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Tube Amp lower power vs higher power and cruising volume

After having Solid State my entire life thus far, I bought a PrimaLuna EVO 300 integrated and absolutely love it. I am currently driving 20 year old B&W CDM9NT's and it does a wonderful job, I never heard my B&W's have that much bass before, even at lower listening volumes. The EVO 300 is rated at 42W. Since I recently purchased it I have the option for a brief time without losing money to possibly move up to the EVO 400 integrated which adds 4 more output tubes and gives you 70W. I believe the 300 and 400 both use the same transformer because they both weigh the same 68 lbs. So my only reason for possibly doing this would be for future speaker upgradability having a little more power. I know my B&W's are not the most efficient and the 300 seems to be driving them very well, volume rarely goes past 9:30/10. So my question, if I get a higher power model, since I listen most of the time at comfortable listening levels, with a higher power tube amp will you have to turn it up higher to hit that cruising speed where it starts to open up? The 300 seems to hit that early and I listen at comfortable levels and good extended bass without having to crank it which is nice when I am listening at night and my wife and daughter are sleeping. Overall I am very happy with the 300 but while I have the option I am trying to decide if the extra for a 400 is worth it. Thanks
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jjss49
6,612 posts
 
ralph is correct to point out to us not to confuse the two technologies, despite the similar naming

berning zotl is fundamentally a different design than ’standard’ otl amps

zotl’s use a ’normal complement of tubes’ - i.e. 4 pcs el34’s 2 per channel like many tube amps - and use a carrier frequency (like radio broadcasting) thru the output tubes bearing the music signal, and then ’strips away’ the carrier frequency before outputting to the speaker load (and in doing so, allows for elimination of standard heavy metal output transformers to perform the impedance matching from output tubes to speakers)... good write up here --->

https://www.lineartubeaudio.com/the-technology

regular otl’s manage the impedance matching by using many paralleled sets of identical output tubes (i recall my fourier amp had 16 pcs 6as7 output tubes to handle the impedance matching --->

http://www.one-electron.com/Projects/Fourier/FC_Tr_ad_1.jpg and
http://www.one-electron.com/Projects/Fourier/FC_Tr_ad_2.png
atmasphere's avatar
atmasphere
11,844 posts
 
Isn’t the Berning amp similar in that neither design has the traditional audio output transformer?
In that regard, yes, since the output transformer used in the Berning is an air-core device.
sandthemall
544 posts
 
@jjss49 

Point taken. However there's a noticeable difference when comparing the dialogue premium vs the Evo 400 power amps in a real world comparison with 88db 6 ohm speakers.

The difference is very subtle with 8 power tubes.
Not so much with 4 tubes. It's as if the volume was cut in 1/2.  It's what my ears are telling me.

 

mesch
3,510 posts
 
Maybe the difference when cutting the  8 tube 70wpc in half, and cutting the 4 tube 40wpc in half, is that what is loss is 'headroom' power and not the 'foundation' power the speaker demands. 

If wishing to run in triode mode I can understand the need for the additional power, comparing 20 to 35wpc into a 88dB 6ohm speaker. Does speaker drop below 4 ohms, or is impedance curve relatively flat?

Just thinking out loud. 
sandthemall
544 posts
 
The speakers are Salk Songtowers. So there is a slight dip below 6 ohms. I use the 4ohm taps...btw, I cannot hear a difference between the two taps. 4 power tubes are more than enough power in ultralinear mode.

I’ve heard the same from another Primaluna owner who’s used both setups.
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