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Class D Amps - Anyone else having second thoughts?

#81
Personally, I really think it's time to stop looking at class D is some new fad that has still yet to prove itself. The technology has been around quite a while and has improved to the point where it is now an equally viable option as a bass amp topology. The category of a micro sized, class D amp may not work for everyone, but then neither does a Fender Jazz or P-Bass. One huge plus to class D, IMO, is that the sound quality to cost ratio has greatly improved in the last few years. Never before have bassist been able to buy such good tone for so little money.
 
#85
My beef with SMPS comes from long term experience in a different industry.

In my day job, the gear we use has been chock full of SMPS for a good twenty years. Some of the manufacturers did a nice job of design, including the publishing of schematics and keeping parts available for purchase. Others used supply modules that can only be replaced - and once the modules are out of stock, you've got a doorstop.

Oh, and the companies selling the modules don't always sell them inexpensively - just this week we spent over $2500 for four supplies used in high end television monitors.

Quality focused firms (like QSC, GB) are not the problem.

Caveat Emptor.
 
#87
Petebass said:
:) I personally can't tell if an amp sounds good or not until I've read the spec sheet.
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Soooooo true

:D

Interceptor said:
My beef with SMPS comes from long term experience in a different industry.

In my day job, the gear we use has been chock full of SMPS for a good twenty years. Some of the manufacturers did a nice job of design, including the publishing of schematics and keeping parts available for purchase. Others used supply modules that can only be replaced - and once the modules are out of stock, you've got a doorstop.

Oh, and the companies selling the modules don't always sell them inexpensively - just this week we spent over $2500 for four supplies used in high end television monitors.

Quality focused firms (like QSC, GB) are not the problem.

Caveat Emptor.
Click to expand...

This.
 
#88
Generalizations tend to fail simply because of the vast number of variables. Often overlooked is the concept of synergy between an amp and speaker system. A speaker can have a spec of 96db / 1 watt / 1 meter, 4 ohms nominal, easily driven by amp X but not so much by amp Z. Why would that be? Variables in the implementation of the circuit. I have tried two different lightweight power amps from the same manufacturer, one of which makes my PJB stack sing, and the other cannot drive it very well at all - cannot control the drivers, utterly intolerant of slight AC supply fluctuations. However, there is nothing 'wrong' with the second amp. It is just a different implementation of the class D design, thus behaves very differently, and has no problems driving my EA cabinets at all. No synergy whatsoever with the PJB Piranhas.
 
#89
lofreek said:
Generalizations tend to fail simply because of the vast number of variables. Often overlooked is the concept of synergy between an amp and speaker system. A speaker can have a spec of 96db / 1 watt / 1 meter, 4 ohms nominal, easily driven by amp X but not so much by amp Z. Why would that be? Variables in the implementation of the circuit. I have tried two different lightweight power amps from the same manufacturer, one of which makes my PJB stack sing, and the other cannot drive it very well at all - cannot control the drivers, utterly intolerant of slight AC supply fluctuations. However, there is nothing 'wrong' with the second amp. It is just a different implementation of the class D design, thus behaves very differently, and has no problems driving my EA cabinets at all. No synergy whatsoever with the PJB Piranhas.
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I have higher expectations. With a modern power amp circuit, the output voltage is proportional to the input voltage, or it's not. Either it clips gracefully or it doesn't. It can handle a reasonable range of anticipated load and operating conditions, or it can't.

If it's not, doesn't, or can't, then there is something 'wrong' with the second amp, namely the design.
 
#90
fdeck said:
I have higher expectations. With a modern power amp circuit, the output voltage is proportional to the input voltage, or it's not. Either it clips gracefully or it doesn't. It can handle a reasonable range of anticipated load and operating conditions, or it can't.

If it's not, doesn't, or can't, then there is something 'wrong' with the second amp, namely the design.
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Absolutely.

...and for the power amp portion of it, there really is little excuse for it not looking like the proverbial "straight wire with gain", in this day and age.
 
#92
NickyBass said:
Mr. Bob Lee, what amp type is the PLX1804? I love mine, and wouldn't give it up for anything---but I'm a little confused about the specs. (It isn't hard to confuse me with specs. :) )
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The PLX amps are all basically Class AB, and the higher-power models in that range (including the PLX1804) are also Class H.
 
