Peachtree Audio Gan400 Amp....Class D moves forward.

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Freo-1

Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #100 on: 31 Jan 2022, 06:01 pm »
As I have said repeatedly, I have been told that the LSA and Peachtree amps use the same amp modules. They have the same lack of post filter feedback. This leads to a frequency response dependent on load regardless of devices, switching frequency, etc. I don't like frequency dependent designs. We have moved passed this in class d.


The specs on the Gan 400 state that frequency response deviation is plus or minus  .4db.  Nothing wrong with that.


The white papers in linked discusses load variation with the GanFET.  Again,  I suspect the design is as intended.  I plan to see if I can find out the back story on this. 


The GanFETs performance simply doesn't need the feedback MOSFETS require. 


One other item worth mentioning:  The differences with the Chord M-Scaler/Hugo-TT2 sample rate and filters are more discernible with the Gan400 than any other amp I tried to date. 






https://www.peachtreeaudio.com/products/gan400

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #101 on: 31 Jan 2022, 06:50 pm »
Your requirement is logically flawed and impossible to satisfy. An amp can't create  "the sound of live, unamplified music in a good acoustic space". All an amp can do is take an input and make it larger, as accurate to the source as possible. The recording, source, the room acoustics, and all the other electronics in the chain play a part in modifying and converting that signal before it gets to you ears, and from there, your own perceptions further interpret the signal. It's an interdependent system. If an amp does anything to modify the signal, it isn't an amp, it's an effects box. The best we can do is to take the source and make it bigger. If the result isn't what you consider "the sound of live, unamplified music in a good acoustic space", there are innumerable possibilities why that is so, from the source material to room acoustics, to distortion in the signal chain. Today's amplifiers produce so little distortion, phase shift, etc., that the problem is almost always somewhere else in the chain, either because of interactions or where distortions are many magnitudes greater.

Right, again I agree with you, an amp should be as neutral as possible.  But since an amp has many different ways to accomplish this, you need some kind of real life reference in order to spot-check to see if neutrality is actually achieved. 

For example, let's assume for a minute that your assertion that the new GaN amps are load-dependent.  Obviously nobody wants to have anything fluctuating based on load.  Again, let's assume this is true of the GaN amps, and we know that it's NOT true of the Hypex amps, because we can see it in the measurements.

Now, people listen to both amps and decide that the GaN sounds better.  How can that happen?  To me, this would suggest that the thing being measured (load dependency) has less effect on sound quality than some other factor that the GaN is actually doing better.  There's something not being measured (but should be), and the GaN is getting this other area right and the Hypex is not. 

This is how you can have an amp that measures better but sounds worse.  It's not a call to dismiss people's feedback as 'subjective' and thus not to be taken seriously.  Rather, it's a call to try to investigate and see what one amp is doing better than the other amp that's not accounted for in the current measurements.  That's the only way to actually know if your amp is any good or not.  Otherwise you just end up in an echo chamber where anyone that criticizes your design is excoriated and dismissed out of hand for the heresy of actually criticizing the amp.

Freo-1

Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #102 on: 31 Jan 2022, 07:45 pm »
Right, again I agree with you, an amp should be as neutral as possible.  But since an amp has many different ways to accomplish this, you need some kind of real life reference in order to spot-check to see if neutrality is actually achieved. 

For example, let's assume for a minute that your assertion that the new GaN amps are load-dependent.  Obviously nobody wants to have anything fluctuating based on load.  Again, let's assume this is true of the GaN amps, and we know that it's NOT true of the Hypex amps, because we can see it in the measurements.

Now, people listen to both amps and decide that the GaN sounds better.  How can that happen?  To me, this would suggest that the thing being measured (load dependency) has less effect on sound quality than some other factor that the GaN is actually doing better.  There's something not being measured (but should be), and the GaN is getting this other area right and the Hypex is not. 

This is how you can have an amp that measures better but sounds worse.  It's not a call to dismiss people's feedback as 'subjective' and thus not to be taken seriously.  Rather, it's a call to try to investigate and see what one amp is doing better than the other amp that's not accounted for in the current measurements.  That's the only way to actually know if your amp is any good or not.  Otherwise you just end up in an echo chamber where anyone that criticizes your design is excoriated and dismissed out of hand for the heresy of actually criticizing the amp.


Largely concur.  Can't dismiss an amp out of hand that one has not heard or measured.  The Gan400 amp has not been measured with its associated power supply yet.   Also, to assume the GaN designer was ignorant of this load variation issue is to assume a lot.   As stated earlier,  the design may be as intended,  based on the operational characteristics of  GanFET boards and (power supply), which would in all likelihood outperform a legacy SMPS.


Will attempt to contact Peachtree to see about a response. 


