recommendations for amplifiers that don't emit tons of heat


I tried a Krell ksa 150 and while I liked the sound, it was like having a space heater in the room. I now have an Audio research vt100. It sounds fantastic, but it makes the room hot as well. Not as bad as the Krell, but it's still a drag in the summer.

I'm guessing I should just suck it up, but I'm curious what cooler running options there are that sound as good (or better)... suggestions?
tripg
@audiotroy
I posted the other components and budget, but not in the original post. I didn't originally post the rest of the components because I'm hoping to change the speakers when/if I can get into a larger room. So, while I realize matching to the speakers is important, they are a potential variable. Sorry for the confusion.

My preamp is Audio research ls27 and speakers are paradigm
studio 40 v4... the rest is Rega p9 turntable, dynavector 20x2 L, Audio Reseach ph6 phono preamp, and Cambridge Audio CD player.

My budget is $2000. I prefer used in the interest of maximizing value.
Thanks for your advice!
I can strong recommend two amps. The B.M.C. M2 monoblocks have fans but very  quiet ones. In balanced XLR and the Koda K-10, they are great!

The other is the H-Cat X-11 amp with automatic focus. It has heat sinks on back. I live in Texas and have had neither of these amps heat up my room.
Trig you fail to mention what is your budget and what is the rest of your system. 

There are tons of modern amplifiers which will best a  Krell KSA 150 it depends on system matching to what amplifiers will work for you.

We have the Nuprime ST 10 which is a 150 watt compact analog switching amp and it sounds fantastic much better than most Class D amplifiers and it is tiny and gives off much less heat then a big Krell, the bass conrol on the Nupirme is fantastic. 

Howerver that amplifer will not sound as good as many of our larger more conventional amplifiers. So again it is going to come to budget. 

The best amplifier in the shop a T+A PA 3000 gets warm but never super hot and that amplifier will run rings around Dan's newest designs. So it all comes down to level of performance you want to get and how much you are willing to pay for. 

Dave and Troy
Audio Doctor NJ
the biggest power consumer in a tube amp is usually the heaters for the cathode
This statement is rarely true- I think the exception used in audio is the 6C33. For most power tubes - like a KT88- the heat made by the cathode is insignificant compared to the heat made by the tube as a result of plate current though it (its class of operation).

As a result, compared to a solid state amp of the amp power and **same class of operation** , tube amps will make marginally more heat.

If you put a tube amp in standby (no B+) even after sitting there all day the tubes won't burn you (the exception being the 6C33). But after being on only a couple of minutes the same tubes will be much hotter if B+ is also applied!

The problem is that if a solid state amp can't bring home the bacon, then it really doesn't matter how much heat it makes. In high end audio, the **sound** produced is the goal. 
Yes---and 1.6 A. x 6.3 V. = 10 WATTS.

And that power is consumed merely to "light up" one KT88 to a quiescent state, where it does nothing more than emit 10 watts of heat and light. Additional dissipation, over and above this wasteful filament dissipation, is required to perform active amplification.
glennewdick---As you say, KT88 filament current is specified as 1.6 Amperes. The related filament voltage is 6.3 Volts. That's TEN WATTS of power dissipation that's consumed merely to "light up" the quiescent KT88 vacuum tube. In that state, the tube is merely at passive idle; it's not doing any functional amplification. It's serving only to emit heat + dim illumination. Additional power is then consumed when the tube is subsequently biased to pass current from cathode to plate. That's truly archaic efficiency.
for an example KT 88’s have a heater current of 1.6 amps each tube....where as the power dissipated is around 5mili amps

Vtvmtodvm the biggest power consumer in a tube amp is usually the heaters for the cathode that's why they waist so much power to run at idle. more tubes you have the more cathodes you need to heat and more heat in the room you get. the Heaters are only so electrons can flow inside the tube they do nothing else.

also tubes are not that good for THD at their max output that's why good designers usually run them conservatively.  

@tripg 
The Ayre were a bit bass shy in their early iterations, but the more current models are not.
I would opt for a good sub, as your speakers aren't floorstanders, should you want full deep bass. 
A Vandersteen sub would allow you to use a lower power amp as it relieves it from the demands of bass frequencies. Plus, it would integrate seamlessly.
B
I’m no model “Mr. Green” when it comes to conservation, but I’m astute enough to see when excess goes so far beyond the bounds of tolerable waste that it deserves dishonorable mention. Truly, some vacuum tube power amplifiers merit that distinction. Other forms of conspicuous consumption pale when compared to the staggering inefficiency that you enable when using a stereo power amplifier that features eight (or more) hi-power vacuum tubes in its output stages.

