, if they've not done so already.

Anyway, I've no interest in getting into a raging debate with you over it, as I'm not really the obsessive type...

 

[restorer-john]

Also, the newest Bluetooth codexes are rapidly approaching transparency, if they've not done so already.

How close are the new BT standards to 'transparent' in your experience? Are there still the issues of digital level/volume control causing very audible distortions at modest attenuation?

My experience with various BT 4.0 implementations left me cold, but it's marched on since then.

 

[MZKM]

Except 4 ohm speakers are not sensitivity rated with 2.83V, they are rated at 2V...

Speakers are rated xxdBSPL/W- 8ohm speakers use 2.83V, 4 ohms use 2V.

I have never seen a speaker (speaker, not speaker driver) rated at 2V, they almost always either use 1W or 2.83Vrms. 2.83Vrms is 1W into 8ohm and 2W into 4ohm, hence why it’s used.

If the same sensitivity, and the sensitivty is given as 2.83Vrms, this Denon amp will get equally as loud for 8ohm as for 4ohm speakers.

 

[MZKM]

Speakers sensitivity is dB/W/1m and not Vrms/W/1m! At exactly the same voltage applied the 4 Ohms speaker will benefit of double amperage, hence double of power, so that means 3dB more per each speaker used.

I didn’t say Vrms/W/1m.

Look up the specs for most any speaker, it most always will be like this:

8 ohm nominal:
XdB / 1W / 1m (equivalent to XdB / 2.83Vrms / 1m)

6 or 4 ohm nominal:
XdB / 2.83Vrms / 1m

 

[pjug]

I didn’t say Vrms/W/1m.

Look up the specs for most any speaker, it most always will be like this:

8 ohm nominal:
XdB / 1W / 1m (equivalent to XdB / 2.83Vrms / 1m)

6 or 4 ohm nominal:
XdB / 2.83Vrms / 1m

https://www.harbeth.co.uk/hifi-speaker/3/Harbeth-SuperHL5-plus-loudspeaker.php
Impedance
6 ohms, easy to drive
Sensitivity
86dB/1W/1m

I am not picking a side in the argument, just saying it might be specified either way.

 

[MZKM]

https://www.harbeth.co.uk/hifi-speaker/3/Harbeth-SuperHL5-plus-loudspeaker.php
Impedance
6 ohms, easy to drive
Sensitivity
86dB/1W/1m

I am not picking a side in the argument, just saying it might be specified either way.

That seems to be an error on Harbeth’s part, as Stereophile measured the speaker at 86dB / 2.83Vrms / 1m.
If that speaker was truly 86dB/1W and 6ohm nominal, then at 2.83Vrms it should be 87.2dB.

 

[pjug]

Still listed on the Denon USA website as "for sale" for $599 list.

It appears to be a better and more powerful variant of the Teac AH-01 (~30wpc) ICEpower DAC/Amp that i brought with me to Panama when I moved here in 2012. The Teac lasted 6 years, but was likely damaged when lightining hit the utility pole next to my rental house and took out other electronics - including my UPS/Battery Backup unit.

It uses Qualcomm DDFA, like the NAD 7050 and the Sonos amps that Amir reviewed.

 

[pjug]

That seems to be an error on Harbeth’s part, as Stereophile measured the speaker at 86dB / 2.83Vrms / 1m.
If that speaker was truly 86dB/1W and 6ohm nominal, then at 2.83Vrms it should be 87.2dB.

Maybe, but sometimes the measurements in reviews don't match manufacturer specification.

 

[anmpr1]

This seems like it's geared toward desktop/office/small room given the features and power, and it would appear it would fit that application well. I can live with modest power 98% of the time.

I would think that for a desktop/PC thing, it would make at least as much sense, and probably be cheaper/more ergonomic, just to buy a set of powered speakers.

 

[dkfan9]

Except 4 ohm speakers are not sensitivity rated with 2.83V, they are rated at 2V...

Speakers are rated xxdBSPL/W- 8ohm speakers use 2.83V, 4 ohms use 2V.

JBL, ELAC, Klipsch, and Bowers and Wilkins all use 2.83V no matter the impedance, as does Stereophile. And in order for a speaker with impedance swings (almost all of them?) to have flat frequency response at a constant volume level from a standard solid state amp (DF>20), it should be flat relative to voltage rather than wattage.

All of which makes this amplifier's identical voltage output into 4 and 8 ohm loads ideal. On the other hand, I wonder about AM performance too.

A question for @amirm : The SNR at 5W is 20dB below the max output SNR, but output should only be ~10dB higher (5-50W). Where is the extra 10dB of SNR at max output coming from?

 

[pjug]

All of which makes this amplifier's identical voltage output into 4 and 8 ohm loads ideal. On the other hand, I wonder about AM performance too.

I don't get what you are saying here. This is what pretty much all amplifiers do, unless they are current-drive amps. Thus the rating of about 2X max power driving 4 ohms compared to 8 ohms.

 

[pjug]

That seems to be an error on Harbeth’s part, as Stereophile measured the speaker at 86dB / 2.83Vrms / 1m.
If that speaker was truly 86dB/1W and 6ohm nominal, then at 2.83Vrms it should be 87.2dB.

Also, some speaker manufacturers just give the spec in dB. I guess you could assume this means at 2.83Vrms but personally I would wonder what the spec means if it is not an 8 ohm speaker.

 

[Xulonn]

I note that here in Europe it has been discontinued and my guess is that the lack of inbuilt streaming is responsible.

My earlier comment in this thread stated that the PM-50 was still available via Denon's USA website, but that was in error. It has been replaced by the PM-60, and I edited/updated my previous post to reflect that. Both have Apt-x Bluetooth streaming as input, and I didn't motice any significant differences in the specs.

 

[SEKLEM]

54W/4R without clipping is pretty much power actually. For small rooms and destop use that is more than enough for sure. Many people are happy with 5W and 5% distortion...

I use Icepower 50ASX2 modules in my active speakers and for speaker prototyping.

That’s the module Amirm will be testing.

 

[dinglehoser]

The DUT is mine. A few functional things to note:

* As with anything with an OLED screen, permanently leaving it on results in burn-in. Unfortunately, there is no display auto-off feature.

* BT connectivity is flawless and sounds subjectively as good as a direct digital or analog connection, at least through connected speakers.

* The PMA-60 is, from what I understand, internally nearly identical.

* It's marketed as a desktop "lifestyle" integrated, and Denon spill ample verbiage on its internal headamp. I'm curious as to its performance and whether it's on discrete circuitry (good) or just tapped from the DDFA output (yuck).

 

[maty]

[Polish] https://audio.com.pl/testy/stereo/wzmacniacze-stereo/2388-denon-pma-50

to English:

* https://translate.google.com/translate?hl=&sl=auto&tl=en&u=https://audio.com.pl/testy/stereo/wzmacniacze-stereo/2388-denon-pma-50

* https://www.translatetheweb.com/?fr...y/stereo/wzmacniacze-stereo/2388-denon-pma-50

[ Denon accurately defined the PMA-50 output power. We expect 2 x 50 W at 4 ohms, and we obtained 2 x 52 W, and 2 x 26 W with twice the impedance. The same power is obtained when driving a single terminal.

Due to the presence of protection circuits that limit the voltage at the output (to avoid high distortion), the measurements do not refer to the usual THD + N = 1%, but just to the level at which the protection is activated.

Sensitivity for analog inputs is close to 0.17 V. The noise level is already severe (at least in the measurements, it is high frequency noise, so their impact on the sound is indirect), the S / N ratio is only 63 dB, and the dynamics barely 77 dB... ]

Ejem...