Class D "digital" amps. Opinions on performance

[Bob Lee (QSC)]

"Class H" is QSC Marketing's version of class D. I use the TC RH450 and LOVE IT! My other amp is SVT with 8x10.

No, class H is linear, based on class AB but with commutation among multiple rail voltages. It is not class D (PWM and non-linear) by a long shot.

 

[bryanspkr]

The Crown K Series was a good example of a class D amp with a heavy conventional power supply, if that's what you mean.

The question is, is that a different animal than these ultralite 2Lb. units that are getting popular?

I'm sure the crowns are quite muscular.

 

[MetroBass]

I have tried just about all of them, and IMO there is only one that does not sound DIGITAL (to my ears) and that's the Genz Benz amps with the 3DPM.

Any other class D amps I have tried just do not sound right to me.

Hope that helps.

100% True statement - digital is digital. No matter how good the best A-D converter is, it STILL produces a square wave output. If you're playing through tubes now, there aren't any of them that sound like a tube amp. They are far from warm and natural. Now, if you want HI-FI dig in, they are definitely that. Also, don't let that (single) tube pre-amp fool ya - it does not warm up the tone, especially when it's sent back through a A-D convertor.

 

[Bob Lee (QSC)]

100% True statement - digital is digital. No matter how good the best A-D converter is, it STILL produces a square wave output. If you're playing through tubes now, there aren't any of them that sound like a tube amp. They are far from warm and natural. Now, if you want HI-FI dig in, they are definitely that. Also, don't let that (single) tube pre-amp fool ya - it does not warm up the tone, especially when it's sent back through a A-D convertor.

An A/D converter puts out digital data. (That's not class D either.) If you want analog from that, you convert it back to analog with a D/A converter.

 

[gnjpowell]

Despite the complexity involved, a properly designed class D amplifier offers the following benefits:

* Reduction in size and weight of the amplifier,
* Reduced power waste as heat dissipation and hence smaller (or no) heat sinks,
* Reduction in cost due to smaller heat sink and compact circuitry,
* Very high power conversion efficiency, usually 90% above one quarter of the amplifier's maximum power, and around 50% at low power levels.

 

[Bob Lee (QSC)]

large toroid?

They had large line-frequency power transformers. I think they were toroidal.

 

[Passinwind]

They had large line-frequency power transformers. I think they were toroidal.

They are, not that it matters that much IMHO. I owned two K2s and one is still in the sub rack at the club I used to mix in. Does the job just as well as the PLX 1802 in there...

Bryan: yes, I have directly compared many topologies. As usual, it just depends on the implementations.

 

[projectMalamute]

"Class H" is QSC Marketing's version of class D. I use the TC RH450 and LOVE IT! My other amp is SVT with 8x10.

This is nonsense.

 

[agedhorse]

A buddy of mine had me play thru his GenzBenz Shuttle into a Neox 212. Then he swapped the Shuttle with his GB750. To both our ears, it simply sounded better.

The GBE-750 and the Shuttle have different preamps, they do sound different regardless of the power supply or power amp type.

To confirm this for yourself, run the GBE-750 preamp out into the Shuttle's power amp in to eliminate the power amp influence from the comparison.

 

[projectMalamute]

No matter how good the best A-D converter is, it STILL produces a square wave output.

total nonsense.

 

[Munjibunga]

OK, I've owned:

Eden WT-800 (2)
Aguilar DB750 (Still have it)
Glockenklang Heart-Rock
Aguilar AG500

Now I have:

GK MB800
Aguilar TH500
TCE RH750
GB Shuttle 9.0
Eden WTX500

Aside from the inherent tonal differences between any two different amps, any difference between big amps and micros is completely insignificant in a gigging situation. Of course, that's for amps of comparable power. We can sit here and talk about subtle differences between the topologies, but I can guarantee you that you won't hear any deficiencies in, say, my MB800 running through my AE410 (which brings up the whole light-weight cab issue). I don't miss those big, heavy amps at all. The convenience of 5 pounds over 50 pounds far exceeds any differences that may exist.

 

[projectMalamute]

The Crown K Series was a good example of a class D amp with a heavy conventional power supply, if that's what you mean.

Also the Crest CD series amps.

I have a couple CD2000's and they suck, kind of a lot. They use an under sized power supply, but it's supposed to be okay because they also use a gimmicky cheap class D output section.

