Class D: Turns Out it Does Suck!

[manisandher]

2 hours ago, wgscott said:

That really is horrifically ugly.

 

Certainly not to everyone's tastes, but I love their simple and functional design:

 

 

And more importantly, I love the way they sound, especially with the Elrog 300B tubes .

 

Mani.

[manisandher]

3 minutes ago, gmgraves said:

The  class D amps' square waves look much better than this SET at 10 KHz...

 

The designer/manufacturer took a frequency response measurement of my amps before shipping them out to me. Taken on the primary of the OPT (as the secondaries don't carry a ground potential), the amps measure -3dB at 7.5Hz and 150kHz, with virtually no OPT resonance visible above 150kHz. Not sure what the 10kHz square wave would like though.

 

Mani.

 

[blownsi]

3 hours ago, wgscott said:

 

That was one of my primary motivations for trying Class D.  I am trying to produce more electricity that we consume. 

 

We also have a serious ecological catastrophe unfolding ...

 

Even if the inferior sound quality allegation amounts to anything more than snobbery, I think I could live with the very minor difference, given the difference in power consumption.

 

Are you guys talking about just electricity consumption during operation or environmental concerns during manufacture?  

[semente]

1 minute ago, blownsi said:

 

Are you guys talking about just electricity consumption during operation or environmental concerns during manufacture?  

 

The best thing to do, environmentally speaking, is stop producing new gear and only buy used.

There's enough audio equipment around for everyone.

 

If you think that it takes over 2.5kL of water to produce a white t-shirt...

[Ralf11]

Live in town, don't drive, don't have kids...  but everybody gets to pick any electricity saving or other energy saving activities

 

Now, what about intermodulation between the scan frequency and the input signal?  Is that a problem with current Class D designs?

[esldude]

2 hours ago, semente said:

 

The best thing to do, environmentally speaking, is stop producing new gear and only buy used.

There's enough audio equipment around for everyone.

 

If you think that it takes over 2.5kL of water to produce a white t-shirt...

That's not so bad on the t-shirt.  It probably only take about another 200 liters to wear it out. 

[jabbr]

9 hours ago, wgscott said:

 

That was one of my primary motivations for trying Class D.  I am trying to produce more electricity that we consume. 

 

We also have a serious ecological catastrophe unfolding ...

 

Even if the inferior sound quality allegation amounts to anything more than snobbery, I think I could live with the very minor difference, given the difference in power consumption.

So for those of us who spend a fair amount of time in a heated, rather than cooled, environment, would a Class A amp with an efficient radiator system be acceptable? Or must we just shiver  

[GUTB]

Since you guys are talking about these Crown amps, let's take a look inside:

 

 

Compared to an NC1200:

 

 

It's widely accepted that nCore is at the top of the class D game. If even nCore modules are unable to impress at the high end, how much can we really expect out of a $300 amp using a generic / unknown class D circuit?

[Panelhead]

21 minutes ago, GUTB said:

Since you guys are talking about these Crown amps, let's take a look inside:

 

 

Compared to an NC1200:

 

 

It's widely accepted that nCore is at the top of the class D game. If even nCore modules are unable to impress at the high end, how much can we really expect out of a $300 amp using a generic / unknown class D circuit?

  I am biased. Own a Crown, never built one of Bruno's designs. But to compare the two take a picture side by side. 

  The pictures make the 8.6 lb XLS-1500 look like a toy. But it is twice as large as the nCore amplifier. The pic makes the two metal oxide power resistors look huge in the nCore amp. 

  I would like to hear Bruno's latest work. Convinced it is top notch.

  

[esldude]

3 hours ago, jabbr said:

So for those of us who spend a fair amount of time in a heated, rather than cooled, environment, would a Class A amp with an efficient radiator system be acceptable? Or must we just shiver  

Well it is true the waste heat is 100% efficient as heat.  Then again if outdoor/indoor temperature differentials are favorable a heat pump can do better than that.   The energy cost of pumping heat can be less than the energy cost of generating heat.  If you know what I mean.  Even though my engineer friend who works with those and refrigeration systems wouldn't be happy with how I have stated it.

 

So in such a case, it still would be better to have class D amps, and run the heat pump a bit more environmentally at least.  Mentally it could be a different story.

[mansr]

5 hours ago, esldude said:

Well it is true the waste heat is 100% efficient as heat.  Then again if outdoor/indoor temperature differentials are favorable a heat pump can do better than that.   The energy cost of pumping heat can be less than the energy cost of generating heat.  If you know what I mean.  Even though my engineer friend who works with those and refrigeration systems wouldn't be happy with how I have stated it.

I read far worse things on this site every day.

5 hours ago, esldude said:

So in such a case, it still would be better to have class D amps, and run the heat pump a bit more environmentally at least.  Mentally it could be a different story.

Clearly we need a combined amp and heat pump.

[semente]

1 minute ago, mansr said:

I read far worse things on this site every day.

Clearly we need a combined amp and heat pump.

 

Will this require galvanic isolation?

[jabbr]

1 hour ago, mansr said:

 

Clearly we need a combined amp and heat pump.

I should mention that in the summer, my Class A amps are used to heat our pool. Much much better than Class D. Floating power supplies are essential.

[jabbr]

14 hours ago, Ralf11 said:

Live in town, don't drive, don't have kids...  but everybody gets to pick any electricity saving or other energy saving activities

 

Now, what about intermodulation between the scan frequency and the input signal?  Is that a problem with current Class D designs?

