Peachtree GAN400 Amplifier Review

[amirm]

I know it is a very expensive instrument and would certainly make a positive addition to ASR investigations. However I'd be looking at warranty and service before making any major cash outlays. As with anything.

No doubt any service requires shipping it back to Germany.

 

[amirm]

If ASR is going to provide AudioGraph measurements (which I hope will be the case), a discussion of its practical (to the consumer) use ought to follow.

We definitely need to do that. The biggest concern right now for me is usability. As I noted, once the amp goes into protection in one test, the sequence keeps going and there is no way to stop it. Or limit what it does. For example, I may want to test 2 ohm in resistive mode but not with 30 and 60 degree angle to avoid the amp shutting down.

 

[dougi]

This link is quite new and hope that it is accessible even without login:

How to test your new Audio Amplifier Design - PowerCube basics and example graphs

Lets see how our test systems can help you design your audio amplifiers. To understand the need of the PowerCube test, you must be aware of how a loudspeaker appears to the amplifier during dynamic conditions.

www.linkedin.com

- with graph examples and explanations.

I thought it was interesting that Soundstage, at least in the review/measurements of the NAD C3050 LE they do some measurements with real speakers. In this case, a two way and a three way. FR, THD, IMD. I assume things that can be done at a low/medium power level so the speakers aren't risked. Even at 1W, the 2-way caused the amp to produce significantly more THD at low frequencies.

 

[amirm]

I think I understand this Power-Cube diagram so far ...
but how long has this power to be delivered from the Amp ?
continuous / 20ms burst / some seconds?
and at what distortion-values (1% / 10% / clip) ?

Only two tests in AP are allowed: max power and burst power. You have seen these results in my amp tests including this one:

Max power on the left is a continuous test but the duration is short. The amp is iteratively run with different input levels until 1% THD is achieved (for a few milliseconds). The one on the right uses a burst sine wave. During the testing, the amp is pushed repeatedly into clipping until the right input voltage is found at 1% THD. So it is pretty stressful while not being constant power for long time.

I can change the THD+N level but that is it.

 

[amirm]

Even at 1W, the 2-way caused the amp to produce significantly more THD at low frequencies.

We have done this testing with headphones and concluded that the measured THD is incorrect. There is back EMF from the speaker corrupting the distortion level. For this reason I stopped testing headphone amps with real headphones.

As to the load that I built to simulate a 2-way speaker, it is there. But unlike this loadbox, it is very low power and at best can handle 5 watts. As a result, its only usefulness is for frequency response errors. As seen in this test, I am simulating that easily with just using a different resistive load (8 ohm vs 4 ohm) to show the effect. This method is very quick whereas hooking up that load and measuring with it takes some time. Seeing how the simulated load is not representative of all speakers anyway, I am not sure it brings much to the party other than appearance of "testing with a real speaker load."

 

[restorer-john]

I don't think I've ever seen an amplifier hit the 4R power wall as hard as this Peachtree.

As for the AP script power cube visual, it's very clunky looking compared to the B&W original style which is way more intuitive and easy to visualize.

The more you look at it, the worse it gets (like one of those 3D holograms).

And why are the impedance scales marked in individual ohm increments? It's only switching 8/4/2/1R with straight lines between points. Unless the box was switching in series combinations and then we'd be seeing deviations not straight lines in any case.

This is way better.

 

[amirm]

And why are the impedance scales marked in individual ohm increments? It's only switching 8/4/2/1R with straight lines between points. Unless the box was switching in series combinations and then we'd be seeing deviations not straight lines in any case.

I think that is a function of the Labview library AP is using for that plot. Agree it is confusing.

 

[anmpr1]

We definitely need to do that. The biggest concern right now for me is usability. As I noted, once the amp goes into protection in one test, the sequence keeps going and there is no way to stop it. Or limit what it does. For example, I may want to test 2 ohm in resistive mode but not with 30 and 60 degree angle to avoid the amp shutting down.

