"Boutique" opamps from chinese vendors. Anyone tested?

[thor.zmt]

Really?

Really. Of course. It is EE101.

Is it not the purpose of the earth to provide low impedance path to external noise currents?

Not really. It is primarily a safety feature.

Now, let's look again at the diagram I posted:



Let's remember EE101, something called Kirchoffs law.

The sum of all currents in any circuit must be zero.

Now lets look at "power outlet" node. Let us inject 1A into this node earth from outside the system shown.

What is effect of this 1 Ampere current on the loop shown? Zero. It does not impact anything.

Except for electrical safety and getting burned to crisp if you touch the gear you could elevate the earth node (and L/N) by 1kV and the change in the current loops shown would be again zero.

QED. The wiring past the point "Duplex Outlet" does not participate in the network that interests us and has any bearing on the audio quality or is able to cause fidelity impairments.

In terms of your diagram, will low impedance (thicker) earth wire not allow the hum/noise currents to circulate between the two devices even easier?

Yes.

And it will reduce the portion of the current that travels via the signal connection and will reduce the interchassis voltage differences, which is what we ultimatley sense as "signal".

Let us assume that the lower part of the loop is truly zero Ohm and zero nanohenry.

Let us assume that the error current from live into earth at one of the two devices is oo Ampere.

What is the error signal present between two grounds in the presence of an infinite error current in one or both chassis IF the mains cable part etc. is 0 R & 0nH?

Thor

 

[zamproject]

Plus, if you call that expensive and not suited for normal living environments I would consider that your poverty is severe. It would look swell in my living area.

Is that a joke I don't get ? shame on you if not...

I have a thought for all the average -poor- musician around the world that probably need to cut themself for 20+years to be able to buy a house for this amount.
I'm sure your kind of pple enjoy listening them on a 100k speaker...

If you can buy it, good for you, but mocking pples that can't, what a disrespect !

 

[thor.zmt]

Signal -to-noise ratio is a figure of merit that sometimes allows comparison, but it actually pertains to a notion of power.

I am simply talking about how it measured. Simple physical measurements of physical quantities defined in identical ways.

Your reasoning is that teh amplitude is limited to 32k

Is entirely true and supported by any textbook on the matter.

You know well that the numerous imperfections in the system would end in results that are notably poorer than the mathematical expectations.

That is another issue.

My issue is to normalise two numbers that originate from different sets of definitions and reference levels and are thus not directly comparable and WORSE are highly misleading.

I noticed you are very proud of your wealth

I am poor.

And no, I would not buy the B&O speakers, but I probably could, if I determined that I needed them.

Reverberant field is one thing. Emphasis/attenuation of eigentones is another.

Reverberant field is down to directivity.

Room modes are down to coupling of the speaker.

A gradient source (cardioid) will couple differently to room modes than a velocity source (dipole) and a pressure source (monopole).

A velocity source will maximally couple to room modes when placed in a pressure minima which is a velocity maxima (e.g. middle of the room where few people place speakers).

A pressure source will maximally couple to room modes when placed in a velocity minimum which is a pressure maxima (eg soffit mounted in the wall or against the wall where many people place speakers).

A gradient source will always couple poorly no matter where it is placed. So a gradient source will excite room modes least.

Although teh linear-phase portion can be EQ'd, tehre is still something that cannot be solved electronically. Attemps to use active slapback cancellation have never been met with success.

We do not do this:



We aim speakers at oblique angles:



Sound radiated into directions that cause slap echo are significantly reduced by the directivity of the speaker.

Note, all this hardly new, it is documented since the mid 80's and I am shocked that it is not better known among professionals in the field.

What do you mean? How can you test a x-over without speakers?

You sum the outputs back into a single channel with all outputs for a given channel combined, no EQ or level correction.

Listen to the summed signal. Now you are listening to what the crossover does compared to a bypass.

You can measure a x-over, but it won't tell you which one sounds good and which one bad.

No. But you can, for example, adjust your crossover points to be able to get good results using a crossover that is less audible or less objectionably audible than another.

You remind me of a customer that goes to a show and asks for listening to a specific pair of loudspeakers. The Salesman says :" I'm sorry sir, this is a silent show, but if you want I can make you listen to them on headphones".

No, we are talking about the effect of the crossover on the sound IN ISOLATION, not the effect the crossover has on the sound of multiple drivers, amplifiers etc they are connected to.

So to speak a foundation test where we just evaluate the crossover. Like it is in a way done here:

RANE Commercial - Knowledge Base

Drivers, directivity etc. are all ignored.