BTW, I stand by the statement that GanFETs in class D is and will continue to be a step forward.

goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #103 on: 31 Jan 2022, 11:15 pm »


For example, let's assume for a minute that your assertion that the new GaN amps are load-dependent.  Obviously nobody wants to have anything fluctuating based on load.  Again, let's assume this is true of the GaN amps, and we know that it's NOT true of the Hypex amps, because we can see it in the measurements.

Now, people listen to both amps and decide that the GaN sounds better.  How can that happen?  To me, this would suggest that the thing being measured (load dependency) has less effect on sound quality than some other factor that the GaN is actually doing better.  There's something not being measured (but should be), and the GaN is getting this other area right and the Hypex is not. 



There are several possible and more probably explanations which are much more plausible than yours: first of all, the load dependency depends on, of all things, the load. Some loads are simpler, easier, less capacitive, etc. and would produce a lessor fluctuation in frequency response. This is one reason why some people raved about the Tripath class d amps of yesterday, and others hated them. Different speaker loads produced different results. Another reason is even simpler: some people just happen to like what the amp does in their system: there may be synergies or issues in the rest of the system that are tamed or improved with the amp's response. Or maybe some people just like it.

As for the lack of post filter feedback not being an issue somehow, please explain what happens to the distortion produced by the output filter. At the low switching frequencies used, they can't use air cores. The largest source of distortion in class d amps is typically the ferrite output filter. So while the advantage of high switching frequencies attributed to GaN devices (the use of air cores) is real, neither Peachtree, LSA, nor Merrill are using a high enough switching frequency, it would seem, to allow them to take advantage of the use of air core output filters, and thus, decrease drastically the distortion inherent in ferrite cores, which could then perhaps allow for open loop designs.

Like I said, GaN has advantages, but unless those advantages are actually being exploited, it's just a gimmick, particularly when the performance is worse than what is achievable with state of the art mosfet class d: see: Purifi.

And speaking of Merrill, while their new amps are beautiful to behold, at $35,000US, I doubt they are 35 times better than the Purifi. They haven't published any measurements that I can find. I guess that people who spend that kind of money on an amp don't really care how it performs, it's all about how it looks.

"I stand by the statement that GanFETs in class D is and will continue to be a step forward. "

Please explain how it is a step forward in class d currently. All I see are GaN amps that measure at best nearly as good as the Purifi and several that aren't close.

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #104 on: 31 Jan 2022, 11:37 pm »
Sigh, I am clearly not getting through.  OK, let me try this again.  Here's a hypothetical for you.  2 amps measure the same, but they sound different. 

Which one is correct and what method would you use to determine which amp was the more correct amp?

Freo-1

Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #105 on: 1 Feb 2022, 12:16 am »
I have contacted Peachtree to ask to respond to a series of questions regarding the Gan400.  I have requested information regarding feedback,  load variation,  power supply data,  and switching frequency.   I alerted them to the threads regarding the Gan400 design and sonic discussions so they can best respond to the assertions raised.  Something tells me Peachtree  might take issue with some of the assertions,  but we shall see.


Need more information on the Gan400 to resolve this discussion, so Peachtree seems like the best place to obtain it. I do think the inherent advantages of GanFET over MOSFETS are easily understood.  The potential for continuing improvement is more so than with MOSFETS.



goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #106 on: 1 Feb 2022, 12:24 am »
Sigh, I am clearly not getting through.  OK, let me try this again.  Here's a hypothetical for you.  2 amps measure the same, but they sound different. 

Which one is correct and what method would you use to determine which amp was the more correct amp?

Give me an example of two amps that measure identically and sound differently in the same system.

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #107 on: 1 Feb 2022, 12:26 am »
Give me an example of two amps that measure identically and sound differently in the same system.

That's why it's called a hypothetical.  It's hypothetical.  Hypothetically, 2 amps measure the same, but sound different.  How do you determine which one is correct?

goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #108 on: 1 Feb 2022, 12:36 am »
I have contacted Peachtree to ask to respond to a series of questions regarding the Gan400. 

Why would Peachtree be the best place make technical inquiries on an amp module they source from a third party?

"Peachtree uses the GaN Systems HEMT and Elegant Audio Systems is listed as one of their partners. If you go to the GaN Systems website, they have reference boards and detailed information about their reference designs. If you look at the pictures in the reference designs, you will see that those also are from Elegant Audio Solutions."


goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #109 on: 1 Feb 2022, 12:42 am »
That's why it's called a hypothetical.  It's hypothetical.  Hypothetically, 2 amps measure the same, but sound different.  How do you determine which one is correct?

your hypothetical question has multi flawed hypothesis- those being 1. that there are two amps that measure identically but sound different, and 2. that sounding "different", a subjective opinion, can be objectively verified.

