Amps that don’t impersonate space heaters.

I had Pass XA30.8 and X260.8 monos. Operating temperature was about 104-105!degrees Fahrenheit. I have Coda CSib V1 integrated now with 18w Class A that is smaller than Pass and runs at around 97-98 degrees. Not as much heat and not enough to become a nuisance. Sounds great too. The equivalent stereo amp is Coda no.8 V1. 

@audphile1 I was going to say that my Coda Continuum No 8 V1 is barely warm.  Mine also runs class A up to 18 watts. 

Yep it’s not enough to heat even a small room. And it sounds superb! The first 18w in Class A is what the Avant-garde are going to use. And most likely never exceed. It drives my Wilson Audio Sabrina (87db and 4ohm dipping into 2ohm) no problems. 

@sls883 I have the same version 1 amp. The reason it's so cool is because it has the heats sinks to cool a 400-watt amp (8 ohm) version 3. This is one of the reasons I bought it plus the fact Coda is a 15-minute drive from my house and I can have it changed to a V2 or V3 within 24 hours.

@willywonka thats cool.  I assume you've met Doug Dale?  Real nice guy.  I've spoken to him on the phone, but never met him.

I bought my first Coda over 20 years ago. It was the original Continuum Stage. The capacitors were starting to go bad.  Doug was willing to repair it for a reasonable price, but with shipping two ways, it added up.  I've upgraded my speakers, so it seemed like a good time to upgrade my amp. Doug took my old amp on trade. 

I’d absolutely take a look at Valvet amps — lower-powered Class A amps from Germany not as well known here, but read the reviews that are universally chock full of superlatives. 

https://highend-electronics.com/collections/valvet

@sls883 Yeah, I've been to his office a couple of times and bought my amp directly from him. He gave me a good deal since we didn't have any Coda dealers in this area. Had some long talks with him. Very interesting guy with some great stories.

The aforementioned Codas run quite cool for their topology, much cooler than Pass IME.

My Parasound A21 also keeps fairly cool. For its bass “slam” and depth, I prefer the A21 to the Coda No.8V1. The latter is slightly more refined however.

I also recommend considering the Michi S5. 

Check out the Benchmark amp. You can just leave it on.

Take a look at the Coda S5.5. 50 WPC Class A amp that runs cool, you can put your hand on it an leave it there. It is superb sounding, probably a little better than your Pass 30.5 according to Terry London. He has heard both amps in his system. Here is info: https://forum.audiogon.com/discussions/the-new-coda-s5-5-amplifier-it-s-a-petite-beast

@helomech i haven't heard the Parasound, but I think I get good slam and depth from my Coda. I suppose speakers, cables, and everything else play into that. 

I also thought I was getting good “slam” from the Coda until I swapped my Yamaha 2100 back into my system, and subsequently the Parasound A21. That experience really highlighted for me the power of expectation bias. 

Apparently bass strength is a common sacrifice with amps employing little to zero global feedback. 

However, I don’t think the OP would notice much, if any reduction in bass going to Coda from low power Pass Labs. The Coda 8 essentially sounded like a Pass XA25 in my system, just with more power and a little more bass extension. 

I recently moved my Coda #8 v1 into a new cabinet that has glass doors on the front, but with an open back. I was worried about heat building up around the amp so I placed a digital thermometer next to it, it reads in the mid-70’s F even after hours of play. I have not heard any complaints about this amp, might be a good choice. 

“Slam” is a very interesting attribute. What does it mean? Do you hear this “slam” when listening to live music? Is this “slam” an accurate representation of what’s on a recording or is it emphasis of particular frequency range that one component features over another? In most cases, “slam” is not real. Accurate reproduction/presentation is what I value in my system. This includes dynamics, tone, focus, layering, separation, soundstage. Coda is balanced pretty well in that regard. Imo

My take on slam is that it is one of the first and easiest attributes of a high end system to detect. It is the very abrupt wave of bass high energy from, say a kick drum on a recording. But in general it is not real. It is typically an artifact of high power solid state amps and often is accompanied by a leaness in the adjacent midbass or midrange, making it stand out more… a very fast rise and fall time. The difference for me was simply striking when I went from a Pass x350 to an Audio Research Reference160 amp. The bass sounded astonishing real and nuanced, like what I heard in a concert… a wave of bass that washed over you, extended in time and nuanced, instead of a single quick thump that disappeared quickly. So, no, I don’t hear slam in the real world and at least for me, I was incredibly happy to trade it for a much more realistic and nuanced sound.

