Class D: Turns Out it Does Suck!

[wgscott]

4 hours ago, watercourse said:

 

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.

 

Get a few solar panels.

[watercourse]

1 minute ago, wgscott said:

 

Get a few solar panels.

 

Ah, forgot to mention a critical point: I'm surrounded by tall trees and solar wouldn't be a realistic option (I looked into it already).

 

BTW, I am still open to hearing if/when Class D catches up sonically to its promise. Putzeys gets a lot of respect these days, though I wasn't thrilled with his modules a few years back. ICE and Tripath amps are a no go (I've owned them). Didn't like Spectron or Nuforce.

 

I was (am still?) a fan of the Cherry amp line, but at this point would only listen to someone else's system, or if there was a tour.

 

None of the big ticket Class D amps interest me given what I know about how finicky they have been to get to sound right. If you spend that much, IMHO you may as well be looking at tried and true Class A or AB lines.

[STC]

1 hour ago, GUTB said:

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.

That's why audiophiles'  should not listen to digital sound. The SQ is poor due to the ADC conversion.  

[GUTB]

49 minutes ago, Ralf11 said:

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

 

Okay. Amps I've owned:

 

Several home theatre receivers....won't pick on them too much no one should expect much from them regardless of class.

 

Teac AI-301DA. Uses an ICE 50ASX2-SE. Basically unlistenable. $350.

 

D-Sonic M3-800S. Uses a Pascal module (latest series not sure which) and a custom input stage. Resolving, controlled, fast, dynamic. Lean on bass. Soundstage depth crushed. $1,400.

 

I've listened to several others at AXPONA, but I can't in fairness judge them based on that experience due to the poor mess of acoustics, bad system tuning, noise and bustle of crowds.

[Jud]

14 hours ago, STC said:

That's why audiophiles'  should not listen to digital sound. The SQ is poor due to the ADC conversion.  

 

And the DAC conversion.

 

Our thread host has managed to prove he never heard decent audio except from a turntable, tape deck, or live performance, because all digital audio works in exactly the way he says is irreparably bad.

[Ralf11]

ok - who else has heard the D-Sonic?  and did it crush your soundstage?

[GUTB]

2 hours ago, Jud said:

 

And the DAC conversion.

 

Our thread host has managed to prove he never heard decent audio except from a turntable, tape deck, or live performance, because all digital audio works in exactly the way he says is irreparably bad.

 

Class D modulation is similiar to DSD -- 1-bit square wave. Except that single-rate DSD suffers from steep ultrasonic noise escalating from 25 KHz, and operates at 2.8 MHz. Class D switches between 400 and 500 KHz, and suffers from massive ultrasonic noise that wreaks havoc on speakers unless filtered. PCM operates at much lower frequencies except it's also at least 16 bits wide. Notice that that the slowest clock you will find in any DAC is 2.8 MHz -- do you guys know why that it?

 

Basically, class D modulation is a super low-resolution ADC.

 

 

[Ralf11]

While I am sorry that your soundstage was crushed and your money wasted, it does seem that this event has overactivated your limbic system.

[GUTB]

3 minutes ago, Fitzcaraldo215 said:

OK, so he listens to exactly two cheapo examples and he concludes that therefore ALL class D is junk. Does anyone else see a flaw in this logic?  

 

There are morons, but then there are total morons.  Unfortunately, some of the total morons wish to make a flagrant, public spectacle of themselves for all to see.  Mind-boggling, and, unfortunately, of totally no use on the question of the audible advantages/disadvantages.

 

The D-Sonic uses one the latest class D modules and is unverisally well-reviewed. $1,400 is in the $1,000 - $2,000 price range for modern class D implementations using NC500 and similiar technology. It cannot be considered an el-cheapo model. Only NC1200 products are greatly more expensive. Jeff Rowland has a $60k product. There's a $15k Technics using the new GaN FETs which would be interesting to listen to.

[GUTB]

Just now, Ralf11 said:

While I am sorry that your soundstage was crushed and your money wasted, it does seem that this event has overactivated your limbic system.

 

I returned the product after 30 days, so I only wasted a few bucks. It was a great learning experience too so I can't call it a waste of time either.

[monteverdi]

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...

I agree that reusing gear is much more environmentally friendly than even recycling  (not much energy required). But if amps (like my class A experiences) are frying themselves overtime the longterm usability is not so great.

