thebes Posted July 4, 2012 Share Posted July 4, 2012 Recently had a Mirror Image Audio 1.1S, a long-gone boutique $5k SS amp in da house. Very enjoyable by the way, but not the gist of this post. This thing consists mainly of a coca-cola sized power caps, a giant toroidal transformer, a large internal fan for cooling, and truly massive heat sinks that become too hot to touch when this puppy has been fired up for awhile. From my albeit limited understanding SS amps run on low voltage DC, there's no Output transformers, and no glass tubes. So why do they run as hot as tube gear? It seems like most of what's going into them from the outlet is coming out as heat so I''m guessing they are woefully inefficient and wasteful. Am I wrong, what gives? Quote Link to comment Share on other sites More sharing options...
willland Posted July 4, 2012 Share Posted July 4, 2012 Thebes, The only thing I can think of that would make an amp like your Mirror Image Audio so hot would be it could be highly biased towards class A which is inherently more inefficient and expells more energy in the form of heat. Many of the older and boutique amps run more in class A to get a little closer to the "tube like" sound that you and so many forum members love with their Heritage. Bill Quote Link to comment Share on other sites More sharing options...
ZAKO Posted July 4, 2012 Share Posted July 4, 2012 Class A bias runs very hot,,,I heat my mancave in the winter with it,,, Quote Link to comment Share on other sites More sharing options...
Guest " " Posted July 4, 2012 Share Posted July 4, 2012 If the amp has heat sinks that are very hot to touch...then yeah...probally running in class A. Class A is a topology in which there is very little switching distortion since the transistors are running at full current all the time. Whereas other amp topologies run the transistors at idle inbetween music signals and switches them on during music passages.....these can be made smaller than class a amps but have switching distortion. Quote Link to comment Share on other sites More sharing options...
MikeFord Posted July 5, 2012 Share Posted July 5, 2012 If the amp has heat sinks that are very hot to touch...then yeah...probally running in class A. Class A is a topology in which there is very little switching distortion since the transistors are running at full current all the time. Whereas other amp topologies run the transistors at idle inbetween music signals and switches them on during music passages.....these can be made smaller than class a amps but have switching distortion. Yup, Class A runs as hot at idle as full power, and to make a class A/B "better" they run class A up to a watt or so, maybe more these days. OTOH these goofy audio days we live in, could be the designer did things to intentionally make the unit run hot. I recall a certain audio designer many years about that wired the lights in the meters so they would dim at higher power levels, looked great. If you have a watt meter you might plug the amp into that and find out how much power it wastes. I say wastes, since modern designs can work very well with very little waste heat at idle, and older designs supported standby modes that reduced the wasted power. Quote Link to comment Share on other sites More sharing options...
JJkizak Posted July 5, 2012 Share Posted July 5, 2012 There are a lot of industrial solid state products that run at 100C on aluminum heat sinks and I personally think it is a product of "Brain Burn". The failure rates were astronomical plus the down time waiting for the assembly to cool down so you could touch it to remove same. JJK Quote Link to comment Share on other sites More sharing options...
thebes Posted July 5, 2012 Author Share Posted July 5, 2012 Ah that's it. Thanks guys. That must be it. It draws about 6 amps at idle at 122 wall volts according to the meter on my variac. In contrast, my tubed Bogen MO100A, 100 watt tube monos, draw only about an amp and a half at idle. Maybe it's me but it sounds like Class A is an inelegant engineering topology, an insult to proper engineering. Quote Link to comment Share on other sites More sharing options...
russ69 Posted July 5, 2012 Share Posted July 5, 2012 Maybe it's me but it sounds like Class A is an inelegant engineering topology, an insult to proper engineering. Actually class a is the elegant solution. The other topologies were designed to increase efficiency but it will cause other issues with switching distortion. Class a is the pure mode. Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 6, 2012 Share Posted July 6, 2012 Maybe it's me but it sounds like Class A is an inelegant engineering topology, an insult to proper engineering. It's statements like this that just......" Makes Me Want To Spit..!!! " [] miketn Quote Link to comment Share on other sites More sharing options...
sunburnwilly Posted July 6, 2012 Share Posted July 6, 2012 Why does my processor run so hot when I can barely get my amp warm ? Quote Link to comment Share on other sites More sharing options...