Maybe not Intermodulation per se, but I remain concerned with what is essentially low sample rate DSD ADC->amp->DAC ...  if we upsample our DSD64 which is 2.8 MHz to DSD512 which is 24 MHz then hard to see how a sub MHz conversion could help? I'd think that if the EMI problem were solved for say 24mhz then you could avoid the extra DAC/ADC loop and just feed a DSD signal in directly.

 

As always everything depends on the implementation. 

 

if if we are really trying to be efficient, just use your iPhone which is turned on anyways  

[Jud]

2 hours ago, jabbr said:

Maybe not Intermodulation per se, but I remain concerned with what is essentially low sample rate DSD ADC->amp->DAC ...  if we upsample our DSD64 which is 2.8 MHz to DSD512 which is 24 MHz then hard to see how a sub MHz conversion could help? I'd think that if the EMI problem were solved for say 24mhz then you could avoid the extra DAC/ADC loop and just feed a DSD signal in directly.

 

As always everything depends on the implementation. 

 

I know I mentioned the use of feedback previously as something that might help, but I remain interested in this issue as well.

[jabbr]

54 minutes ago, Jud said:

 

I know I mentioned the use of feedback previously as something that might help, but I remain interested in this issue as well.

Yes, though I'm unsure how much it helps with the noise issue -- complicated issues and undoubtedly complicated solutions 

 

Now if the amp could be switched at 24 MHz without creating a radio transmitter -- then a nifty nonfeedback power DAC  

[gmgraves]

On 5/4/2017 at 2:22 PM, semente said:

 

The best thing to do, environmentally speaking, is stop producing new gear and only buy used.

There's enough audio equipment around for everyone.

 

If you think that it takes over 2.5kL of water to produce a white t-shirt...

 

On the surface, it seems reasonable to buy second hand gear over new. The problem is that while tubes can be easily replaced, and transistors rarely, if ever go bad, the same cannot be said for capacitors. They only last 10-20 years at the most, and unless one is electronically inclined, and can change the capacitors oneself, it's an expensive job, and if you have older tube equipment, those multi-section power supply capacitors aren't even available any more. 

[watercourse]

On 5/5/2017 at 4:27 AM, mansr said:

Clearly we need a combined amp and heat pump.

 

I have my Pass situated right next to the intake vent for my heat pump (this is necessary during the warm summers). Too bad the intake is on the floor and heat rises. If I install ceiling fans, my heat pump system becomes less efficient by virtue of increased energy consumption.

Anyone at CA have a system that stores energy generated by stationary bike? Have owned several Class D amps and am not budging from Class A now that I've tasted the honey. I clearly need some carbon offsets to maintain this habit.

[Ralf11]

My Sunfire is still going strong at age 22 !!

 

(I do listen to it for impending doom however)

[ElviaCaprice]

For near field listening, having the correct DAC with built in amp, wouldn't it be best to use high efficiency speakers and leave out any separate preamp/amp?  As long as you can drive the speakers to sufficient volume, you have the advantage of lower cost and preventing stray DC current/electrical noise from tainting the sound, even with a class A tube amp? 

[GUTB]

So, what it looks like is that class D is inferior (sound quality-wise) by nature.

 

Class A takes an analog signal and makes it larger. It does nothing more.

 

Class D takes an analog signal, converts it to a 400-500 KHz square wave, and then converts the square wave back into an analog signal while applying a filter to get rid of the high-frequency noise. What goes in, isn't what comes out.

 

The fundamental problems of class A are: efficiency and noise.

 

The fundamental problem of class D is: low sound quality.

 

Class A will probably never be able to solve its fundamental problems. It has to run at at full power all the time, pouring energy into un-used cycles constantly. Anything less, and it's no longer class A.

 

But can class D solve its fundamental problem? It seems likely! More importantly, has class D solved it's problem already? You guys with class D, don't be shy. Talk about your class D amps, your setups, the sound you get from them and how they compared with other amps.

 

[Jud]

6 minutes ago, GUTB said:

So, what it looks like is that class D is inferior (sound quality-wise) by nature.

 

Class A takes an analog signal and makes it larger. It does nothing more.

 

Class D takes an analog signal, converts it to a 400-500 KHz square wave, and then converts the square wave back into an analog signal while applying a filter to get rid of the high-frequency noise. What goes in, isn't what comes out.

 

The fundamental problems of class A are: efficiency and noise.

 

The fundamental problem of class D is: low sound quality.

 

Class A will probably never be able to solve its fundamental problems. It has to run at at full power all the time, pouring energy into un-used cycles constantly. Anything less, and it's no longer class A.

 

But can class D solve its fundamental problem? It seems likely! More importantly, has class D solved it's problem already? You guys with class D, don't be shy. Talk about your class D amps, your setups, the sound you get from them and how they compared with other amps.

 

 

Since you've successfully fended off all attempts at educating yourself so far (i.e., what you've written is exactly what you were saying to start the thread), why should anyone bother to make the effort?

[Ralf11]

change your name from gutb to Tenacious D

[GUTB]

19 minutes ago, Jud said:

 

Since you've successfully fended off all attempts at educating yourself so far (i.e., what you've written is exactly what you were saying to start the thread), why should anyone bother to make the effort?

 

I'm sorry, but it seemed to me I was the one doing the educating. In return, I was "educated" with: "Troll", and "You're wrong", and "class D is great".

[Ralf11]

you're not backing up your conclusions about Class D

 

Let's forget about mechanism, and just explain which Class D amps you've heard, the cost, and how old the design is with some specifics on the particular SQ flaws each time