Old class A vs New class D.
- Thread starter noobydoo
- Start date
lizard84
Abider
When a noted Magnepan tweeker mentioned in a conversation that a certain Class D amplifier brand would compete with amps costing 5 times its $2000 price I was intrigued enough to order one for a trial, soon after it arrived my McIntosh was pulled with the intention of placing it back in service rather quickly. It never happened, that Class D amp combined with my tubed Modwright preamp is as botrytis says in his sig, "Just Bliss!!!!"
bsandovalb
Active Member
I have had some bel canto class D amps... heard their newer bel canto hypex monoblocks (ref 600’s) and also a pair of hypex monoblocks (cant remember the modules)... it is a technology that has made great progress... for me they are ideal for multichannel set ups, tv set ups, as they can be on 24/7 generating zero heat, taking very little space, and sound quite good....
However, imho they are still not there with good quality class A amps... they cannot beat a good and heavy transformer with a nice power supply.... for casual listening and iffice, small systems where space is limited, class D is great, for critical listening.... just not there!
However, imho they are still not there with good quality class A amps... they cannot beat a good and heavy transformer with a nice power supply.... for casual listening and iffice, small systems where space is limited, class D is great, for critical listening.... just not there!
slimpikkins
Super Member
Hey guys, great conversation here. What happens to a "chip" amp or class d when it runs out of gas? Does it clip and send a square wave to your speakers and take out your tweeters? Or does it just shut down? That Lepai lp7498e is $85.00 with blue tooth connection, pretty cool.
jazzmans
Super Member
speaking for the lepai, it gets progressivly 'dirtier' the louder it goes. I've had it shutdown only a couple of times, momentarilly while I was driving two pairs of Magnepan speakers (1.6 and 2.5r) simultaniously then it just turned back on agian.
unless you're using REALLY inefficient speakers, or are in a huge space, it gets plenty loud before the distortion starts to become audible.
unless you're using REALLY inefficient speakers, or are in a huge space, it gets plenty loud before the distortion starts to become audible.
Tom Bombadil
AK Member
Current higher-end Class D amps are drawing rave reviews from pretty much all of the audiophile magazines. The Bel Canto 600M was reviewed last year by The Absolute Sound, who had this to say about it:
"In the past I’ve reviewed lots of power amplifiers. Once I even had a dream that I was twenty feet tall with a Krell 160 monoblock under each arm striding across the urban landscape yelling, “I am Amp Man!” (imagine Godzilla, only prettier). Luckily I had that dream only once. But with the advent of compact and lightweight switching amplifiers such as the REF600M no audiophile need experience the “pleasures” of lugging around a 60-plus-pound amplifier because it was the only device that could deliver the power and finesse needed to drive a top-echelon system.
How good is the REF600M? To my ears it’s good enough to qualify as the best all-around power amplifier I’ve heard to date, regardless of technology or circuit topology. Its combination of extremely low noise (that makes it suitable to drive even highly sensitive loudspeakers), precision three-dimensional imaging, relaxed and natural harmonic balance, and power capability makes for a potent package. Couple all its sonic achievements with its relatively modest price, and you have a power amplifier that could well be a benchmark reference for many audiophiles for years to come."
Archguy
Official Roiurama Factory Rep
Yeah, running two pairs of Maggies from a single Lepai isn't something even I'd do--in fact my only Lepais run bookshelf monitors from Mission and Polk. But they do that remarkably well. Most of the time I'm listening to acoustic piano jazz at moderate levels, though. A few times I've cranked up rock music and the Lepais display a bit of strain and glare, which I think is to be expected. You can only ask so much of them. But taken for what they are, I call them small miracles. And (as I mentioned before) as the tech continues to advance it's not hard to foresee the end of the 50- or 100-lb amplifier in anything but the esoteric top-end of the marketplace.
Yep, like that.
audiosignal
Active Member
The big question in my mind about the newer, more expensive class D amps in general is, can you repair them (or find someone who can) for a reasonable cost, particularly when the manufacturer obsolete them after a number of years, and replacement boards are no longer available?
With vintage class A or AB, I think there’s hope for repair, but with newer high end class D amps (which is much more sophisticated), I don’t know.
With vintage class A or AB, I think there’s hope for repair, but with newer high end class D amps (which is much more sophisticated), I don’t know.
DaveVoorhis
Addicted Member
It really comes down to the availability of individual components. If a class D amp is built from discrete MOSFET outputs and popular discrete drivers, or discrete MOSFET outputs and a common MOSFET driver chip like an IR2210, it will probably be indefinitely repairable. If it's built using "chip amps" and they're plentiful or still manufactured, it might be indefinitely repairable. If it's built using non-standard, limited-production, and/or obsolete-and-unobtainable custom parts, no.
However, the same applies to vintage class A or AB. Some were built using readily-available NOS or still-manufactured components; others -- like some discrete transistors and STK power modules -- are now essentially unobtainium.
slimpikkins
Super Member
You and me both Buddy.
