Class D amps sound inferior?

[StatesideRambler]

What do we do when we get to "Class Z"? Does the world end?

Thence it’s class clown ... or class clone. Or class act. Class warfare. Or for working musicians: economy class.

 

[agedhorse]

Back in the day I bought a Contrabass Servo-drive Subwoofer (I still own). I was powering it with the Carver. The Carver would get so hot to the touch it could burn you. I was impressed the Carver never blew up. Then I spoke to the designer of the Sub and he recommended Crown or Crest power-amps. He said since the sub is motor driven it needs an amp stable to 2 ohms or less and not many power amps fit that bill at the time. When I bought the Crest the sound difference was night and day. Not only that but the Crest never got hot or broke a sweat. The Subwoofer engineer said it was all about the power supply and he didn't recommend using power-amps with switching power supplies. Again I wont pretend to know what he is talking about. All I can tell you is the audio quality was night and day.

So running the Carver into an effective 2 ohm load won’t sound very good, I wouldn’t expect it to because of the way the VI limiting works into a very reactive load. This is no surprise to an amplifier designer.

IMO, it has almost nothing to do with the power supply, PROVIDED that it’s adequate for the task at hand. There are several ways to skin the power supply cat. The Carver phase control supply had a peculiar operating quirk that inhibited the highest rail when the temperature got too high. This cuts the rated power down by over 50%.

 

[byacey]

So running the Carver into an effective 2 ohm load won’t sound very good, I wouldn’t expect it to because of the way the VI limiting works into a very reactive load. This is no surprise to an amplifier designer.

IMO, it has almost nothing to do with the power supply, PROVIDED that it’s adequate for the task at hand. There are several ways to skin the power supply cat. The Carver phase control supply had a peculiar operating quirk that inhibited the highest rail when the temperature got too high. This cuts the rated power down by over 50%.

Depending which amp he was using, it may not have even been rated for a 2 ohm load. I think it was only the PT1800 and PT2400 that could drive 2 ohms.

I never worked on any Servodrives, but I think it's possible their motors could have dropped even lower than 2 ohms.

I was winding some crossover coils on my little armature lathe years ago, and I tried driving the 1/8 HP induction motor with an oscillator driving a Carver PM1200 in an attempt at variable speed control for the chuck. It worked, but the amp certainly didn't like it as it warmed up pretty quickly. I went back to using AC line voltage and loosened up the drive belt so it had lots of slippage, enough that I could stop the chuck just by putting more tension on the wire being fed onto the coil form.

 

[agedhorse]

My general experience with Carver amps was that they were not optimized for lower impedance loads. Some clever ideas, novel approaches, and beautifully executed cosmetics but with challenges when used in love sound applications. There were some attempts to improve this (Clair, Showco), but ultimately other approaches and executions by Crown and QSC specifically, won out until class D became commercially viable.

 

[seamonkey]

What do we do when we get to "Class Z"? Does the world end?

Class Z was already marketed by Zetex (defunct) years ago - it was Class-D anyhow.

There are so many different Class-D designs, topologies, that the term "Class-D" is mainly a marketing term. The term will stick around for a long time as it implies: highly accurate, efficient, lightweight, reliable, versatile, - over previous popular classes of amplifiers.

 

[MultiScaleMale]

Pretty sure the local lakefront outdoor venue (~2-3000 capacity) is still using a rack of Carver amps for mains and monitors.

 

[byacey]

Pretty sure the local lakefront outdoor venue (~2-3000 capacity) is still using a rack of Carver amps for mains and monitors.

In a fixed install, I found them to be quite reliable, as long as they weren't abused. The odd time a rail switching transistor would short, but the amp would still get through the show. I don't recall too many catastrophic failures with them.
Once in awhile, if run really hard, the triac would short causing the transformer to run hot, and the power switch wouldn't shut down the amp.

 

[OregonJim]

What do we do when we get to "Class Z"? Does the world end?

It took over 100 years to get from Class A to Class H. The first amplifier showed up around 1912. I wouldn't worry too much...

 

[MultiScaleMale]

In a fixed install, I found them to be quite reliable, as long as they weren't abused. The odd time a rail switching transistor would short, but the amp would still get through the show. I don't recall too many catastrophic failures with them.
Once in awhile, if run really hard, the triac would short causing the transformer to run hot, and the power switch wouldn't shut down the amp.

And they're already racked, on wheels, and most importantly, paid for several times over, so run 'em 'til they die.

 

[byacey]

And they're already racked, on wheels, and most importantly, paid for several times over, so run 'em 'til they die.

With someone who know how to repair them, they could be kept going indefinitely, as long as parts are available.
I had a transformer in one that was grossly overheated; being no longer available, I rewound it, and it's still working to this day.

 

[agedhorse]

Class Z was already marketed by Zetex (defunct) years ago - it was Class-D anyhow.

There are so many different Class-D designs, topologies, that the term "Class-D" is mainly a marketing term. The term will stick around for a long time as it implies: highly accurate, efficient, lightweight, reliable, versatile, - over previous popular classes of amplifiers.

