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Class D Switching Power Amplifiers and Power D/A conversion

Anaview AMS0100-2300 build
Anaview AMS0100-2300 build
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Old 17th February 2015, 02:02 PM   #11
Sebollo001 is offline Sebollo001  Argentina
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Hi Ssmith,

Thank you very much for your comments/feedback regarding this very interesting Anaview power module. I think your findings pretty much agree with two comments about exactly the same setup, built by Finnish professional speaker manufacturer Amphion. They call it the AMP100.

In the following link, you can find some comments from an audiophile point of view:
6moons audioreviews: Amphion One18


In the next link, more comments and a comparison against the Ncore NC400 module, from a professional sound engineer:
https://www.gearslutz.com/board/high...d-test-87.html (read post No. 2591)

With the components you currently have on hand, you can create a very versatile setup:

1 - For good CD recordings, DSD, SACD, Vinyl, or for detail analysis:

TEAC DAC -> (XLR) -> Anaview Amps

2 - For a warmer, more forgiving sound, or bad recordings where you are ready to sacrifice some neutrality:

TEAC DAC -> (RCA) -> Audio Note preamp -> (RCA) -> Anaview Amps

So without changing a cable run, just moving a switch, you can get two types of experiences. This setup would please the "detail" hungry, as well as the "tone" hungry audiophile.

Im currently using a pair of Anaview AMS1000-2600 power modules in BTL mode driven directly by a Benchmark DAC2 in balanced configuration. In the future I may be interested in adding a tube preamp or buffer, to gain some versatility and explore the tone possibilities beyond the current neutrality of the sound.

For such reason, I'm very interested in your tests with the new input buffers, as well as more feedback regarding the sound of your tube preamp (Output Impedance around 2 KOhm) directly connected to the amplifiers (Input Impedance from 1,3 to 13 KOhm).

BTW I think the matching between your TEAC DAC and the Anaview modules is already excellent. An input buffer will probably do nothing or may even subtract transparency to the signal. The only issue in this case MAY be the digital volume control, but it depends on the listening levels you normally use.

Thanks again!
Sebastian
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Old 17th February 2015, 07:02 PM   #12
Julf is offline Julf  Europe
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Quote:
Originally Posted by Sebollo001 View Post
In the next link, more comments and a comparison against the Ncore NC400 module, from a professional sound engineer:
https://www.gearslutz.com/board/high...d-test-87.html (read post No. 2591)
Interesting, considering the nc400 seems to have better specs. What is teh topology of the Amphion design? Is the output choke included in the feedback loop?
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Old 17th February 2015, 09:56 PM   #13
Sebollo001 is offline Sebollo001  Argentina
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Hi Julf,

I was also surprised by the comments regarding the NC400. Do you happen to own an NC400 based amplifier BTW?

However, I realize that specs are important but don't tell the whole story. Don't you agree?

For example, the NC400 has better specs than the little Anaview amplifier, but also better specs that its bigger sibling the NC1200 power module, or even than a Pass Labs XA-100.5 amplifier!!!

There's clearly much more going on in the design and performance of these amplifiers than their plain specifications.

Also, I think it is really difficult to measure real life performance. For example, a THD vs Power @ 6,65 Khz chart won' t tell you how the treble is distorted when at the same time there's a high power bass signal being amplified. Typical case of a low key piano note, with high pitch attack and deep bass.

I have a theory as why these Anaview modules sound so transparent and detailed. I can be wrong, but I think is related with the lack of an input stage or buffer.

The NC400, as a DIY friendly module, already includes a discrete input stage that allows the user to match the amplifier with all kind of preamps, with a wide range of output impedances, or even passive volume control circuits.

As good as this discrete input stage is, and like every electronic circuit, it also introduces distortion. There's always a trade off, no free lunch here.

In fact, the NC400 THD specifications are probably measured without considering the input stage, only the power module, same as the NC1200 specs that probably don't consider the IC input stage (which is easily removed to allow OEMs to build their own front end circuitry).

By not including an input stage, the Anaview amplifiers seem to be more OEM oriented. This fact presents a challenge and an opportunity to the DIYer. On one hand, improper impedance matching with the preamp can lead to channel imbalance and premature LF rolloff. On the other, using the right preamp can lead to the highest level of detail and transparency.

This might explain the reviews and comparisons mentioned in my previous post.
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Old 18th February 2015, 06:30 AM   #14
Julf is offline Julf  Europe
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Quote:
Originally Posted by Sebollo001 View Post
I was also surprised by the comments regarding the NC400. Do you happen to own an NC400 based amplifier BTW?
Yes.

Quote:
However, I realize that specs are important but don't tell the whole story. Don't you agree?
Depends on the specs.

Quote:
For example, the NC400 has better specs than the little Anaview amplifier, but also better specs that its bigger sibling the NC1200 power module, or even than a Pass Labs XA-100.5 amplifier!!!
Yes. I think all 3 are better than our ears and our speakers.