There have been some epically hot periods in metropolitan Chicago this summer. I have had a long running affair with a pair of Avantgarde Uno s2’s and don’t really require a great deal of power. I have two dissimilar but equally compelling amps (a Pass 30.5 and a BAT vk-56) both prodigeous producers of heat creating a sauna like environment in my library/listening room the HVAC system not withstanding. What, if anything, have you boys and girls found that might replicate the qualities of my beloved amps minus the potential for 3rd degree burns and heat prostration?

@williamjohnston If you don't like the heat consider a class D amp. There are some now that rival class A tube or solid state amps in terms of sound quality (with a very good first Watt)- no harshness and actually lower noise so no problem running on horns. I have a set on my speakers which are 98 dB. They replaced a set of class A triode OTLs. I don't miss the tubes at all.

@ghdprentice you nailed it. Realistic and nuanced is exactly what I’m looking for as well. Accuracy of tone, expression, dynamics and articulation win any day over artificial “slam”.

@atmasphere Agree, I run a class D in warm weather and no heat streaming off.  In fact, can turn it up and let it run for hours and no heat coming off.  I haven't found one that sounds toe curling wonderful, but it isn't turning the room into a sauna.  On the brighter side, in Chicago, you need to worry about too hot for 2-3 months? 

@hoosierinohio Agreed, but I run a class D because of its sound quality. The low heat and energy draw is a side benefit.

I use Parasound Halo A21+. A beast at 500 watts per channel at 4 ohms. It gets a little warm to the touch but not enough to affect room temp at all.

A/ B amp with first 6 watts pure A.

Simaudio, accuphase or luxman(class a/b). I have both and neither run that hot. I live in Chicago as well. Stay away from pure class A. 

I also live in the Chicago area, and the amp I use that never gets more than room temperature is an Anthem P-2 you can play it all day and night at full power and it never even gets warm to the touch.

ADG monoblocks sound very good for the money and produce little heat… and come in a carrying case and look like tubes to boot. I’ve had them in my system. 

I used to run a BAT VK55SE amp and loved the sound, but couldn't bear the high temps in the summer. I picked up a pair of Atmasphere Class D monoblocks prior to last summer and haven't looked back. Much as it bothers me, I never put the BAT back in service during the 'dark season' as the Atmasphere Class D amps just sound too good to put on the shelf.

I'm running them with a BAT VK33SE preamp, into a pair of Raidho X1 monitors, in a studio-like (i.e. very near field) setup and absolutely love the sound. 

Per his comment above, I'm in the same camp as Ralph: The sound the Atma Class D amps put out has everything I need to enjoy hours of listening, deep into the music, and without fatigue. The fact of them running with virtually no heat is but a mere side benefit.

GanFet or Class A (sliding bias tech) SS amps

Class A done well has special qualities that seem to come at a price. Only tubes seem to extract a similar price, thermally. I can suggest a couple of options:

Combine a tube section preamp with a well-designed Class D (e.g., a ProJect Pre Box RS2 Digital and a NAD C298).

Use a modern GaN FET amp: Peachtree’s Carina GaN for example.

Use a hybrid amp with partial class A topology, NuPrime IDA-8 is compact and is a Class A- Class D hybrid which has been a successful model in that company’s lineup.

Your horns should do well with any of them.

@ghdprentice Thank you for the succinct description of high quality bass reproduction. I loved my slam back in my younger days, and noticed that it disappeared as I got into better gear, to be replaced by a more complete reproduction of the music. The nuance in the low frequencies is one of the best parts of a quality system. 

Seconding the Atma Class D's. Tube amps and A/B amps just roasted me in my hot and small upstairs bedroom. Atma's solved that issue with zero heat and they don't even get warm. I don't think I'll ever be selling them. 

