new GAN amplifier

Not sure what all this has to do with a new GAN amplifier, but the Wilson Alexia

BJT's and their ability to drive into these kinds of loads, and the BS statement that OTL can do it too🤣

Absolute Sounds test report Quote:
With the combined EPDR of impedance and - phase angle the Wilson Alexia presents a scary 0.9ohm load to the amp 

https://www.absolutesounds.com/pdf/main/press/WA%20Alexia%20HFN%200313-4web.pdf

georghifi,

You appear to be misinterpreting what EPDR means. An EPDR of 0.9 ohms does not mean the amplifier sees an 0.9ohm load, it means that the power dissipation in the amplifier is equivalent to what it would see with a 0.9 ohm load. It sounds the same, but it is much different. When the load and current are in phase, the output transistor has the lowest drop across it (rail to load) when the current it at a maximum, hence power in the device at this voltage is not high. When the current is out of sync, you can have a maximum current when the voltage drop across the transistor is higher, hence the peak power across the transistor is much worse. Again, this is not "load" impedance, this is a mathematical formula to generate a convenient number to represent dissipation in a linear amplifier.


Here is the kicker. This problem is much worse for BJT transistors because BJT transistors experience secondary breakdown at high voltage and current, especially at high temperature. So in addition to taking into account the additional heat dissipation, you need to take into account secondary breakdown mechanism, which may mean doubling up devices, where one would normally be okay. MOSFETs don't experience secondary breakdown and don't mind that peak power, as long as average power is taken into account.

Here is the 2nd kicker, this problem does not exist at all for Class-D amplifiers.

Post removed Nov 20, 2019

I agree, not worth the effort, what a Class-D w****r.

Cheers George

The only thing you two are succeeding in doing, is keeping this post recent until someone adds something useful.

@georgehifi 

Loudspeaker efficiency 101:

Less efficient loudspeakers tend to have more voice coil heating and so are more compressed than loudspeakers of higher efficiency:

http://www.aes.org/e-lib/browse.cfm?elib=5251

https://www.stereophile.com/reference/1106hot/index.html
https://www.researchgate.net/publication/323935533_Voice_coil_temperature_in_loudspeaker_performance...
https://www.tonmeister.ca/wordpress/2014/01/16/bo-tech-thermal-compression-compensation/
http://www.cieri.net/Documenti/JBL/Documenti%20tecnici/JBL%20-%20Dynamic%20Linearity%20and%20Power%2...
https://www.linkedin.com/pulse/power-compression-vs-thermal-distortion-loudspeaker-alexander-wilson
-and on and on. This is simply not a matter of debate. As you can see from these and similar related documents, all loudspeakers have voice coil heating as their actual efficiency is rather low. You get less voice coil heating if the driver is more efficient. This results in less compression. Now you might think that you can just throw more power at a lower efficiency speaker to deal with this, but this results in more heating- exacerbating the compression effect.

The only thing you two are succeeding in doing, is keeping this post recent until someone adds something useful.

Totally agree.

This is simply not a matter of debate.

Keep believing this in the "wrong context you are saying it in" and your cred will suffer for hiend audio, just like your statement.

    atmasphere   Our OTLs do a nice job on the Alexia

Given that you have been and are repeatedly misusing the term EPDR, I am not sure how you can make a definitive statement about the OTLs.

Given that you have been and are repeatedly misusing the term EPDR

So you believe the atmasphere statement, that his OTL’s can do a nice job of driving the Wilson Alexia’s as well?? also delusional🤦‍♂️
Give it up you two, looks like your colluding, maybe your his new Class-D partner? Like tweak is with ricevs.

Gfi,

I know I am not, and never have been, anything more than a customer to Ricevs.

Aside from his correcting my error in saying the EVS has no fuses, the only times I have heard from him were to ask about when I will receive the GaN, and to prep me for his newest ’upgrade’. the PPT cards, which he says blows away the cubes that I was forced to buy or I would not get the amp

That you would continue to make that accusation, for me at least, calls anything you say into question

Reader beware of Gfi, the thread destroyer

So you believe the atmasphere statement, that his OTL’s can do a nice job of driving the Wilson Alexia’s as well?? also delusional🤦‍♂️

:)  He had the amps built to match the finish of the speakers- here's what they looked like:http://www.theaudiobeat.com/equipment/atma_sphere_ma2_mk31.htm

