Could Class D really be that good?


I've heard statements praising modern class D amplifiers all the time but was sort of hesitant to try. Lately, one particular model caught my eye, the Fosi V3, which costs sub $100 but is praised for having refined sound like class A/B. To fulfill my curiosity, I quickly ordered one and tried it with my Burchardt S400II and Wharfedale Linton speakers. Basically, this is a neutral sounding amp but, to my surprise, the sound is clean, open, airy, with full mids, wide soundstage, good imaging/separation, with nearly null traces of the edginess, dryness, or lean sound that traditional class D amplifiers have. The background is just as quiet as my current systems. The core is the TPA 3255 chip from TI and comes with a 32v, 5A power block, which is supposed to deliver approximately 65 watts per channel (into 8 ohms). It drives the S400II/Linton without any hesitation, as well as my 130-watt-per-channel high-current Parasound A23. Very impressive.

Measurement is not everything. However, according to the lab test results, when operated under 10-60 watts, the distortion level (THD) is below 0.003%, better than a lot of high-end (price) gears. I am going to build around it for my fourth system with upgraded op-amp and LPS. I believe it will outperform my current mid-end (price) amplifiers.

I know, I know, quite a few Audiogoners' systems are above $100k, and mentioning this kind of little giant that costs a fraction could be rather embarrassing. But I thought this is just like gold digging with a lot of surprises and fun. Don't you think?

lanx0003

Did you not read what I said?  I said the amps will all measure the same.....this is absolutely true.  While it is true that when changing parts the distortion changes....because all noise and veils are distortion.  However, you CANNOT measure a change in measured distortion when changing passive parts. 

@ricevs Oh I read what you said. But it was false, as is the above statement. You certainly can measure a change in distortion when passive parts are replaced! The idea that this isn't so is laughable.

Yes, some will laugh at their own folly.  I would llike to see you prove this statement: "You certainly can measure a change in distortion when passive parts are replaced!"  Show us the beef!  Where are your graphs?  Show us the volumes of statements from other high end audio designers who have tested this and show graphs.....please.......I have NEVER in my entire life heard of any high end audio designer, engineer, manufacturer say this except for you.  If this statement were true then every time a manufacturer made the sound better by upgrading the jacks, fuses, wires, resistors, damping of parts, capacitors, power supplies, power supply parts, etc. into infinity.....they would state it.....and they would show graphs to prove it. They would say.  We found a better cap.....we replaced our super last years cap with a new one and not only does it sound better but the distortion went down .001 percent of distortion.  But no one has ever said this....because you CANNOT measure the distortion of most parts. 

A Furutech AC inlet sounds better than the one you use.  If you replaced yours with a Furutech would your amp measure better?  (By the way, the Furutech ones with Rodium plating sound different from the ones with gold plating....same with their NCF technology.....do they measure differently?  does Furutech claim such?).  Removing the steel hardware on your power supply transformer and raising it off the chassis improves the sound.  Can you measure that?  I listened to three different brands of tiny .1 percent nichrome surface mount resistors that all looked the same and all of them had slightly magnetic end caps.  This was a 75 ohm resistor on the output of a Crystek clock.  One brand sounded much better than the others.  Did that change the measurements of the Oppo I was modding?  Hardly.

If you are using junk parts....like bad electolytics, ceramics, very inductive resistors and put them in a sensitive place then not only will the device sound bad but it will measure worse than using a better made part.  But what high end manufacturer uses junk ceramics as a feedback or coupling cap?  The knowledge on caps and their sound and distortion was first published in Audio Magazine by Marsh and Jung back in 1980....I am sure you remember that.  That article changed what high end manufacturers did.  They realized that bad dialectric caps sounded bad.....so they all changed to film caps and the high end electrolytic caps market (Elna, Blackgate, etc.) started.  Conrad Johnson started using all film caps in their power supply (no electrolytics whatsoever).  However, every brand of super high end film caps sounds different (including all the various models from the same company).  For instance....Clarity cap makes many models of film caps.  They claim the better ones "sound better".  There is no mention of lower distortion measurements on their site.  If they could measure lower distortion....they would brag about it....obviously.

Ralph, I wish you the best.....but if you are going to sit all by yourself on that tiny branch and saw away......well, eventually.....you fall.  

Here is an article about using really bad parts in portable audio devices......yes, those seriously bad parts can be measured.......However, we cannot measure the parts that are used in high end audio......unless you are Ralph....he must have super sensitive test equipment no manufacturer of better sounding parts has.

 

I don't believe it's necessary for components to be of poor quality to show disparities in measurement. Take the Fosi V3 and Aiyima A07 as examples. Both of them use the TI TPA 3255 module, but Fosi utilizes quality passive parts like Japanese/German capacitors and inductors. Both use the same stock op-amp (active). These disparities in the quality of passive parts are sufficient to produce audible differences in THD, as shown in ASR measurements.

Sorry, wrong.  You have no idea what is producing those different numbers.  You just want to believe in something.  Those Wima Polyester caps that they use (both Fosi and Ayima now use the in all their latest gear) are crap.  I replace them with modified Wima polyprop caps that are oriented so the outside foil is to ground.  The Ayima Max and all the latest Fosi and Ayima amps all use the same inductors and capacitors yet still measure different.  Lots of things in the design can influence the measurements.  Fosi is now adding feedback around the output coil and this lowers the distortion and makes it less load variant (ie....measures flat at 8 ohms and 4 ohms).  The only way to know if a single component (or several) changes the sound and or measurement is to use the same amp and just change the parts.  Then you will actually KNOW something.

I have NEVER in my entire life heard of any high end audio designer, engineer, manufacturer say this

Hm. Not been around, apparently.

The only way to know if a single component (or several) changes the sound and or measurement is to use the same amp and just change the parts.

Wait- what? So if you change parts it does change the measurements?