I don't know if it's that or just the worst limiter ever known to man, but if you hit the clip limiter hard you can hear the thing sag and come back up to power, like a super long release setting on a compressor. barf.

Hit a comparably rated CA9 just as hard and it smooshes down for just milliseconds before going right back to pounding out your guts.

 

[Nedmundo]

Aside from the inherent tonal differences between any two different amps, any difference between big amps and micros is completely insignificant in a gigging situation. Of course, that's for amps of comparable power.

That's been my experience, limited though it is. I have a G-K 700RB-II and an MB-500, both of which I've run through G-K Neo112 cabs. Doing the A-B comparison, I certainly hear a difference. Relative to the 700RB-II, the MB-500 can have a "synthetic" quality to its tone and a little less "heft." But much of this difference disappears with EQ adjustment -- mostly cutting treble and high mids on the MB-500 -- and in a band mix the difference is negligible. On stage, the MB-500 has tone, punch and presence similar to the 700RB-II. I don't push either head very hard, and perhaps I'd hear more of a difference if I did.

 

[kraigo]

I've been using class D power in my PA rack for quite a while. I noticed no difference in "sound" after replacing QSC PLX (class H, I believe?) with class D.

Maybe I need to add some Golden Ears to my setup?

Golden ears will soon get pawned for the latest and greatest because it's "SO much better" than what you already have. I often think it's better to have "silver ears".

KO

 

[seamonkey]

* Very high power conversion efficiency, usually 90% above one quarter of the amplifier's maximum power, and around 50% at low power levels.

The curve is different, it's steaper. And I'd say it's more left of one quarter.

This is typical of the curves I've seen published for class-d versus class-ab

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Effects, Class D gets warm when played at low volume. It feels warm mainly because the surface area is small.

At high volume, they don't get much warmer.

Given a typical power outlet, you can get much more power to the drivers using class-d than you can with class-ab. With SMPS the class-d amps are smaller and lighter. FOH is getting big into this, not just for lightness and saving power but because they are transparent amplifiers.

 

[bongomania]

100% True statement - digital is digital. No matter how good the best A-D converter is, it STILL produces a square wave output.

Are you intentionally ignoring the fact that the discussion is actually about ultralight amp topologies, and has nothing whatsoever to do with A/D converters?

 

[lowfreq33]

100% True statement - digital is digital. No matter how good the best A-D converter is, it STILL produces a square wave output. If you're playing through tubes now, there aren't any of them that sound like a tube amp. They are far from warm and natural. Now, if you want HI-FI dig in, they are definitely that. Also, don't let that (single) tube pre-amp fool ya - it does not warm up the tone, especially when it's sent back through a A-D convertor.

Class D amps are not digital. No A/D convertors involved.

 

[seamonkey]

I see some claim some amps "sounds digital"
Only bad digital "sounds digital". IMHO ... YMMV
And the standards far exceed what human hearing can differentiate. Low bit depth and low bit rates are essentially gone from MI use.

Good digital doesn't sound like anything.
The music industry is more $$$ today than it ever has been. You can't buy music that hasn't passed through the digital domain anymore. Digital doesn't add or take away anything from the sound. It allows the sound to be transported without change.

I can't deny some may have golden ears and can hear things outside of the normal curve. I personally can't hear it, and 99.9% of the audience can't. And I doubt there could ever be a test that proves .01% can hear it.

 

[gnjpowell]

"Class D amps are not digital." True, and a very common and understandable error. "D" is the fourth letter in the alphabet and simply follows "C". Pure coincidence that "D" happened to be the next letter and was used during the time when things were going digital.

 

[bryanspkr]

100% True statement - digital is digital. No matter how good the best A-D converter is, it STILL produces a square wave output. If you're playing through tubes now, there aren't any of them that sound like a tube amp. They are far from warm and natural. Now, if you want HI-FI dig in, they are definitely that. Also, don't let that (single) tube pre-amp fool ya - it does not warm up the tone, especially when it's sent back through a A-D convertor.

So, What does "sound digital" mean?
Cold? Uncontrolled, Distorted. Poor transient? Is it the Preamp? Is the amp pumping or oscilating? Under what conditions. Max Volume? Without pushing even order harmonics? As opposed to what one is used to? Or what kind of taste one has?
I think the only way to know is with all things being the same except for the power amp.