Old class A vs New class D.

[SVI2004A]

OCL class A with plenty of big SanKen finals.... bugger class D... don’t want my sound chopped up like it’s a victim of the freakin triad

 

[RobRoy]

Hello all. So I just watched a review of a Lepai class D amp. This little thing supposedly puts out 160 watts into 4 ohms with low distortion, all at the price of a night out on town for 2. Should I be tossing out my Luxman 5m21 , which is only rated at 100wpc into 8 ohms to make room for a pair of these? Discuss

I am a HUGE fan of these class D amps, but I understand their limitations. As a musician I love my Crown Class D PA amps. I even use one for my bass.

A high powered old school bass amp could weigh upwards of 100 lbs. These new amps weigh somewhere around 7-15 lbs. And in a typical PA you could be looking at two to four stereo amps. It adds up. So, for live sound it's a no brainer. The old stuff is as useful as an old Pinto.

But for Hi-Fi and/or studio work, sound quality trumps weight, even if the difference is only slight. And given enough time you WILL hear the difference in most class D amps.

That being said, I think of Class D vs Class A as the same battle going on between tube and solid state back in the early to mid-70's. But solid state got better, if you get my drift.

 

[RobRoy]

Lepai lp 160. I'm obviously being provocotive. This arose out of a discussion I had with a friend who recently purchased a samsung home theater system that purportedly has 1000 watts system power. I tried to explain to him the concept that all watts are not created equal but it fell on deaf ears. (pun intended)

I sold Hi-fi back in the 70's. We had a section of electronics outside the hi-fi area where you could buy things like "Soundesign". I would "mine" customers from that area and get them into a system with, typically, a pioneer SX 434, a cheap Garrard turntable and one of a various array of name brand spekers in their bottom line.

The first thing I had to point out to them was that 200 watts of "peak music power" in a Soundesign was equal to about 3 watts, RMS at 8 ohms with acceptable THD.

 

[RobRoy]

I wish they would just rate these things like they used to, stating reasonable (say under 1%) THD into 8 and 4 ohm loads and 20-20k bandwidth. You have to be really careful these days trying to figure out what they are leaving out when stating specs.

Seems we went backwards in that respect.

I remember in the 70's you could go to hi-fi stores and grab free spec sheets on all sorts of equipment (I still have a stack of those). But around 1980 it changed. Specs (and spec sheets) sort of disappeared and I started noticing manufacturers replacing them with subjective phrases like "smooth", "warm" and "crisp" sound. That's when I knew the stuff was on its way to being commoditized.

 

[RobRoy]

AB seems a good efficiency compromise between A and D, to me. Plus, AB designs have been refined over decades by many. Class D keeps improving, though. The cheap, high-distortion models failed to impress me. Yeah, an eight-watt Lepai can sound kinda okay, but my cheap eight-watt tube amp sounds better.

Because my ears are 64 years old and spent too much time in close proximity to a loud drummer, Class D is more than fine for me.

I still use my old 70's separates, but only because I love using them and they are cool, not because they sound any better.

On a related issue - tape hiss is no longer a concern to me. Even when playing old non-dolby cassettes. It's a distant memory.

 

[RobRoy]

They have come a long way since the Infinity SWAMP, a unit I heard at a reviewer friend's home back in the 70s.

I tend to call class D "digital switching amp". I honestly forgot where I got that phrase from. I actually remember those things. We handled infinity speakers (I sold the stuff in the 70's). This is in the back of my memory right next to where I keep the info on Elcassettes. Your link was my secondary index used to draw it out.

 

[Pio1980]

Kenwood L-07M were considered one of the first switching amps.

Class A/B linear, Afaik.

 

[RobRoy]

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.

The whole concept of "repair" may be entering a paradigm shift. Heck, I replaced the spark plugs on my car at 138k miles and it turns out it didn't need it. I'm starting to see the new spark plugs in cars as virtually (if not literally) permanent.

And the same with these amps. They don't cost nearly as much to produce, should not cost nearly as much, and in the EXTREMELY unlikely event the fail, you simply replace them, like I did with my 4 year old Westinghouse flat screen TV when it failed. Oddly, I'm glad I did because I got a SIGNIFICANTLY better flatscreen for the same price I paid for it originally.

 

[noobydoo]

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.

I completely agree. As I mentioned I simply used it as a rule of thumb. Regardless of the THD numbers if you need really complex circuitry in order to achieve lower thd there is bound to be a tradeoff somewhere. I've always sought amps that were as close as possible to the straight line with gain idea. Love my class A amps for that reason. I'm fairly ignorant when it comes to class D(t) but I'm open to trying them out. Then again I still drive a 93 volvo wagon so it may be a while before I take the leap.

 

[RobRoy]

Kenwood L-07M were considered one of the first switching amps.

Yep. We sold those. One of my sales team mates bought a pair. Sounded pretty good. Sounded great, actually.

In those days they still used standard power supplies so they were still pretty heavy.

 

[restorer-john]

It is but also has a switching PS.

The L07ms are not a switching amp, they were never 'considered' a switching amp they do not use a switching power supply.

Go download the schematic and have a look.

You may be thinking of a Sony TAN88B from the same era. It used a SMPS and was one of the very first PWM amps.