The next step would be to listen to these theoretical crossovers using "perfect" coincident, time aligned and omnidirectional in free space.

Thor

 

[sahib]

I was enjoying your posts up until now when you started bordering on being obnoxious. You do not worry about the electrical principals. I know them well

According to you, we make the earth wire impedance zero and there is no voltage drop across it and that part is taken care of.

We then make the signal ground wire impedance zero (which you missed) and there is no voltage drop across it either and that is taken care of too.

Then the noise currents developed on the equipment chassis have magically disappeared? is that it?

I have a CD player with a built in amplifier and it is experiencing noise. It is not interfaced with any other equipment. Since, according to you, the mains earth path has no bearing on this, how is your super duper metal armoured robotic cable will help? You are talking nonsense.

 

[thor.zmt]

Is that a joke I don't get ? shame on you if not...

It is a snarky joke.

We are discussing technical principles and how they may improve the operation of speakers in rooms. Given a specific example the reaction is:

At 130+ kg and $100+k, it hardly qualifies as a speaker "that can be easily placed in normal living environments".

So my reaction is to as snarky and snide back. What do you expect?

I'd like to debate the Technology and it's merits, demitits and if, how and why this is better (or not) than your average Genelec, KRK or related monkey coffin.

Instead I get what I get.

I have a thought for all the average -poor- musician around the world that probably need to cut themself for 20+years to be able to buy a house for this amount.

My point is the technology. The technology, correctly understood, can of course be applied to much less expensive products. But if we get it dismissed as pointless because of cost and weight out of hand, this cannot happen.

I'm sure your kind of pple enjoy listening them on a 100k speaker...

I am rather acquainted with people who are very well off an in many cases have very large sum's in their music systems, to the point of having dedicated spaces etc.

A friend in Hong Kong owns a 2,000sqft industrial unit he has fitted out as listening space (and man cave) that is worth over a million USD and he has probably over a million USD in his Audio collection (calling it a system does not do justice).

So what? I'm happy for him and after I had to give up my own unit in HK, I liberally tended to invite myself to his place for whole weekends to the point that I probably spent more time there than he did.

If you can buy it, good for you, but mocking pples that can't, what a disrespect !

I felt rather mocked when technology discussions are brushed off with "it's too expensive" so I retort "you are just too poor" and that may not only apply to monetary affordability.

So I am not mocking poor people who cannot but a 120k pair of speakers, but those who sidestep discussing technology with such transparent avoidance.

Thor

 

[thor.zmt]

I was enjoying your posts up until now when you started bordering on being obnoxious.

Given that basic electronics of this are so obvious and simple, I presumed from the way you wrote I needed to refresh your memory.

We then make the signal ground wire impedance zero (which you missed) and there is no voltage drop across it either and that is taken care of too.

I did not miss that at all. Did you notice something I wrote earlier?

I use CAT6 STP for line cables one pair signal, three pairs ground, shield to shell on XLR.

Why three out of four pairs for ground and only one pair for signal (and separating XLR ground and the chassis-chassis connections)?

However that is a lot harder done to minimise the impedance of the signal cable ground loop.

It is more easily done for a mains cable to minimise the whole loop impedance.

In fact, I also recommend to break the connection between earth and signal ground completely if possible at all and using 100R/100n with a suitable diode clamp to pass electrical safety tests between signal ground and earth.

Another interesting trick is to take braided tinned copper (flat stuff) and use this to link all chassis with very low DCR and inductance. This too minimises inter-chassis potential.

All this together always makes for ghostly quiet systems without hum and birdies.

But all that is not as easy as just using a suitable mains cable, which can get us a long part of the way.

Then the noise currents developed on the equipment chassis have magically disappeared? is that it?

No, however the voltage dropped in the wiring past "duplex outlet" is not relevant to the system being discussed.

For the audio part of the system anything relevant stops at "Duplex Outlet".

Do you disagree? Can you illustrate how changing the common potential at "Duplex outlet" in the example changes the currents circulating in the audio related circuitry?

If of course we have two such systems connected to two such duplex outlets each with it's own 20m cable to the distribution panel and interconnect them, then we have a BIG problem, which is why we normally do not do that.

I have a CD player with a built in amplifier and it is experiencing noise.

And that noise is caused by the earth wire in the mains cable?

Or just because the design is poor?

It is not interfaced with any other equipment.

So the current loops are inside the device. And the noise originates in the device, due to either noisy power supplies or other poor inherent design.