#93
As far as I'm concerned class D amps and neo speakers are the greatest thing since Leo invented the P-bass. But though I'm just a semi-pro local gigger, I can't see how there's really any room for debate.

I use AI amps for electric and upright gigs--400 watts, 3 lbs, compact. Sounds as good as anything I've ever used, except a big tube head overdriven, and when I need that sound I put a pedal in the chain. I have not been able to hear any sonic difference that a real world, live audience or band mate is going to notice. Why in the world would I want to lug a big, heavy tube head?

If you're either playing only in the basement, or hiring guys to lug the gear for you, then I can maybe see the logic of a conventional amp. But otherwise, it's just no comparison. I can fit the 400 watt 3 lb AI head in my gig bag. That says it all.
 
#96
JonnyAngle said:
Stupid question of the day:

Do class D amps clip? :hiding:
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Yes. All amps clip. The question is: How do they behave when driven to their clipping threshold? In my view, clipping behavior should be a consideration in the design of any gear intended for musical or portable use. The Class-D amps that I have tested tend to have fairly "soft" clipping response, which is probably more musically forgiving than the "hard" clipping typical of Class-AB solid state amps.
 
#97
Bob Lee (QSC) said:
I don't happen to own a class D amp yet, but I would have absolutely no qualms at all about using a good one, especially one designed by agedhorse, Pat Quilter, or any other exceptional designer.

Tone? If you even half know what you're doing you can dial in the tone you want on any good amp, regardless of its class of amplifier circuitry.
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That all rings perfectly true -

My only concern about the current crop of class D amps is the frequency of failure (perceived or otherwise). I've read too many threads about frustration with GK and Carvin class D amps - and the one class D amp I have direct exposure to crapped out within 2 weeks. That said, I've played *many* at stores that gave me serious GAS (GB & EA leap to mind) - - and I have not read too many complaints about either company's class D amps... Perhaps what I've been seeing is that the low-end builders (GK / Carvin) are making all the class D amps look bad...?
 
#98
I'm a fan of good sound, whatever technology can produce it is fine. Playing for my own personal enjoyment, the various class D amps I've owned or tried seemed to be lacking richness/weight (distortion?) in the lower mids & lows. I readily admit that the sometimes subtle tonal differences between many of the amps we discuss about on TB will never be perceived by an audience in a venue, especially ones with mediocre (at best) acoustics. That said, I try to choose products that can be repaired by local techs, and hopefully not just replaced outright. Part of that comes from not wanting to give in to the 'newer is better, it's all disposable anyway' train of thought. Part of that also comes from wanting to spend my dollars locally.

agedhorse said:
Class D amps aren't too hard either but usually it's less costly to replace the entire class D section because of the economies of scale when building large quantities.
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What might a player expect to pay for a replacement class D output section? That may be something to consider when making a new amp purchasing decision. Is a $599 amp still a great deal if it craps out and needs a $300 component replaced a few years later? Just like in owning a car, the true cost is what it takes to keep it on the road, not the showroom cost.
 
#99
So specific amp - speaker interactions, long discussed in high end and pro audio circles, do not really exist? I'm not fabricating this. Certain speaker types, such as electrostatics, have always been problematic for many power amps, price and / or topology notwithstanding. Speakers with severe dips in impedance, same issue.
 
#100
koobie said:
What might a player expect to pay for a replacement class D output section? That may be something to consider when making a new amp purchasing decision. Is a $599 amp still a great deal if it craps out and needs a $300 component replaced a few years later? Just like in owning a car, the true cost is what it takes to keep it on the road, not the showroom cost.
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FWIW, even in the highly unlikely event that my Shuttle failed tomorrow, I'd run right out and buy another one. I've had well over a hundred gigs (most being four-hour gigs) on my Shuttle 6 with zero issues. I've treated my Genz reallly rough during that time as it is small and gets thrown into my gig bag and slammed around.

It's a lot cheaper if you don't have to have anything fixed in the first place.

As far as tone -- that's why amps have EQ sections. I get fantastic tone out of mine, and regularly get compliments from fellow bass players who want to see what I'm playing.
 

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