2. amps-preamps
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Peachtree GaN 1 Beta

Before I start my post here is my current system for reference:

Auarlic Aries G1 --> Denafrips Terminator or SW1X DAC --> Audio GD HE1 XLR preamp or Sachs preamp --> various tube amps --> Cube Nenuphar Mini's w/ a pair of REL S510 subs. Cables and power conditioning commensurate with the rest of the system.

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As warmer months approach I have been looking for a cool running amp to replace my Line Magnetic LM-518 and other tube amps for a few months as they run pretty hot.

I've been interested in the GaN FET amps and just purchased a used LSA Voyager 350 Gan FET amp which I should receive in a few days. I've tried class D amps before and while they checked a lot of boxes I just didn't feel drawn in. However, I like to explore so I figured I'd try the GanFET and since the amp has zero feedback and my speakers seem to prefer amps with little or no feedback I figured it be worth checking out.

Today, Peachtree Audio sent out an email inviting users to a beta of their new Gan 1 amp. Here are some excerpts from their email:

 

What is the GaN 1?

In basic terms it is a 200 Watts-Per-Channel (WPC) Power Amplifier designed to be the sole interface between your digital audio device with a variable output, like a Bluesound NODE, and your speakers. The GaN 1 is a simple, pure and cost-effective audio solution: connect the GaN 1 to a streamer and a pair of speakers and you have an amazing Hi-Fi system. That's it...no DAC, no preamp and no input switching. The signal path from the music to your speakers is remarkably short and free of artifacts. Want to hear the intricate details in your music that have always been there, but you couldn't quite make them all out before? Then the GaN 1 is for you!

What makes the GaN 1 so special?

First and foremost is the GaN-FET amplifier module. It has several inherent advantages in a power amplifier that even the best MOS-FET designs simply cannot achieve. A GaN-FET power stage provides a precise high-power reproduction of the Class-D PWM signal with extremely high linearity. This linearity eliminates the need for ANY feedback, ultimately allowing for the best possible audio quality providing clean, clear middle and high frequencies and a tight, solid reproduction of low frequencies. GaN-FETs track the complex audio waveforms MUCH more accurately than MOS-FETs, resulting in significantly more transparent and natural sound. The difference is something even a casual listener can hear and appreciate. The GaN 1 is also designed so that it does NOT require a digital-to-analog-converter (DAC). The digital audio signal at the input directs the amplifier outputs to drive the speakers. Although DACs have continued to improve over the years, there is no DAC better than NO DAC! This concept is not new as similar devices known as "Power DACs" made quite a splash in our industry years ago. But this time around, by executing the concept with GaN-FETs, the bar is raised to an entirely new level.

Key Features at a Glance:
▪ 200 WPC state-of-the-art GaN-FET module
▪ ZERO feedback design
▪ Regulated 450-Watt power supply
▪ Coaxial S/PDIF input with native support up to 24-bit / 192kHz
▪ DAC-less design
▪ Power on/off trigger port
▪ All aluminum chassis
▪ No cooling fans

 

This sounded really interesting to me and since I have a good streamer I signed up for the amp beta only. One aspect that intrigues me is to create an extremely minimal signal path. My speakers are single driver, crossover-less design. Employing the GaN 1 will mean the system will be Auralic Aries --> GaN 1 --> Cube Nenuphar Mini's. Will that lead to a more engaging sound vs the full system? Will the Voyager GaN 350 outperform a tube amp in the full system? Who knows, should be fun to find out....

Now, I have no idea how either of these GaN FET amps will work with my speakers. The Cube Nenuphars seem to prefer amps with low damping and no negative feedback, which is more common with SET tube amps and Class A solid state amps. I'm not sure of the damping factor of the GaN FET amps, but both are Zero feedback designs, and both have way more wattage than I need. For reference, I have a 1.5 wpc 45 tube amp that sounds amazing with the Cubes, so high wattage is not required. I am interested though in what these amps will sound like compared to my tube amps, and I am particularly interested in what the streamer direct to amp Peachtree will sound like.

I am also looking to acquire a First Watt SIT-3, which is a great match with the Cubes, but now that they are no longer produced prices have gone above my current comfort level. If I can get one I will throw it into the experiment.

The Peachtree won't be shipped until sometime in June, or possibly later. In the meantime I will get the LSA Voyager in the next few days. I might even be able to get it hooked up this weekend so stay tuned, should be an interesting experiment...
abd1
atmasphere's avatar
atmasphere
11,632 posts
 

So Ralph, are you saying that the data output (to be sent the the input of the Gan 1) sampled at 96kHz would not necessarily be a restrictive limiting factor to the ultimate performance of the Gan -1?

I am. The limitation is in the word length, not the scan frequency.

Gentlemen. I see that @kuribo has entered this thread. I've crossed swords with him in the past, but on this point of load dependent frequency response he is correct. @ricevs , if you want to find out what the effect of this might be, try a load that varies between 3 and 16 Ohms over the audio band (which is typical of many speakers) and find out what actually happens. Its not sufficient to look at the difference in FR with a simple resistive load.

Now I made a career of building zero feedback OTL tube amplifiers so I have a fair amount of hands-on experience with this. The output impedance of the amplifier plays an enormous role here. So I would expect that the FR of a zero feedback class D amp to be less 'reactive' (if you see what I did there) than that of a tube amp. The variable here though is the output choke, which is a critical part of any class D design, especially a GaNFET, which will require the choke to operate at a lower frequency rather than a higher one, on account of its inductive kickback being used to initiate the off state of the output device.

Its complicated.

Now how much this will affect the audio FR with a variable load is a good question. The On resistance of GaNFETs is stupidly low, so if it were up to them this would be a non-issue. IOW the output filter choke is really the variable. Based on my own experience (since a number of our prototypes were zero feedback) my guess is its a minor issue.

kuribo
524 posts
 

@atmasphere

Gentlemen. I see that @kuribo has entered this thread. I've crossed swords with him in the past, but on this point of load dependent frequency response he is correct.

Nice to see we agree on something.

To properly evaluate the performance, a simple constant, purely resistive load is not going to do it. Few speakers present such a simple load.

Additionally, without post filter feedback, there are other issues besides load dependent frequency response that can be present.

In all, it's a poor design in comparison to other currently available class d amps that have orders of magnitude better performance. Just more marketing, all aboard the GaN train!

donnylovely
105 posts
 

1db is more of a non-issue than an issue. Sorry we can’t all afford to buy the best preforming amps in the world, that’s more of a non-issue also, always going to be something that preforms better.

dolfan
104 posts
 

@kuribo what other class D amp in this price range should I try? 

kuribo
524 posts
 

@donnylovely

1db is more of a non-issue than an issue. Sorry we can’t all afford to buy the best preforming amps in the world, that’s more of a non-issue also, always going to be something that preforms better.
 

Now you actually admit the frequency response is load dependent after denying it time and again?

The actual performance into a real world varying reactive load is almost certainly materially worse than than 1dB, which is into a best case, non-reactive, constant resistive load.

We can't all afford to buy the most expensive amps but those who can afford the $1500 GaN 1 can certainly do better for the same or less money. There are plenty of better engineered and performing amps available - Ncore, Purifi, and Orchard, etc. are all much better performing and better engineered without riding the GaN marketing coat tails.

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