I guess I wasn't exactly clear--I was referring to voltage equality at max power output, and along with that, THD+N equality up the voltage ladder between 8 and 4 ohm loads. Obviously any reasonably low output impedance amp will deliver double wattage when speaker impedance drops, until it hits its power limits. See the NAD C 328 and D 3020 for Class D integrated amps, and almost any AVR for A/B amps, which do not double their 8 ohm power into 4 ohm loads.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.
That website tends to measure more noise than other sources. See the Denon AVR-X5200W at audio.com.pl and at Sound and Vision, the Anthem STR at audio.com.pl and at Stereophile, and the Yamaha A-S801 at audio.com.pl and at Audioholics. Audio.com.pl are the ones out of step with everyone else on noise figures, not @amirm , so I would look to them for answers. I've got no explanation but many entirely unsubstantiated guesses: most amps filter 60hz+H noise better than 50hz+H noise, European models have some additional circuitry that generates noise, audio.com.pl has a noisier signal chain, or audio.com.pl has noisier power at their testing location or is located near some other noise-generating source.[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...
Got it. Speaking of max power spec, it is unfortunate that amplifier manufacturers are advertising the 4 ohm power spec without making this clear, like Denon is doing https://usa.denon.com/us/product/hifi/amplifiersI guess I wasn't exactly clear--I was referring to voltage equality at max power output, and along with that, THD+N equality up the voltage ladder between 8 and 4 ohm loads. Obviously any reasonably low output impedance amp will deliver double wattage when speaker impedance drops, until it hits its power limits. See the NAD C 328 and D 3020 for Class D integrated amps, and almost any AVR for A/B amps, which do not double their 8 ohm power into 4 ohm loads.
My power measurements are for clean power. For dynamic range I usually allow the amp to go to max power, clipping and all. This is why I just added the 5 watt measurement. Indeed when testing this amp, I first stopped prior to clipping and got good few dBs lower dynamic range.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?
Yes, very confusing, especially for Denon, who sells AVRs that rate power output for 8 ohms (ignoring the absurd headline 800 watt one channel max burst x however many channels BS). I've finally conditioned myself to look at mini amps as 4 ohm rated, but I'm still learning to look at the numbers like I look at AVR headline numbers since so many "50 watt" mini amps are 50 watt at 10% THD (obviously not the case here).Got it. Speaking of max power spec, it is unfortunate that amplifier manufacturers are advertising the 4 ohm power spec without making this clear, like Denon is doing https://usa.denon.com/us/product/hifi/amplifiers
Gotcha. Makes sense, thanks for the clarification. The 5W number certainly makes it easier to compare across publications as well (e.g. Stereophile at 1W/8 Ohm) when comparing amps (noise floor is my top interest as far as my own future amp shopping)My power measurements are for clean power. For dynamic range I usually allow the amp to go to max power, clipping and all. This is why I just added the 5 watt measurement. Indeed when testing this amp, I first stopped prior to clipping and got good few dBs lower dynamic range.
That website tends to measure more noise than other sources...
Is that a new record for switching frequency? That's well into the AM band. How does am radio go near it?
I see that IRF2092 has 800KHz switching freq. too, so I guess it's a legit freq.
It's interesting. Especially since the distortion and other numbers match other sources quite well in every comparison I've done, as they do here with the PMA 50.You are right about the numbers. SNR-A at 1 watt differ too much. Why? I do not know.
This picture is a picture of PM-30, not PM-60.Denon PMA-60
http://www.on-off-on.ru/catalog/hi-fi-komponenty/009911/
Picture optimized
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