There’s a Supertramp track, that fit’s this claim of "doing a nice job" of that amp driving the Wilson Alexia’s, it’s called "DREAMER"

With serious lack of damping factor, and far less current than an 80’s NAD 3020 integrated can give.
This thing on the Wilson Alexia’s would become the worlds most expensive monoblock tone control, in the worst possible way.
Might work if it just drove the mids and highs.
https://www.stereophile.com/images/1213Walexfig01.jpg

Hypex ncore nc1200 doubles the output at 2 ohm. Georgehifi builds the Lightspeed Attenuator that measures poorly but sounds decent. He has this obsession of GANs that have one metric pumped up, cost more, but do not perform better than ncores or Purifi. Getting into technicals with him is a waste of time, because he then inundates with irrelevant links and/or retreats to subjectivist positions. " Many, me included, prefer scotch to bourbon".

GaN are faster and present lower drive capacitance which theoretically allows for a higher switching frequency - which has encouraged many people including George. However, regardless of power device used efficiency is always inversely proportional to switching frequency.  Class D will get a bit better but will never quite be able to outperform the best traditional linear class A / AB designs above about 5kHz. However, in terms of bang-for-buck they are increasingly hard to beat as full range amplifiers and the best on offer are close to absolute best below about 500Hz. As was pointed out they don't have problems driving highly reactive loads - apart from treble range and up due to output filter interactions. 

In my current setup I'm using hypex NC500 amplifiers to power my woofers and an ultra LD class AB amplifier for mids / tweeters. A best of both worlds implementation.


 

georgehifi,

Considering most tube amplifiers with transformers, which many audiophiles love, and use regularly even with hard to drive speakers, have a damping factor <=20, your overall argument at least w.r.t. listening enjoyment is questionable.

If you look at the amplitude response curve and impedance curve, you will notice throughout the base, they are somewhat inverted. So the amplifier will not act as a "tone control", it will act as an equalizer to smooth out the response. That may not be a bad thing euphonically.  Are you 100% certain that low damping factor is always best?

arty_vandelay,

Please compare data for your favorite top A/B amp U-LD Mk4, given by the creators at www.siliconchip.com.au (August 2015) and the newest D-class from Bruno Putzeys - Purifi 1ET400A (www.purifi-audio.com). The D-class beats the A/B in all major categories. THD+N 20-20kHz is better with Purifi at 10W (ten) than with U-LD at 100W. From your coveted 5kHz, Purifi stays at 0.00029% (up to 20kHz) at 10 (ten) WATT and U-LD reaches 0.0008-0.001% at 100 WATT! The tough 18kHz+19 kHz intermodulation figures are given only by Purifi, AFAIK. But this is all academic. Both amps are an overachievement for the human listener, appreciated mostly by AudioPrecision analyzers which are not precise enough for some of their metrics.
PS. The U-LD amps are not on offer any more, are they discontinued?

The LKV Veros PWR using the Purifi 400A modules with a Class A front end sounded wonderful at the Capital AudioFest driving Sonner monitors, great first exposure to Bruno's latest module!

Are you 100% certain that low damping factor is always best?

Yes of course it is, unless I can think back to the 80’s when there was a speaker with purposely an over damped design, as Linn/Naim (Ivor Tifenbrun & Julian Veriker) in cahoots back then tried to do with the dual B139 Isobaric speaker which had no bass!! when driven by a Krell!! of of all amps.
That speaker to have bass needed an amp that was designed to have poor damping factor, hence Linn/Naim cornered the market with that little marketing duo, as anything else driving the Isobaric sounded wrong.

So the amplifier will not act as a "tone control"

Wrong, on the Alexia that OTL amp will have anything but a flat frequency response driving those speakers, to think otherwise remember Supertramp "Dreamer"

If you look at the amplitude response curve and impedance curve, you will notice throughout the base, they are somewhat inverted.

Now in effect your saying that, the OTL’s lack of bass drive current, and poor damping factor, will be a perfect match for the Alexia, and an amp like the Gryphon Antillion is not!!!!
I’ve never heard such a crock of **** I’m sure now you two are ******* in each others pockets.

Wrong on both counts.

A lower damping factor will, and especially in the case of the Alexia where one just has to look at the frequency response/impedance curve to see it, often correct peaks (valleys) in the frequency response. It is like a built in equalizer :-)

And .... most people don't know this, so I will not fault you, but high damping factor often results in more distortion in dynamic drivers. So no, high damping factor is not always better. Different yes, but better ... not necessarily so.