[Jud]

9 minutes ago, GUTB said:

 

Class D modulation is similiar to DSD -- 1-bit square wave. Except that single-rate DSD suffers from steep ultrasonic noise escalating from 25 KHz, and operates at 2.8 MHz. Class D switches between 400 and 500 KHz, and suffers from massive ultrasonic noise that wreaks havoc on speakers unless filtered. PCM operates at much lower frequencies except it's also at least 16 bits wide. Notice that that the slowest clock you will find in any DAC is 2.8 MHz -- do you guys know why that it?

 

Basically, class D modulation is a super low-resolution ADC.

 

 

 

Since you've said you're the one doing the educating in this thread, I'm sure you know far more about this than Bruno Putzeys, designer of one of the world's best ADCs used by audiophile labels.  So please educate us and Bruno about how to make a good ADC.

[GUTB]

5 minutes ago, Jud said:

 

Since you've said you're the one doing the educating in this thread, I'm sure you know far more about this than Bruno Putzeys, designer of one of the world's best ADCs used by audiophile labels.  So please educate us and Bruno about how to make a good ADC.

 

I don't know about his ADCs.

 

Can someone find the the quote where Bruno Putzeyes says that class d sounds good in SPITE of being class d?

[Fitzcaraldo215]

11 minutes ago, GUTB said:

 

The D-Sonic uses one the latest class D modules and is unverisally well-reviewed. $1,400 is in the $1,000 - $2,000 price range for modern class D implementations using NC500 and similiar technology. It cannot be considered an el-cheapo model. Only NC1200 products are greatly more expensive. Jeff Rowland has a $60k product. There's a $15k Technics using the new GaN FETs which would be interesting to listen to.

D-Sonic "universally"  well-reviewed? What reviews would that include, exactly?  

 

My friend, you are, among other obvious faults to your thesis, just not at all well educated on the available products, duh!  But, little  things like that should not limit you from proclaiming from the mountaintops that you have discovered the ugly and unfortunate truth about Class A, that you know all about this technology and that you can objectively lead us all to reality.  

 

Dream on.

[GUTB]

2 minutes ago, Fitzcaraldo215 said:

D-Sonic "universally"  well-reviewed? What reviews would that include, exactly?  

 

My friend, you are, among other obvious faults to your thesis, just not at all well educated on the available products, duh!  But, little  things like that should not limit you from proclaiming from the mountaintops that you have discovered the ugly and unfortunate truth about Class A, that you know all about this technology and that you can objectively lead us all to reality.  

 

Dream on.

 

Which class D amps impressed you?

 

Do current class D modules switch at 400-500KHz? Does it not matter?

[crenca]

31 minutes ago, GUTB said:

 

 

Basically, class D modulation is a super low-resolution ADC.

 

 

 

 

I think you are correct in that it can be thought of in this way, but are not all solid state amp's limited (or not) in this manner?  All transistors in a Class A/AB designs have a switching speed...I seem to recall that most are around the 1 Mhz range (could be way off here)...

[semente]

40 minutes ago, GUTB said:

 

I returned the product after 30 days, so I only wasted a few bucks. It was a great learning experience too so I can't call it a waste of time either.

 

What speakers were you using? 

[Jud]

1 hour ago, GUTB said:

I don't know about his ADCs.

 

Obviously!

 

The point is, as you said yourself, a Class D amp operates analogously to an ADC-DAC sequence.  Putzeys is generally acknowledged to have designed one of the world's best ADCs.  However, since you have so clearly been able to spot the inherent terrible design flaw in all Class D amps he has obviously missed, you must be far more knowledgeable than he.  We therefore await further valuable education from someone who must be one of the world's experts.

 

Just kidding!

[Innocent Bystander]

On 5/6/2017 at 7:43 PM, gmgraves said:

 

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. 

