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Class D vs Class A or A/B

#23
Well, this got technical, I was wondering where some bass amps like Peavey or whoever, have a class D amp and a Class A/B amp, and what the difference would be or which one is better or a least why they state what it is if it doesn't matter? From what I'm reading, it doesn't matter? I was thinking that the massive power but cheap amps show class D and more expensive less powerful amps show class A/b, so I draw from that, that class A/B would be cleaner?
 
#24
MichiganMadDog said:
Searched for this, didn't find anything so here it is:
Anyone hear or know if it makes a difference in buying an amp if it's class A, A/B, or D? Pros/cons?
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Are you talking about an "amp" as in an all in one bass amp, or are you talking about a separate amplifier to mate with your pre-amp? If you are talking about an all in one unit, then every amp is going to sound different. The overall tone of each amp is result of the entire design from top to bottom, so it's really impossible to tell just what the power section alone is bringing to the table. You need to find an amp that you like and not worry about what's under the hood.

If you are talking about a separate power amp, then there will be differences in how your preamp sounds when mated to different amps/topologies. Best advise is to take your preamp with you and audition various models to see what works for you. IMO, which doesn't always go with the others here, there are differences in how the various amps sound and respond as part of your overall signal chain. As a good example of this, I just spent some time with a SMPS my engineer made up for our Valkyrie amp. The difference between how the amp sounded with the SMPS and the large toroidal transformer were clearly obvious to everyone in the room, although there are those on TB who would say power is power and the power supply can have no affect on the tone of the amp.
 
#26
Yes - Class A is standard for mic/line level and small signal devices, especially using discrete transistors, although I would venture than 99% of audio ICs have A/B outputs because they are so much more efficient. As more and more devices become portable and battery powered, every microamp counts.

As far as sound - Class D has come a REALLY long way since it's inception. It is clearly capable of making great bass amps, and some of them are good enough for full range audio. It is fast becoming the standard for high powered PA stacks and arrays. I have not checked the latest specs, but the good class D amps may even be cleaner than A/B for bass frequencies, and a lot more efficient.
 
#27
You might find Class A bass amps per se in the studio (a friend who builds amps has a design) but as said above, AB1 and D are all you'll gig with. Both sound like crap when they clip unless (like Genz Class D) they do some extra things to help with the approach of no headroom. Try to get extra headroom when you buy.
 
#30
Bassamatic said:
As far as sound - Class D has come a REALLY long way since it's inception. It is clearly capable of making great bass amps, and some of them are good enough for full range audio. It is fast becoming the standard for high powered PA stacks and arrays. I have not checked the latest specs, but the good class D amps may even be cleaner than A/B for bass frequencies, and a lot more efficient.
Click to expand...

Here's a good read:
[Invalid or Expired Link Removed]

Class-D is older than most would think, but technology wasn't prevalent until the 1990's to
manufacture in mass.

Now it's everywhere. From small scale to huge power amps.

The lowest measured THD is a class-d amp.
 
#34
there are a lot of different classes of amplifiers, but the main ones are A, A/B, and D. I had a link to a site that described the topologies but was lost along the way. On the Peavey website I think.

Other amplifier classes (H, G, & T) start getting into switch-mode power supplies that monitor the signal level to regulate the voltage rails...if I remember correctly.

As already mentioned, it is not uncommon to find Class A in preamps. Mostly found in high end home theatre and recording studio gear. I would not expect Class A in too many solid state bass guitar preamps though.

Most power amps are A/B or D. Class D becoming more and more prevalent. Class A would be too inefficient but up to 40W is not uncommon. I believe Nelson Pass has designed a 100W Class A power amp with a patented design of his. Very cool, or should I say HOT. :cool:

Don't agree with earlier statement that Class D has best measured THD. This all depends on the amplifier design...and don't forget about the power supply. Also consider that measurements are not everything - listening is as important. With Class D there is a lot of out-of-band garbage that can effect how it sounds. Depends a lot on the switching frequencies and the amplifier design. Also keep in mind, that AFAIK, in Class D topologies the signal is deconstructed and then reconstructed with filters.
 
#35
rumblinbass said:
Other amplifier classes (H, G, & T) start getting into switch-mode power supplies that monitor the signal level to regulate the voltage rails...if I remember correctly.
Click to expand...

That's not correct. No amplifier class specifies a type of power supply, though G and H use multi-tiered supply rails. Class "T" is Tripath's approach to class D.
 
#37
seamonkey said:
Just one manufacturer:

http://www.newclassd.com/
"THD levels which are below our measurable limit of 0.0003%"

Well below what human hearing can detect which is 1% for those that fit under the bell curve.

Class-AB can also be well below human hearing. Both being well below, you won't hear a difference.
Click to expand...

Assuming THD is the only important metric...
 
#40
dincz said:
I thought class H involved modulating the supply rail voltage. Wouldn't that be easier with a SMPS or is it just as feasible with linear regulators?
Click to expand...

You could modulate the supply voltage rails, but its more commonly done by commuting two or more tiers of rail voltages. No regulators necessary, and it can be done with line-frequency or high-frequency power supplies.
 

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