Class D vs Class A or A/B

[agedhorse]

You mean a line-frequency power supply, Andy.

Gee, and to think I have been so careful too... you caught me red handed with my fingers in the electrons Bob

 

[ThisBass]

US Patent 03011025 in 1961 by Herbert W. Sullivan

Thank you

Do you know the dates when he started and finished his work?

 

[Jeff Scott]

US Patent 03011025 in 1961 by Herbert W. Sullivan

Ed's brother?

 

[ThisBass]

I have an amp with Powersoft internals. It is great. Still you have to use gain matching to compare amps.

Input resistance and input sensitivity shall be provided.
Sometimes the output resistance of a preamp that drives 10k input may attenuate the signal level a little bit.
These situations are seldom, but not impossible.
And consider, unbalanced line out signal into a balanced input attenuates -6dB to the signal level.

I was subtly excluding MI tube amps.

superb insight!
I love it to explain how the legendary class AB ampeg SVT sound is done. But this tube amp is also very very off topic to the thread like MI.

It's fair to say things like the passband behavior as they approach clipping can easily be duplicated with signal processing, small tube amps, or fancy feedback. It throws off thread to even mention it.

I tried to read out the sense five times and then give up.
I don't understand anything.

 

[ThisBass]

Ed's brother?

who is Ed?

 

[ThisBass]

I have an amp with Powersoft internals.

Through it into the garbage can.
It's obvious not the wattage you paid for.

 

[Jeff Scott]

who is Ed?

Here you go!

http://en.wikipedia.org/wiki/Ed_Sullivan

 

[ThisBass]

I'm so sorry,
ähm,
I wanted to ask,
who is ed's brother ?

 

[agedhorse]

Ed's brother?

Ba-da-boom

 

[bassakwards]

Are all Class D bass amps based on the ICE (or Powersoft) modules? It was very interesting reading some of the earlier posts, such as Genz Benz and Aguilar implementing these modules with various methods of power management and different design goals. Just wondering if any manufacturers are using something else. Or is class D so complex that it is not practical/cost effective to do this any other way?

 

[agedhorse]

Each amp manufacturer approaches this differently. Most use some kind of technique to manage these factors regardless of amp class. Some do a better job than others.

 

[teemuk]

Are all Class D bass amps based on the ICE (or Powersoft) modules?

No.

Just wondering if any manufacturers are using something else.

Yes, many of them use something else, ranging from other OEM class-D modules (like Hypex UcD's), to several families of class-D chipsets from various manufacturers, to semi-discrete designs (with e.g. gate drivers in an IC package) all the way to fully discrete designs.

is class D so complex that it is not practical/cost effective to do this any other way?

Yes, they are complex, but it doesn't mean everyone must resort into using a single family of OEM modules for the job. Yes, class-D can be "done" in many other ways as well.

 

[BbbyBld]

Or is class D so complex that it is not practical/cost effective to do this any other way?

In the theoretical sense, they are pretty easy to understand and simulate. In practice, they blow up in your face a lot and scare the $hit out of you. Some designers don't like to deal with that.

 

[R Baer]

Just wondering if any manufacturers are using something else. Or is class D so complex that it is not practical/cost effective to do this any other way?

One of the main advantages to using an off the shelf class D module, is the fact that a company like B&O has already spent the tens of thousands of dollars needed to get all the proper testing and certifications done. These cost alone make developing a class D amp from scratch quite cost prohibitive for anyone but the very largest amp manufacturers. That little CE and FCC symbol don't come cheap.

 

[agedhorse]

In the theoretical sense, they are pretty easy to understand and simulate. In practice, they blow up in your face a lot and scare the $hit out of you. Some designers don't like to deal with that.

How true, how true...

 

[agedhorse]

One of the main advantages to using an off the shelf class D module, is the fact that a company like B&O has already spent the tens of thousands of dollars needed to get all the proper testing and certifications done. These cost alone make developing a class D amp from scratch quite cost prohibitive for anyone but the very largest amp manufacturers. That little CE and FCC symbol don't come cheap.

Roger, I think you have a decimal point off...

