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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You seem to be happy with the power you have. The higher power amp may not sound any better. I think the money might be better spent elsewhere. 4 extra tubes adds to upkeep costs as well. 
+1 Mesch. I’m not sure but the "synergy" with the current arrangements might be affected, also. (In other words, you could mess it up by changing!)

There would be a wide range of speakers amenable to your present arrangement, too, so you’re not really avoiding a problem by sticking with what sounds good.
Thanks @mesch and @hilde45 for helping to talk me down off a ledge. It all makes sense. 
You also have the option of moving to KT-150 power tubes if additional power (and improved sound) is the goal.  Having said that if it were me I would always wonder and would probably end up moving up at some point.  I would move up if money is not an issue.  I own an HP Integrated with KT-150's and love it.
@testrun thanks. I tried KT88's and they were just too bright in my system, maybe its the B&W tweeter, so I am hesitant about any KT family as I seem to prefer that warm voluptuous EL34 sound.
I agree with those who recommend staying with what you have. You’re very happy with your sound quality performance, congratulations . I’d appreciate this good situation and continue to enjoy it. It’s ’possible’ that the additional 4 output tubes for increased power could potentially alter the fine amplifier and speaker synergy currently achieved. So yes, leave (Very) well enough alone. BTW I agree with the perspective that the el34 tube is likely a very good match for the B&W tweeter.
I would not move up for the sake of power unless I felt that my speakers were in need for more. To me the 4 additional tubes just complicates things. Very possibly providing more power without improving sound. Other's who have experience with both amps may chime in. I would only move up the line if it was proven to be that the more powerful amp sounded better,, and the money would not make greater improvement elsewhere in the system.

Running KT150s would improve power without additional tubes. Wether the sound is improved would be subjective. Would depend on the nature of improvements sought.

If I were seeking the sound provided by tube amplification (I am) I would not be in the market for speakers that are difficult to drive. Just my take based on preference and budget. 
I've owned a PL HP(Evo400) for 5 years. 

Since your not listening at concert levels, you're good. It's not a 4's good, 8 must be better thing. You probably would be fine even if you did like to put the volume at 1:00+. Buy different speakers(more efficient) if you feel the need to satisfy your nervosa. Roll the two innermost tubes for a subtle change, power cord, power conditioning, AC regen, fuse. If itch persists, get the EVO 400, or even better get separates.
Usually in tube amps (with output transformers) the smaller amps are the better sounding, usually on account of the output transformer, but also in how the power tubes are driven by the driver circuit (by far the lessor variable).

If you don't overload the amp I would see no reason to go for more power! It will just be wasted as heat, and highly unlikely that it would sound better. BTW the KT88s were likely more bright due to distortion rather than the tweeter (which is the same tweeter you were using with the EL34s). This is the same distortion that makes solid state amps bright- higher ordered harmonic distortion. A tiny amount more is audible as the ear uses them to sense sound pressure, so its very sensitive to their presence.
In regard to the volume control setting (Plenty loud at only 9 30-10 o’clock). this has more to do with the amount of gain rather than amplifier power.
1 Your source may have a high voltage output.
2 The amplifier may have a low input voltage (High sensitivity).
3 The amplifier (Integrated) may simply be a high gain design.
FYI, give your amp, tubes, caps inside time to settle in if it’s all brand new. Break-in / burn-in is a real thing, and it will smooth out some more once you get 200+hrs on it. Let this occur before changing more output or small input tubes or cables. Patience will pay off, as many learn later... If it’s brand new, more smoothing out is yet to occur.

If you can manage to stick with the 300, you might be saving yourself a future step-back-down step later on. More tubes is more heat, more maint, cost,and does not always sound better. I’d prefer to have less tubes, less noise, with the same transformers, fwiw.
+1 on the comments above.

I had a bit of brightness and thanks to advice from @decooney I got some nice KT77's for my outputs and they were a happy change from some rather harsh JJ KT88s. A change of signal tube in the preamp also made a difference.

I am very new to all this, but I am learning (as a general rule) that once one has good gear, the best place to educate myself about changes are with tubes and cables. Input tubes first, then other tubes and perhaps cables. It's very system dependent, and I'm just repeating what (I think) I've learned.

