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A change in efficiency to the final sound

I have a p/p tube amp running a pair of 6Ca7's for about 30 watts per channel .
I have read here that p/p tube amps sound their best when they have to work a bit harder , as opposed to a SET amp that sounds best near idle .
My present speakers are claimed to be 92 db. eff.
If this amp is driving a pair of speakers rated at 85 db. efficiency , should it sound a bit better due to working a little harder or closer to its optimum level ?
Conversely , would the same amp sound a bit worse driving a more efficient speaker of 99 db. due to it working less hard or further away from its optimum level ?


Thank you

saki70
saki70 OP
907 posts
 
kalali ;
I forgot  , in the post that you responded to , to add that the volume levels would be adjusted to be the same for both speaker tests .

Does that change your thinking ?
jrwaudio
343 posts
 
As in life, everything is a trade off
Good discussion on PP vs SET

Watch "Single-Ended Vs. Push-Pull Tube Amplifiers 
https://youtu.be/zSJlyTgpsd0

Before I convert my VAC from triode to PP
l will use the same speaker tap ( 4 ohm)
and listen to the speakers with the same volume setting using a sound meter
saki70 OP
907 posts
 
jrwaudio ;
   I would be interested in what you find out there . 

Now if I could hear from someone that has done it the other way two different speakers on the same amp , that would complete my information quest !

Thank you .
charles1dad's avatar
charles1dad
10,250 posts
 
I don’t believe that the VAC amplifier switches between SET and push pull (PP) operation. Rather it switches between PP triode versus PP ultra linear output. This particular VAC amplifier  is a class AB circuit. SET amplifiers are by default pure class A exclusively. Technically speaking the KT 88 if used to run single ended would be a SEP class A (single ended pentode) as opposed to SET (single ended triode) which are DHT (directly heated triode). Such as 300b,2A3, 845,, 211 etc.
Charles

kalali's avatar
kalali
1,977 posts
 
"...I forgot , in the post that you responded to , to add that the volume levels would be adjusted to be the same for both speaker tests .

Does that change your thinking ?"

What I stated was how the efficiency values are interpreted. If you compensate for the efficiency by increasing the volume, then you're basically asking the amplifier to work "harder" which in case of most tube amplifiers, particularly low powered SET designs, means more distortion. Aside from the speaker efficiency, another important criteria is the speaker's impedance and how it varies as a function of the frequency. Typically, the higher the impedance the less demand from the partnering amplifier which also translates to less distortion. 
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