Switching/D-class amps and their supposed improvements over the years;

[Joe Smith]

I do own an Aiyima A04, the original one, and it is a fine amp - definitely can't play as loud as the A07, though. I use that one in my bedroom system with a 32v supply, and it's perfect for the low volume levels I would want there. I don't perceive any different or better sound from the 3251 chip versus the 3255. That one has Burson Audio V5 op-amps that they sent me for free to test - they sound fine - I didn't perceive a huge difference from the Aiyima stock op-amps.

If you can find one of the original A04s, I would say they are best used for low volume listening.

 

[elshaddai]

I think the RSL iA255.1 probably offers desktop users the biggest value with Bluetooth, RCA and USB input, pre out for subs, bass/treble adjustments and an optional 90Hz HPF switch on the mains. All for $110.

 

[Joe Smith]

I think the RSL iA255.1 probably offers desktop users the biggest value with Bluetooth, RCA and USB input, pre out for subs, bass/treble adjustments and an optional 90Hz HPF switch on the mains. All for $110.

Yeah, I keep forgetting about that one. It does have a lot of features for the money and looks to have pretty good components too.

 

[Mark S.]

Noticed that there seemed to be a problem with the supply of TPA3250/3251 chips starting a few years back (but not for the 3255), I guess that might be the reason for the discontinuation of models using them and the 'pending' status of E3 Audio's. ETA >> the FX-Audio FX502SPRO (of some infamy here at ASR) is also awaiting stock.

 

[Mark S.]

Yeah, I keep forgetting about that one. It does have a lot of features for the money and looks to have pretty good components too.

Ah, but for me (and I daresay many others) that's not actually a plus - I prefer minimalism, fewer points-of-failure and notionally more attention (and budget) dedicated to the essentials.

 

[Mark S.]

I do own an Aiyima A04, the original one, and it is a fine amp - definitely can't play as loud as the A07, though. I use that one in my bedroom system with a 32v supply, and it's perfect for the low volume levels I would want there. I don't perceive any different or better sound from the 3251 chip versus the 3255. That one has Burson Audio V5 op-amps that they sent me for free to test - they sound fine - I didn't perceive a huge difference from the Aiyima stock op-amps.

If you can find one of the original A04s, I would say they are best used for low volume listening.

As a matter of fact I'm keeping an eye out (got an eBay search notification running). Wanna sell yours?

 

[Gregss]

Hello All,
While not putting down lower cost class D amps, you can get an amp that blows away most older amps in pretty much all ratings and prices - for around $1200.
To me that is a steal. IMHO FWIW

IE: Buckeye and others.

Greg

 

[Ropeburn]

The real improvement over the years hasn't been in class D amplifier chips, but discrete, proprietary designs with meticulously fine tuned feedback paths: ICEpower, Hypex, Purifi.

The latest iterations are so ludicrously good in all aspects that matter (frequency response and load independency, distortion, noise, damping factor and last but not least power) for still very affordable prices, amplification can be seen as a solved problem now.

 

[Beershaun]

In the price range you mentioned I'd look at the AMPs Amir has reviewed and recommended. Like others have said the Amiya A07 and Topping has recently produced an Amp as well.

Another way to approach what you want for low level music is adding a powered subwoofer if you don't already have one. It really helps give you audible low frequency response at low SPL. That's been my experience anyway.

 

[mhardy6647]

Ah, but for me (and I daresay many others) that's not actually a plus - I prefer minimalism, fewer points-of-failure and notionally more attention (and budget) dedicated to the essentials.

You might like single-ended triode amplification! It really doesn't get much simpler.
High output power can get a little cumbersome, though.

 

[Mark S.]

You might like single-ended triode amplification! It really doesn't get much simpler.
High output power can get a little cumbersome, though.

I prefer low idle-current / high-efficiency devices that I can leave powered on 24/7. I rarely shut down my PC (a steady waste of 35w when I'm not using it - gasp! Greta would be appalled) and leave both DACs and both amps powered on, been my habit for maybe 20 years, never had a hardware failure (even of an HDD) that I can remember. Degradation from power/thermal cycling is more likely to cause failures than days, weeks and years idling for most electronics that pull fractions of amps idling.

 

[Mark S.]

In the price range you mentioned I'd look at the AMPs Amir has reviewed and recommended. Like others have said the Amiya A07 and Topping has recently produced an Amp as well.

Another way to approach what you want for low level music is adding a powered subwoofer if you don't already have one. It really helps give you audible low frequency response at low SPL. That's been my experience anyway.

I used to use a sub, but room reinforcement and EqAPO has given me surprisingly good bass even from small (decent) bookshelf speakers.