willland Posted July 6, 2012 Share Posted July 6, 2012 Why does my processor run so hot when I can barely get my amp warm ? The processor is asked to do a ton of stuff and does not have the heat sinks that your Parasound amp has. Your Marantz pre/pro is basically a computer. Put your hand on the bottom of your laptop after a few hours of "processing".[6] Bill Quote Link to comment Share on other sites More sharing options...
thebes Posted July 6, 2012 Author Share Posted July 6, 2012 Haruumph! Lifted from the internet: "Actually, the idea that a Class-A amp draws a continuous steady current from the supply is true in one case only. A single ended amp using a current source as the collector load will draw a continuous steady current - but only if it uses a single supply. In the case of a dual supply, the same amp will draw a continuous current from one supply, and a varying current from the other. (My thanks to Geoff Moss for pointing this out - a detail that few published designs have ever mentioned !)" I'm sticking with my statement. Engineering should be more than simple, it should be elegant. Like listening to Beethoven while wearing a smoking jacket and sipping from a crystal glass of rare brandy.. Class A sounds like simple brute force, employed because the engineer wasn't smart enough to come up with something that worked better. The more I think about it, the madder I get. Why I Could just... Quote Link to comment Share on other sites More sharing options...
tigerwoodKhorns Posted July 6, 2012 Share Posted July 6, 2012 Thebes, Think of it as an old car that got really bad gas milage. Plus those huge heatsinks made sweaty audiophiles feel manly... 1 Quote Link to comment Share on other sites More sharing options...
oldtimer Posted July 6, 2012 Share Posted July 6, 2012 Get a good ole made in usa sunfire amp. Cool runnings mon. 1 Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 7, 2012 Share Posted July 7, 2012 Class A sounds like simple brute force, employed because the engineer wasn't smart enough to come up with something that worked better. Well in my experience to date Class A when properly designed is the reference in sound quality that the other forms of amplifiers have to measure up to.....of course if anyone feels different to each his own. The engineering decision to use a well designed standard (brute force) pwr supply isn't lazy in my opinion but does have advantages in long term reliability if done properly. The compromise (which all designs must have in one area or another) is the low watts available versus the operating watts of the amplifier in this design form. IMO using high efficiency loudspeakers with these (brute force pwr supply) low wattage class A amplifiers (Tube or solid state such as Pass and First Watt designs) is extremely elegent with potentialy very long term reliability performance and above all reference quality sound reproduction. Now if your not willing to except the inefficieny of the previous design mentioned then other engineer options are available today such as this Kell design. http://www.stereophile.com/solidpoweramps/694krell/index.html Now this is a high wattage design but could be designed and scaled for low wattage Class A amplifiers also if someone desired for the efficiency. What would some potential compromises and sound quality of this unit be? The power supply and it's associated tracking circuity will have a much higher parts count which has the potential for a higher long term failure rate versus a (brute force pwr supply). I see no reason anyone would expect this (smart pwr supply design) would sound any better than one designed with a (brute force pwr supply) and IMO it would just equal it's performance at best if the tacking pwr supply is not perceptable and a high quality horn system might be the best loudspeaker for testing such a design with IMO. miketn Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 7, 2012 Share Posted July 7, 2012 Think of it as an old car that got really bad gas milage. I agree the performance of new cars is awesome when comparing gas milage but if you have ever had one with an intermitent electronic issue and the cost of tracking it down it can sure make you miss them old cars.[] Quote Link to comment Share on other sites More sharing options...
JJkizak Posted July 7, 2012 Share Posted July 7, 2012 In the old days we used to hop up the buggy with bigger carbs, LP fuel injection, HP fuel injection, variable cam timing, four valves per cylinder, 4 tube headers, dry sumps, lightweight pistons, 4.56 gear ratio and now everything comes from the factory with that and ten times more with reverse flow coolant (higher compression cooler heads) 6 bolt mains, aluminum block and heads, turbos, 8 speed automatic transmissions that make the car jump tall buildings and still get good gas milage, tuned exhaust systems and everything computer controlled. Where is the poor guy who used to open the hood and tweek the carburetor? PS: I called GM in 1967 about how to break in an L-88 Corvette? They said and I quote: Start the engine and push the accelerator pedal to the floor and go like hell. There is no break-in because of the moly rings which seat instantly and the ,002" of aluminum facing on the valves for instant sealing also." They also said that you cannot break that engine. I said, "OK man, far out" JJK Quote Link to comment Share on other sites More sharing options...