The mains cable has no impact, because it is now relatively in the same situation as the mains wiring from "duplex outlet" to the distribution panel in our example.

Since, according to you, the mains earth path has no bearing on this, how is your super duper metal armoured robotic cable will help?

Naturally, it will not help at all. Again EE101 and Kirchoff.

No mains cable can help in your case, because the mains cable is not part of a signal/current loop that affects the audio side and cause the noise.

You are talking nonsense.

Am I? Show where.

Thor

 

[sahib]

Am I. Show where.

Thor

Everywhere.

You have a close loop circulating a noise current. You make the loop impedance zero and magically apply Kirchhoff's law and boom. the noise currents disappeared. Apply Ohm's law and see where you end up.

To stop the noise you have to bring discontinuity. That means cutting the wire. That means, removing the signal ground in one of the equipment from the chassis earth. The equipment is still compliant in terms of earth protection.

In my CD player example the noise is magnetically coupled. No internal design fault. If mains earth has no bearing then where is this current going to flow into? It will follow the path with the lowest impedance within the equipment. What is that path? The signal ground. Here we go. The noise has entered the loop.

You are talking nonsense.

 

[Newmarket]

Abbey takes objection to my assertion that, once we correctly normalise 16 bit PCM to be actually comparable with analogue systems such as LP (the specific example I used) and magnetic tape, the supposed "96dB" dynamic range of 16 Bit PCM is revealed to be 76dB (theoretically 78dB) and has much less advantage over classic analogue systems than commonly claimed.

Yeah - that was about it - the comparison thing and SNR / DR definition.

And this will the ratio of direct sound vs reflected sound, agreed?

Yes

Correct, the immediate reflection that passes your head will be integrated in the HAAS Window, so we can ignore that.

Whoa ! You want to ignore events in the HAAS window ? No !

Rest of points taken although it does seem that you are making quite a few assumptions about 'the room' shape and what might be in it.

Let us assume first a hypercardiod pattern, with the acoustic axis oriented to cross notably in front of the listener.

This means a centered listener will actually listen "off axis" and as the listener moves laterally towards a given speaker, this speaker will become actually quieter and the one the listener moves away from will become louder. At least over a reasonably wide window that reaches nearly the lateral distance between speakers.

This is usually achieved with a 60 degree or so dispersion and a 45 degree "toe in" with a standard equilateral triangle placement of speakers and listener.

The sound hitting the wall behind the centered listener will actually have most of the sound impacting significantly to the left and right of the listener, before being reflected away from the listener towards the side wall opposite from the speaker.

The sound will naturally reflect with a certain degree of diffusion, which will reduce intensity both by path length and by spreading the sound intensity across a larger area.

From the sidewall, the majority of the sound will be reflected to the wall behind the speakers, from where it will be reflected to the sidewall next to the speaker that originated it, attenuated, diffused and with a significant accumulated delay, usually sufficient to avoid the HAAS Window, and thus avoiding tonal changes, but instead being perceived as low level delay/reverberation.

Is it perfect? No.

Is it a major improvement over any old monkey coffin (never mind B*se 901 or Omni's)? Hell yeah.

Thor

 

[thor.zmt]

Everywhere.

You have a close loop circulating a noise current. You make the loop impedance zero and magically apply Kirchhoff's law and boom. the noise currents disappeared.

Nope.

I said the current can be infinite, but with zero impedance in the loop there is no voltage difference and as we use voltage signaling there can be no noise.

Thus all else being equal, less impedance in the ground "loop" reduces noise levels.

To stop the noise you have to bring discontinuity. That means cutting the wire.

That is not according to electrical code.

That means, removing the signal ground in one of the equipment from the chassis earth. The equipment is still compliant in terms of earth protection.

No, it is not. Check the relevant documentation.

You can do that, BUT you must use a clamping circuit that limits the fault voltage from all and any accessible metal parts must be less than 2.5V with 25A flowing.

A simple clamping circuit could be anti-parallel 50A diodes. They pass all agency compliance tests, I designed it into enough gear.

Even often seen earth lift switch is not "legal", unless you stand on the exceptions possible for "non consumer" equipment, but that is flimsy and may limit sales channels.

In my CD player example the noise is magnetically coupled. No internal design fault.

You mean from external magnetic field or internally from the mains transformer?

If mains earth has no bearing then where is this current going to flow into? It will follow the path with the lowest impedance within the equipment.

Correct.

What is that path? The signal ground. Here we go.