I will ask you this once. Stop insinuating I have any sort of business relationship with atmasphere. It is inflamatory and wrong. Stick to the facts, period.

in the case of the Alexia where one just has to look at the frequency response/impedance curve to see it, often correct peaks (valleys) in the frequency response. It is like a built in equalizer :-)

You are **** ** *t , the OTL’s are fixing nothing, they just can’t drive those Alexia loads, (and are a tone control because of it), read carefully, they say it twice.:
Stereophile on Alexia
" The peak in the midbass is entirely due to the nearfield measurement technique."
" The broad peak in the midbass will be mostly due to the nearfield measurement technique"

More more you two try to gig your way out of this BS, the more ridiculous you look, with your comments made about OTL’s trying to drive speakers with horror loads like the Wilson Alexia’s ect ect.
Next I’ll put money on is you’ll drag out the (autoformer band-aid fix) solution.

in the case of the Alexia where one just has to look at the frequency response/impedance curve to see it, often correct peaks (valleys) in the frequency response. It is like a built in equalizer :-)

You are both "Dreamer’s", the OTL’s are NOT fixing/correcting anything, as there’s nothing to fix on the Alexia’s.
They can’t drive those Alexia loads, because of "lousy damping factor" and "minuscule current delivery" (and are a tone control because of it) not "equalizing" as you say, read carefully, Stereophile say it twice.
Stereophile on Alexia:
" The peak in the midbass is entirely due to the nearfield measurement technique."
" The broad peak in the midbass will be mostly due to the nearfield measurement technique"

The more you both try to dig your way out of this nonsense, the more ridiculous you look. With your comments made about OTL’s and them trying to drive speakers like these Wilson Alexia’s ect ect that have horror loads.

Next I’ll put money on is you’ll drag out the (autoformer band-aid fix) solution.

Please compare data for your favorite top A/B amp U-LD Mk4, given by the creators at www.siliconchip.com.au (August 2015) and the newest D-class from Bruno Putzeys - Purifi 1ET400A (www.purifi-audio.com).

Best to use third party measurements such as these... https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-purifi-1et400a-amplifier.7984/page-1

Distortion (IMD) is still higher than a decent classic blameless AB design above 10kHz.

The Hypex modules I'm using sound pretty good as full range amplifiers, but with the AB driving mids / tweeters the fidelity goes to another level.  

As Putzeys himself has stated, Class D amplifiers sound good in spite of being class D, not because of it. 

A lower damping factor will, and especially in the case of the Alexia where one just has to look at the frequency response/impedance curve to see it, often correct peaks (valleys) in the frequency response. It is like a built in equalizer :-)

And .... most people don't know this, so I will not fault you, but high damping factor often results in more distortion in dynamic drivers. So no, high damping factor is not always better. Different yes, but better ... not necessarily so.

 A poor damping factor will raise the designed loudspeaker system Q to beyond the point of optimum damping, and because low frequency impedance is typically modulated by the signal itself distortion will always be lowest when driven by an ideal voltage source. Noting too, if damping factor is close to "1" by definition half the power is also being dissipated in the source impedance. That's definitely not desirable. 

Not surprisingly perhaps, 99.9% of high-end commercial speakers are not particularly amplifier friendly and are clearly designed to be driven from a very low impedance source (ie. ideal voltage source). 

arty_vandelay
You wrote:
"Distortion (IMD) is still higher than a decent classic blameless AB design above 10kHz."
Do you mean this part of Amirm's test:
"I was surprised to see the rise in distortion with frequency. I had hoped that the super high gain-bandwidth of the 1ET400A would do away with this. Not an audible concern though as the distortion products here are all in ultrasonic range. [...]The Benchmark AHB2 does a lot better since it has much cleaner ultrasonic spectrum.".
Well, ASR is known for measuring audio phenomena that no human can hear. A concern for bats, perhaps. As for the 18khz+19kHz IMD, Purifi is absolutely tops, not to say that no other manufacturer provides those data. Amirm writes:
"Bruno had encouraged me to run intermodulation test with 19 and 20 kHz tones. I matched levels with Benchmark AHB2. I was surprised to see so much lower intermodulation distortion with 1ET400A. The first pair of sidebands is more than 10 dB cleaner and the rest almost don’t exist!".
The Benchmark AHB2 is Amirm’s/ASR reference A/B amp. "The cleanest amp on the planet".
As for subjective perceptions of audio, to paraphrase the local classic, "there are many, me including, who like tubes best".

