2. amps-preamps
  3. 140387-15288

The Future of Audio Amplification

I have recently paired an Audio Research DS225 Class D amplifier with an Audio Research tube preamplifier (SP8 mkii). I cannot believe how wonderful and lifelike my music sounds. The DS225 replaced an Audio Research SD135 Class AB amplifier. Perhaps the SD135 is just not as good as some of the better quality amps that are out there, but it got me thinking that amazingly wonderful sonance can be achieved with a tubed pre and Class D amp. I have a hunch that as more people experience this combination, it will likely catch on and become the future path of many, if not most audiophile systems. It is interesting that Audio Research has been at the forefront of this development.
distortions
kosst_amojan
2,095 posts
 
@mr_m 

The kind of distortion is extremely important. 1% being composed of a nice, clean second harmonic isn't good in my opinion, not because it doesn't sound good, but rather because you're basically using the amp as a tone control. That's significant color to add to a signal. That's not to say it sounds bad. A lot of people want that kind and level of coloration. Nobody likes complicated distortion. Some fuggly mix of 5th, 6th, and 7th order distortion at .1% is going to be a lot more offensive than a big, pretty 2nd order at 1%. The kind of distortion is more important than the amount. 

The problems you see in class D are the same you have with class B. The lower the power output, the more the distortion dominates. Class D just tries to minimize the distortion by reducing the time the transistors transition from off to on by pulsing them very rapidly. But no matter what, transistors switching off and on will always make huge amounts of high order distortion. It's unavoidable. It's just imppossible to fully filter it out. If it were possible, it would have been applied to class B amps by now. 
Post removed 
scott_w's avatar
scott_w
257 posts
 
My amp is the Digital Amplifier Company's 'Cherry' amp, it's class D. And it's so delicious it makes me tinkle. Combined with my Schiit Freya preamp, everyone is a big winner here at the casino tonite. 
atmasphere's avatar
atmasphere
7,068 posts
 
But no matter what, transistors switching off and on will always make huge amounts of high order distortion.
@kosst_amojan
It doesn't work that way IME. What makes distortion in a class D is how well the encoding scheme works. For example if PWM, any offsets generated by the comparator (or otherwise) can cause distortion. This means you have to be careful in such a circuit to block any DC that might come from your triangle wave generator- and in that circuit, the quality of the triangle wave is pretty important too.
Its not uncommon for the encoding scheme to have troubles at lower levels. For this reason I prefer PWM as its problems are more likely to be at higher power levels rather than at low levels.

Each encoding scheme has its upside and also difficulties! But the switching of the outputs themselves do not contribute to distortion, which is a major advantage of Class D, since the operation of class A, class AB and B this is not the case.
michaelgreenaudio's avatar
michaelgreenaudio
643 posts
 

LOL, I had to go look up what an E-bike was, isn't that sad, I'm getting old or lazy lol.

As far as A AB or D my favorite would be based on Tuning. That means, parts in a big heavy chassis? Nope, I can beat those up with a low mass amp of any type. Amps that have tons of dampening? Nope I want something I can apply variable tuning to. Amps with shielded transformers? Nope, I like open field designs. There are lot of criteria I have for amps A AB and D isn't one of them.

JA measuring amps means zero to me. I'm more interested in his latest test equipment (JA is a test equipment junky, in a good way).

Distortion? I haven't met anyone from this forum yet that deals with a well rounded view of distortion and the effects of. Lets see would that be effects or affects (wink). Here's a quick example. I walk into a listening room to listen with some guy talking about amp distortion and how he can hear it. Now we're standing in an untuned room and our breathing is at 10dB without anything else happening. He talks and I instantly can hear the room distorting, why and where. No music yet and we're at 55dB. So we turn on the music and I'm hearing all kinds of things happening that can and should be Tuned to give us the best soundstage for that recording, 65-95dB. Then after I do some tuning he's going to want me to tune it differently to his ears.

What am I thinking about his claim to hear the difference in .02 distortion? Excuse me I have to use the bathroom and read my Stereophile :)

Michael


More to discover