PA-1 compared with BasX-A300 - greater clarity

[whitwye]

Sept 23, 2020 13:37:29 GMT -5 garbulky said:

Check this out on page 7 and especially page 24 for the PA-1's ICE module.
"Output Stage
The output stage is a full bridge topology with a
2 nd order filter, thus the power output on the
terminals Vo+ and Vo- is balanced. The filter design is a part of the proprietary HCOM topology and has been chosen as a compromise between demodulation characteristics, efficiency and filter compactness"
"Warning: The balanced speaker outputs are both “hot” with a common-mode DC level equal to VD/2
(27.25V). Shorting one of the terminals to ground will cause high stress to the module and
should be avoided. Balanced probes should always be used for monitoring and measurements. "

app.efo.ru/storage/ice/icepower300asc_datasheet_1_2_20150204.pdf

Cool. The link's not working just now, so appreciate the quotation. So then both speaker wires are hot, as if this were a 220 household AC circuit rather than 110, and the speakers just aren't grounded.

Does this imply that the similar guts in the XTZ EDGE A2-300, although fed by RCA inputs, produce balanced outputs to the speakers?

[garbulky]

Sept 23, 2020 16:52:57 GMT -5 whitwye said:

Sept 23, 2020 13:37:29 GMT -5 garbulky said:

Check this out on page 7 and especially page 24 for the PA-1's ICE module.
"Output Stage
The output stage is a full bridge topology with a
2 nd order filter, thus the power output on the
terminals Vo+ and Vo- is balanced. The filter design is a part of the proprietary HCOM topology and has been chosen as a compromise between demodulation characteristics, efficiency and filter compactness"
"Warning: The balanced speaker outputs are both “hot” with a common-mode DC level equal to VD/2
(27.25V). Shorting one of the terminals to ground will cause high stress to the module and
should be avoided. Balanced probes should always be used for monitoring and measurements. "

app.efo.ru/storage/ice/icepower300asc_datasheet_1_2_20150204.pdf

Cool. The link's not working just now, so appreciate the quotation. So then both speaker wires are hot, as if this were a 220 household AC circuit rather than 110, and the speakers just aren't grounded.

Does this imply that the similar guts in the XTZ EDGE A2-300, although fed by RCA inputs, produce balanced outputs to the speakers?

Not necessarily. That one is a stereo amp, so I don't know if that one is balanced.
Also if it's rca inputs, it's likely not going to be using a fully balanced signal path. You lose the fully balanced signal at the rca inputs. You can use an XLR splitter and use them on both the PA-1 and XTZ though I don't know if it affects it if one is balanced and the other is not.

[leonski]

Exactly what I said. DO NOT ground either speaker lead on these modules. Or cross connect in ANY fashion with another module....

Some B&O moduels have POWER OUT which can be used for Unpowered moduels of same or LESSER power output.


The note of Full Bridge is just one of the 2 topoloities used in D amps. Half Bridge being the other. ALL have that filter on the output which is the source, IMO of many 'D' amp
problmes.
Phses shift caused by such filters along with speaker impedance sensitivity. I saw one 'D' amp from another builder advertised as 'Load Invarient'....but they limited the frequency response to 20khz.
Not to mention time at power limits where if exceeded you can damage such filters.     

I've seen square wave output photos from 'D' amps and the 10khz version is awful. A huge SAWTOOTh along the top of the squarewave is the power frequency......you can count the 'bumps' and do the math.

THAT'S why all the 'improvements' in 'D' amps are mainly a non-starter. Tech hasn't changed. Physics hasn't changed. Marketing guys are busy.    The main emphasis is on doing the same or better for LESS COST.

I'll bet the parts count on the new amps is 20% less than the originals...if not even lower.    


As for single ended V balanced?   you should lose 3db or 6db level going to single ended.   Those kinds of conversions are usually pretty good.....so not to worry.  

[whitwye]

Sept 23, 2020 17:26:58 GMT -5 garbulky said:

Sept 23, 2020 16:52:57 GMT -5 whitwye said:

Cool. The link's not working just now, so appreciate the quotation. So then both speaker wires are hot, as if this were a 220 household AC circuit rather than 110, and the speakers just aren't grounded.