I am most grateful for all of these intriguing responses. I am only familiar with Coda by name but I am obviously taken with many things spawned by Threshold. I didn’t see them at AXPONA but believe they have a presence in Chicago. Class D is also an intriguing idea. Again, I have scant personal experience but the dimensions and weight are most appealing to a person addicted to swapping out amplifiers and who will celebrate his 74th birthday soon. The fact that many suggestions accept balanced input a distinct plus as this is a cult I joined long ago. I wasn’t aware that Atmos-phere made a class D amp. Have always respected Ralph’s products. I have never owned one but OTL has always fascinated me since meeting ‘Gizmo’ at a CES in Chicago long, long ago. Again, appreciation to and for you all. 

You want a great amp that runs cool? McIntosh MC312.

I recently changed my electronics to Pass, but have to say that the MC-312 (and probably the MC-462) are great sounding, very well built amplifiers and they never get above warm. More specifically, the heat generated will never be felt from your listening position or in your room.

Seems like a semi-Coda thread going on here  I'll contribute.

Stay away from pure class A. 

Well, I have always thought this too, based on what I have read, where I am at in the middle of BC Canada this past July saw 23 days exceeding 30 degrees Celsius (86 F), 20 consecutive days exceeding 88F, with the highest temperature reaching 108F in that span. So yeah, heat from my system is a concern. But I read from others than the Coda class A units ran cool, so I gave it a go. 

I picked up a 100 watt Class A Coda to run my high channels on my maggies, while the bass is still powered by my Class D Apollon NCx500. Some may find this surprising: Both amps have been powered on for over 24 hours, and playing music for 2 hours. Using a digital thermometer gun, the highest surface temperature reading I can get on the Coda is 33 degrees Celsius, and on my Apollon the temperature reading is 35 degrees C. 

So I could claim my class D amp runs hotter than my 100 watts of class A. Go figure.

This of course doesn't give an indication of the total wattage consumed, but simply staying away from Class A because it is "hot" appears to be based on old technology, or simply a myth. 

I love my Proceed HPA-2!  Still around for 1200-1600.  Not bad for a dual monaural amp that retailed for 3500 20 years ago. 250/8 500/4 bridgeable.  I power a pair of DCM Time Frame 2000's to concert levels and neither amp or speakers break a sweat.  It also has somewhat more to offer HT as there is also a HPA-3 for folks that like all channels with the same amp characteristics.  I've owned mine now for 6 years and it does everything I could ask, and dream frankly.  Your system should make you smile and mine surely does!

@williamjohnston keep us posted if you audition any of the suggested amps

I bought a pair of used PS Audio BHK 300’s. They do run warm, but unless you run them hard, they don’t get burning hot. According to Paul, the P in PS Audio, the first 5 watts are class A. Because their input stage is tube, you can roll a couple of tubes and change the sound of you want or need to.

All the best.

Slam” is a very interesting attribute. What does it mean? Do you hear this “slam” when listening to live music? Is this “slam” an accurate representation of what’s on a recording or is it emphasis of particular frequency range that one component features over another? In most cases, “slam” is not real. Accurate reproduction/presentation is what I value in my system. This includes dynamics, tone, focus, layering, separation, soundstage. Coda is balanced pretty well in that regard. Imo

“Slam” is perhaps not the best descriptor for what I was trying to convey. To be more concise, my Yamaha seems to provide better woofer control and authority than the Coda 8 in the lowest two octaves, even with speakers that have a -3dB point of ≈35Hz. It wasn't notable until I swapped the Yamaha back into the system. Otherwise the No.8 did sound quite balanced, but then so does the Yamaha. So it doesn’t seem to be a linearity effect, but more to do with outright extension and damping factor. The Coda has more power on paper but the Yamaha 2100 sounds more powerful in practice—more “effortless.” That’s the best way I can describe the difference. 

My Parasound A21 sounds more powerful on the whole than either aforementioned amp, but it still doesn’t seem to plumb the lowest octave quite as deeply as the Yamaha. But among the dozens of amps I’ve owned, the Yamaha digs the deepest for some reason. That’s not to say the Coda is a slouch in that regard, it is certainly better than the majority of Class D amps, without question. 
 

@helomech Coda CSib appeared to have less bass than my Pass monoblocks initially in my system. As I spent more time with it, I realized the bass Coda produces is accurate, fast and tuneful. There’s plenty of it too. It will not shake walls which usually comes at the expense of quality of the bass and you end up with a one note huge bass output that lacks definition, texture and speed. Highly dependent on speakers, associated equipment and personal preferences though…

@audphile1

I know the sort of thing you’re referencing regarding bass quality vs quantity, but that’s not what was going on with the No.8 vs the Yamaha. With the Yamaha, the bass sounded as though it dug a whole half octave deeper. I asked Doug at Coda if having the V1 boosted to V2 or V3 level would bridge that gap but he didn’t think it would.

