[Robert57]

Having heard the new D-200 monos in the Modwright room at RMAF I was extremely impressed with the non-fatiguing, realistic organic  sound that came from this great system (paired with Dan's SWL9 Preamp), and I am fairly sure these will be my next amps. I appreciate your telling me that you design mainly by your ear, not just to a set of specs.

One issue that concerns me a bit, though, is the fairly rapid roll-off of  D-200's frequency response after 20kHz. For Redbook CD's I suspect this is a non-issue. But  I am still intrigued by the ability of SACD (and maybe whatever successor HD format emerges) to reach much higher --beyond 40 kHz. Yes, this is well above the 15-20kHz we humans are supposed to be able to hear individual notes, but people who play with super-tweeters swear that this HF extension greatly improves the midrange as well as the treble--better defined and three-dimensional music overall. And strangely these benefits seem to come not just with Hi-res (SACD and DVD-A) but also with Redbook CD (probably after upsampling) sources. A recent Circle post underscores these findings:

http://www.audiocircle.com/index.php?topic=22156.msg196680#196680

http://www.townshendaudio.com/supertweeter.htm

Dusty, could please share any more measurements on the HF performance of the D-200 mono's. Do I recall your saying it extends to 40KHz at -3db?  And could you and others please share their thoughts/ experiences on the super-tweeter effect and Hi-Res and upsampled music/ amp requirements. Is there any possibility of the D-200 being tweaked to have the filter roll off above 40-50KHz? I would like to feel I have the amp extension to be able to fully exploit the potential of SACD, not to mention upsampled CD, possible with a super-tweeter added to the mix.

[dhiebert]

Here is the D•100 frequency response from CI Audio site. As far as I understand, the D•100 and D•200 use the same amplifier modules, but just have different power supplies. That should imply essentially the same frequency response.

[CIAudio]

The graph above is correct (-3dB @ 50k).
It's my opinion that you would hear nothing different if it was ruler flat to 50k. Wider bandwidth is usually desired so the filter doesn't affect phase at audible frequencies...in our amplifiers, this is compensated for in another way. The fact that higher resolution formats are capable of frequencies beyond 20k doesn't mean there is anything audible there.
Try our amplifiers against something with rated bandwidth to 100k and decide for yourself