As for subjective perceptions of audio, to paraphrase the local classic, "there are many, me including, who like tubes best".

Horses for courses. I don't care too much for tubes but I'm a fanatic for pristine treble, and that includes a ruler flat response out to >100kHz.   

Measurements of the purify look good but keep in mind those IMD measurements conducted at relatively low power and with a LPF in line. 

Btw, the new Halcro Eclipse is now the new "benchmark" for low distortion.   

>100kHz response?  Some species of bats indeed can detect 200kHz but they can't hear the human range sounds.
Then there is the question of transducers, I think I came across once a lab specimen that goes high ultrasonic. Then there is the problem of mics, top studio Telefunken U47 (9k $) goes only up to 20kHz.  So, other than Batman music recorded with lab mics and played by lab transducers it might be a tall horse to climb.

>100kHz response?  Some species of bats indeed can detect 200kHz but they can't hear the human range sounds.
Then there is the question of transducers, I think I came across once a lab specimen that goes high ultrasonic. Then there is the problem of mics, top studio Telefunken U47 (9k $) goes only up to 20kHz.  So, other than Batman music recorded with lab mics and played by lab transducers it might be a tall horse to climb.

Of course we can't hear 100kHz. The desirability of a flat response out to >100kHz has to do with minimizing the side effects from the cascading of low pass filters starting all the way from the recording process itself - as you correctly identify includes tranducers too.  

Always need to be mindful of the time domain. 

All digital audio is built around the sampling theorem, not the other way round.  There are places in the signal chain where high sampling rates make sense. The final reproduction stage is not one of them. Why, and how it can be harmful is well explained here:
https://people.xiph.org/~xiphmont/demo/neil-young.html

All digital audio is built around the sampling theorem, not the other way round

I wasn't singling out digital audio, but it's worth mentioning the use of oversampling to remove the necessity for analog brick wall filters in AD-DA conversions. Class D amplifiers don't require brick wall filters but they do still add multi-pole low pass filters to an already band filtered signal path for playback of a wide range of recorded music that's already passed through a diverse range of low pass filtering even before it leaves the mixing desk for digital recording and mastering.  

For the record (no pun intended), my highest fidelity recordings are all high res 24/192 digital. To my ears they're the closest thing to real live music. 

purify look good but keep in mind those IMD measurements conducted at relatively low power and with a LPF in line.

Not just low power Arty, but "very low" power, as the testing equipment used, the Audio Precision in line external Class-D switching noise filter has a LP slope of 52db per octave, and any more than a few watts through it would burn it out a flash.
Would be very nice if you could listen to normal power music through this AP filter, as then everyone would love Class-D (even me), virtually no switching noise or phase shift in the audio band, no heat, light weight, low power and cheap, what could be better

Cheers George

I see you are parroting what someone told you about using the AP to measure a Class D amp. Funny I have tested Class D at 100’s of watts on our AP. Can’t imagine how I did that ....

I’m talking about the Audio Precision’s auxiliary AUX-Filter which goes between the Class-D and the AP Analyser, it’s a 52db per octave passive low-pass filter and can only take low power, it eliminates the Class-D’s switching noise for testing purposes only can’t be used for real music levels, even Stereophile state they can only put low power wave forms through it with it in use.

I said it years ago if you have a look in their comments, when Stereophile first started using this AP AUX switching noise filter, I complained they weren’t showing us anymore what is representative of what comes out of the speaker terminal of Class-D with this AP filter in between the Class-D’s output and the AP Distortion Analyser, especially the screen shots of the 10khz square waves.

As you can see years back Stereophile used to show with (top) and without the AP low pass filter, and it’s always used at very low power.
Today they never show the square wave "without" the filter in line (bottom), which is not representative what’s coming out of the speaker terminals.
https://ibb.co/MnK3mcm

I am going to guess I have far more experience with AP equipment and getting the most out of it than the average Stereophile writer who is a casual user. Hint that filter is optional dependent on external circuitry and amplifier performance.

I am going to guess I have far more experience with AP equipment and getting the most out of it than the average Stereophile writer who is a casual user.

Yes your the best, and yes your a"Dreamer".

JA (John Atkinson) would have so many more hours than you on AP test gear it’s not funny. That all he does all day every day, is measure everything Stereophile reviews and subcontracts out as well.