 

[KingBubba]

I have 4 chip amps now. They are kind of fun to collect and at the low prices they are definitely throwaways if they kick the bucket. I first bought a Lvpin (Lepai) L2020 for $9.98. I was surprised how well it performed. I then bought a Bluetooth 3116 that was super small with one huge volume knob on the top. It outdid the Lvpin substantially, with a clarity and intensity that seemed almost impossible. I next bought a Breeze 3116 which I had not tried until last night after trying out my Nobsound double 3116 amp. The Nobsound seemed week and I suspect that it needs a PS that is more than the 22 volt 3.3 amp PS I am using to compare all of these last night. The overall winner was the little $20 Breeze, followed in a close second with the tiny $21 Bluetooth 3116.

I now have 4 great little amps that I can use anywhere for about $100. You can't beat that with a stick.

 

[audiosignal]

The whole concept of "repair" may be entering a paradigm shift. Heck, I replaced the spark plugs on my car at 138k miles and it turns out it didn't need it. I'm starting to see the new spark plugs in cars as virtually (if not literally) permanent.

And the same with these amps. They don't cost nearly as much to produce, should not cost nearly as much, and in the EXTREMELY unlikely event the fail, you simply replace them, like I did with my 4 year old Westinghouse flat screen TV when it failed. Oddly, I'm glad I did because I got a SIGNIFICANTLY better flatscreen for the same price I paid for it originally.

“...EXTREMELY unlikely to fail...”.

he he, not in my experience. More parts count generally means more things that can go wrong, and they do fail, sometimes brand new out of the box.

Troubleshooting and repairing a high-end class D, due to their complexity, is much more time consuming, difficult, and risky, assuming you can even do it at all. Tiny surface mounted components, including proprietary chips and no service manual available. Good luck with all of that.

Yeah, I can throw out a $2K - $10K high end class D amp when it breaks, treating it like a disposable BPC and buy me a new amp to replace, but I don’t want to do that.

 

[Pio1980]

Otoh, TI and other standard chips of high reliability, cranked out like pennies, will revolutionize a broad sector of mid-fi without compromising SQ or bank accounts. The rest depends on implementation.

 

[DaveVoorhis]

More parts count generally means more things that can go wrong

Do you consider a single integrated circuit to be many parts, or one?

Some integrated circuit manufacturing processes now specify an estimated mean time to failure of 5700 years.

 

[RobRoy]

“...EXTREMELY unlikely to fail...”.

he he, not in my experience. More parts count generally means more things that can go wrong, and they do fail, sometimes brand new out of the box.

I actually almost brought that part up. In fact, when I sold in the 70's I told customers that if it didn't fail within a very short time, say an hour or week, it probably would not fail at all.

 

[RobRoy]

Troubleshooting and repairing a high-end class D, due to their complexity, is much more time consuming, difficult, and risky, assuming you can even do it at all. Tiny surface mounted components, including proprietary chips and no service manual available. Good luck with all of that.

I agree. If a thing can't really be repaired at reasonable cost, I would not purchase it unless it carried a nice long term warranty.

This is why I would never buy an Audi, BMW or Mercedes out of warranty.

But for me one of the advantages of class D is that it is cheap. I paid 300 for a Crown unit that puts out around 400 WPC and has built in crossover and bridging functions at the push of a button.

If it breaks, meh.

 

[Rex81]

The nice thing about the Crowns is that they're engineered and built to withstand their intended use: Professional DJ and sound reinforcement. Have you seen how this stuff gets treated? Left on for days on end, cranked to the max, sits outside in a freezing car night after night, dropped, tossed, beer spilled on, and everything else you can think of.

That 8 lb amp will put up with a lot more abuse and last a lot longer than most 50lb monsters, I'm sure.

 

[Archguy]

I agree. If a thing can't really be repaired at reasonable cost, I would not purchase it unless it carried a nice long term warranty.

This is why I would never buy an Audi, BMW or Mercedes out of warranty.

Funny you should mention--I just wrote about that very experience. I bought mine two years old with a four-year factory warranty, and extended warranty after that. Car was fine, only 20K miles, figured I'd keep it! WRONG.

 

[RobRoy]

Funny you should mention--I just wrote about that very experience. I bought mine two years old with a four-year factory warranty, and extended warranty after that. Car was fine, only 20K miles, figured I'd keep it! WRONG.

Ha! I had a friend (he passed away a couple of years ago) that had an "exotic car repair" company. He covered mostly upper end European cars. He told me an interesting story about Mercedes. This is second hand and I may not get it right:

He said that auto manufacturers are required by law to make available to the public any auto repair manuals so that repair shops and back yard mechanics can repair their vehicles. If they don't they have to pay something like a $10 million a year fine.

My friend said that Mercedes was happy to pay that fine every year. He then got into the work arounds and hoops he had to jump through to repair Mercedes.

On youtube there are a lot of videos on why not to buy a mercedes or how to do cheap repairs yourself. The latter almost makes them worth it. I found very interesting the one on how to change the oil in a particular model that was rather exotic. An oil change cost hundreds at the dealership, but the guy showed you how to do it and it was actually pretty simple except it has two drain plugs and the old fashioned "internal" oil filter rather than a spin on. Interestingly, the oil filter was quite similar to the one on my 1960 john deere 1010 tractor that I just changed the oil in last week. So much for "german engineering".