Don't forget class T (Tripath)

 

[tony caskey]

As my rig is a pedalboard, and people hear me through the PA, I am completely unaware of the class of amplifiers that I'm playing through - most likely class D. I don't even get to hear what I actually sound like in the audience (I'm on in ears). All I know is I keep getting booked for gigs. There are things worth worrying about - what class you amplifier is is not worth occupying brain cells on.

that is why you have to give away those old amps. their are 10 tons of them out there

Back in the early 90s I bought a Carver Class D power amp. It was light and it was loud however the bass sounded too mushy for my taste and still preferred the bass sound of my Crest power-amp, although the Crest was twice the weight of the Carver. That experience left a bad taste for anything Class D. I think the current crop of Class D amps have improved a lot. So much so that when I compare my new Class D amp to my older heavier amps the tone difference is very minimal and considering the weight savings worth the minimal difference. However one opinion still hasn't changed. If you are driving subs and need to drive a set of speakers at 2 ohms Class D will still struggle or just shut down compared to my Crest. My Crest CA9 doesn't even break a sweat in this type of setting. That's all.

they got a lot better since then, Dark Glass 900, bassman 800 pro, even my even my hartke KB 1-12 sounds organic and musical

 

[Ellery]

I think what's happening here is folks splitting hairs over subjective perceptions of sound qualities that can't be accurately communicated with the written word. When I started on building my rig I avoided Class D because of what I read on TB and FB, and was told by bass players I had talked to. Years later I "compromised" and got a Class D head to build a small rig, a Genz Benz, and lo and behold, every negative comment about these amps I had trusted turned out to be total [baloney]. Just a bunch of hot air from people who never could have tried out enough examples to speak intelligently on this subject. Of course we all want different tones but I see no shortcomings due to the type of transformer. That old GB Shuttle sounds fantastic, even through my 6x10 cab. If I had known I would have had one from the beginning!

 

[agedhorse]

I think what's happening here is folks splitting hairs over subjective perceptions of sound qualities that can't be accurately communicated with the written word. When I started on building my rig I avoided Class D because of what I read on TB and FB, and was told by bass players I had talked to. Years later I "compromised" and got a Class D head to build a small rig, a Genz Benz, and lo and behold, every negative comment about these amps I had trusted turned out to be total [baloney]. Just a bunch of hot air from people who never could have tried out enough examples to speak intelligently on this subject. Of course we all want different tones but I see no shortcomings due to the type of transformer. That old GB Shuttle sounds fantastic, even through my 6x10 cab. If I had known I would have had one from the beginning!

This is exactly the situation that I was describing earlier, propagated by folks that did not WANT to understand technology and the evolution of bass gear. Amps have evolved since the beginning, just like speakers and music styles, and believe it or not, they continue to evolve. The only real compromise is the beliefs in player's minds.

 

[lug]

This is exactly the situation that I was describing earlier, propagated by folks that did not WANT to understand technology and the evolution of bass gear. Amps have evolved since the beginning, just like speakers and music styles, and believe it or not, they continue to evolve. The only real compromise is the beliefs in player's minds.

Basses must be heavy to sound good.
Cabs must be front-ported to sound good.
Basses must used X tonewood to sound alive.
You must have all tubes to sound good.
Players must practice to sound good.

Ok, I may be a bit sketchy on that last one.

 

[micguy]

Players must practice to sound good.

Ok, I may be a bit sketchy on that last one.

That last one is absolutely true for me.

 

[GreyBeard]

What level of distortion is audible? I think 5% was once discussed on these forums.
I think much of the above discussion is akin to spitting in the ocean. It makes a difference that might be measured but never realized.

Bass amp distortion numbers are pretty meaningless. It is more about slam and compression. Most players I know use some sort of distortion devise like a pedal or preamp.

 

[Rich Fiscus]

25255824[/URL], member: 68399"]Just because the pulse has 2 states does not make it digital, all the critical information is contained within the timing of the pulse relative to the zero crossing of the AC waveform, the pulse just turns the device on (the device turns itself off at the next zero crossing. (via option isolation)

This is, IMO, another example of a non-linear analog process. The percentage of dimming information is contained within the timing of the pulse. At 0% dimming, there is no pulse, and at 100% dimming there is just a DC voltage (no pulse in either case, normal operation)

[note that in this discussion, I am refraining from sarcasm, this is a confusing enough topic without it ]

I’m not an engineer, but when I learned digital circuits, digital logic was always implied. It was the distinction between pre Anatasoff-Berry analog computers and post ABC Boolean Logic machines.

Opening the definition to every use of binary states would seem to make it a pretty meaningless term. It seems about as technically useful as grouping devices by what color the components inside are.

 

[dponbass]

I don't know man ... I'm a huge Walkabout fan and have gigged and recorded with mine (ver 2) for 15 years ... I use it whenever I can, but when the Walkabout runs out of gas, which with 300w @ 4ohms, it's been known to do, my WD800 fills in nicely and I have never noticed any lack of "heft" "slam" (or whatever term you want to cook up) from the WD800. IMO/IME (and many others too) the WD800 just takes what the Walkabout does so well and expands its capabilities in a great way. Nothing but love here for the class D power section of the WD800!

I used it up against the first Mesa WD, could have easily been more setting related (more mids) and I just didn't pay close enough attention or perhaps the volume wasn't equal- I'd rule nothing out. I felt like all were close, but the dimension wasn't there. I'd definitely like to give them another try, just need more gigs lined up to justify opening that can of worms.

 

[Pilgrim]

Can we PLEASE GET PAST THIS???

The class D amps are proven by the experience of years and thousands of gigs and concerts. I don't freakin' care if you have imaginary bogeymen in your head about Class D, there are thousands of really good musicians who use them and are delighted with them.

If you don't like them for real or imagined reasons, DON'T USE THEM!!

If (like me) you welcome them and are grateful for the versatility, low weight great sound they offer, USE THEM!

But stop asking the same question of others when the track record of Class D amps is well established and your ears are the only ones which count for you.