Does this imply that the similar guts in the XTZ EDGE A2-300, although fed by RCA inputs, produce balanced outputs to the speakers?

Not necessarily. That one is a stereo amp, so I don't know if that one is balanced.
Also if it's rca inputs, it's likely not going to be using a fully balanced signal path. You lose the fully balanced signal at the rca inputs. You can use an XLR splitter and use them on both the PA-1 and XTZ though I don't know if it affects it if one is balanced and the other is not.

Found the link to the current spec sheet. If I'm reading that right the outputs are balanced, apparently no matter the inputs: link to PDF is at icepower.dk/products/amplifier-power-modules/as-series/#comparison-chart. The AS1 is just the ASC renamed. My surmise is the ETZ has two of these off a common power supply. The doc also claims no loss of gain when feeding an unbalanced signal in.

Update: Yeah 2 amp sections, the second parasitic on the 1st's power supply (an A1 hanger module attached to the AS1). Ref: audiophilestyle.com/ca/reviews/a-class-d-exploration-and-comparative-review-of-ps-audio-wyred-4-sound-and-xtz-r795/.

Whatever, both the PA-1 and XTZ A2-300 grab the speakers so that I can feel the percussion in my chest, at quite moderate volume, and hear details from stringed instruments that were just a wash with the otherwise fine-sounding BasX amps into the same speakers. For instance, listening to Revolver the signature of the Vox amps is clear through the ICEpower-based amps. It's a more generic-sounding guitar sound through the BasX amps. (Yeah, I had a Vox back when. The sound takes me back.)

[garbulky]

Sept 23, 2020 18:03:16 GMT -5 whitwye said:

Sept 23, 2020 17:26:58 GMT -5 garbulky said:

Not necessarily. That one is a stereo amp, so I don't know if that one is balanced.
Also if it's rca inputs, it's likely not going to be using a fully balanced signal path. You lose the fully balanced signal at the rca inputs. You can use an XLR splitter and use them on both the PA-1 and XTZ though I don't know if it affects it if one is balanced and the other is not.

Found the link to the current spec sheet. If I'm reading that right the outputs are balanced, apparently no matter the inputs: link to PDF is at icepower.dk/products/amplifier-power-modules/as-series/#comparison-chart. The AS1 is just the ASC renamed. My surmise is the ETZ has two of these off a common power supply. The doc also claims no loss of gain when feeding an unbalanced signal in.

Update: Yeah 2 amp sections, the second parasitic on the 1st's power supply (an A1 hanger module attached to the AS1). Ref: audiophilestyle.com/ca/reviews/a-class-d-exploration-and-comparative-review-of-ps-audio-wyred-4-sound-and-xtz-r795/.

Whatever, both the PA-1 and XTZ A2-300 grab the speakers so that I can feel the percussion in my chest, at quite moderate volume, and hear details from stringed instruments that were just a wash with the otherwise fine-sounding BasX amps into the same speakers. For instance, listening to Revolver the signature of the Vox amps is clear through the ICEpower-based amps. It's a more generic-sounding guitar sound through the BasX amps. (Yeah, I had a Vox back when. The sound takes me back.)

View Attachment

Great description of the sound. Very similar to my impressions.

[whitwye]

Just learned of an instrument to explore sound I'd never heard of, the CymaScope, which produces visual representations of patterns of sound (https://www.cymascope.com/cymascope.html). What might these do for revealing aspects of reproductive fidelity?

[KeithL]

Very interesting...

It appears to be a way of visualizing sound waves by observing the movements in a pool of water.

The website is also very interesting - and some of the resulting artwork is very attractive...

And I am a big fan of science-based artwork...

However, to be honest, it interests me more as a new art-form than as a new field of sound science.

I should point out that we already have many extremely useful and precise ways of imaging sound.

For example, you can see the actual shape of the electrical waveform on an oscilloscope...

And you can see the precise frequency components of a complex sound using a spectrum analyzer...