Listed below are basic performance specifications for three closely comparable stereo power amps. One is solid state, the other two are premium vacuum tube power amps. Take a look; compare the data. Also, be assured that what’s shown is entirely representative of equivalent product offered by other makers. The specs are as extracted from the relevant source's website.

(1) Parasound model Halo A23 (solid-state) stereo power amplifier: Continuous full power output = 125 Watts (x2) into 8Ω, 200 Watts (x2) into 4Ω, 20 Hz - 20 kHz, both channels driven.
Total harmonic distortion: < 0.06% at full power output.
Power required: 25 Watts in standby idle, 700 Watts at full power output into 4Ω loads.
Mains fuse (USA): 6.3 Amperes.
Street price: $995. ea. (Audio Advisor, on-line site).

(2) VTL Amplifiers Inc. model ST-150 (tubes) stereo power amplifier: Continuous full power output of 150 Watts/channel is loosely claimed, but conditions of measurement are not specified.
Specified power output = 120 Watts into 5Ω (driving both channels assumed, but not specified).
No power output ratings were provided for 8Ω loads and 4Ω loads.
Total harmonic distortion: < 3.0% at 120 Watts into 5Ω load, 20 Hz - 20 kHz.
Power required: 240 Watts* in standby idle, 800 Watts at “full power” (no conditions given).
Mains fuse (USA): 15 Amperes.
Listed price: $12,295. ea. in Canadian dollars (Melbourne Hi Fi, Victoria, Canada, on-line site).

(3) VAC (Valve Amplification Co.) model Phi 300.1a (tubes) stereo power amplifier: Full power output of 150 Watts claimed, but no conditions specified, so refer distortion measurement (next).
Total harmonic distortion: < 3.0% with 135 Watts/channel continuous avg. power at 1 kHz into a 4Ω load when connected to the 8Ω output tap (stereo mode).
Power required: No power consumption stated. It’s likely slightly > than for VTL ST-150*.
Mains fuse (USA): No info provided.
Listed price: MSRP $22,000. ea. (Scott Walker Audio, on-line site).

*Both tube amps draw more power when in standby mode than a 55 inch Sony LED/LCD TV set does when in use. Note that 240 Watts standby is equivalent to continuously burning four 60 Watt incandescent light bulbs without shedding any usable illumination—just generating lots of heat.
The Absolute Sound recommended the Goldmund designed NuForce STA 200 at $1299. It is currently priced for $499 at Audio Advisor, which has a generous trial policy (AA also carries the NuPrime STA 10 and IDA 16). I think that the unusually high gain of the STA 200 makes it helpful to have a home trial, (especially pairing it with the tube based ARC LS27).
@jackput

do you have any experience with other Audio Research amplifiers? If so, can you describe any sonic comparison?

I have a vt100, and have a friend with a D200.
Wow! So many suggestions... thank you all for your thoughts and information. I've got some serious researching to do!

Question regarding Ayre: one common theme in many reviews is "bass shy". What are your thoughts? Bass is an issue in a small room, so "bass shy" is extra concerning. 


Primare A34.2 or A60, which has a DAC.
http://www.primare.net/product-list.asp?m=1

I'd surely place these on my must-demo list; but I don't think you'll find any used A6s yet.

I decided to give class D a shot and purchased the Audio Research DS450. It is the best sounding amp that I've heard in my system. My friend and I have compared it to 4 other amps, including a Pass class A design, and it has come out on top every time. The closest competitor was another class D amp, the Hypex NC400 amps. They are available as a kit for around $ 1,500.00.
Ie: McCormack DNA amps-

They run cool when at normal house volume. Only very slightly warm to the touch %99 of the time.

 Any descent SS amp would be good,... A/B is recommended.
How about a used Sunfire 300 - not too heavy, reliable, sound amazing, and run very cool to the touch. used ones are about 500-800 for the 300 W model.

