ive read on other big name forums the “commutating rail amplifiers of the 80’s are all in the landfills now”.
is there something inherently wrong with them? i have a 1984 vintage class G integrated that has been running every day for a few years now with zero issues and it plays metal through cheaper speakers unlike some of the most high end amps and speakers ive listened to
a friend of mine has a 1988 vintage class G integrated from another manufacturer that sounds quite great as well and having put in a lot of hard time hooked up to 4 speakers and playing drunk loud often
the luxman r-117, proton 1200 amplifier, and NAD power envelope amps are among a few class g examples people have enjoyed. i had a r-117, i really enjoyed its sound; and people who own the protons say they sound phenomenal
so why does class G seem like it has a bad reputation?
ill admit on some more demanding but far more revealing speakers my ‘84 vintage integrated doesnt sound anything special. its lack of high/low end extension is really noticeable but on some kenwood kl-a900’s its not noticeable at all and they sound almost unreal with metal and rock. even with mcs 683-8295 speakers it sounds super special compared to other equally big name top tier conventional AB amps
i think the word im looking for is musicality and oddly in my experience so far their magic is reserved to seemingly cheaper speakers.
is there something inherently wrong with them? i have a 1984 vintage class G integrated that has been running every day for a few years now with zero issues and it plays metal through cheaper speakers unlike some of the most high end amps and speakers ive listened to
a friend of mine has a 1988 vintage class G integrated from another manufacturer that sounds quite great as well and having put in a lot of hard time hooked up to 4 speakers and playing drunk loud often
the luxman r-117, proton 1200 amplifier, and NAD power envelope amps are among a few class g examples people have enjoyed. i had a r-117, i really enjoyed its sound; and people who own the protons say they sound phenomenal
so why does class G seem like it has a bad reputation?
ill admit on some more demanding but far more revealing speakers my ‘84 vintage integrated doesnt sound anything special. its lack of high/low end extension is really noticeable but on some kenwood kl-a900’s its not noticeable at all and they sound almost unreal with metal and rock. even with mcs 683-8295 speakers it sounds super special compared to other equally big name top tier conventional AB amps
i think the word im looking for is musicality and oddly in my experience so far their magic is reserved to seemingly cheaper speakers.
They are actually Class A/B switched rail amplifiers. Classes of amplifier describe the bias and systems in use.
The normal recognised types are Class A, A/B, B and D. Other letters are an attempt to describe different designs but are in fact a variation of either A or B with switching rails for slightly more efficiency.
This type of amplifier was widely used in the high powered PA amplifiers back in the 80s and 90s but in reality are no more efficient than Class B but expensive to produce. Some Class G or H amplifiers were only 50% efficient.
Now it is more common to use the far more efficient Class D switching amplifier.
Here is a chart of expected results;
The normal recognised types are Class A, A/B, B and D. Other letters are an attempt to describe different designs but are in fact a variation of either A or B with switching rails for slightly more efficiency.
This type of amplifier was widely used in the high powered PA amplifiers back in the 80s and 90s but in reality are no more efficient than Class B but expensive to produce. Some Class G or H amplifiers were only 50% efficient.
Now it is more common to use the far more efficient Class D switching amplifier.
Here is a chart of expected results;
Attachments
Not true. They are manufacturing even now, although Class D amplifiers are taking the primacy.
No. In a case when class G (H) and class B amplifiers have the same maximum output power, class G (H) amplifier is more efficient than class B at low and medium power outputs. Efficiency is the same at their maximum output wattage.
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Don't know if I agree they have a bad reputation, but it's more complicated (and expensive) than a straightforward AB amplifier without rail switching and it's less efficient than class D. 40 years ago there were not many options if you wanted higher efficiency for high power, but today most designers probably see class G as a bit of a "neither here nor there"-solution.
im not sure this is accurate. the amp in question was built for only a few years before the company reverted back to a dual mono transformer traditional AB design where the power consumption goes from 270 watts to 670 watts much like a dual mono amplifier i have from 1979. the class G integrated my buddy has also has power consumption of 270 watts while being rated for the same rms power and dynamic power as the dual mono transformer designs that seemed to precede as well as succeed the class G dual rail designs.
