How many watts per channel are enough?

I am considering my first tube amp (Prima Luna Prologue 5 or Jolida 502 p). I lean toward the Prima Luna but it only has 34 watts per channel. Is that sufficient to drive my Jm Labs Daline 3.1 speakers (rated at 89db into 8 ohm)? My preamp is a Jolida 5 t. The room is 12 by 24 with high ceilings. I listen primarily to jazz and classical at low to moderate volume. Thank so much for any advice.
If by low-to-moderate volumes you mean peaks up to say 90dB (perhaps pushing to the mid/high 90s), then you should be fine, with ample headroom -- just don't do something silly like set the seating 20'+ away.

I found 60 Watts/ch to be perfectly adequate on 93 dB/Watt speakers for "loud" levels supporting peaks over 105dB and seating about 8-10 feet away. A more moderate level buys you the luxury of some more distance, less Watts, and less efficient speakers -- probably still with more headroom to boot. Classical tends to be more demanding, with its huge dynamic range and typically high crest factor, but you should still be OK here. The only time I audibly clipped that 60 Watt amp was with a Sheffield direct disc recording of Firebird Suite, on an accidentally-too-loud volume level set during the REALLY quiet intro...then WHAM!!

In your case, you'd possibly start hitting trouble if you wanted to push peaks over 100dB.
Sufficient, but just barely.
89db for speakers is rather inefficient.
I would say no way.. but if you never ever want to crank it up, you might get by with 34 watts.

To play softly only takes a watt. the trouble is the moment you add in any real bass notes and are slightly louder ...zoom you are using way more watts.
I do not have the link wit this info, but my speakers use about 1 watt up to 20 watts at lower listening levels.. Then a moderate level with bass the wattage jumps to 80watts.. as soon as I crank it up a little the wattage needed is 400 watts..

Same for your 89db efficient speakers.
I think you should look for a more powerful amp.
Or more efficinet speakers.
If you had 92db efficient speakers. you could easily use the amp you want.
To be sure, you'll run out of headroom real quick once you start pushing that
volume knob into loud territory. That's why they make efficient speakers and
powerful amps!

I'm a fan of efficient speakers for sure. Even those *honest* 93dB/Watt speakers
I had were a little on the low side for me. I found the step up to 95dB or 96dB to
be very worthwhile. Unfortunately, the efficiency ratings assigned by
manufacturers seems to be oft abused and "fudged". Speakers should be
measured anechoic, not just on a single frequency that happens to be a
significant peak, and (ideally) not at the expense of decent bass extension. In-
room efficiency ratings are...misleading.

I've seen a posting from a well known system/room optimizer who measured a
set of "famous maker" 97 dB/Watt speakers at 3dB LESS than a 96dB/Watt
speaker from a different manufacturer.
It is hard to tell without having experience with the amps

the reason I say this is because I once had a Stingray amp (rated at 40 watts) and it was quite lively driving my Maggie 1.6 speakers however, Rogue 120M (120 watts) sounded a bit dull and lacking dynamic range. Both had new tubes.

maybe the archives have more info on the ability for each amp to drive a real life load.


good luck
Agree with Liz. You've got a nice sized room. I'd be looking for 50 to 75 tube watts at the very minimum. I think a good rule of thumb with amps is to err on the high side. Of course, I'm not talking about 400 wpc mono-blocks. But in your case, I advise erring on the side of more watts.

Btw, I listen to classical music too. Just listened to Beethoven's 9th. Before that, Prokofiev's Symp #1. The drums rolls are really dynamic. I think a 34 wpc amp will run out of runway real fast trying to keep up.
Based on your listening levels, that's plenty. Even in a relatively large room, such as yours, you'll be fine. Especially given the speakers relatively benign load on the amps.
I use the PL 5 with Opera Platea floorstanders (86 db sensitivity) in a 26' x 15' X 9' room. I use either EL 34 or 6CA7 tubes, which give you a few less wpc than if you use KT88s. I listen to CDs almost exclusively. The front end is a Musical Fidelity CD PRE 24 cd/ preamp.