Also, for me, The Room is a big unaddressed area to consider. I have REW software and a microphone, and I'm learning how to deal with that issue. (The elephant in the room IS the room, I think the saying is.)
congrats on your purchase. I’ve owned a PL Dialogue integrated a couple of years and am very happy and impressed. The thought that went into the design is superlative and so is the sound. I agree with recommendations not to switch amps as you can always install stronger power tubes like the KT150. I use KT120s.
You "absolutely love it"!  Then why change?  (Of course, audiophilia is an aspect of life, and I have to admit, in other areas of my life, faced with a comparable situation, I have just plunged blindly on; you never know which partner might make you forget all the previous ones.)
If you’re happy and that seems to be the case. Keep what you have.
If you are contemplating a future speaker upgrade, sensitivity is where it's at. 
You have more than enough power for any efficient speakers.
Sometimes it’s best to leave well enough alone and enjoy the music. I’m guilty of upgraditis when my system sounds sublime. I’m starting to just listen to the music now. I’d wait on any upgrade. You will know when it’s time. 
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

The great Robert Harley said, "If the first watt isn't any good why would you want 200 more of them?" Its not the amp that "opens up" its the speakers. Tube amp sound is mostly like Ralph said transformers and driver circuits. Its superficial repeating what they heard audiophiles who think its the tubes. More power is not the answer. Doesn't seem like you need it anyway. Only reason you mention for wanting more power is to enable buying even worse sensitivity harder to drive speakers in the future. Now why would you want to do that???! When you have a really sweet sounding amp, I would think the priority would be to buy speakers it can drive, and not the other way around. Problem solved.

Were the KT88's broken in? 

Can you try the 400 to see if what you hear is life changing or maybe a changeling?

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


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...

70W vs 42W is only 2.2dB. You can almost get that by leaning forward in your chair. 

I got a DPHP because at the time my speakers were lower sensitivity and I wanted a little extra headroom. I was in denial thinking I’d want broadcast volume thump available from a tube amp when the reality is I rarely push it above 90dB any more which could be done on 10W. Plus I still have my old higher power SS integrated if I’m aiming to do damage rather than just listening. 

Since I was new to tubes, I didn’t fully understand how expensive it is to roll power tubes when you have 8 of them or what I would enjoy most from its character. I doubt I’ll ever feel a burning desire for KT150s just for the novelty at a cost of $600+. It cuts down on the experimentation side of things which was one of the reasons I wanted a tube amp in the first place. Hoping Santa brings me some GL KT77s to compare to the 7581As I’m using now. 

In my opinion, it’s about matching speaker sensitivity to the amp.  That said, I have found that “higher power” amps, especially solid state, you have to search for the sweet spot on the volume knob. That point where every instrument is playing at its best. I currently drive high sensitivity speakers with 6 watts of set power and It is perfection, at least to my ears. Not just at the sweet spot but exactly what you are experiencing, at lower volume levels. If you are thinking about a less efficient speaker, something like a maggie you will need lots more current and watts.  Had some 3.5r’s and found them as sensitive as a rock, they needed lots of juice.  Sounded great but needed the proper amp. If you are going to stay with what you have, for a while, don’t rock the boat. That said if your next step is falling for a different speaker, no matter the efficiency, cross that bridge when you get to it. 
To the OP.
Much good advice given already.  Seems like you're in a sweet spot, where you have an integrated that is designed to handle double the tube complement. 

But as you say " volume rarely goes past 9:30/10 " I sort of cringe. Aside from being meaningless, you really don't know if the amp craps out at
"11:00 or 12:00" or wherever.  You may be playing at 4 watts, in that case a 3db increase (double the perceived volume) would cause the amp to output 40 watts, ten fold increase.  Seems to me I would want to know where the amp STARTS to sound overdriven. 

This is anathema to many audiophiles, but I like a lot of headroom.  Give me 500 watt mono-blocks to play at 75 watts and bounce up to who knows where.

After all that if your rig thrills you everyday, you've hit the grand slam.
Don't change a thing!

I own the Evo 400 power amp. I also auditioned Evo 300 power amp.

I say go for the Evo 400.

It won't sound any better but what you will notice is that the switch to triode mode makes almost no difference in volume. The Evo 300 will drop in volume quite a bit more.

The Evo 400 does make changing out tubes a bit more expensive, however, after swapping tubes out with the dialogue premium during my audition period...El34s won that contest for me.


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...
The David Berning stuff is wonderful. I am not sure if these designs are as adverse to lower impedance speakers as other OTL designs seem.
The David Berning stuff is wonderful. I am not sure if these designs are as adverse to lower impedance speakers as other OTL designs seem.
The Berning ZOTL amps are not OTLs by any stretch (read the patent), although a brilliant design nontheless. They have no worries with low impedances.
Isn’t the Berning amp similar in that neither design has the traditional audio output transformer? 
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 --->

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 ---> and
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.

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.


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. 
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.
Stick with the amp you have now if it’s working out. If you have enough power now, and you are very happy with the sound, don’t change the amp or the sound might change. More power sometimes sounds brighter.