300@8 / 600@4 / 1200@2, /  stable to 1 Ohm


Karan KA-I 180Mk2

2x180W/8 sliding bias , cold like a stone ...second hand, almost new like ex demo  in TX about 5.000 $
I also run 2 linn 4200 amps into a pair of Pioneer S-2EX (TAD) speakers.
Depending on how your speakers are wired, biamping ( sending the 
signal twice, once to the tweeter and the other to the bass) will allow 
more power to reach the bass drivers.  The Linn amps have an amazing
ability to render the musical sound stage.  I've compared them to Bel Canto 500s and was disappointed by the BC 500's lack of
dynamics and flat soundstage,
so all digital amps are not the same.  I also use a pair 
of Linn 5105 in a bedroom about the same size as your current room
and the Linn sound staging, bass, and speed are also there,
The Linn 5105 is an affordable stereo amp you might want to look at.
The Linn amps have signal sensing so they will power up or down seamlessly. I guess I'm a linnie when it comes to their amps. 
I had a similar dilemma a year or so ago.  I have a Pass Aleph 4 (100W/channel) that sounds great but is also a great space heater. Was looking for a suitable "summer" amp that didn't compromise on sound.  I auditioned quite a number of Class D and Class A/B amps and others, including many, if not most, of those mentioned above.  Ended up stumbling upon a used Linn Akurate 4200 at a good price, 4 channels w/200W each into 4 ohms.  Though I wasn't looking to bi-amp my speakers, that's what I ended up doing.  Sounds much better than all the alternatives I heard by some margin.  Runs cool, doesn't idle at 500W, and takes up little space.  My electric and air-conditioning bills dropped substantially, and the air-conditioner can now keep up when I listen to music even on the hottest days. Something about the pitch and tunefulness that just sounds right. Violins and sopranos don't have that edge that I hear so often even on many very high priced tube and solid state amps.  Linn doesn't seem to have much of a presence here in the U.S. where size, power specs, and "slam" matters so much and seems to impress many listeners.  Linn's focus seems concentrated on Europe where listening spaces seem to be smaller and more intimate.  I listen to quite a wide variety of music including a lot of classical music. I don't think Linn gets its due.
@don_c55 SST is still alive and well thanks to Wyred 4 Sound.

The original ’Son’ is now the Mk2 version. It runs warm, but not hot. Excellent amp, and phenomenal for the money.

(Spread Spectrum Technologies Son of Ampzilla Mk2)

RIP JB.
Tripg ,
Buying used saves money if you're going to sell it later . If you can audition the 250 Watt Gilmore Audio Raven stereo class D amp at $1750 new , you may want to keep them . I bought his mono block Raptors with identical specs , save power , and these are as fine as the best I know .They are special and work with all music and should drive any speaker, including Magnepans very well . I've used passive volume control and now a tube preamp and either works well .. They run cool to the touch always and are heavy, although only 12 inches square . Mark Gilmore is a joy to deal with . My two cents' worth , since you asked .. 
 Joe
I have YBA amps (signature mono locks and 2 delta). They are barely warm including their heat sinks/fins after playing 6-8 hours. They are very rare to find (French made). I don't know much about the chinese version if they run cool. By the way, I live in Phoenix and don't want any thing that gets hot! 
Giri
I like the latest Krell amps very much and they can be bought here for very good prices. True high performance audio. Class A bias with rear fans that are VERY quiet. Some serious engineering went into these amps and they look pretty good in person. Compared to Pass 250.8 and could have gone either way. Truly. I very much like a higher biased amp. Purchased an Agostino Momentum Stereo amp and it runs very hot but sure is good. Do look at the Krell. 

Also the main force that controls the speakers is Damping factor not how much power you have.

Definition. Amplifier damping factor (DF)is defined as “the ratio of the load impedance (loudspeaker plus wire resistance) to the amplifier internal output impedance.” This basically indicates the amplifier's ability to control overshoot of the loudspeaker, i.e., to stop the cone from moving

so you wont necessarily need more power. like my self and gdnrbob said try a smaller quality amp you will be surprised.

Your speakers are pretty efficient, so you could probably get away with lower powered amp, say 60-90 wpc, which should have enough headroom for demanding passages.
Perhaps an Ayre AX-7e? or a McCormack Micro Drive?
I am running a pair of Zu Omen Bookshelf speakers with both amp/integrated. The Ayre seems a little bit warmer than the McC, but has wonderful clarity.
B
Post removed 
I was thinking 8X10 room without furniture is relatively small so you'll probably sit only a few feet away from the gear. One other option, depending on the height of the room, is to put the amplifier on a real high stand as close as safely possible to the ceiling. Won't solve the problem but might help a little bit.
My Son of Ampzilla 2000 runs very cool!

Has 100 wpc into 8 ohms, 200 wpc into 4 ohms, and will drive a 2 ohm load.

2400 watt power supply transformer, and superb sound.

No longer made.