It comes down to four items to consider:

1. how loud you play your stereo
2. what types of music you listen to
3. how noisy is the street you live on
4. do you live in a private house or an apartment house

I live in NYC (Queens) in an apartment house on a major road which connects to the LIE and supports a major bus route and a fire house.

With all that said, the PL5 will play plenty loud if you listen at low to moderate levels. If you like your music loud, you are probably looking at a solid state amp or a more expensive (and powerful) tube amp.

I have to disagree with some of the other posters. You should have no problem at all driving your speakers with either of the 2 amps you list. Your speakers are not that difficult a load. Also, you really can't rely on watts as a measure of how powerful the amp is. There is no common standard that equipment makers use for their ratings. They all do it their own way. For example, if you took ten 100 wpc at 8 ohm amps from ten different manufacturers and tested them all the same way, every single amp would put out a different amount of watts.
I have to agree with Zd542, the wattage ratings have not been very consistent in my experience. However, I think you should be ok unless you want to play really loud. Is there a way you could audition the amps before buying?
Agree w/Zd524...I had two 25W amps (one tube and one SS), and the tube amp hit a brick wall REAL quick, while the SS seemingly never got tired. It's more about impedance swings and phase angle, not sensitivity.
Zd 452, I agree with you. When I bought my speakers last year the guy was running a 40 watt tube amp on them. I could not believe 40 watts would power these speakers. They are a difficult load at 85db sensitivity. When I got them home my 100 watt tube amp almost ran out of steam at high levels. All watts are not created the same.
Zd542, legally they would all be required to put out at least 100 Watts. I agree that 89 dB isn't that inefficient, but 39 Watts is really on the low side for a room of that size.
Your taste in music seems sane, but speaking from experience, only if you (and your friends) drink a lot, you own a disco ball and/or play a lot of beerpong, love to dance all night to Dubstep, and your listening room is in an abandoned shoe factory, 36 watts might be light (in that case simply buy the speakers, subs, and amps from a band or DJ that gave up). A Jolida 502P with "factory upgrades" is about the same cost or less than the Primaluna. I have one (502p) running supposedly 90db speakers (Silverline testing noted perhaps they are less) in a room a bit larger than yours and it has plenty of power to spare, sounds astonishingly good, and includes balanced inputs and "easy biasing" (you could buy 2 wired mono and double your fun for less than the cost of virtually any other decent stereo tube amp)...I do use a REL sub with it but the amp runs full range, and has 85 to 115 watts peak depending on what specs you read. If you "actively listen" to normal music within 12 feet of your speakers, a 65 watt per side amp will give you all the juice you need unless you have hearing issues, really thick hair, or very bad taste in music...Jolidas are very rarely reviewed for some reason which is why I blather about mine. Not sure why I blather about other things, but really...who cares?
Hey, follow K.I.S.S. (keep it simple, stupid), the general rule of thumb is to use double the required RMS output, fuse or breaker protect the speakers, and listen for audible distortion. This setup can even be used to lower THD. If you have 8 Ohm speakers and a 4 Ohm amp you can cut THD in half while maintaining proper power output. I, for instance, use 12 ohm speakers L/C/R/SR/SL on a 8 ohm amp. This technique works wonders for sound quality while maintaining volume levels.
Ditto on most of the thoughts here.

34 watts is not enough headroom for the 89 db efficient speakers you have. On the other hand, 34 watts would be plenty for my 101 db efficient Zu Superflys.

Go for at least 50 wpc, preferably 75 or 100 wpc.
As others have eluded to, not all watts are the same. In particular tube amps are'nt the same as SS, also SET amp watts are'nt the same as a push pull tube amp. The most suprising is SET amps. You really can drive speakers you should'nt be able to. This may be due to the high current and large output transformers. There is also the issue of driving into clipping, tube distortion seems much more acceptable, than SS distortion.

My 20watt Ayon Spark, sounds significantly louder and more dynamic, than the 50watt Class A Pathos Inpol2, I also use.

All I am saying is, what should'nt work on paper, often seems to and vice versa. The only answer, as always, is to try the amp with your speakers, in your room.
"Zd542, legally they would all be required to put out at least 100 Watts. I agree that 89 dB isn't that inefficient, but 39 Watts is really on the low side for a room of that size."

