Looking for 200 watt Amp to drive Dynaudio Heritage speakers

@audio_is_subjective You have a cart to carry your oxen??

To me, those impressions are mostly consistent with the current comment,

“lack of soul or engagement."

@mitch2 Right- but apparently, only holds true for those examples. They don't represent all class D amps any more than saying something like that represents all class AB amps. And there are plenty of the latter that suffer the same problem and are bright and harsh to boot.

But there are class D amps that are as involving and as musical as the best tube amps, perhaps even better as just pointed out. The ones I'm playing at home are more revealing than the triode OTLs I was playing for years prior but just as engaging so I don't miss the tubes at all.

it seems that lack of soul or engagement is a common theme more so than other critiques.

@marco1 I get that- I've experienced that myself. I think that comes from the designer not understanding that just because the amp is high efficiency that they still need to have a really robust power supply. If its not there the amp wimps out when you turn up the volume.

There's more to it than that of course. In exploring class D amps over the last 20 years, my impression is they vary in sound more than the worst to the best tube amps do. That's a pretty wide range.

I've been playing triode class A amps for most of the last 45 years if that's any help in understanding where I'm coming from...

 The comments regarding Class D lacking “soul” is what was most interesting to me as I very much feel the same way when comparing my new Class D amp to either the tube or Class AB Solid State amps I also currently use in my systems.

@marco1 That has nothing to do with the class of operation and everything to do with how the class D amp is designed.

200W into 8 ohms. 100 amperes peak per channel. 45 lbs

@som FWIW Dept.:

The 100A has nothing to do with the output power just so you know. That’s probably the current that flows when the power supply is shorted for 10ms. I guarantee that if 100A flowed through the output section it would be permanently damaged.

The math tells you what is up. Power is mathematically related to speaker impedance and current:

P = R x Current squared

(R is the speaker resistance)

So if we give the amp the benefit of the doubt that it can double power as impedance is halved, and so use a 1 Ohm load, the current squared is then equal to the power. That’s 100 squared or 10,000 Watts. That doesn’t ’square’ with 200 Watts into 8 Ohms if you see what I did there. If it can double power right to 1 Ohm it would be 1600 Watts- to my knowledge no-one makes a 10,000 Watt amp that might be considered hifi.

If we use that current rating as a short circuit value (essentially a measure of how much capacity is available in the power supplies) then this makes more sense. We make a tube amp that has 80Amps available by that measure (the MA-2).

Owning relatively insensitive speakers myself (sensitivity of 86 dB at 2.83 Vrms and 1.0 meter on axis) that also have a low’ish impedance (4 Ω nominal, 3 Ω minimum, low reactance), but a high power handling capability, has led me to appreciate how more power (650 wpc/8 ohms/side in my case) can bring them to life in a way that results in a weightier, more tonally rich delivery that increases my overall sonic enjoyment.

@mitch2 Just a few items to point out here. The first is that the more power you need, the harder it is to find electronics that also sound like music. To that end, if you really need 650 Watts for your speaker to sing, they are next door to criminally inefficient, since you’re likely to never really get them to sound real.

As speakers become less efficient, a common problem is thermal compression, where the voice coils (in particular that or those of the woofer(s)) heat up with musical notes, thereby dynamically reducing current flow with those notes. The more efficiency you have, in general the less you deal with this problem and of course its far easier to find electronics for them that are musical.

Also FWIW there is no need for higher efficiency speakers to have less resolution or bandwidth. My speakers at home are 98dB and are flat to 20Hz; they are some of the most resolving speakers I've heard.

People have asked us why our class D is only 100 Watts (into 8 Ohms; clips at 125Watts and 250 into 4) and the answer is above. If you really need more power than that you need 1000 Watts, as 10x more power is needed to sound twice as loud.

Simply doubling power is only 3dB, hardly audible. So this is really far more about how the amp behaves with a musical signal than it is power! Even with a speaker of 86dB, the first 5 Watts are still the most important.

Your comment in the OP is probably the reason they were not recommended, because they are only rated at 100 wpc into 8Ω.

@mitch2 The speakers in question are 4 Ohms.

So I decided to give the Dynaudio HS speakers a whirl with the Conrad Johnson amp which is 125 watts per channel. I didn't expect much, but was sort of blown away. The CJ amp totally opened up the speakers in a way I didn't expect and made me realize I can get away simply powering them with the CJ amp. 

@bluethinker The difference between 100 Watt and 200 Watts is 3dB, which to the ear is barely noticeable. As you found out this is really more about how the amp plays with the speaker than it is power.

There are some things to consider when using tubes with 4 Ohms. First, although tube amps have 4 Ohm taps, the output transformer often loses an octave of bandwidth between 8 and 4 Ohms because its less efficient. This loss, which is usually less than 20Hz, results in less impact due to phase shift in the bass. If you measure the temperature of the output transformers with a thermal camera you'll also see they are running warmer into 4 Ohms- and that heat is power made by the output tubes.

You'll also find that the speaker cables are far more critical using 4 Ohm speakers so its best to keep them as short as possible (an argument for monoblocks). This is particularly true of tube amps which tend to have a higher output impedance.

There are class D amps now that don't take a back seat to tube amps of any kind in any way (except overload character) that can make the power you were asking about.