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?
There are a lot of good Class D designs out now. You may pick up some ideas in this thread:

Class d is a cool running option,if you don't like the sound and some people don't then find a Solid state class a/b amp that you like.

Probably wouldn't want a tube amp for the heat issues that they can have also.

It would help us maybe give you a list a candidates if we knew,

Your budget
The rest of your system,primarily your speakers.
Room size
Sound levels
Types of music that you listen too.

  I use a digital amp company cherry plus amp.  Very clean and powerful and runs cool.  I pair it with a tube preamp and it sound very nice
I owned as McCormack DNA 500 for a while and it never got
hot. One of the cooler running amp's I've owned.

Thanks for your responses! I'll check out that link.

In the meantime...

Kenny, I have and audio research ls27 preamp and paradigm studio 40 v4 speakers. The room is 8x10, and it's lined with shelves of records, making it even smaller. No room for floor standing speakers, and placement is suboptimal. I realize such a small room has limited potential, but all the upgrades have been fruitful so far, and I've also bought keeping a future space change in mind. So while I need something that sounds good with the studio 40's, there will likely be a speaker change at some point and I want an amp that can handle bigger speakers.

I always buy used and my budget is $2000
And I listen to a very wide range of music. I’m a jazz drummer so the drums need to sound real!!! But in addition to jazz I also listen to Indian music, European classical, African drumming, korean music, indie rock, etc at mostly moderate levels.
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. 
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.
Paradigm studio 40... but hopefully I’ll be in a larger space in which I could use floorstanding speakers in the next few years
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.

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.


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,

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.

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.
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.
Roksan Caspian M2.
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

Almost any other solid state amp out there will be cooler than the KSA-150 or the VT100. Just saying.
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.

[email protected] / [email protected]
all the power i will ever need.
Look at Nuforce Reference 18 monos used or some of their new stuff under Nuprime in that price range
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.

Ayre also makes some great 5 series amps. 150 watts into 8 ohms. They should run around $2250 - $2600 used. Very transparent. 
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 !!
If you want tubes, Primaluna amps running pretty cool.
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!
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.
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.
The hottest amps sounds the best.
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.
Post removed 
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.

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.

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. 
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! 
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 .. 
@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)

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.
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. 
Karan KA-I 180Mk2

2x180W/8 sliding bias , cold like a stone ...second hand, almost new like ex demo  in TX about 5.000 $
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.

[email protected] / [email protected] / [email protected], /  stable to 1 Ohm

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.
Primare A34.2 or A60, which has a DAC.

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

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. 


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.
NuPrime STA 10 or IDA 16
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).
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 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.

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.  

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