Thanks. My suggestion (FWIW, and should you spring for the device), would be to limit extremely low impedance tests, unless the manufacturer claims that as a feature for his amp. Otherwise, from a practical standpoint, and certainly with many domestic loudspeakers, such capability is probably not too important. But I would defer to those with more expertise in the testing field.

On an historical but certainly related note, in 1977 or '78, Aczel was 'testing' (mostly an informal listening test) the British Tangent RS2 loudspeaker. One amp used was the then new Mark Levinson ML-2. The Levinson was one of the first consumer amplifiers designed specifically with low impedance loads in mind. Rated at 25 watts (8 ohms), it could double its output going south--50 watts into 4 ohms, 100 watts into 2.

However, with the nominally 16 ohm Tangent, the ML-2 frequently clipped on 30 ips second gen master copies of piano music (sourced, I believe, from Max Wilcox), and played on his Studer A80.

Alternately, the oddball Futterman H3aa OTL amplifier (an amp that became unstable with loads less than 6 ohms) was able to drive the Tangent to remarkably loud levels. The Futterman could put out (probably) 100 watts into 16 ohms, whereas the Levinson's 14 volt output didn't have much to offer a 16 ohm loudspeaker. [Tangent impedance was 11.5 ohms at 70Hz, 9 ohms from 500 to 2000 Hz, and 20 ohms at 6kHz.]

 

[restorer-john]

Is this the $30k+ load box we're contemplating? You'd expect somewhat better integration with the AP for that sort of money. You would also think the script could stop and flash an error if the AP stops getting a valid input during the sequence (in other words the amp has gone into protection).

And the power cube result is only valid for 1kHz and 20mS, so it's going to get a ton of pushback IMO.

Also, is the duration of each test impedance combination variable? ie Does the AP take longer sometimes to find the THD target as that can obviously un-level the playing field resulting in premature shutdowns.

I think you should do an extensive review on the unit for sure. Cheers.

 

[anmpr1]

This is way better.

I'd have to do even more digging, but sometime after the PL came out, Stereo Review put the nominally 4 ohm AR LST loudspeaker (think--2 AR3a per side) through its paces. I think this was actually a test of distortion audibility.

Two of the amps used were the Crown DC-300 (150 watts/side 8 ohms; 250 watts/side 4 ohms--per Crown spec sheet), and the Phase Linear. The Phase was preferred to play 'louder', even though, like the Crown, it was also driven into clipping on peaks. Just not as often as the Crown.

Looking at the PowerCube, it is easy to see that the PL made twice the watts as the Crown at 4 ohms (wish I had a graph for a DC-300), although at the extremes of inductance the output began to collapse.

It is why Paul Klipsch said the world needed a good five watt amplifier. Or something like that. With his loudspeaker, it didn't matter, too much. However, if you have Apogees in your living room, you would like a PowerCube before you buy.

 

[Vigovsky]

Some of the tests of my VR-03B balanced amp (based on Purifi 1ET400A) that I made in 2021.
This is a test with different frequencies and powers.
I made various measurements of a signal current waveform amp with a resistive load 6 ohm.
(oscilloscope + generator) + resistors was very hot...

The amplifier provides excellent sound and is stable in operation.

 

[carlosmante]

For an informed opinion about GaN technology in audio amplifiers. .

 

[laudio]

If I'm paying that much for a GaN amp that looks like a modem, might as well up the ante to a Hi Fi Rose RA-180 and get some bling.

 

[AndreaT]

I am unconvinced that Gallium Nitride technology has an advantage in producing superior quality of sound. Its niche seems to be for high-power broadcast and narrowcast applications and where space/weight is at a premium (military applications). For me it is a pass, especially at that price.
Thank you Amir for the addition of 3D surfaces correlating three variables. They bring back the memories of studying thermodynamics.

 

[kongwee]

I
This is way better.

It should include VA.

 

[restorer-john]

Some of the tests of my VR-03B balanced amp (based on Purifi 1ET400A) that I made in 2021.
This is a test with different frequencies and powers.
I made various measurements of a signal current waveform amp with a resistive load 6 ohm.
(oscilloscope + generator) + resistors was very hot...

