Electro said:
This has always been very puzzling to me :? I can understand the reasons behind level matching but why would you compare two amplifiers that you were testing at only one volume level ?
Here are few tips I picked up along my audiophile journey how to break through the cheats and manipulations of manufacturers. The technically more erudite members please correct if I have something wrong in the list.
The most important specification in an amplifier:
- power output (continuous W RMS in 8 ohms 20Hz-20kHz at less than 1% distortion, both channels driven)
- minimum speaker impedance capability (if something like 2 ohms power rating is shown but in IHF or musical power, not RMS, they are manipulating)
- pre and power gain (if it is bigger than the amplifier you are comparing it to, it will sound better, louder, lively, clear, transparent, present)
- input sensitivity (if it is lower than the amplifier you are comparing it to, it will sound better, louder, lively, clear, transparent, present)
Human hearing is not linear and to us at lower levels louder is better, clearer, lively, transparent, powerfull. Manufacturers are quite aware of this fact and cheat with added loudness gains instead of real amplification. The only real power your amp has is in the continuous W RMS in 8 ohms 20Hz-20kHz at less than 1% distortion, both channels driven.
Only way around this is to level match two amplifiers and compare them at the same loudness +/-0.1dB, before clipping. You can do multiple tests at different loudness levels, as long as you have them level matched with a microphone recording the output, not using the scale on the volume knob.
Considering most speakers today are under 90dB, it feels much better when the amp pushes the speaker much earlier in the volume knob. We all have to admit that an amplifier that needs to be turned further on the volume knob feels emasculating. What is actually better is when the amp can be turned up all the way in without having it stressed (distortion, noise). Always good to have the speakers bottoming out on you before the amplifier does. But also no one wants to feel like a eunuch when he grabs the boob knob.
Simple example with my amp (so others don't feel attacked). The Roksan Kandy K2 has more power than the more expensive Caspian M2. Manufacturer says the topology is very similar and they share a lot of parts, so build quality is more or less the same. Biggest difference in architecture being the Caspian has balanced XLR outputs and unlike the MOSFET Kandy, it is a bipolar topology. So why is it exactly double the price?
Dealers and buyers will tell you the Caspian sounds more powerfull, bigger, more in control, more detailed and it justifies the added expense. Lets ignore the dealers since they have much bigger markup for selling the Caspian, focus on the buyer.
Roksan Kandy K2 BT:
Line level input sensitivity: 500mV
Total gain from pre and power: 37.3dB
Roksan Caspian M2:
Line level input sensitivity: 240mV
Total gain from pre and power: 40dB
So the Caspian is more sensitive and has significant 3dB loudness gain ahead of the Kandy. If you think 3dB is insignificant, bare in mind it takes double the power from the amp to make a speaker 3dB louder. We can hear very well the 3dB boost considering 6dB sounds twice as loud to our hearing. Just 1dB advantage in loudness when comparing amps, translates to better sound.
Are these real amplification advantages? No, this is voicing to appeal to a consumer with inneficient speakers in a small room, with listening habbits that never surpass the 10 o'clock mark on the volume knob (anything above is vulgar).
This is my theory. Anyone with an EE degree to provide feedback if it makes sense?