Not necessarily. I sent a 25 year old Musical Fidelity P270 to the manufacturer a couple of years ago: they said the caps tested fine and didn't change them -and that is despite the high internal temp of this part class A amp. (If it was just the caps I would change them myself - it is one of the easiest things to do if you can use a soldering iron - but I sent it to have it upgraded, though unfortunately it turned out they could no longer do it so it turned ito a service check)

[4est]

3 hours ago, Innocent Bystander said:

Not necessarily. I sent a 25 year old Musical Fidelity P270 to the manufacturer a couple of years ago: they said the caps tested fine and didn't change them -and that is despite the high internal temp of this part class A amp. (If it was just the caps I would change them myself - it is one of the easiest things to do if you can use a soldering iron - but I sent it to have it upgraded, though unfortunately it turned out they could no longer do it so it turned ito a service check)

 

This is very correct. I have many older amps that have caps older than 20 years. On point with this topic, I have a class A Bedini 100/100 that has been used on and off since the early 80's with all originals. Also, multi-section power caps are readily available. They do not always come with the little twist tab attachments and the infinite variety they used to, but a clamp works just fine. A lot comes down to how good the parts were in the first case and what the dielectric is. Many people are thinking of older inexpensive gear such as Dynaco and Heath or the oil impregnated paper small signal caps that dry up and fail. If you are (un)lucky enough to have oil filled caps, they can last forever....

[Sam Lord]

15 hours ago, crenca said:

I think you are correct in that it can be thought of in this way, but are not all solid state amp's limited (or not) in this manner?  All transistors in a Class A/AB designs have a switching speed...I seem to recall that most are around the 1 Mhz range (could be way off here)...

 

Most AB amps with bipolar outputs are using for output stages some number of pairs of (NPN) MJL4281As and (PNP) MJL4302As which have gain*bandwidth products (Ft) of 35MHz.  Most of the transistors feeding them will have higher Ft.  Older versions in the big steel TO3 cans had typical figures around 3MHz.  But there is no switching on those designs except in cutoff, where the device stops conducting because of insufficient voltage across the base/emitter and emitter/collector junctions.  Those low-voltage dropouts in the +-0.6V region are the bane of class AB and must be addressed with some kind of correction, typically lots of feedback.  DC bias currents reduce those events to higher current operating regions, i.e. loud passages.

 

15 hours ago, GUTB said:

 

Class D modulation is similiar to DSD -- 1-bit square wave. Except that single-rate DSD suffers from steep ultrasonic noise escalating from 25 KHz, and operates at 2.8 MHz. Class D switches between 400 and 500 KHz, and suffers from massive ultrasonic noise that wreaks havoc on speakers unless filtered. PCM operates at much lower frequencies except it's also at least 16 bits wide. Notice that that the slowest clock you will find in any DAC is 2.8 MHz -- do you guys know why that it?

 

Basically, class D modulation is a super low-resolution ADC.

 

I love this argument.  So all other amps are ADCs that switch at 60Hz, or rather 120Hz rectified.  Lessee, where is that audio range?

[mordante]

On ‎3‎-‎5‎-‎2017 at 0:30 AM, Ralf11 said:

The signal that goes INTO class AB or class B is NOT the signal which comes OUT.   What comes out of class AB or class B is a modulated and filtered facsimile with cross-over distortion.  That's why it has been pointed out that class AB or class B is mathematically, physically inferior to linear class A amplification.  Of course, there are benefits to this trade-off, as always.

 

That reminds me of DAC topology and DSD resampling discussions.

 

Does anyone know if the Aavik U300 integrated amp uses class D? It's a very nice sounding amp. Also I think Avant Garde Speakers use class D amps.

 

Still I doubt if I would buy class D. While I like the U300 I think I still might prefer Vitus or Symphonic Line.

[GUTB]

I listened to to a Linnenberg Allegro monoblock setup at AXPONA that impressed me. I walked over to the price sheet expecting to see $10-15k, it was "only" $5,400. I arranged for an in-home demo which I expect to receive today. The amp is class A/B, features a very high-speed, high-bandwidth design (350 KHz after filter). Very high peak current draw for the size/price. Very low noise for class A/B (-116 dBA, non-weighted). It'll be interesting to compare the sound through my speakers compared to the class D products I've owned.

 

[Ralf11]

It is the electrolytic capacitors that tend to not last over 20 years or so.  Or maybe it is just the  electrolytic capacitors that were used in the 1980s or 1990s.

 

Now to get back on topic...

 

My Sunfire amp uses them and it won't last forever, so what Class D amp will sound better and costs less than the $3,000 Benchmark AHB2??

[cjf]

On 5/4/2017 at 6:57 AM, Jud said:

 

I like your taste. 

Thanks