Freo-1

Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #110 on: 1 Feb 2022, 12:43 am »
Why would Peachtree be the best place make technical inquiries on an amp module they source from a third party?

"Peachtree uses the GaN Systems HEMT and Elegant Audio Systems is listed as one of their partners. If you go to the GaN Systems website, they have reference boards and detailed information about their reference designs. If you look at the pictures in the reference designs, you will see that those also are from Elegant Audio Solutions."


Well, it's got their name on it.  They can at least clear up the power supply questions,  whether it's a different board  compared to the LSA.   My thinking was that they would contact the vendor if they weren't able to answer.  I would think they would know the technical details of their product.

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #111 on: 1 Feb 2022, 12:48 am »
your hypothetical question has multi flawed hypothesis- those being 1. that there are two amps that measure identically but sound different, and 2. that sounding "different", a subjective opinion, can be objectively verified.


I'm not hypothesizing anything.  I am proposing a problem and I am curious how you would go about investigating and solving it. 

goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #112 on: 1 Feb 2022, 01:03 am »
Load dependent frequency response vs load invariant frequency response. Which is Purifi and which is the GaN amp module said to be used by Peachtree and LSA?








Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #113 on: 1 Feb 2022, 01:18 am »
Load dependent frequency response vs load invariant frequency response. Which is Purifi and which is the GaN amp module said to be used by Peachtree and LSA?












So remind me again, which one sounds better?

goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #114 on: 1 Feb 2022, 01:21 am »
I'm not hypothesizing anything.  I am proposing a problem and I am curious how you would go about investigating and solving it.

Your problem, as defined, can not be tested since 1) there are no two amps that measure identically and 2) "sounding differently" is an example of qualia which does not lend itself to a scientific third-person analysis.

 

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #115 on: 1 Feb 2022, 01:25 am »
Your problem, as defined, can not be tested since 1) there are no two amps that measure identically and 2) "sounding differently" is an example of qualia which does not lend itself to a scientific third-person analysis.

 

I could argue that you are simply being obstinate to try to avoid answering the question in an honest manner.  OK, let me try a different track.

Lets say you develop a new way to measure an amp.  Some amps measure very high on this new measure, and other amps measure very low on this new measure.  How do you determine if this measurement has any correlation to an amp's sound?

goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #116 on: 1 Feb 2022, 01:26 am »


So remind me again, which one sounds better?

Your words:

"For example, let's assume for a minute that your assertion that the new GaN amps are load-dependent.  Obviously nobody wants to have anything fluctuating based on load.  Again, let's assume this is true of the GaN amps, and we know that it's NOT true of the Hypex amps, because we can see it in the measurements."

I just showed you that my assertion is true, you don't have to assume anything.  You just said: "Obviously nobody wants to have anything fluctuating based on load." so you tell me how it sounds, since you have dismissed it above.

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #117 on: 1 Feb 2022, 01:28 am »
Your words:

"For example, let's assume for a minute that your assertion that the new GaN amps are load-dependent.  Obviously nobody wants to have anything fluctuating based on load.  Again, let's assume this is true of the GaN amps, and we know that it's NOT true of the Hypex amps, because we can see it in the measurements."

I just showed you that my assertion is true, you don't have to assume anything.  You just said: "Obviously nobody wants to have anything fluctuating based on load." so you tell me how it sounds, since you have dismissed it above.

Please be more explicit.  Why does someone NOT want a fluctuating load? (and I agree, if we can avoid it, we should).  But why should we avoid it?

goryu

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #118 on: 1 Feb 2022, 01:35 am »
I could argue that you are simply being obstinate to try to avoid answering the question in an honest manner.  OK, let me try a different track.

Lets say you develop a new way to measure an amp.  Some amps measure very high on this new measure, and other amps measure very low on this new measure.  How do you determine if this measurement has any correlation to an amp's sound?

Perhaps you should spend some time reading the research of Dr. Floyd Toole and many others who have attempted to correlate audio phenomena with human perceptions, i.e., psychoacoustics.

Tyson

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Re: Peachtree Audio Gan400 Amp....Class D moves forward.
« Reply #119 on: 1 Feb 2022, 01:40 am »
Perhaps you should spend some time reading the research of Dr. Floyd Toole and many others who have attempted to correlate audio phenomena with human perceptions, i.e., psychoacoustics.


I have.  Maybe you should read him.  Because he actually you know, listens to stuff.  And has other people listen to stuff.  And then correlates that data of people listening to stuff to the things being measured.  Which has been MY ENTIRE POINT THIS WHOLE TIME. 

I'm not angry, just putting the main point in caps because you seem to have missed it pretty much continuously this entire thread.