One recurring theme I encountered in researching this phenomenon is that bass roll-off is a common trait among amps employing zero global feedback. I can’t say for sure what the culprit is but I owned about 5 different pair of speakers at the time and the same difference was audible with all of them. With my Magnepans specifically, I was not impressed with the Coda despite its alleged current output. Putting the A21 to the Magnepans following the Coda was a revelation.

I do still like the Coda amp on the whole. It was very quiet at least, much quieter than most amps.

One recurring theme I encountered in researching this phenomenon is that bass roll-off is a common trait among amps employing zero global feedback.

@helomech I've seen zero feedback amps that go full power to 1Hz and don't seem to lack any bass at all. IOW its not a common trait.

@helomech just out of curiosity what preamp did you use with coda

@audphile1 

I tried a variety of preamps. The Benchmark LA4, Topping A90D, Mac C49, and the preamp section of the Yamaha integrated. 

Go Class D, Atma, Hypex, Purifi, ADG. I don't think you would be sorry.

The Buckeye 1ET9040BA is barely warm to the touch and has the accuracy, insight and musicality I had hoped for. Very low SNR so not to intrude on your high sensitivity speakers.

Otherwise maybe a First Watt?

You're lowest heat, yet still awesome option is a nice simple SET.  You don't need muc power but any class A SS amp will have more watts than you need and all the heat associated with them.  

Your BAT uses the 6C33C tube that is one of the hottest ones out there.  It runs about twice the temperature and radiated heat goes as Texp4 so the increased tempeatrure adds a lot of radiated heat.  Also the BAT makes much more power than you need.  A imple 300B or 2A3 amp will be less heat than a TV screen, perhaps 100 watts (heat, not sound). Your BAT is likely 3-400 watts.  

An even lower power option is the Decware SE84series which is about 50 watts and plenty of power to drive those speakers.

Jerry

@helomech interesting. 
My Wilson Sabrinas are 87db and dip into 2ohm. 
I have 2 amps - CSIB and Boulder 866. Different bass but the Coda isn’t lacking. I’m slightly puzzled by your findings but it could be room and speakers. My system is in a pretty small room - 15x13

I started using class D am[lifiers in my space-constrained home office a few years ago.Earlier this year I picked up cherry, 4 yr-old pair of Bel Canto 600M monoblocks. I can't say enough good things about these amps.They have a smooth, refined, powerful sound. They're a real taste of the high end. And of course they put out very little heat.

I do the AGD Audions for the summer and switch to Primaluna mono blocks for the winter. I look at it as a space heater that sounds great! 

Go check out Derek Sanderson’s Fleawatt amps, you’ll be very surprised.  When I A/B’d it against a 6B4G SET amp, I had trouble justifying tubes, it just made no sense in running tubes when I listened to it….

You can go class D or you can just reduce the amount of power.  Think of it this way.  Class A is 25% efficient.  So you pass is delivering 30w x2 so that means 90w x 2 is just burning off as hear.  

You need 1 very good watt to drive those speakers.  Even Class A, 1-5 watts may remain extremely inefficient but if you you were to take say a 5w PX25 amp, it will burn off 15w x 2 instead of 90w.  

Flea watt tube amps are the way to go.  I offer Art Audio which are lovely amps and are magical with Avantgarde, particularly the PX25 but it is a lot more than your current amp.  Any good manufacturer that produces a 45, 2A3 or PX25 will give you what you want I think

You need 1 very good watt to drive those speakers. Even Class A, 1-5 watts may remain extremely inefficient but if you you were to take say a 5w PX25 amp, it will burn off 15w x 2 instead of 90w.

Flea watt tube amps are the way to go.

A good class D amp can sound even better and despite being able to make considerably more power, actually draw less power at idle and at any power level the amps mentioned in this post can make. At the same time it can be stone cold to the touch even after running all day. Plus there’s a good chance a class D set of amps would take up less room and would certainly weigh less. Literally no downside.