The amplifier provides excellent sound and is stable in operation.

The overall look of your amplifier is excellent. I really like the instrumentation style volume pot knob and the shaft driven motorized Alps (or replica). Reminds me of the Teac Reference range from the late 90s.

Large toroidal TXF and 20,000uF per rail is a bit light IMO. I don't believe you will get anywher near the ET400A's capabilities with that PSU, but the completed amp looks better than just about any other Purifi-in-a-can I have seen- well done.

 

[Scytales]

Stand Alone – AudioGraph

www.audiograph.se

It is an eval unit. Have to decide if I am purchasing it. Will probably do a stand-alone review for it.

I highly suggest you try to master this new piece of equipment in order to keep it.

In France, a famous engineer, Étienne Lémery, who has passed away for some years now, had devised an analogous test method for power amplifiers in the eighties. His lab results were essentially published in the very technically oriented magazine Le Haut-Parleur (The Loudspeaker) which was published for the first time in 1925 (!) and diversified under numerous titles. The pro-audio oriented edition of Le Haut-Parleur which is entitled Sono Magazine still exists today.

The reactive load test devised par Lémery was one of the most stringent measurements published by these magazines and it is very discriminant between amplifiers, both to test their ability to sustain level under real world conditions where it matters the most (in the bass, where a port-tuned speaker could very much phased out voltage and current, precisely where music demands level much more than in the high treble !) and to test their safety features.

By the way, the amazing Italian guys of Audioreview magazine have devised an even more stringent test called TRITIM 100 : power measurements and high level measurements of power amplifiers on resistive and reactive loads (+/- 60°) with a test signal containing simultaneously 4 frequencies of different level each (1 in the bass, 1 in the medium and 2 closely spaced in the treble), both in continuous and impulsive conditions and at different output levels spread 6 dB around the nominal output level of the DUT. A very tough test, indeed.

 

[pma]

The amplifier provides excellent sound and is stable in operation.

What is the measurement bandwidth (or sampling frequency) in the 900Hz square oscilloscope shot? The plot look is highly suspicious, there is no trace of overshoot and there is no trace of switching frequency residuals of the Purifi. Would you please post 10kHz square response?

 

[DanielT]

In my experience not only audible but easily measurable. I have some load dependent cheap class D amps and a few of them exhibited rising HF response with a particular pair of speakers I own. Lots of testing was done, even sending the speaker to the company to be analyzed. Turns out it was my amps. Only until I was able to get a hold of an amp that didn't have the load dependency was I figure it out. Since then I've been looking around trying to find an amplifier that won't do this but also won't break the bank.

A07 (class D in green)vs. Audiosource Amp100 (class A/B in orange), I had to do this quickly at a friends house and forgot my mic stand so I did my best to hold the mic in the same spot. Speakers are Parts-express Cnotes.

View attachment 271688

Here's another measurement that I took that shows how bad it can get.

View attachment 271692

I thought this was super interesting because it kinda took a big poop on my long held belief that amplifiers generally don't sound different. It looks like they absolutely can. I was also surprised that no one really seemed to think anything of this when I shared my info.

I became interested in that, so here:

Which amp of these two is best for the Elac Debut Reference DBR-62?

Which amp of these two is best for the Elac Debut Reference DBR-62?Edit: Prerequisite, starting point that the amplifier is able to reproduce the signal as linearly as possible together with the speaker in question. In this case, remove the amp power (or rather start from the test below for...

audiosciencereview.com

 

[Vigovsky]

The overall look of your amplifier is excellent. I really like the instrumentation style volume pot knob and the shaft driven motorized Alps (or replica). Reminds me of the Teac Reference range from the late 90s.

Thank you. Yes! I also really like these handles and I cut them out on a CNC machine.
Photo of some of my favorite TEAC amps with great sound and similar instrumentation style volume pot. I have two of them.
With this power supply, I am confidently getting 380W per channel into 6 Ohm in this small case. This is quite enough.
Best wishes,
Ruslan Vigovsky