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Class D popping up everywhere. Innovation?

Volume4

Volume4

Sep 15, 2009
749
12
Long Island
#1
I'm a little concerned.....and maybe I just don't fully understand.....but isn't a Class D power section digital?

I'd love tubes someday but I'm all for SS amps, on the condition that it stays Analog.

I'm not starting a Analog vs Digital debate...just wondering if others like me who have made up their mind in the Analog camp feel the same concerns/questions.

As far as my googling of it, seems like it works much like a ballast for a fluorescent lamp.

It seems pairing a tube preamp with a Class D power section, you're kind of defeating a purpose within your own amp.

Am I wrong? Is anybody else inclined to stay away from a Class D amp for these reasons? Can Class D be legitimately Analog?
 
#5
Class D does not mean digital. Class D amplifiers are switching amplifiers.

That said, they are SS in the output section; it's not really "defeating" their purpose. A tube preamp with a Class D SS power section is considered a hybrid, and is different than an all tube amp. Each has their place.
 
#6
Isn't there a sticky for this yet? I would have sworn that there was one posted a while back on different amp types.
 
#7
I didn't find too much on this by searching or reading the FAQ.

I hopr I'm not asking dumb questions here, I hope I'm wrong....I really like the idea of the Orange Bass Terror :D

I actually didn't think the D was for digital, but the concept of it seems digital to me.

This is from Wiki, and it seems like what's happening is a lot like what a D/A converter does in a CD player. The end result is always going to be "Analog" because that's the only way to get speakers to work.

Unless I'm misunderstanding.....which is very possible.... the signal does not stay Analog the whole way through the chain.

Before these higher quality designs existed an earlier use of Class D amplifiers and prolific area of application was high-powered, subwoofer amplifiers in cars. Because subwoofers are generally limited to a bandwidth of no higher than 150 Hz, the switching speed for the amplifier does not have to be as high as for a full range amplifier. The drawback with Class D designs being used to power subwoofers is that their output filters (typically inductors that convert the pulse width signal back into an analogue waveform) lower the damping factor of the amplifier.


The letter D used to designate this amplifier class is simply the next letter after C, and does not stand for digital. Class D and Class E amplifiers are sometimes mistakenly described as "digital" because the output waveform superficially resembles a pulse-train of digital symbols, but a Class D amplifier merely converts an input waveform into a continuously pulse-width modulated (square wave) analog signal. (A digital waveform would be pulse-code modulated.)
 
#9
Yes, most definitely.

But there always seems to be a tradeoff...a compromise....:hiding:

I'm just trying to figure out what it is.

Or is this just a modern sound thing?

Can you get old school warmth and tone from a Class D?

For instance an Ampeg B100R.... I owned one years ago and miss it.... is a very warm SS amp and many agree it's very close to a real Portaflex, but not quite. So there is a tradeoff...and a fair one because it's a great sounding amp.

Now can this be achieved with Class D?

If so, wouldn't it seem like this is going to take over amp manufacturing? It would make sense.

But I suspect there is still something that will keep many amps filled with Mosfets....I'm just wondering why.
 
#10
i used to try to be reasonably informed of the differences between tubes and ss, because i always preferred tube sound over ss for guitar...when i moved over to bass, i found ss pretty decent actually and used ss amps...lately, i'd moved back to ampeg SVT tube amp...

then i bought a genz benze shuttle combo, with a class D amp...this combo sounds amazingly warm and rich to my ear...i won't get into describing the sound with words, what with dancing about architecture, etc...but i am quite pleasantly surprised at what i hear from this 210T combo...the midrange in particular, has a quality that is exactly opposite of what i'd describe as 'digital' or even ss for that matter...

the markbass lm2 is described quite often as being very 'tubey' sounding, and it's [DEL]class D as well[/DEL] class AB (thanks for the correction, fellas)

anyhow, just my 2 cents on the class D sound and how it can compare to ss or tube, as it can be designed to sound differently depending upon the goals...the GB shuttle combos sound phenomenally warm and can easily get more old-school than most of the other ss amp/cabs i've used, while retaining the ability to do the modern thing too...
 
#12
Bob Lee from QSC was kind enough to share this link with me. It is a link to the forum on the QSC site and explains a bit about amplifiers - Class A, B, AB, H, D, etc. Part one explains Class D.

Link Removed

Dave
 
#13
Volume4 said:
Yes, most definitely.

But there always seems to be a tradeoff...a compromise....:hiding:

I'm just trying to figure out what it is.

Or is this just a modern sound thing?

Can you get old school warmth and tone from a Class D?

For instance an Ampeg B100R.... I owned one years ago and miss it.... is a very warm SS amp and many agree it's very close to a real Portaflex, but not quite. So there is a tradeoff...and a fair one because it's a great sounding amp.

Now can this be achieved with Class D?

If so, wouldn't it seem like this is going to take over amp manufacturing? It would make sense.

But I suspect there is still something that will keep many amps filled with Mosfets....I'm just wondering why.
Click to expand...

Most Class-D amps use MOSFETs for the output devices. Of course they are controlled differently.

There was a time period when Class-D power amps did achieve a soft clipping behavior similar to tube amps. As it has been explained to me, this effect has pretty much been eliminated by new designs, meaning that like Class-AB solid state power amps, Class-D power amps will probably trend towards "perfection" in an idealistic sense.

As these designs move further away from "old school" characteristics, it will become necessary to simulate the tone of historical designs through some sort of analog or digital modeling. Of course there are theological debates over the efficacy of modeling, from which I will conveniently recuse myself. :D

Predictions that transistors would supplant tubes have not been borne out. In fact, there has probably been a resurgence of tubes in the past decade. Likewise, so long as there is a perception (real or not, doesn't matter) that Class-D falls short in the tone department, they will never completely take over.

Indeed, this is a feature of any technology that is used in the arts. Nothing ever becomes obsolete. Rather, the new stuff simply takes its place alongside the old stuff, and we all benefit from the greater variety of choices.
 
#15
I think some clarifications are in order...

Class D is a NON-LINEAR amplifier, and it is not "digital" in the normal sense of the word.

Digital for most purposes means that there are digital words, made up of addresses and data, or serial data streams, that can be stored in memory, can have arithmatic operations performed on them to create new data.

In a class D amp, the pure analog signal is chopped up very, very fine into a pulse train where the width of the pulses varies, and/or the number of pulses varies to reflect an analogy of the original analog signal. This is done at typical line level (~+4dBu) or a little higher THEN this low voltage pulse train is efficiently lefel shifted up to a much higher voltage. This high voltage pulse train is run through a low pass integrating filter to reconstruct the original analog audio but at a higher voltage (and thus power).

Like any amplifier, overload characteristics can be manipulated by the topology of the amp as well as any signal conditioning that's used, to create various types of overdriver response.

Regarding damping factor, the output inductors really do not create much of a problem, and besides, most conventional class AB power amps also have output inductors that have DCR that's pretty similar to class D output inductors.
 
#18
I just got a Genz-Benz Shuttle 6.0. I say THANK HEAVENS for class D. it sounds warm and wonderful - and the tube preamp lets me get tube distortion as needed. AND - the amp weighs 3.75 pounds. And I'm 59, so I'm very familiar with tube sounds...and my back is familiar with heavy bass cabs. No more heavy cabs for me - EVER.

The new Class D's - and Genz-Benz in particular - are absolutely marvelous. What matters with an amp is how they SOUND. The OP needs to go play through one and his questions will be answered.
 

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