45rpmspinner
Super Member
For the last 8 months or so I've been running Class D 90% of the time.
Both of the TI EV modules I own hold up very well when compared to my A/B dual-mono Sansui.
Just as authoritative, but with increased dynamics and "musicality".
The Sansui sounds somewhat "ponderous" by comparison [geez it pains me to write that].
Wattage ratings on the Class D units are a PITA.
Texas Instruments does actually put out more meaningful data, but you have to look for it.
So, just as an example.....
TI's TPA 3251 EV module hooked to a 36v power supply will put out 75 wpc at 8 ohms with 1% THD.
At 70 watts into 8ohms, THD quickly drops to 0.1.
At 60 watts it's around 0.01.
At 50 watts it's 0.003....and then pretty much bottoms out at 40 watts and below with 0.002-0.001 THD.
1 watt at 4 ohms, the distortion level is basically flat at 0.005 from 20hz to 10khz [at 8ohms, the base line is lower].
With increased wattage, distortion levels drop even lower [0.002 to 0.0007] across most of the range, with the exception of a peak which develops at 10khz.
At 75 watts into 4 ohms, that peak is still pretty small at 0.02.
Lastly, I have to say that complaining because you can't run a quad of Maggies off a Lepai is possibly the most bizarre comment I've read on this site.
There's a big difference between running an 8-10 watt Class D amp and one which puts out a clean 60 watts or more.
Both of the TI EV modules I own hold up very well when compared to my A/B dual-mono Sansui.
Just as authoritative, but with increased dynamics and "musicality".
The Sansui sounds somewhat "ponderous" by comparison [geez it pains me to write that].
Wattage ratings on the Class D units are a PITA.
Texas Instruments does actually put out more meaningful data, but you have to look for it.
So, just as an example.....
TI's TPA 3251 EV module hooked to a 36v power supply will put out 75 wpc at 8 ohms with 1% THD.
At 70 watts into 8ohms, THD quickly drops to 0.1.
At 60 watts it's around 0.01.
At 50 watts it's 0.003....and then pretty much bottoms out at 40 watts and below with 0.002-0.001 THD.
1 watt at 4 ohms, the distortion level is basically flat at 0.005 from 20hz to 10khz [at 8ohms, the base line is lower].
With increased wattage, distortion levels drop even lower [0.002 to 0.0007] across most of the range, with the exception of a peak which develops at 10khz.
At 75 watts into 4 ohms, that peak is still pretty small at 0.02.
Lastly, I have to say that complaining because you can't run a quad of Maggies off a Lepai is possibly the most bizarre comment I've read on this site.
There's a big difference between running an 8-10 watt Class D amp and one which puts out a clean 60 watts or more.
Archguy
Official Roiurama Factory Rep
There will probably be dozens of different answers to your question. In my own case, I figure it's around one (whole) percent, but there are many relevant variables. That being the point at which THD is bothersome, not just noticeable. Meanwhile, chasing the places to the right of the decimal point has oftentimes brought about deleterious effects with no appreciable gain. It being a matter of what circuit designers felt it necessary to do to gain that next trivial increment. Another thing to keep in mind is that harmonic distortion is only one type, and in some cases intermodulation distortion can be more irksome.
jazzmans
Super Member
I wasn't so much complaining as saying that they are much more stable then we've been led to believe.
I was actually A/B ing to compare the sound of the two sets of speakers, and turned on one pair without turning the other pair off ,I didn't notice until the amp shut off, then turned on again.
I've got another lepai 7498 that's been serving as an amp powering anywhere from 3-8 pairs of speakers simultaniously (through an autoformer speaker switcher) for the last five years, with no hiccups.
I'm sold, likely I'll never buy another class A/B amp again.
I don't know at what % of distortion I can hear it, but It's probably low, I'd have to hook up an oscilloscope and listen to see when I could hear it, I guess.
noobydoo
Active Member
Just wondering, did you mean.01 or .1. Although there are obviously exceptions I always used .01 as a rule of thumb. This isn't because I claim to be able to distinguish the difference between say.01 and .06 but I did find , in general, that amps that had lower distortion figures tended to be those that were better overall in terms of the build quality and the engineering that went into them.
Archguy
Official Roiurama Factory Rep
Understood, but I am saying there can be diminishing returns and even negative returns in the pursuit of the next "part per million." Speaking of negative, too much negative feedback has serious deleterious effects on SQ yet gooses your (THD) numbers nicely.
In my note I actually meant one whole percent, one part per hundred, which is generally tube amp territory nowadays. Without an oscilloscope test as Jazzman says I'm really just guessing. But overall I don't think THD has been an issue for decades.
You'll notice that some serious high-end equipment now advertises considerably higher THD numbers than mass-market gear. It's actually something I like to see, because I know their focus is on more important things.
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cpt_paranoia
Addicted Member
You'll be hard pressed to see 1% THD with a scope.