And you can make extremely precise observations of the phase relationships between multiple channels using what we used to call a vectorscope.

(That's something that used to work very well - and was trivial to do - with old-style analog oscilloscopes.)

And you can check out many of those options for yourself using readily available digital tools - including REW.

I did notice that some of the articles they referenced crossed the line from science or art into "metaphysical mumbo jumbo".

Yes, a water molecule will vibrate for a while if you hit it with the right sort of energy (think MRI)

And, yes, if you drop a pebble in a pond, you can figure out afterwards where it landed by analyzing the patterns in the resulting ripples.

And, yes, the resulting ripples most certainly can also result in some very attractive artwork.

And, yes, impurities in the water will alter those patterns, quite possibly in ways which can provide useful information.

However that does not imply or infer that water has some sort of "mystical hitherto-unsuspected memory properties".....

(Any more than we would suggest that a bell or a tuning form "remembers being struck"...)

To be honest I am not at all convinced that we lack information about audio signals or fidelity.

We can analyze an audio signal far more precisely and accurately than we can hear it with our ears.

(An interesting side note there: Some insects can directly hear the actual direction of a sound wave; we humans cannot.) 

The problem is that we have plenty of information, but our ability to interpret it seems to have lagged somewhat behind.

And that's something we need to work on.

Sept 24, 2020 14:39:04 GMT -5 whitwye said:

Just learned of an instrument to explore sound I'd never heard of, the CymaScope, which produces visual representations of patterns of sound (https://www.cymascope.com/cymascope.html). What might these do for revealing aspects of reproductive fidelity?

[KeithL]

I agree for the most part - except that I would say that the tech HAS in fact changed.

Note that I'm taking a LOT of liberties in the interest of simplification here....

All Class-D amplifiers basically work by modulating some sort of square wave.

This digital signal is modulated by the audio signal.

The digital portion of the signal is then filtered out - leaving the desired audio signal.

(Somewhat like how you might imagine a "power DAC" would work.)

A typical Class D amplifier from a few years ago might have used a digital carrier frequency of 120 kHz or 200 kHz.

Because this isn't that far above the range of audio frequencies the filter required to reconstruct the audio signal tends to be intrusive.

The main trade-off is between effective filtering, efficiency, and sensitivity to load impedance.

This is why historically many Class D amplifiers tended to work quite differently depending on the impedance of your speakers.

Ideally, this situation can be almost entirely eliminated by simply using a much higher frequency for the digital portion of the process.

This makes filter design much simpler by providing a wider separation between the frequencies you want and the ones you want to filter out.

The catch there is that we are using square waves - which are actually made up of an infinite series of harmonics.

In order to make a 100 kHz square wave that actually appears square you need a frequency response extending into the high mHz.

If you fail to provide this, your square waves have rounded edges, efficiency drops, things run hotter, and a variety of other problems occur.

(The reason those old Class D amps ran at only 120 kHz was because it was hard to find high-power switches that worked well above that.)

Modern technology has brought us high-powered switches that work reliably at much higher frequencies.

(Some modern Class D amplifier modules use gallium-arsenide switches that operate in the gHz range.)

This, in turn, allows us to build Class D amplifiers that run at much higher frequencies.

Which, in turn, has allowed filters to be used that work much better, and work well with a much wider range of load impedances.

It has also made possible a variety of improvements in terms of feedback and timing.

Which, in turn, has lead to improvements in terms of lower distortion, and higher damping factors at audio frequencies.

Also, to be quite honest, our engineers have had a LOT more practice...

Designing a Class D amplifier has gone from an arcane science to something they actually teach in engineering school...

Therefore, new techniques are discovered, and old mistakes are avoided...

We no longer have to compromise and decide which flaws and shortcomings we can live with...

In technology parlance... Class D technology is now mainstream...

Sept 23, 2020 17:42:27 GMT -5 leonski said:

Exactly what I said. DO NOT ground either speaker lead on these modules. Or cross connect in ANY fashion with another module....

Some B&O moduels have POWER OUT which can be used for Unpowered moduels of same or LESSER power output.


