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Should the sound level in Triode mode be lower than in Tetrode

I've just got Manley Lab Series 100 vacuum tube monoblocks. And I am a bit confused what to expect from TRIODE / TETRODE modes. The user manual says that: 

"...When the switch is in the upper position, the amplifier is in TRIODE mode which will produce half the power of TETRODE operation."

In the same user manual under the Specifications section I find that the Output Power for: 


TETRODE: 135Watts (@1.5% THD 5 ohm load)

TRIODE: 65 Watts (@1.5% THD 5 ohm load)

I have been running a number of db level measuring tests by switching from TRIODE to TETRODE mode keeping the volume knob unchanged. But it appears that the sound volume remains exactly the same in both TRIODE and TETRODE modes. Shouldn't I expect the sound level in TRIODE mode to be half of what in TETRODE mode?  

esputnix
mijostyn's avatar
mijostyn
8,570 posts
 
1/2 the power is only a 3 dB difference, not much. The amps input sensitivity may also change affecting the volume level. The real question is which mode do you like the sound of better. If you can't tell a difference between the two just keep it in tetrode mode. 
czarivey
5,946 posts
 
@imhififan not quite.
it all depends on load. Both Mack truck and Honda Civic can cruise at 50mph, but the load is what makes it different.
imhififan's avatar
imhififan
2,217 posts
 
it all depends on load. Both Mack truck and Honda Civic can cruise at 50mph, but the load is what makes it different.
Yes, if you connect a 100dB sensitivity speaker to the 100 Watts amplifier and a 86dB sensitivity speaker to the 250 Watts amplifier, the 100dB speaker will sounds much louder!

if the gain of both amplifier are identical and connect to a pair of identical speakers, the required output power of both amplifier is less than 100 watts to provide that degree of loudness (volume), the output volume of both speaker should be same.

BTW, a 250 Watts amplifier can’t provide 2.5 times louder volume than a 100 Watts. The difference of both amplifier output is about 4dB.
According to psycho-acousticians that a level 10 dB greater usually means "double the loudness" or "twice as loud". In this case, you need 1000 Watts to get twice as loud!
If I would connect a right channel output of a preamp to a 100 Watts monoblock and its right-channel to a 250 Watts one then the right speaker will be 2.5 times louder than the left one.

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