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ecodoppler 11th April 2008 09:22 AM

German Class D
Someone know Hi-Fi Akademie Class D amplifiers?

Calvin 11th April 2008 07:03 PM


Yes! :-)


Capaciti 12th April 2008 03:39 PM

Hi ecodoppler,

yes very well and its not a secret that i recommend those Amps of HiFiAkademie especially in combination with electrostatic loudspeakers.
Class-D amps are the one and only which do not care about the load they drive.

I do not know why the HiFiakademie amps sound best to me of all Class-D i listened so far, but i guess its due to the fact that these amps do not have a feedback loop in the high frequencies. As a result you need to be carefull not to provide a lower impedance than 2,5 ohm.

How should i summarize ? Spend the 800 Euros for a ready to run assembled amp (2x250 watts at 4 ohm), connect them to any speaker - it will rock it !!!


ecodoppler 13th April 2008 06:16 AM

Thank you Capaciti for your reply. I've a pair of Magneplanar 3.3/R matching to a Krell KSA 50; I've decided to replace it with two mono high power DIY Class D Amplifiers. I chose Hypex modules (probably the most famous in DIY community) but I could chose HIFi Akademie amplifiers; the problem is that they are not so well-know as Hypex and the website doesn't use English.
Best Regards

Calvin 13th April 2008 06:21 AM


apart from "..fact that these amps do not have a feedback loop in the high frequencies" I agree totally with Capaciti.
Of course does the feedback loop work over the complete frequency range. What he probabely meant was ´pre filter feedback design´.

What I like about the HAs is their elaborated design based on the Kiss-principle. They work flawlessly and have yet not interfered with other devices (EMC-problem). A post filter design like the UCDs may be good for better measurement values and because of their reduced reaction to different load impedances may be more universal. But sonically I like the shorter and more direct signal paths usually better.
The included extension slot allows for the very easy implementation of an analog or digital crossover PCB. They come as a stereo pair on one print. This reduces internal wiring and keeps the layout of the completed amp professionally clean (though I sometimes wished to have a mono-module at hand). You may reduce cost by building the amp from scratch, or use the completed modules (which allows even beginners to DIY a working amp.

As Caspaciti said. These amps are a really fine match for ESLs. My experience is that amps that don´t include the power stage (or in this case its output connectors) within a global feedback loop seem to work more stable and sound better with complex loads like ESLs. Since these transducers have a resolution of details far superior to any dynamic speaker, You can hear the tinyest problem. And so far every amp working with global feedback could be recognized. Voices simply sound less dynamic and natural.
This might not come to Your ear with the easier to drive dynamic boxes. But even then the performance of the HAs is at minimum on level with UCDs and alikes.


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