i think everyone is aware class G and class H are a spinoff of class AB but they are not considered dual rail AB amps. hence class G and class H
thats what i hear but i also notice all these hypex and ICE amps all have 4/5 star reviews saying they lack in basic areas of frequency response and are still not yet viable replacements to AB spinoff designs for many people. i dont trust class D yet.
the class G amps are always rated for like 270 watts power consumption for the same rms and dynamic output as dual mono AB designs with power consumption ratings of 670 watts and my electric bill definitely shows far less money spent than my optoma nu-force sta-200 running the same system at the same volume levels
many people say they had issues with 2 ohm loads and blowing up among other things. even pioneer spent what i can only imagine was a lot of money on their iteration of class G with their A series of integrated only to immediately revert back to the “tried and true” dual mono design with a 670 watt power consumption rating. the a88x looks so cheap and simple compared to the a80. its obvious they gave up on it after a very short amount of time.
who still makes class G gear other than Arcam?
ive heard emotivas gear is class G but ive also heard its pretty mid tier lukewarm performance like adcom.
Arcam though intrigues me
Indeed. Poor SOA of power transistors in the day were a good reason for class G. Not so much now with better devices, and the extra complexity made them more expensive. And almost always the commutation transients showed up on the output, but they were short so didn't increase THD too much, but could be audible.
Jan
Modern class G or H can get the commutation noise down to you can’t hear it but you can find it with instrumentation levels. Early models actually produced spikes - now you can get it down to a bit of wobble in the transfer curves. Faster transistors made that possible. Since the wobble does not occur at zero crossing at low output but instead only occurs when the music is loud, it ends up being completely masked.
It is of limited benefit for low volume hi-if use, where you could run a Phase Linear without a fan and not burn your hand on it. It’s a big deal for power consumption and heat when putting out hundreds, thousands, or tens of thousands of watts of average power. Things are moving toward class D in that space, but the real reason for that is weight reduction. Those amps are NOT as durable, even in the upper professional brackets, but those guys have ALWAYS replaced amps every two years. For the same reason people trade cars every two years - so it’s only in the shop for oil changes. In the case of amplifiers, blowing the dust out of the fans.
It is of limited benefit for low volume hi-if use, where you could run a Phase Linear without a fan and not burn your hand on it. It’s a big deal for power consumption and heat when putting out hundreds, thousands, or tens of thousands of watts of average power. Things are moving toward class D in that space, but the real reason for that is weight reduction. Those amps are NOT as durable, even in the upper professional brackets, but those guys have ALWAYS replaced amps every two years. For the same reason people trade cars every two years - so it’s only in the shop for oil changes. In the case of amplifiers, blowing the dust out of the fans.
I really enjoy the way of operation of class G, I develop audio amplifiers/electronics and I have in mind to develop two class G amp modules for Diy but still thinking haven't decide yet, for who want to check what I develop can check it here or reach me.
They are wrong.
You should trust class D amp - listen to one, read reviews (with measurements!).
Problems with 2 ohm loads doesn't depend on the class of operation.
One can avoid 99.999% of the “problems” associated with class D by running the damn thing off a regular transformer. Assuming it’s running off +/-80V or less.
What kind of "problems" would be caused by a switching supply for class D amplifiers? Not doubting, just curious.
They are always undersized and can’t deal with Vcc/RL, just the “average current draw”. And usually that’s a “typical operation average with music”, which is even lower. And when they do misbehave, it’s not pretty.
ICEpower is not cheap either. Not ridiculously expensive, but not Aliexpress cheap — which is what everybody seems to want.
A properly developed SMPS for audio (such as the ones by Hypex and ICEpower) will always have the current limit set for the peak loads of the amplifier. It's just not thermally able to deliver continuous power into the load (which you don't really need anyway for music).
If you see cheaper amps coupled to off-shelf industrial grade SMPS modules then it's a different scenario because those typically have current limits quite close to their rated power output. However, for most home-uses you will never draw peak current from the amplifier and so a slightly undersized PSU in this respect can be a perfectly valid engineering trade-off.
I think the “landfill” claim is more internet myth than reality. Well-designed Class G amps like the Luxman R-117 and Proton 1200 prove they can sound great and be more efficient than AB in real-world use. They’re more complex and less common now due to Class D, but not inherently flawed. I’ve also found Class D still doesn’t match the musicality of some of these older designs.
Oh, okay, just lousy engineering. I was concerned something more fundamental might have flown under my radar. The heavy metal can go back on the drawing board...
