What tube amp for Harbeth 40.1

@gte357s ,

’I don’t think the speakers draw power, but it is the amp pushing power, right?’


The speaker / amp relationship is pretty murky, at least to me, but the important thing to remember is that to get the same volume from the M40s a lesser powered amp might be forced into clipping, even if it’s for mere milliseconds.

Clipping happens when an amplifier runs out of power a bit like a car with a tiny engine going up a very steep hill. If there isn’t any protection built in to the amp, clipping can be disastrous for the loudspeaker.

With a more sensitive loudspeaker you certainly wouldn’t want to keep the volume knob in the same position unless you wanted to use it outdoors or in a much larger room.

This is assuming that it was capable of being played much louder in the first place. Not all more sensitive speakers are, but size is a good indicator.

It’s also worth remembering that loudspeakers are horribly inefficient devices. Hence the temperatures inside the voice coil can reach hundreds of degrees.

Much like car engines, most of the power going in is converted into heat. not sound (or in the case of the car engine, power). Overheating is a common enemy of both.

For those who like to play loud, thankfully before we are able to destroy our speakers by overheating, we should get a warning by experiencing a compression (and likely much distortion) in the sound.

It might simply not be worth going beyond a certain point of the amp volume dial as the speaker will tend to only get hotter, not louder.

https://en.m.wikipedia.org/wiki/Power_compression

I stream a Cambridge Edge NQ through balanced cables to a McIntosh 275 into Harbeth 7-ES3 speakers and I am extremely happy with the result, as I age, my hearing has deteriorated so I can't analyse the result except to say it is the best music I have enjoyed in 50 years of Hi Fi / audio experience

Try some Manley💪

I run the Leben 600x w my Devore 0/93.  Very nice combination.  PM me if you want to discuss the amp further.

I watch that video, it is interesting.  But I have a question.  Is it really the speaker drawing power?  I don’t think the speakers draw power, but it is the amp pushing power, right?  
I have a question. if we play the same music, volume knob at the same level, to a more sensitive speaker, will it display that it is pushing the same 750W power? 

The amp makes the power and the speaker draws the power it can based on its impedance and the voltage that the amp makes. So for a given voltage, if the speaker draws one watt and its impedance is 8 ohms, into 4 ohms it will draw two watts if the amp is making the same voltage. Its a mathematical relationship.

Regarding the more sensitive speaker question, if the impedance is the same the power will be the same. Now the thing about more sensitive speakers is if the impedance is 8 ohms or more, the amp will not have to work as hard to make the same sound pressure level and usually will make less distortion. If it makes less distortion, it will sound smoother and more detailed (since distortion can mask low level detail). Now solid state amps in general tend to make higher ordered harmonic distortion compared to tubes, and so tend to sound bright, even though that distortion is fairly low. The reason we perceive it as bright is because the ear uses higher ordered harmonics to sense sound pressure and is thus keenly sensitive to their presence. It is this simple fact that is why tube amps are still around.


The reason solid state amps tend to sound bright is that usually they don't have *enough* feedback (some get around this by having none at all). Its pretty hard to design a circuit that allows for really high amounts of feedback (+35dB). So most simply don't. The result is that the application of the feedback itself, while suppressing some distortions, actually adds some of its own (which is almost entirely higher ordered harmonics; that which is not is IMD and both are very audible). Unless you can get over that 35-40dB range, this will be a problem, and its been a problem in solid state design since the inception of the transistor.


To get around this problem, many solid state amp manufacturers have resorted to a simple technique called 'lying'. But our ears don't lie- we've been hearing brightness and harshness in solid state amps for the last 60 years; that is why tubes and tube amps are still around decades on from being declared 'obsolete'.