Don Richard Posted July 8, 2012 Share Posted July 8, 2012 Class D is the ultimate answer for a transistor amplifier - cool running, efficient, powerful, sounds good. Class A, although workable, has all of the disadvantages mentioned earlier and is also tapped out as far as future development and/or evolution is concerned. Class D is an emerging technology with continual innovation and improvement, occuring daily it seems. Quote Link to comment Share on other sites More sharing options...
thebes Posted July 8, 2012 Author Share Posted July 8, 2012 Class A sounds like simple brute force, employed because the engineer wasn't smart enough to come up with something that worked better. Well in my experience to date Class A when properly designed is the reference in sound quality that the other forms of amplifiers have to measure up to.....of course if anyone feels different to each his own. The engineering decision to use a well designed standard (brute force) pwr supply isn't lazy in my opinion but does have advantages in long term reliability if done properly. The compromise (which all designs must have in one area or another) is the low watts available versus the operating watts of the amplifier in this design form. IMO using high efficiency loudspeakers with these (brute force pwr supply) low wattage class A amplifiers (Tube or solid state such as Pass and First Watt designs) is extremely elegent with potentialy very long term reliability performance and above all reference quality sound reproduction. Now if your not willing to except the inefficieny of the previous design mentioned then other engineer options are available today such as this Kell design. http://www.stereophile.com/solidpoweramps/694krell/index.html Now this is a high wattage design but could be designed and scaled for low wattage Class A amplifiers also if someone desired for the efficiency. What would some potential compromises and sound quality of this unit be? The power supply and it's associated tracking circuity will have a much higher parts count which has the potential for a higher long term failure rate versus a (brute force pwr supply). I see no reason anyone would expect this (smart pwr supply design) would sound any better than one designed with a (brute force pwr supply) and IMO it would just equal it's performance at best if the tacking pwr supply is not perceptable and a high quality horn system might be the best loudspeaker for testing such a design with IMO. miketn Uh oh, I'm in a contrarian discussion with my mentor and electronic guru. This will probably not turn out well. Especially since he knows what things like "slew rate " actually mean. Yes all designs have tradeoffs, but it still seems the trade-offs, low distortion versus heat and the need to own your own personal nuclear reactor are not to me, imo, the hallmarks of elegant engineering. The tradeoffs seem too stark. Now as a "no compromise-low distortion" engineering design, I can get behind that descriptive. But elegant? I don't know. Think about it. I'm not an engineer but hundreds, if not thousands of engineers, have similar problems with Class A and it's one of the reasons they keep trying to come up with better solutions than betting the farm on that good first, and very inefficient, watt. Maybe it's just semantics we're arguing over, but given all of the other topologies invented since those early Class A tube radios, I'm not so sure. I did read the article on the Krell, by the way, and I'm pretty sure the technical descriptives are not written in English.[] Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted July 9, 2012 Share Posted July 9, 2012 Think about it. I'm not an engineer but hundreds, if not thousands of engineers, have similar problems with Class A and it's one of the reasons they keep trying to come up with better solutions than betting the farm on that good first, and very inefficient, watt. My friend if you own efficient horn systems you would be well advised to be "very" concerned about "miliwatts" let alone the first watt. If you have a Klipschorn rated at 104db @ 1watt/1meter then lets do a chart to see what area of amplifier power performance might be most critical. 10watt = 114db 1watt = 104db .1watt = 94db .01watt = 84db .001watt = 74db .0001watt = 64db .00001watt = 54db So in a typical sized home listening room and considering the noise floor of the room, the average and peak levels that many people will be listening at you can get a reasonable idea were the critical performance range falls. So if inner detail resolution, clarity, dynamics, tonality....etc ie: everything that high quality reproduction is about then what happens way before you get to your first watt is critical to performance with efficient horn systems like the Khorn. Bottom line it's about what works best for your needs and I hope this shows that for many its a very good option for very good reasons. "Yes all designs have tradeoffs, but it still seems the trade-offs, low distortion versus heat and the need to own your own personal nuclear reactor are not to me, imo, the hallmarks of elegant engineering." Just so you know my Cary CAD 2A3se mono amps use 76 watts ea.. and IMO an elegantly engineered solution for my efficient horn system and like great horn designs deserve high respect because the technology is based on sound technical bases and what does the fact that it is an old or mature technology matter if it has and continues to stand the test of time. It's simple and beautiful my friend at least from my point of view....[] miketn Quote Link to comment Share on other sites More sharing options...
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