Stop "trying" to big note your self, and go back to saying how good OTL amps are for driving bad speaker loads like the Alexia’s, that only made you look half as bad, we can’t follow two ridiculous claims at once.

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-purifi-1et400a...
The above was explained ad nauseam from post #558 in this thread at ASR

The above was explained ad nauseam

No it wan’t explained why a screen shot of a 10khz square wave couldn’t be shown direct from the Purifi 1ET400A speaker terminals, as the speakers see it, as Stereophile shows a few years ago here https://ibb.co/MnK3mcm (top pic) but now Stereophile also don’t show it without the external filter, because it’s not a good look for their advertisers to show that kind of barely recognizable square wave. 

Instead the screen shot that is shown, had been extensively cleaned up after it had gone through an A.P. AUX external -52db LP testing filter (bottom pic), fooling readers/viewers into thinking that it comes out this clean from the Purifi 1ET400A speaker terminals. A hoax in my view.

You asked for the file, Amirm said he didn't have it and you said "If you don't have it that's fine". It's all there if anybody wants to read this interesting thread.

Thanks Pirad. You just confirmed what I already expected that he doesn't know what he is talking about and just parrots what he reads. It would never occur to him that external custom filters could exist Or that the amplifier would filter out the high frequencies themselves rendering the filter use unnecessary.


John Atkinson is just using the tools available to him. He doesn't have an engineering or signal processing background (I expect you don't either). Many of us design custom interfaces to do all sorts of things with our AP units (or build whole devices to achieve what AP products can"t).

🤦‍♂️

There you go, big noting yourself again, putting **** on John Atkinson (Stereophile) is a real good way to get reco.
Go back to shilling that OTL’s can drive Alexia’s, that made more sense.

I’m not the one idolizing a reviewer of an audio magazine reviewer that would be you, and because you just basically parrot what your read you have no clue about what’s possible with this equipment so I don’t know why you were claiming limitations you don't have the experience to claim?? You take one thing read about one accessory and assume that must apply to any time you use AP equipment. That is not the case. It is no different than with epdr which you continuously referenced even though it had absolutely nothing to do with class D amplifiers.

I’m not the one idolizing a reviewer

No but you rubbished him, and that in many eyes makes you a total loser. JA of Stereophile gives more to the audio industry in his little bench testing finger that you ever could.

Like I said if I’m parroting, it’s because of continuing false statements like you make, "that OTL’s can drive Wilson Alexia’s to what they’re capable of doing".

Go back to spruiking and telling OTL tube owners, their amps are great for speaker loads like Wilson Alexia’s ect ect , your good at that kind of false statements.

It is no different than with epdr which you continuously referenced even though it had absolutely nothing to do with class D amplifiers.

And EPDR (impedance + -phase angle) loading that the amp sees is fact, your the only one who says it’s not.

You don't even understand what EPDR is and you just proved it yet again. EPDR is a number exclusively for linear amplifiers to represent equivalent PEAK power dissipation in the output devices. You have brought it up repeatedly in Class D threads. EPDR has no meaning in a Class D amplifier and that you keep bringing it up shows you don't understand EPDR or you don't understand Class D.  I will let you tell us which that is.


I read an article not long ago that said JA has tested over 300 amplifiers. We have ran that many tests in design variations across synthetic loads in a week on automated stations running 24/7. Not faulting JAs work, but putting his expertise in perspective. You don't seem to appreciate just how sophisticated companies and design groups can be set test and measurement. What Stereophile does only scratches the surface.  You idolize that because you don't have experience to put it into perspective.

Your the best mate!!! (in your own mind) "No more responses to anymore ** you say."
Now go back to the Misc Forum spruiking about voodoo snake oil along with your SR "fuser" mates geoffkait, uberwaltz, oregonpapa ect ect, or how OLT tubes can drive Alexia’s

You make me laugh Georgehifi. Anyone who knows my posts knows how ridiculous your statement is. Actually you are just like uber and Frank and geoffy. You take things you read, without fully understanding them, then try to apply them to all situations.

You have misapplied EPDR repeatedly in Class-D threads. You wrote those threads, not me. EPDR does not apply to Class-D. People that actually design amplifiers, test them, etc. know this. That is a big statement about your knowledge.

You also believe that AP equipment cannot test Class-D beyond a few watts. That is also not true. That is another statement about your knowledge.