I didn't check the UCC before I posted so I'll take your word for the legal aspect of it. Is far as my post, I'm 100% correct. There's no standard for ratings. The question is not if 34 watts are enough but how good those watts are. I'm not guessing on this. You don't have to take my word for it. If you don't believe me look into it.
I don't know if this is of any use to you but here is a amp power calculator. Maybe someone can chime in on what the recommended amount of headroom in db should be.
There are a lot of nice used amps with more power for sale;I would look into buying a used more powerful amp.
If it does not work out then resell and not take a big hit in the wallet.
I also agree with Zd542. Watt ratings of amplifiers is like horsepower ratings of cars. It is tricky.
You'll be fine on most recordings with 34 watts, but not on some recordings. And I suspect that a major reason for the diversity of opinion in the previous responses is that people listen to different kinds of music.

Given that your listening is at "low to moderate" levels, the most significant variable is likely to be the DIFFERENCE in volume between the loudest notes and the average notes on the recording. Some well engineered classical recordings which use minimal or no compression will have a ratio of peak to average volumes in the vicinity of 30 db, which means that 1,000 times as much power will be required for brief volume peaks as for the average volume level of the recording.

Most rock recordings, on the other hand, are compressed such that less than 10 times as much power is required for volume peaks as for the average volume level of the recording.

Neglecting room reflections, it can be calculated that at a centered listening position 10 feet from the speakers 34 watts into your 89 db speakers will produce a sound pressure level (SPL) of about 100 db, assuming the specs are accurate. Averaged over a broader set of positions, but at that same 10 foot distance, the corresponding figure is 97 db. "Moderate volume" probably means an average SPL in the area of 70 to 80 db. Many of the symphonic classical recordings in my collection that are especially well engineered, meaning in particular that they are minimally compressed, will reach SPLs of 100 to 105 db at my listening position on brief volume peaks, when played at that kind of average level.

Finally, it appears that although your speakers are nominally rated at 8 ohms, they reach a minimum impedance of 4.1 ohms at some frequencies. That will further reduce your chances of success with a marginally powered tube amp.

Hope that helps. Regards,
-- Al
Thanks, Wilson667. It should be noted that the Crown calculator applies to one speaker, not two. The results it gives are consistent with the calculations I provided above when extrapolated to two speakers, and assuming 0 db headroom.

I would not count on headroom specs, if provided for the particular amplifier, to be either meaningful or helpful. The amount of time that the specified headroom can be sustained for is not usually indicated, and can be expected to vary widely depending on the particular manufacturer's approach to "specmanship." Also, sound quality may degrade significantly at power levels in that region, to a greater or lesser extent depending on the particular design.

-- Al
I want to thank everyone very much. I decided to give the Prima Luna a try. I have a 14-day audition period. I am purchasing it from Kevin at Upscale Audio, who based on my due diligence has an excellent reputation. He would be surprised if the 34 watts are not sufficient.

The Prima Luna website explains, "if two amps are . . . both . . . using a pair of KT88 tubes per channel, how can one be rated at 40 watts per channel, the other at 80 watts per channel? This is a simple engineering and math question, and these are the two possible answers:

The higher powered amp isn't really meeting it's specified power rating and/or the tubes are being run very hard to get that extra power. . . .

The benefit of doubling power from 40 watts to 80 watts will only increase maximum volume levels by approximately 3dB."

That makes a lot of sense.

You are tapping the amp out on musical peaks. Most tube amps have distortion climbing when tapped out and bandwidth narrowing. The distortion many times sounds like congestion. Remember, double your power and you only get 3db. Also, check to see if 34 watts is 34 watts. If at full power you have good square waves, distortion less than1% and bandwidth the range the of speakers then you will get an idea what you will need. I think you need at least 100 wpc of power. Jallen

"Hey, follow K.I.S.S. (keep it simple, stupid), the general rule of thumb is to use double the required RMS output, fuse or breaker protect the speakers, and listen for audible distortion. This setup can even be used to lower THD. If you have 8 Ohm speakers and a 4 Ohm amp you can cut THD in half while maintaining proper power output. I, for instance, use 12 ohm speakers L/C/R/SR/SL on a 8 ohm amp. This technique works wonders for sound quality while maintaining volume levels."

