busb said:
oldric_naubhoff said:
JMacMan said:
Exceptions would be the TacT, Lyngdorf and Sony S-Master Pro series, and as the wikepedia article states, these are less appealing from a design POV due to the inability to effectively implement global feedback schemes to lower distortion; instead each part of the audio chain needs to be corrected individiually/locally via DSP; there is also the problem of the amplfiers high output impedance due inablitiy to implement global feedback.
this is totally incorrect. the only reason why class D measures well is because they use high levels of negative feedback. therefore such amps have very low output impedance, as a bonus. however, you'll never get an open loop class D amp that will measure well. even a SET next to such an amp will be a benchmark impossible to beat.
JMacMan said:
It has a massive linear power supply, but nonetheless can deliver a tested 170 watts per channel x 7 channels, all channels driven into 8ohms at < 0.01% distortion, so is no slouch on the measurments side of things, and does it all whilst remaining exceptionally cool running - no mean feat.
yeah. I'd like to see how the measurements change at 0.5W or into high frequencies. it's well known truth that amps that solely rely on loop negative feedback to get decent standard THD measurement (at 1kHz) don't measure quite well at low power levels and into high frequencies (if the open loop gain is very narrow).
Normally large amounts of neg feedback would be frowned apon but that feedback is applied to the modulated signal rather than the in-band output directly. As for measuring THD at 1kHz, the only thing that's going to reveal is whether a broken amp has been successfully repaired or not rather than equating THD with SQ. As for HF distortion, as long as those out-of-band products don't mix down into the audio spectrum, they are surely insignificant? THD will always rise when measured at low levels due to noise contributions overtaking harmonic content in amplitude.
What I can't understand is why anyone would go to the trouble of either designing or using off-the-shelf class D modules powered from an inefficient linear PSU rather than using switch mode technology. Both class D & switch mode supplies have far more to go wrong due to their innate complexity - that's my issue with such technology: reliability.
It's good that there are members here with significant technical knowledge/understanding who can explain some of the finer, more in-depth nature of things, as I find it very interesting, so appreciate your comments and insight.
My personal approach to HiFi has come from the other end though, i.e. as a trained classical musician and music lover, who likes to know how things work on a reasonably in-depth level, with respect to HiFi and other interests such as Photography, as knowledge is empowerment when it comes to consumer buying decisions generally, but I'd not generally describe myself as being an in-depth technical expert with respect to amplifier technology &/or electronics design, despite being interested.
I'm probably more interested overall and all things considered, in the end result as to how a system reproduces music, more than the finely detailed method of getting there, albeit I'm stil interested in that to a degree; just not as much as some.
As an example, my new active speakers feature(?) Class AB amps on the mid/tweeter, and Class D ICE power on the bass - which is of interest to me, along with other design points/details - but I couldn't tell you what the distortion figures are as the manufacturer doesn't quote them, and I have no test reviews with that information; suffice it to say they reproduce music to a level amongst the best speakers I've ever heard, which on balance, is as much information as I personally need to know, along with the design details, to justify the cost of admission.
A solution that offers both emotional and intellectual satisfaction perhaps?
Others may well be able to argue the pros and cons of the design specifications far better than me, and it's great to hear about those details as I find it interesting as I say, especially as my knowledge is limited compared to some, and it's another very valid area of this hobby, but ultimately for me, with my musical rather than technical background, it's the end musical results that count the most rather than the method of getting there, speaking personally, as far as my involvement in the hobby of HiFi is concerned.
Others of course, come at it from different angles, such as the technology, so it's great to read in-depth comments on that side of it - much appreciated.
John...