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
My amps are using the latest Icepower modules (IceEdge) and switch at 500K......however, with the right massaging, they produce sound that is beyond my own designed class A amps
I see just someone shilling his wares.
Massaging 500khz switching frequency will only get you half the way to a happy ending.
Try 1.5mhz like Technics did, and you'll finish on a bigger high. Or 3mhz and you be in orbit.
It will come soon enough, as I said EPC the makers of Technics SE-R1 GAN transistors are the Formula 1 pioneers of the Class-D world, just like they did with Mosfet transistors many years back, and look how quick they took off, must have made EPC some crazy big royalties, they are inventors that sell their patented inventions to the highest bidder. The forula 1 guys of Class-D.

http://epc-co.com/epc/AboutEPC/Team.aspx

http://epc-co.com/epc/Applications/ClassDAudio.aspx

Cheers George


This morning on the morning show they said electric cars are not going to take off for another 15 years. Where are we at with class D right now? Everyone keeps saying that the future is class D but where is that in the future?
They’ve been saying that since the 1910s- but about 1912 Ford and Edison had an electric that could cruise at 60mph and had a 100 mile range, using Edison’s nickel iron batteries, which had a service life of about 25 years. Imagine what things would look like if Edison’s labratory hadn’t been burnt to the ground 2 weeks after Ford and he made that announcement! See ’Internal Combustion’ by Edwin Black.
Class D is very attractive because of energy, just like electric cars. The difference is that we can have Class D although IMO it still has a way to go.
@georgehifi
this then allows the low order switching noise output filter to do it’s job completely without leaving any effects and any left over switching noise artifacts within the audio band.
I think you don’t understand how the filter works, based on this statement. The Technics filter does not filter out all the residual, which is what the leftover switching artifact is called. The residual is always a very clean sine wave; the real question is what amplitude does it have? The filter really has nothing to do with ’left over switching noise artifacts’!! What can happen in a class D is the switching noise can radiate into other parts of the circuit where it can be rectified and amplified. Again, the filter has nothing to do with this- the noise problem is dealt with through good layout and compact (surface mount) design.
@minorl

In car audio it was really the only way to go to get the power output needed. you can’t do it from 12 VDC.

Just a correction: My Denon car stereo amp that I had in my Bronco (RIP) made 150 watts per channel and was an AB amplifier. It employed an inverter to boost the DC voltage. Inverters were used back in the old days when car radios had tubes in them, although they were a different technology, using something called a ’vibrator’ which was essentially a high speed relay that reversed the DC to the power transformer about 50 times per second.
@kosst_amojan
It’s also nice not having a massive pile of filters trying to turn garbage into a signal again.

This statement is problematic. If you listen to digital, something similar is happening there (and of course its an objection that analog guys often raise). And the Berning amplifiers employ a filter at their output too- and those amps are class A or AB despite a switching component that has to be filtered- and it gets very good reviews!


The filter on a class D is usually quite simple; there is not a ’massive pile’. If you raise the switching frequency sufficiently, the inductance of the speaker itself can be sufficient to attenuate the residual. The filter is there mostly to prevent the speaker cable from acting as an antenna for the switching frequency. Because the filter is usually set somewhere well below the switching frequency, the residual is a simple low distortion sine wave which won’t cause interference to higher frequency (radio) services.
the noise problem is dealt with through good layout and compact (surface mount) design.
Really then no one one yet has been able to rid of this, and they are mightier minds than you. Only Technics has so far been able to reduce it greatly, with double the switching frequency speed and then the normal output low order filtering of it.

As you can see in this simulated 1khz square wave shot, the ideal is the "grey" square wave no ringing.
The "red" is the what’s available today and it hasn’t changed, the last photo below is whats representative of today’s class-D’s
The Technics is the "blue" uses the GaN transistors, very fast quickly settling and reduced ringing, much closer to resembling the ideal grey square wave.
https://ibb.co/87Kh2mV

And now bench tests of Stereophile, use a special very low power high order -100db line filter between amps output and test gear input.
(Audio Precision’s auxiliary AUX-0025 passive low-pass filter),
Which eliminates noise between amp’s output and test gear input so reader can’t see it anymore.

1khz square wave with AUX-0025 filter in place:
https://www.stereophile.com/images/1212AM1fig03.jpg

1khz square wave without AUX-0025 filter in place:
https://www.stereophile.com/images/1212AM1fig02.jpg

Cheers George

The esthetic beauty of tubes is appealing to many (and deemed silly to others), and with modern technological improvements accumulated over a century or so of refinement, tube amps are currently good enough to still be considered among the best sounding music reproduction devices out there. I think it's based on the relative simplicity of their designs along with the linearity of tubes relative to other things, and hats off to Class D designers for making efficient and explosively powerful amps that work well and fit into small spaces (like live sound speakers). However, for many of us tubes are simply more fun...I was floored when I first heard the little single ended amp I now use, and felt that everything I knew was sort of wrong. Dynamic range from 12wpc? Yep...matched with efficient speakers of course. Noise? No problemo...Heat? Only 4 tubes there sparky, and they last a long time. I can live with the thousands of SS A/B and D watts I use mixing live shows, and my 10 or 12 tube watts in my hifi rig...as long as tubes are available.
Tubes are way cool and if not for deciding to try the latest and greatest new amp technology (Class D) first I might well have headed down the tube amp path several years back but hasn’t happened and I have little interest these days. Technology does in fact keep advancing and you don’t know what is possible until you try it so older technologies face more challenges these days than before perhaps.
Looks do count though and tube amps still look way the coolest by far.