1. Home
  2. analog
  3. 167639-151430

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
jjss49's avatar
jjss49
6,926 posts
 
yes

3 db difference, all else equal
Post removed 
imhififan's avatar
imhififan
2,258 posts
 
I can connect left channel output of the preamp to a 100 watts power amp and the right channel to 250 watts one, and expect both the left and right speakers sound with the same volume just delivering a different headroom quality?
Yes, if the gain of both amplifier are identical and the required output power of both amplifier is less than 100 watts to provide that degree of loudness (volume).

Let’s put it this way, the max. output power of an amplifier is the top speed of a car, the volume control is the cruise control of a car.
If you set the cruise control at 50mph on two cars, one car with top speed of 100mph and the other car with top speed of 200mph, both car will run at 50mph as the cruise control setting.
Now, if you set the cruise control at 130mph on both cars, the one with top speed of 100mph will run at 100mph and can’t go any faster, the one with top speed of 200mph will run at 130mph as the cruise control setting without problem.
ghdprentice's avatar
ghdprentice
9,497 posts
 
@imhififan 
+1 Well put.
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. 
More to discover