The note of Full Bridge is just one of the 2 topoloities used in D amps. Half Bridge being the other. ALL have that filter on the output which is the source, IMO of many 'D' amp
problmes.
Phses shift caused by such filters along with speaker impedance sensitivity. I saw one 'D' amp from another builder advertised as 'Load Invarient'....but they limited the frequency response to 20khz.
Not to mention time at power limits where if exceeded you can damage such filters.     

I've seen square wave output photos from 'D' amps and the 10khz version is awful. A huge SAWTOOTh along the top of the squarewave is the power frequency......you can count the 'bumps' and do the math.

THAT'S why all the 'improvements' in 'D' amps are mainly a non-starter. Tech hasn't changed. Physics hasn't changed. Marketing guys are busy.    The main emphasis is on doing the same or better for LESS COST.

I'll bet the parts count on the new amps is 20% less than the originals...if not even lower.    


As for single ended V balanced?   you should lose 3db or 6db level going to single ended.   Those kinds of conversions are usually pretty good.....so not to worry.  

[whitwye]

Sept 24, 2020 16:32:14 GMT -5 KeithL said:

Very interesting...

It appears to be a way of visualizing sound waves by observing the movements in a pool of water.

The website is also very interesting - and some of the resulting artwork is very attractive...

And I am a big fan of science-based artwork...

However, to be honest, it interests me more as a new art-form than as a new field of sound science.

On the one hand, I tend to agree.

On the other, I learned of this device from an email list where Brian Josephson mentioned it approvingly. He both has a Nobel and entertains ideas at and beyond the edge of science: en.wikipedia.org/wiki/Brian_Josephson.

[KeithL]

New ways of visualizing things can be extremely useful and informative.

And they can often enable we limited humans new ways to recognize and make use of previously confusing or hidden information.

But... they can also be a distraction.

There is also a sort of middle ground where certain types of visualizing things may work for some people and not others.

For example, if you're "color/visually oriented", then showing a sound wave as patterns or colors may make the information more accessible to you.

But, if you're more used to numbers and statistics, the opposite may be true.

I should point out that people with either type of mind may have difficulty seeing things that are not easily seen "using their mode of thought".

For example, an awful lot of audiophiles lately insist that "all DACs must sound the same"...

They base this conclusion on the fact that most good modern DACs have admirably low levels of noise, THD, and frequency response issues.

However they seem incapable of considering that those same DACs have major differences in their TIME BASED response characteristics.

(Their impulse response is very different - which is very obvious if you look at a different sort of display or measurement.)

I have to admit that I also have one major issue with this distinction when it comes to the audio field...

And this is almost certainly significantly due to the fact that my background is scientific rather than artistic...

That distinction is what some people have come to refer to as "the woo-hoo factor"...

(I'm going to pick on vacuum tubes as an example because, as far as I am concerned, they really are simply an excellent example.)

In terms of technical performance vacuum tubes have been surpassed some time ago by solid state electronics for most applications.

Specifically, when used in audio amplifiers, tubes have higher distortion and higher noise.

And the output transformers that are virtually unavoidable in order to connect power tubes to loudspeakers make matters worse.

Along with distortion, they add phase shift, and cause some unfortunate impedance issues, which limit the amount of feedback that can be used.

Therefore, in technical terms, there is nothing whatsoever that tube amplifier can possibly do to "produce better imaging than solid state gear".

What they do is to produce complex phase anomalies that many people find sound pleasant and interpret as "great magical imaging".

They may, in essence, "swirl the apparent locations of sound sources around in ways that sound both pleasant and 'natural' ".

And, as a result, they may produce an effect that sometimes sounds more like live sound...

But they are doing so in the same way that yellow sunglasses can deliver a very realistic impression of a bright sunny day.

(Quite possibly more so than glasses that actually allow you to see the real colors accurately.)

The problem is that people with an artistic mind-set sometimes confuse "flaws that end up sounding great" with "things technically done better"...

(And this can be a real problem when you're honestly trying to figure out WHY they sound the way they do.)