 

[Mark S.]

You might like single-ended triode amplification! It really doesn't get much simpler.
High output power can get a little cumbersome, though.

....

Notwithstanding it's undoubtedly poor measurements I have no problem believing that, (ahem) subjectively, that amp sounds better than almost any SS, but it's pretty onerous having main components that are service replacement items and are in danger of expiring prematurely if ambient temperatures go over 30°C!

 

[mhardy6647]

Notwithstanding it's undoubtedly poor measurements I have no problem believing that, (ahem) subjectively, that amp sounds better than almost any SS, but it's pretty onerous having main components that are service replacement items and are in danger of expiring prematurely if ambient temperatures go over 30°C!

That one's been trouble-free for 20 years with the exception of one 6SN7 (a used plinker of unknown provenance that I was using in it at the time) driver tube that self-immolated and one of the output tubes' bypass capacitors, which failed due to prolonged exposure to too much heat from being placed too close to the resistor. Those monster brown caps (in the photo above) solved that problem.

Actually vacuum tube hardware is far more robust, albeit at the cost of electrical efficiency (which can be mitigated in a push-pull output design, of course).
Best of all, all of the components in that amp are readily available and have been for decades. Actually the James OPTs in it are no longer made, but there are plenty of other options for replacement OPTs if ever needed. The power output triode (2A3, in this case) was introduced by RCA in 1933 and has, as far as I can tell, been in continuous production somewhere in the world ever since.


EDIT: Yes it sounds great -- and it measures OK, all things considered. It is a 3 watt per channel amplifier, after all.
But it will put out its full three watts (at about1% THD) across its bandwidth all day and all night without any fuss -- which is apparently something the Class D modules cannot and apparently weren't designed to do. So there is that.

 

[Ropeburn]

Vacuum tube technology is indeed far more robust than you may think at first, and scalable too - if money and size isn't a factor.

The MiG-25 fighter jet's electronics for example were mostly tube-based, including the Smerch-A radar system with a power output of 600kW (!). That's comparable to the original Bugatti Veyron's nominal power output. The plane's electronics were so durable, it was said the electromagnetic shockwave of a nuclear blast would make contemporary (solid state based) NATO planes fall out of the sky due to severe electronic systems failure, while the oldschool MiG tube systems would've kept working. Not even talking about the immense mechanical stress when being thrown around the sky in a powerful jet fighter.

 

[Mark S.]

Vacuum tube technology is indeed far more robust than you may think at first, and scalable too - if money and size isn't a factor.

The MiG-25 fighter jet's electronics for example were mostly tube-based, including the Smerch-A radar system with a power output of 600kW (!). That's comparable to the original Bugatti Veyron's nominal power output. The plane's electronics were so durable, it was said the electromagnetic shockwave of a nuclear blast would make contemporary (solid state based) NATO planes fall out of the sky due to severe electronic systems failure, while the oldschool MiG tube systems would've kept working. Not even talking about the immense mechanical stress when being thrown around the sky in a powerful jet fighter.

I remember hearing about that back in the day. There was also the $millions NASA spent developing zero-G pens, the Russians used pencils.

 

[JW001]

Vacuum tube technology is indeed far more robust than you may think at first, and scalable too - if money and size isn't a factor.

The MiG-25 fighter jet's electronics for example were mostly tube-based, including the Smerch-A radar system with a power output of 600kW (!). That's comparable to the original Bugatti Veyron's nominal power output. The plane's electronics were so durable, it was said the electromagnetic shockwave of a nuclear blast would make contemporary (solid state based) NATO planes fall out of the sky due to severe electronic systems failure, while the oldschool MiG tube systems would've kept working. Not even talking about the immense mechanical stress when being thrown around the sky in a powerful jet fighter.

Yes! Soviet technology was the best!

 

[GXAlan]

I remember hearing about that back in the day. There was also the $millions NASA spent developing zero-G pens, the Russians used pencils.

Just because this is audio science review

FACT CHECK: NASA's 'Astronaut Pen'

Space race legend claims NASA spent millions of dollars developing an 'astronaut pen' that would work in outer space, while the Soviets solved the same problem by simply using pencils.

www.snopes.com

 

[Ropeburn]

Yes! Soviet technology was the best!

It really wasn't. They were so far behind in development, the technology they used only coincidentally proved advantageous for specific scenarios. Here: wild nuke bombs being set off, with planes in the sky nearby. The cold war certainly was a wild time.

 

[JW001]

It really wasn't. They were so far behind in development, the technology they used only coincidentally proved advantageous for specific scenarios. Here: wild nuke bombs being set off, with planes in the sky nearby. The cold war certainly was a wild time.