25A is weak...you're a funny guy. If you sent 25A through your speakers it would fuse the voice coil into a solid mass! It would throw your woofer into your lap...
Another takeaway from this graph is the close spacing of the traces -- all within about 0.1dB of each other. This indicates the amplifier's very low output impedance across its operating range, and its commensurately high damping factor. Although it's not shown here, when we measured the output impedance and calculated the damping factor with a 4-ohm load, we got a very high 1600 from 20Hz to 4kHz -- and from 4 to 20kHz the damping factor rose even higher, to almost 2000. .
1st gen Purify amp are stunningly close to perfection in terms of distortion. How perfect does perfect have to be? Anyway, I'm sure imperceptible improvements are possible, not to mention superior implementations hopefully at lower cost of manufacture.
VTV Amplifiers, ( e.g. ), is now selling only implementations of the 1ET6522SA, no more 1ET400A. But I'm very satisfied with their 1ET-400A I bought several years ago and have no plans to "upgrade".
I'm waiting for more amp makers to use GaN FETs. Do they sound better or is it just another technology? None of the mainstream (Hypex, ICE, Purifi, etc.) are using them, yet.... that I know of. I see a number of eval boards from different suppliers (who sell GaN FETS) but only a few small audiophile companies that are actually using them in their Class D designs.
According to Bruno Putzeys, Gan FETs can improve performance a bit but not fundamentally. In the linked article is a link to a piece by ICEPower who have studied the difference and don't think it worth making the switch. In a pocast, Michal Jurewicz of Mytek, claimed that Gan FETs cost 10x the MOSFETs they replace. My take is that companies promoting gan FET class-D amps to audiophiles are using it as a marketing hook or they don't really understand the cost-benefit trade off in using them.
In YT video Putzeys was asked what has been the biggest step forward in class-D design and he replied 'math' i.e. how to apply more feedback and include the output inductor inside the loop.
At the end of the day, I'd rather take a super-simple single-ended tube OR TI Equibit PCM-to-PWM conversion. That is unless one requires a TON of wattage..
I don't require a 'ton of wattage' but about 100-wpc is a good place to start for my Tannoys even though the manufacturer recommended starts at 30-wpc. Sure they make sound but they come alive dynamically with more power.
I have Atma-Sphere's Class D monos that use GaNFETs. 100 watts and sounding very nice.
They have "proper" transformers in their power supply that account for about 50% of their weight. Sadly no 12V trigger, but they consume only 7 watts each when on but idle.
I'm looking for an alternative to a 12V trigger that will do the same job. I bought a device recently but it requires a "master" device (preamp) that needs less than 1 watt in Standby to trigger the "slaves" to go off. Sadly, my NAD M33 uses about 12 watts in standby despite the Spec saying <0.5W. Clever but out-witted by NAD!
At only 7 watts each at idle you can leave the Atma-sphere monos ON 24/7. If you need a way to power them ON/OFF remotely you can use a remote controlled ac outlet. Not an elegant solution but it works. This one has dual outlets and there are several similar devices on Amazon.
I wish more audiophile brands would include 12v triggers as standard on all of their gear. This isn't the 1960's! Some brands actually have the nerve to charge you extra for a fricken 12v trigger. This is my current pet peave. It used to be preamp makers who refused to incorporate remote control. Their cop-out response was a bogus claim that it adversely affects audio quality when in fact they were just too cheap or lazy (probably both). How many preamp makers today do not offer remote control? None?
Oops! I just checked your Profile and it says you're in the UK. I'm sure there are similar devices with UK style AC Plug/Outlets.
Yes Abe, lots of remote controlled blocks in the UK market, for example this Energenie 4-way block. Some can be shouted at if you use Alexa!
I could use these, but it's not as convenient as a trigger (and the remote is likely out of signed between the sofa cushions), so I have suggested to the Energenie people that they consider building a trigger-operated block that would allow a single trigger cable from the preamp to power up or down 4 other amps, subs, DACs, etc. That would be a great solution!
Intended for Internet-of-Things (IOT) hobbyists this "IOT Relay" has a control input (3.3-48VDC) that powers ON/OFF a couple AC outlets.... but it has US style outlets.
I saw a 12v triggered outlet made by Niles many years ago but it might be out of production. I'm not sure.
I suspect improvements will be very small and no reason to change from a 1st to a 2nd generation Purifi amp, but if moving from another Class D (or any other technology), it is probably best to look for a Purifi amp with a 2nd generation board.
Much bigger differences are likely according to the implementation of Purifi. There are lots of "garage-built" Purifi amps that use the cheap Eval(uation) board, whereas others such as NAD and T+A build under license after authorised tweaks to maximise performance and the use of superior additional components such as power supply. Just look inside these amps to see the difference in power supply, RFI-protection measures, etc. Not all Purifi amps sound the same!
I see that the Benchmark AHB2 is top of your graph. This is just about the dullest (though probably most accurate) amp that I've ever owned. Choosing an amp based on SINAD is frankly daft if you want one that provides a degree of excitement approaching a live performance.
Looks like he's saying the Benchmark sounds fantastic on good material but he doesn't like it for bad program material. All I can say is that I've had euphonically-colored tube amps in the past, and I always ended up replacing them because they were getting between me and the music. I like revealing and neutral.
Anyway, I've AB'd the Benchmark with e.g. my A-21. The Benchmark was a bit more neutral -- better in the highs and neutral in the midbass, while the A-21 seems a bit warm there -- but it wasn't as good on piano (go figure). But the differences were subtle.
> I was proving that the same amp board (apples-2-apples comparison) can be worsened by expensive inhouse subjective "improvements"
If you think a Purifi amp based on the cheap Eval board will reproduce music better than a Purifi NAD M Series or T+A, I guess you have never compared them.