(Just as some artists may insist that "hand mixed paint is purer" - rather than admit that they like the way the lumps look in hand-mixed pigments.)

That gadget is a really interesting and creative way of visualizing waveforms using a liquid as a "visualization medium"...

And, because of that, it may enable us humans to better visualize certain complex things which we previously had problems with...

And, yes, that may even enable us to notice patterns that we failed to see before...

However, at the same, time, it may obscure other details, or even create the illusion of details that are merely artifacts of the technology.

But I do NOT believe it will actually reveal (or prove) hitherto magical properties of water that were until-now unknown...

(But, as I said, it's enough for me that it looks very cool... )

Sept 25, 2020 10:33:48 GMT -5 whitwye said:

Sept 24, 2020 16:32:14 GMT -5 KeithL said:

Very interesting...

It appears to be a way of visualizing sound waves by observing the movements in a pool of water.

The website is also very interesting - and some of the resulting artwork is very attractive...

And I am a big fan of science-based artwork...

However, to be honest, it interests me more as a new art-form than as a new field of sound science.

On the one hand, I tend to agree.

On the other, I learned of this device from an email list where Brian Josephson mentioned it approvingly. He both has a Nobel and entertains ideas at and beyond the edge of science: en.wikipedia.org/wiki/Brian_Josephson.

[leonski]

As a Science Guy I demonstrated interference patterns in a tub of water.....Use light to project a SHADOW on the bottom of the tub....much easier to see that way.
generate 2 sets of waves....I'd use the round part of a TeaSpoon and you'll see constructive and destructive interference.
With a helper? Have your helper generate a low frequency wave. You can than vary YOUR frequency to get various effects. Have some different sized objectsin the water so you can
see effects of long V short wavelength on the reflection or diffraction of the waves.
If you put an object in the path of the waves you can also see reflection and diffraction. Wavelenght which is longer or shorter will each react differently when reaching an obstacle.

www.youtube.com/watch?v=Jqm4f55soJQ

you can also simulate the classic Double Slit Experiment by this method, but do not get 'quantized' results.

As for D amps? Still all are either full or half bridge. And so what if the switching frequency is not multiples of the original 200khz? That DOES help, of course, and may make the reconstruction of the original wave easier.

One real neat ARTISTIC / PHYSICS demonstration is SAND on a drumhead. Check out THIS video.

jarphys.wordpress.com/2013/11/16/sand-vibration-art/NO Fundamental changes.

[whitwye]

A curious aspect of the visual thinking versus language-based thinking debate is that it's been known since the 70's that people have separate working memories for the two. We can typically focus on between 5 and 7 items at a time, in each, implying they are as it were different circuits or modules. Each working memory reaches its capacity separately. Being maxed out on the number of verbal ideas you're juggling doesn't prevent bringing more into current focus visually, and vice versa.

In physics they say the two great theories, relativity and quantum physics, are fundamentally at odds in ways that are beyond my competence. Einstein's thought experiments were visualizations; many quantum physicists insist visualization is counter productive, they prefer to "just do the math." Not sure what that has to do with the incompatibility of the theories though....

Back to the immediate topic: One thing that's evident with the better amps and speakers, at least to my ears, is how some of the special effects on my Yamaha pre-pro, which were sometimes of use with some source materials, are now counter-productive -- not only the bizarre reverb effects claiming to reproduce various performance halls, but also the "enhanced" mode for compressed materials. That "enhanced" mode made Spotify's Ogg Vorbis compressed music sound more real through the Basx. Through the PA-1s, enough more of the original sound comes through that that's no longer the case. Similary the DAC in the ERC-3, which before was clearly preferably to the Yamaha's DAC for CDs in the higher frequencies, but not quite as musical in the bass end of the spectrum, now shows its superiority down into the bass range too. My guess is that the Yamaha's DAC treatment is adding extra harmonics, which creates more realism only if some other stage is stripping them out to some degree, and the PA-1s lose less of such detail than the BasX does. Similarly for those reverb effects, clearer amplification presents more of the original reverb from studio or performance venue, so adding more is too much, while if those are lost in the chain it's a corrective.