Regarding your post, I have to ask, are you serious or just kidding around. I really don't mean to offend in any way if you are being serious, I just don't think I fully get what you are trying to say here. You use your system for an example. Can you list your components? I do find the post very interesting. Its possible that I'm just not reading it correctly. And like I said before, I'm not at all trying to offend you, even if we end up disagreeing on some things.
Higher wattage amps make you feel better about things unless you're an "efficient speaker with a single ended mini watt amp" dude, in which case you feel better when you point that out.
As many as you think you could ever possibly use, then double that.
Consider the fact that often you can save some money by buying the lower powered version of a well regarded design and get the benefit of a greatsounding amp without extra power you likely don't need. Pass Labs makes that point all day. And remember, a tube amp that is pushed in louder musical transients can still sound sweet as the character of the distortion (2nd order) is more ear friendly than a solid state amp clipping, which is a sound nobody should have to endure.
Buy a Lamm M1.2R, that's something serious and you can close that chapter.
Rule of thumb applying the correct amount of RMS power to a loudspeaker. To get the very best performance from a loudspeaker as explained to me twenty years ago by a speaker designer, find out what the maximum RMS power the driver magnets and the crossover capacitors can sustain over the long term of continuous power and divide by two.
If the speaker has a max of 500 watts rms continuous then use a 250 watt amp. There should be at least a 50% volume of continuous current to the magnets. By filling the magnets continuously with current volume at 50% or higher, results in cooler temperatures to the voice coils and crossover network. When you under power a speaker and drive up the volume, you increase the chance of clipping the amp and over heating your drivers causing the coils to fry. If your using a 60 watt tube amp, Match it with a speaker that has a max of 120 watts rms to get outstanding performance. There are a lot of low power full range speakers that are perfectly suited for tube amps.
You sure that isn't "multiply by two"?
Why would you multiply by two? The formula is to divide in half by 50% or 2 into the total amount of rms wattage
the speaker allows. If a speaker has a max capability of 1000 watts and you multiply by two, thats too much current
at 2000 watts. Goodbye Charlie. You just fried your speaker with too much power. You can damage your speaker
under powering by clipping your amp or too much power. However, in most cases most amps are much more bullet proof today with built in safety shut down thermal switches if clipping occurs compared to thirty years ago.
Both amplifiers will more than serve your requirements adequately.

Experience has shown me that WPC to not always serve as the ideal measure of power. Not to dismiss the spec out of hand, but it is an algebraic (steady state) measure, while we live in a world of calculus (dynamic).

Instead, I'll put forth the contrarian assertion that the ubiquitous transformer coupled push-pull tube amplifier with two tubes per channel will drive a loudspeaker far more similarly than differently in terms of seat of the pants power whether using 2A3 (10 - 15 wpc), 300B (20 - 25 wpc), or EL34/6550/KT88 (30 - 75 wpc). Doubling the number of output tubes to four shows the correlation still holds up. In other words, we will often draw surprising conclusions in regard to amplifier power if we move away from drinking by the label.
Your far safer using a bigger amp than the speakers can handle because now you have the luxury of using only SPLs to determine maximum speaker output, ie: pain threshold:)
Use nice, round figures...50,75,100.
Contrarian Assertion is the name of my old dude punk band.
I have a 34 WPC PrimaLuna Prologue 5 power amp. I have found that because of the ability of tube amps to distort musically, 34 watts of tube bower sounds more like 75 watts of solid state power. The amp will distort at or above 34 watts as rated but unlike transistors that hit a brick wall at their power rating and sound terrible above it (and can destroy your speakers), tube amps distort 'gracefully' and don't clip (or at least don't clip as abruptly).
I've had a pair of Quicksilver Mid Mono amps for about three years and have had them paired with several speakers .  With Revel M106 at 87 dB sens they sounded great with 40 watts at moderate levels but crank it up and they lost their composure fast.   Same speakers with a McCormack DNA 125 and they would play loud without strain.  

Klipsch Heresy III with 40 watts is amazing, dynamic  and effortless at all volumes.    I have used them with a B&K 2140 and they sounded ok, but no contest to how the first few watts of EL34 goodness sounds.