Try a not-cheap Class D amp. It’s all about noise floor of the PSU and proper filtering of the Class D carrier frequency. When the filtering is not done right*, there might be harsh / fatiguing artifacts like ringing or overshoot on sharp transients. With cheap PSU’s the noise floor will not be quiet. A good Class D amp with a good PSU can have a noise floor in the single digit microvolts rms. Pressing your ear to the AMT will sound like nothing with no music playing - you can’t tell it’s on. Transformer coupled output tube amps tend to have softer transients so will sound “smoother” by their intrinsic nature of having large inductor as part of the output signal path. The noise floor of a tube amps tend typically will have audible hum on the woofers though.
However, I do enjoy a good Class AB or even better, a Class A amp driving an AMT. But there is no reason to avoid Class D for the tweeter like an AMT, if the amp is done right.
* Done right requires high quality shielded inductors and film caps on the output. These components alone, often are more expensive than an entire assembled amp board from an inexpensive Class D offering with free shipping! ($50).
Here is the measured noise floor in my TPA3255 implementation with a good SMPS. Inputs shorted and 10ohm dummy load.
I use this amp with AMT’s (Heil and Dayton) and ribbon tweeters (RAAL) routinely with great results.
However, I do enjoy a good Class AB or even better, a Class A amp driving an AMT. But there is no reason to avoid Class D for the tweeter like an AMT, if the amp is done right.
* Done right requires high quality shielded inductors and film caps on the output. These components alone, often are more expensive than an entire assembled amp board from an inexpensive Class D offering with free shipping! ($50).
Here is the measured noise floor in my TPA3255 implementation with a good SMPS. Inputs shorted and 10ohm dummy load.
I use this amp with AMT’s (Heil and Dayton) and ribbon tweeters (RAAL) routinely with great results.
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I use Buckeye Hypex Ncore to drive a pair of speakers with Mundorf AMT tweeters and it's fabulous. The crossover is passive. Frequency response is linear and the sound is accurate. If you don't like the sound of it then it's more likely a crossover problem than an amplifier problem unless you're using a really cheap Class D amplifier. Newer Class D stuff is great all the way up to 20KHz.
Thank you for your quality response! I will probably stay with tube amp to power the AMT's but will switch from the KT-88 amp to the EL-34 PH amp.
I think it sound a bit smoother. Another plus is that the signal feeding these amps is from an active CX.