Atma-Sphere Class D Mono blocks

[PLF]

This review on 6moons (link below) has piqued by interest in this class D amp - Laiv Harmony GaNM from Singapore.

It is shame they will not be in Munich in two weeks time (I believe neither will Atma-sphere) at the high end show..

It is would have been interesting (for me) to see what class D seems to be currently achieving.

Harmony GaNM

6moons.com

 

[Holmz]

The problem with most of those 6-moons reviews is that they are all flowery and AI, with almost no meat on the bone.
The words to meaning ratio is very high.

 

[Kingsrule]

The problem with most of those 6-moons reviews is that they are all flowery and AI, with almost no meat on the bone.
The words to meaning ratio is very high.

Totally agree...they are useless

 

[PLF]

The problem with most of those 6-moons reviews is that they are all flowery and AI, with almost no meat on the bone.
The words to meaning ratio is very high.

Srajan's writing can be a bit cumbersome but I do find some of his reviews useful, certainly interesting and inspires me to some check equipment out. Laiv is a case in point.

 

[Holmz]

Srajan's writing can be a bit cumbersome but I do find some of his reviews useful, certainly interesting and inspires me to some check equipment out. Laiv is a case in point.

I guess having engineers building gear and English majors doing writing keeps everyone getting their slice of the action.

 

[PLF]

I guess having engineers building gear and English majors doing writing keeps everyone getting their slice of the action.

Sorry to say this, Holmz, but that is just nonsense.

If you don't like him, that is fine, but there is no need to make things up.

He is not a native speaker, perhaps this impacts his writing. I don't know.

For what it's worth, his background includes being in classical orchestra (the Bundesjugenorchester, the federal youth orchestra, fairly prestigious) in Germany in his youth.

 

[Ron Resnick]

Totally agree...they are useless

Srajan is writing in a foreign language (English). I cut him slack on his writing.

 

[Kingsrule]

Srajan is writing in a foreign language (English). I cut him slack on his writing.

Relax...Its not personal just a statement of fact

 

[treitz3]

Let's please stick to the thread subject, and shy away from posts about an individual poster. Thank you.

Tom

 

[KLH007]

This review on 6moons (link below) has piqued by interest in this class D amp - Laiv Harmony GaNM from Singapore.

It is shame they will not be in Munich in two weeks time (I believe neither will Atma-sphere) at the high end show..

It is would have been interesting (for me) to see what class D seems to be currently achieving.

Harmony GaNM

6moons.com

I think the most interesting takeaway from the review is that the LAIV GaN amp is less resolving and softer than the wide bandwidth Kinky A/B amp, and voiced that way intentionally.

 

[PLF]

I think the most interesting takeaway from the review is that the LAIV GaN amp is less resolving and softer than the wide bandwidth Kinky A/B amp, and voiced that way intentionally.

Yes, that got my attention and it's not what I would instinctually think class D to sound like (at least the ones I have heard so far), but I don't see why they can not be voiced that way. As I said, it would be interesting for me to listen to them,. hopefully matched to appropriate speakers.

I am intrigued to see how Class D develops - the price points seem low, the form factor favourable and hopefully reliability will be good. There will be other Class D amps at the Munich show in 10 days (Eversolo, Nuprime, Matrix et al) but have heard most of them before.

 

[MrC.]

IMO/IME the class D power supply has to be as robust as the power supply of any high quality amp. I think because the idle current can be so low, many have produced class D amps using competent modules that turned out bad because the power supply was insufficient.

The input buffer is important too and it seems that many in high end don't understand how to design one and perhaps how opamps work. I'm not completely sure of that last bit, but if you have to resort to tubes or some kind of boutique opamp for your input buffer IMO you have an unaddressed fundamental problem somewhere.

Hi Ralph. I've heard it said that tubes are ideal voltage amplifiers and that transistors are ideal current amplifiers. For an input buffer the grid of a tube provides almost unlimited impedance. Why not use an input tube before a class D output stage?

 

[morricab]

Hi Ralph. I've heard it said that tubes are ideal voltage amplifiers and that transistors are ideal current amplifiers. For an input buffer the grid of a tube provides almost unlimited impedance. Why not use an input tube before a class D output stage?

Rogue Audio is doing just that…

 

[DonH50]

Hi Ralph. I've heard it said that tubes are ideal voltage amplifiers and that transistors are ideal current amplifiers. For an input buffer the grid of a tube provides almost unlimited impedance. Why not use an input tube before a class D output stage?

Ralph @Atmasphere can answer definitively, but here are a few points to ponder:

1. The Atma-Sphere Class D amplifier's input impedance is 100 k-ohms, which is comparable to many tube amplifiers (and higher than some). That is effectively "unlimited" for audio components since preamplifier (or other source) output impedance is usually (very) low.

2. "Ideal" in this context is subjective but it is true that transistors generally provide higher current capability and tubes greater voltage range. Higher gain and greater feedback allows transistor circuits to operate with lower distortion, though the intrinsic distortion series of uncompensated tubes is lower (but any practical circuit has some feedback, even the "zero-feedback" circuits).

3. The input impedance of a bipolar transistor depends upon bias current and can be very high, but is very circuit dependent. Just as a tube circuit could have very low input impedance (but rarely does, at least for audio). There are trades such as gain and bandwidth for low bias current.

4. Transistors such as JFET and MOSFET devices have very high ("unlimited") input impedance, much like tubes, and like tubes there are trades for high input impedance. JFETs are often used for phono preamplifiers due to their high input impedance and low noise (as well as distortion characteristics similar to tubes). Designs must balance numerous variables to optimize the circuit (and thus product) for the application.