James Bongiorno's best sounding amp IMO.
Most any Class D amp is relatively small, very power efficient and runs cool. Many good ones out there. I use a Bel Canto c5i in an enclosed audio cabinet and also have other BC 500w/ch power amps. Neither ever gets even slightly warm.
Y'know, if you like the sound you are getting there is a much less expensive option, which is simply to have a vent installed to the outside that allows the heat to escape the room rather than warming it up. This can be done for a few hundred dollars at most (which if really sophisticated might include a wall switch with a fan to help move the air). I've seen this be very effective!
Regarding larger amplifiers my Son of Ampzilla mk2
Is very fast. The late great James Borngiano was a great designer.
This amp has a Huge 2,000va transformer for control and I believe 12 bipolor
Transistors per channel and over 100k in capacitance.  And grounding eliminates ground loops in this amp low level detail is very good also.
The matching preamp is very good also ,but I have a custom Lundahl transformer based 4P1L - DHT preamplifier Which being single ended really pulls the music out. TIP OF THE DAY - Buy Stabilant22  to put on all Audio connections just one mating side very thin coat,first clear everything with Isopropyl Alcohol 99%
If possible.lasts for years and by far the most technologically advanced on the market . If it's good enough for NASA,then I am good with it also. I use on tube pins and everything else give it a solid 30 minutes to dry, great stuff !!
tripg- you read into the analogy correctly. We have an A'gon comrade with Anthem I225 Integrated amp. It's rated at 225 watts into 8 ohm/310 into 4ohm. He's running Paradigm Studio 100 v3. The speakers do not flinch or suffer any driver compression. He works the amp hard and it does not get hot. And its not sluggish. These are in your pricepoint - new with warranty. Now, are their more transparent amps out their? Of course. 
https://www.anthemav.com/products-current/collection=performance/model=pva-2/page=overview

https://www.anthemav.com/products-current/type=amplifier/model=mca-225/page=overview

Ayre also makes some great 5 series amps. 150 watts into 8 ohms. They should run around $2250 - $2600 used. Very transparent. 
Look at Nuforce Reference 18 monos used or some of their new stuff under Nuprime in that price range
My McCormacks' get pretty darn hot during the blossoming buzz,
 had them cranked for about 2 hours, at must yell to hear guy next to you, as we were in the backyard, and the speakers pointed towards open windows.
 They performed magically, the new capacitors are not even fully broken yet...... as told by Dan Babineau. 
Very happy with these.
The warmup is a bit long, but once zero'd in, its just stunning, its like a laser beam of sound just directly hits you and is perfect !

will never part with them.

600W@8 / 1000W@4
all the power i will ever need.
Almost any other solid state amp out there will be cooler than the KSA-150 or the VT100. Just saying.
@audioman58
I’m not 100% on what you mean by braking... assuming it’s analogy for greater control over the speakers, that’s my experience too. The power isn’t so I can rock out and anger the neighbors, but the opposite. In my experience, more powerful amplifiers don’t need the volume as high to get a full, convincing sound.

Is there a point where it gets too powerful, and the sound suffers? I’ve read extremely powerful amplifiers can sound sluggish. Not sure what to make of that.

And budget is $2000. I prefer the bang for the buck of buying used... reputation for reliability is important



No mention of price point above.
I have the latest Spread Spectrum Son of Ampzilla MK-2,and I could not be happier It runs in pure class A to 10wpc then class AB .up to 220wpc into 8ohms,
340wpc into 4ohms and throws off very minimal heat. Class leading performance 
And compact in size. $4200 retail.
Those Paradigms like high current/voltage amps like Anthem. Paradigm is the parent company of Anthem. I've heard the two paired and they sound great. 
I wouldn't be afraid to push 200 watts through your speakers. Your going to maintain driver control better than if your easing in to 70-80 watts. You want better braking.
Your speakers are 92db and nominal 8 ohms and with your small room you don't need that much power. you could getaway with 20-70wpc in a quality class A/B that will not over heat your room. Class D is an option but I would listen to one first see if its your cup of tea.  There is quite a few quality amps in your price range and at the lower watts you can get more for your money as your not buying power.


tripg,

There is this class d stereo amp for sale on audiogon that you may want to look at it would have 200 watts a channel into 8 ohms and class d amps have great bass with tremendous slam.

Just a thought,

Kenny.
tripg,

With the info you gave us of your present status and also you may be in the position to upgrade speakers later.

You probably could find a class d amp used that would not exceed your budget or another possibility is the new Schitt audio Vidar that sales for 700.00 and I have heard a little bit of feedback on it that it sounds pretty darn good,I haven't had a chance to listen to it.

Kenny.
Space is actually one of the big issues for me. I'd love for instance, a pair of Parasound monoblocks, but have no room at all.
@gdnrbob
Paradigm studio 40... but hopefully I’ll be in a larger space in which I could use floorstanding speakers in the next few years
@tripg 
McCormack's have a very good sound at a very good price. SMc Audio will perform upgrades that will bring them to current standards, too.
The DNA-1 I owned didn't put out that much heat, either. It was warm, but not a space heater like my Atma amps-which I love to death.
What are your power needs/speaker? It would help in giving you a recommendation.
Bob
Cmach, do you have any experience with Audio Research, Krell, Bryston, or Aragon? If so, how does the McCormack compare?

I realize there are tons of variables, but any information is helpful.