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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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Showing 4 responses by jjss49

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jjss49
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@sandthemall 

just so we don't unnecessarily muddy the waters, on the primaluna's amps (and others with the switch), when the triode mode is activated (from base mode ultralinear) the power tubes screens are tied to their grids with a small value resistor (usually 200 ohms) and the ultralinear tap on the transformer winding is bypassed... this results in a 3 db reduction (half power) in output from the power tubes....

this happens whether we are dealing with 2 or 4 power tubes per channel...
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jjss49
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yes as said below, the position of the volume knob is a red herring w.r.t. amp power ... it really doesn’t have much to do with when the amp will start to exhaust its power reserves and start to clip - input sensitivity and gain of the input tubes account for that rotary position as much as speaker sensitivity

i agree with what others have stated... stick w what you have... i think the 2 tubes per channel models would if anything, sound a touch cleaner than the 4 tube/channel models... that has been my experience with audio research amps... a minute very subtle difference that can become significant as tubes age and matched sets grow apart - the pl amps have auto bias so this may be somewhat minimized but it is still a consideration

my experience with my hp amp is that rolling the two middle 12au7’s can alter the sound character a good bit, as well as, of course, the power tubes ... pl amps give the user a lot to do (triode / ul too) - fun amp to own


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jjss49
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Tube amp sound is mostly like Ralph said transformers and driver circuits.

miller

yes, mostly true i would say, but it is interesting that in an amp like a primaluna dialog hp that allows you to hear different power tubes with the same input stage and transformers -- the different character of various power tubes (el34/kt77, 6l6, 6550/kt88) is immediately noticeable, as is even different makes of tubes (chinese vs russian kt88’s for instance)

another point to add here is that a bit of an oddball amp (but an utterly brilliant one) is a david berning (linear tube audio) zotl amp which is devoid of output transformers... i haven’t messed with one of these OTL since 20 years ago with the ginormous fourier triomphe otl’s ... but the zotl40 ref i recently got in is a revelation, so clean clear and extended top and bottom with lush mids and wonderful imaging (and so small and light in form factor)... very very impressed with what this little company (lta) has done...


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jjss49
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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
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