5. Cost and reliability of including a tube circuit in a SS design are among reasons to stick with transistors, but as stated above it is a design choice and a tube input may not fit the goals. A tube requires a high-voltage supply and buffering to drive a SS output stage, meaning additional power supply complexity, with added requirements for a class D amplifier to handle the potential high-frequency noise fed back from the output (as well as coupled/radiated internally) and work with the very high internal (loop) gain of typical self-oscillating class D amplifiers. The high impedance and low gain of typical tube circuits means high isolation from the power supply and any other (e.g. switching) noise must be achieved for high performance. Staying with SS devices can make that much easier.

FWIWFM/HTH/IME/IMO/etc. .- Don

 

[Holmz]

Sorry to say this, Holmz, but that is just nonsense.

If you don't like him, that is fine, but there is no need to make things up.

He is not a native speaker, perhaps this impacts his writing. I don't know.

For what it's worth, his background includes being in classical orchestra (the Bundesjugenorchester, the federal youth orchestra, fairly prestigious) in Germany in his youth.

His writing is just fine, and I do not dislike the fellow.
It is just that the review did not say a whole lot.

 

[Atmasphere]

Hi Ralph. I've heard it said that tubes are ideal voltage amplifiers and that transistors are ideal current amplifiers. For an input buffer the grid of a tube provides almost unlimited impedance. Why not use an input tube before a class D output stage?

In a nutshell, distortion.

In a class D amplifier the issue with the input buffer (where the tube would be) is driving the comparitor, which is an analog circuit at the heart of any class D amp which tells the output transistors when to switch. The comparitor tends to have a low input impedance, typically about 2000 Ohms. That' s hard load for a tube. So if you are using a tube, the only reason to do so is to get some of the distortion of the tube. This is simply because in the end, you're going to have to use an opamp or the like to drive that comparitor input (which would be used anyway if the tube wasn't there).

You don't need a lot of gain in the input buffer. You might get a little bit of gain out of it (for example we get a gain of 2, IOW 6dB, out of ours) but its mostly there to drive the comparitor.

At that point the tube's distortion will dominate the distortion signature of the class D circuit if the latter is at all competent. Since the ear interprets distortion as tonality (in the same way you can tell the difference between a fiddle and a Strativarius), intentionally introducing distortion doesn't make sense if you want the amp to be transparent. It might be helpful if the amp has a problem with distortion that is unpleasant to the ear (such as higher ordered harmonics). So I see using them as a band-aid.

On top of that the tube will fail. So it becomes a reliability issue and a variable as to how the amp will sound, since tubes of the same type and even manufacturer and run can sound quite different.

 

[Holmz]

Srajan is writing in a foreign language (English). I cut him slack on his writing.

This reminds we of when Zelenskyy was getting the grilling from the reporter.
I laughed and said, “Costume”.
The Mrs said, “English is his third language.”
(The word was totally correct, and ideal in the context.)

I do like his writing on equipment that I am considering, but it is written in a way similar to an astrology piece.

 

[Dinkydau]

@Atmasphere

What would you advise for speaker cables with these amplifiers? I have purchased a pair, and based on your recommendation I found elsewhere I am using mogami 2549 XLR interconnects with them. It seems your amplifiers work a bit different than most, as the interconnect makes less difference, though I haven't done any tests yet to hear that for myself.

Do speaker cables still matter a lot? Is it best to keep them as short as possible?

Also a comment about burn in: I have had a really bad experience with cable burn in / settling earlier this year. When I got the amps I had to move my speaker cables of course, so I expected some settle time. For some reason the first two days it sounded very nice, easy to listen to, contrary to my earlier experience with moving cables, which resulted in bad sound within an hour. But after two days the sound became fatiguing, exaggerated highs, no "flow". So now I'm not sure what exactly contributes to this, whether it's the amplifiers or the cables or both. If you have anything to say about this subject I would highly value your opinion.

 

[Atmasphere]

@Atmasphere

What would you advise for speaker cables with these amplifiers? I have purchased a pair, and based on your recommendation I found elsewhere I am using mogami 2549 XLR interconnects with them. It seems your amplifiers work a bit different than most, as the interconnect makes less difference, though I haven't done any tests yet to hear that for myself.

Do speaker cables still matter a lot? Is it best to keep them as short as possible?

Also a comment about burn in: I have had a really bad experience with cable burn in / settling earlier this year. When I got the amps I had to move my speaker cables of course, so I expected some settle time. For some reason the first two days it sounded very nice, easy to listen to, contrary to my earlier experience with moving cables, which resulted in bad sound within an hour. But after two days the sound became fatiguing, exaggerated highs, no "flow". So now I'm not sure what exactly contributes to this, whether it's the amplifiers or the cables or both. If you have anything to say about this subject I would highly value your opinion.

You might want to check the phase and make sure you got the connections right. That is always my first advice.

I've found the class Ds are far less sensitive to speaker cables than our tube amps. But nevertheless I recommend keeping speaker cables as short as possible, especially if the speakers are low impedance. At low impedances speaker cables can be quite critical. This is why monoblocks with a balanced input can be an advantage as that allows for short speaker cables, with long interconnects. As long as your preamp supports AES48, the interconnect cables will have little sonic impact. In this way you can minimize cable interaction with the system.

 

[Dinkydau]

Thanks for the reply. I will try a few different short speaker cables, starting with mogami as those are cheap and apparently their speaker cables are pretty good too.

If the issue doesn't sound familiar it's probably not related to the amplifiers. The phases are correct, that's something I checked, but there may be other problems because there's always been some an intermittent kind of noise or unclarity (also before I had these amps).