Quote:
Also, I think it is really difficult to measure real life performance. For example, a THD vs Power @ 6,65 Khz chart won' t tell you how the treble is distorted when at the same time there's a high power bass signal being amplified. Typical case of a low key piano note, with high pitch attack and deep bass.
The frequency of the high power signal won't matter - it is the power, not the frequency, that is important. If you have additional HF distortion when the amp is heavily loaded, it won't matter if the load is at 50 Hz or 5000 Hz. Thus measuring the THD at 6.65 KHz at full power tells you what happens to the treble when there is a simultaneous high power signal.

Quote:
I have a theory as why these Anaview modules sound so transparent and detailed. I can be wrong, but I think is related with the lack of an input stage or buffer.
The input stage is the equivalent of one preamp stage. Are you saying that using a preamp lets down current class D power amps?

Quote:
In fact, the NC400 THD specifications are probably measured without considering the input stage, only the power module
As far as I know the nc400 measurements are for the complete module, including the input stage.
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Old 18th February 2015, 08:50 AM   #15
ssmith is offline ssmith  Kenya
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Looking at those links, I can understand that the Anaview may be preferred over the nc400 in certain applications -- in particular studio/mastering and nearfield listening. Certainly the absence of a buffer stage may provide added transparency (I'm guessing here), the power is more than adequate for nearfield, and the low impedance input is a non-issue with many modern DACs. Plus the modules are significantly cheaper, with the PSU built in -- not a trivial consideration for a manufacturer.

The absence of a buffer has its pro and cons. In some systems it may not need one, providing the resulting blindingly-accurate sound meets the taste of the listener. In my situation, running it direct from the DAC, there's nothing wrong with the sound but it's just not quite my taste -- although I will revisit this configuration once the system has settled in and may change my mind.

But when dealing with certain preamps/long cable runs, it may benefit from a buffer, providing for added build complexity.
Even then, the absence of a buffer also provides for some flexibility -- the builder can go for transparency (I'll be trying a diamond buffer -- and will then experiment with various preamps) or tone (why not insert a tube input stage?).
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Old 18th February 2015, 09:11 AM   #16
Julf is offline Julf  Europe
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Quote:
Originally Posted by ssmith View Post
Plus the modules are significantly cheaper, with the PSU built in -- not a trivial consideration for a manufacturer.
This is probably the major factor.

Quote:
the builder can go for transparency (I'll be trying a diamond buffer -- and will then experiment with various preamps) or tone (why not insert a tube input stage?).
Or use DSP...
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Old 18th February 2015, 05:36 PM   #17
ssmith is offline ssmith  Kenya
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Originally Posted by Julf View Post
Or use DSP...
Precisely what I intend to play around with at some point
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Old 18th February 2015, 05:49 PM   #18
ssmith is offline ssmith  Kenya
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Quote:
Originally Posted by Sebollo001 View Post
For such reason, I'm very interested in your tests with the new input buffers, as well as more feedback regarding the sound of your tube preamp (Output Impedance around 2 KOhm) directly connected to the amplifiers (Input Impedance from 1,3 to 13 KOhm).
Hi Sebastian,
Many thanks for your comments!
At the moment, with the tube preamp directly feeding the unbuffered inputs of the Anaview in SE, my ears do not notice any issues and the sound I'm getting is very pleasing.
However I'm looking forward to the test with the diamond buffers -- I have all the parts and am just waiting on the boards from Per-Anders (they were out of stock). Assuming my SMD soldering goes without a hitch they will hopefully be installed in 3-4 weeks from now.
One major pleasure I'm getting with these amps is just having them on all day and not worrying about the bill!!!
all best, ssmith
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Old 18th February 2015, 08:45 PM   #19
Sebollo001 is offline Sebollo001  Argentina
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Quote:
Originally Posted by Julf View Post
Yes. I think all 3 are better than our ears and our speakers.
We can think that within their spec limits, all 4 (including the Anaview) are better than our ears and our speakers.
Quote:
Originally Posted by Julf View Post
The input stage is the equivalent of one preamp stage. Are you saying that using a preamp lets down current class D power amps?
No. As you said, the input stage is similar to one preamp stage, and main purpose is to adapt impedances. So, if you already have a good matching preamp and the interconnects are not long, why add another stage to the chain? I tend to think that in this case, less is more.
Quote:
Originally Posted by Julf View Post
As far as I know the nc400 measurements are for the complete module, including the input stage.
It is not clearly specified in the NC400 datasheet.
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Old 18th February 2015, 08:57 PM   #20
Sebollo001 is offline Sebollo001  Argentina
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Quote:
Originally Posted by ssmith View Post
At the moment, with the tube preamp directly feeding the unbuffered inputs of the Anaview in SE, my ears do not notice any issues and the sound I'm getting is very pleasing.
Thanks for the feedback ssmith! This is great news! You are already getting excellent results, even without having the best impedance matching. This encourages me (and probably other Anaview power module owners), to try tube preamps directly connected to the modules.
One potential issue that has not been addressed yet with this modules, is the same tube preamp directly connected to the module, but the later configured in 2 CH mode, where the input impedance is not only low, but asymmetric between channels.
Rgds,
Sebastian
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