Developing a line of (high reliability) integrated class D amplifier modules and bringing to market involves staggering costs in both prototyping and regulatory areas. Not knowing specifics, it would be reasonable for a product like that to involve 10 individual prototype revisions, along with managing the paperwork to get from concept to finished, approved product. Figure $5k per prototype revision including labor and you are at $50k right there. Then you have the cost of managing the agency approval process, there are things like CE, UL/CSA, CB Scheme, C-tick for safety, and CE, FCC for EMC/RFI. The paperwork is staggering, the safety reports can exceed 250 pages and the agency time to inspect and test. The EMC reports can be 75 pages, with a lot of testing and investigation time as well. The testing, retesting and report writing for the prototyping for all of this can easily exceed $100k because of the complex nature of the product. Then, managing the parts procurement process including the (safety) critical components adds another layer to the process. This is all in addition to the usual design costs for a highly complex device. In order to make sense, these devices must be manufactured in very high quantities or these NRE (non-recurring engineering) costs completely overrun the cost of the product itself.

 

[seamonkey]

Yet with all this complexity, the value proposition to the customer is higher than it has every been!

 

[agedhorse]

Yet with all this complexity, the value proposition to the customer is higher than it has every been!

It really is. This is a great time to be a bass player, lots of really nice options that just weren't possible at a cost most of the market was willing (or able) to pay.

 

[Calaverasgrande]

An excellent question. I'll start off by saying that the MB800 may have ruined me for ever bringing heavier amps/heads to a gig. That being said, the main differences that we are seeing in our testing comes when we apply the burst power tests. Of course, these results vary based upon the design of a given output section (regardless of topology), based upon the power section of the amp, based upon how that amp designer addressed limiting and clipping, and based upon other factors related to the overall design of the particular amp(s) being tested. I'll also say that the more modern class-D heads which we have tested appear to be improving with regard to how they handle burst power and how they respond when pushed to their limits.

There will certainly be some class-D amps which test "better" - even on the burst tests - than some class-AB amps. But at least with regard to the question above, while the GK MB800 (class-D) was able to hit just over 125% of its rated power in our burst tests, the GK Fusion 550 (class-G) was able to hit over 145% of its rated power in this same burst power test [Note: we were not publishing the results of our burst power tests back in issue #3, which contains our Fusion 550 review, but we have run this unit through the current BGM burst power test and it exceeded 800 watts at 4 ohms.]

In typical gigging use, a player may not notice that difference. But to reiterate my answer the question above, the main difference we see between and amongst the various amp topologies we test is how they handle burst demands. Not saying one topology is better/worse than the other, only that this is where we are seeing some distinctions in our tests.

that is interesting to me.
I see some comments defending how Ampeg has used burst power ratings for it's solidstate amps. Basically the argument being that burst power is more accurate because it simulates how bassists play.
IMHO that may be true for bassists like Wooten that play lots of staccto lines. Some of us prefere a more sustained sound. I personally play with a hint of overdrive even when I play clean. And when I play full overdrive/fuzz I guarantee it is a higher average level signal.
So what Tom says here has me now wondering which amp topology may favor a high average signal level with lower peaks over a more staccato style, lower average signal level that may have higher peaks.

 

[ThisBass]

that is interesting to me.
I see some comments defending how Ampeg has used burst power ratings for it's solidstate amps. Basically the argument being that burst power is more accurate because it simulates how bassists play.
IMHO that may be true for bassists like Wooten that play lots of staccto lines.

no doubt about it.

Some of us prefere a more sustained sound. I personally play with a hint of overdrive even when I play clean.

IMO it is never possible to play "clean" and with a "hint of overdrive" twice at the same time.
Btw the definition what is "clean" at all is a very confusing story.

And when I play full overdrive/fuzz I guarantee it is a higher average level signal.

No it is not. Some times the average is the same, probably most of the time the average is a little less.

In general the distorted signals sound louder by the same average.

I suppose you balance both "sounds" to the same loudness.
The distorted sound average will then probably be smaller.
The peaks/transients are reduced anyhow.

So what Tom says here has me now wondering which amp topology may favor a high average signal level with lower peaks over a more staccato style, lower average signal level that may have higher peaks.

The question explains by itself.