Is it? Really? Normally I find that coupling from mains transformer to chassis is greater than coupling from mains to power supply ground.
A lot depends on precise design. If we have an electrostatic screen in the mains transformer connected to chassis (good design practice re conducted emissions and guarding against other EMC issues) it will be almost the sole source of leakage.

Of course, in most cases "signal ground" = "earth".

Now where is the loop impedance lower? Signal cable or mains cable?

You are talking nonsense.

Actually, you are.

And you suggest solutions that are in violation of electrical safety requirements.

Thor

 

[thor.zmt]

Whoa ! You want to ignore events in the HAAS window ? No !

No, I am stating that sounds that arrive within the HAAS window are integrated with the first arrival sound, that is the first arrival sound appears louder.

This window is around 2mS or translated into an acoustic pathway, ~ 70cm total path.

Rest of points taken although it does seem that you are making quite a few assumptions about 'the room' shape and what might be in it.

These are reasonable assumptions.

Living rooms commonly are rectangular and if you prefer Japandi or Scandi design fairly bare, you are likely to find relatively "light" soft furniture and laminate/wooden flooring mostly bare.

In other words, the most acoustically "unfriendly" environment that we will find in what people call living environments.

Missing walls from open plan arrangements are not a big deal in our example, though adding absorptive treatment on the matching present wall or increasing distance to the present wall can reduce the remaining imbalance.

Now if you have a heavily irregular living area things get more interesting, but again, the more controlled the speakers dispersion is the more they are reduced.

Now that is strictly for relatively normal sized living spaces and not for concert halls.

These have different requirements as have open air venues and so on.

It is important to match the acoustic properties of the sound producing system to the requirements of the application, no "one size fits all" solution exists.

I think we should really take speaker related debates out of this thread.

Thor

 

[sahib]

A lot of mumbo jumbo to bamboozle.

At the end of the day it all comes down to this.

You make the earth wire zero impedance, and the noise currents cease. Bravo. I wonder why they are trying to find superconductor.

Buy my robotics mains cable and all of your ground loop problems will disappear. Sell it to some idiot who does not know better.

Incidentally. what I meant by disconnecting signal ground from earth within the equipment is to explain the discontinuity concept. If you can bring some filtering within the loop where the noise currents are shorted then that is also bringing a discontinuity.

 

[thor.zmt]

You make the earth wire zero impedance, and the noise currents cease.

Nope, Noise currents cease to matter. A small but significant difference.

And making the loop impedance lower makes the problem lower AND is the easiest measure that can be taken, out of all available measures with commercial equipment.

By my robotics mains cable and all of your ground loop problems will disappear.

I am not selling anything. What makes you think I do?

You can buy the cable from your usual industrial suppliers and assemble your own. It's cost is notional. As there are multiple actual manufacturers of the raw cable I simply described it in generic terms.

Incidentally, the cable I had prototyped with this raw cable; that was not manufactured but was instead "disintegrated" and has silly prices and which I very much disrecommend and hence cannot be purchased; did include the "safe earth lift" with diode clamps I commented on (plus the other electronics) but aimed for very low inductance in the earth path nevertheless.

Thor

 

[sahib]

Nope, Noise currents cease to matter. A small but significant difference.

What?

Do you real mean by matter the noise currents cease within zero impedance wire?

I am sorry but this is getting more surreal than Kafka now.

I'll terminate this conversation.

Edit:

Also congratulations. You make the current infinite and the voltage goes to zero. That's a new one. Just work on your maths to go beyond simple arithmetic, which you can't even get it right.

 

[thor.zmt]

What?

Do you real mean by matter the noise currents cease within zero impedance wire?

I am sorry but this is getting more surreal than Kafka now.

I'll terminate this conversation.

I agree. You deliberately and constantly misrepresent what I have written and which is very clearly stated.

This conversation has run it's course.

Thor

 

[Newmarket]

You make the earth wire zero impedance, and the noise currents cease.

tbf he hasn't claimed that the current disappears or ceases.
Just that voltage differential is low when the impedance between units is low.

For another view on this see link where supplementing the "Earth connection" by means of parallel conductors is discussed with real world installation references. The focus of the article is screen connection at both ends but it all comes together.

https://www.emcstandards.co.uk/file...oise_for_emcj_may_02_pdf_version_4_may_02.pdf

 

[thor.zmt]

tbf he hasn't claimed that the current disappears or ceases.

Some people lack what I call "moral affordability" and thus cannot integrate new information that conflicts with deeply held beliefs after first deconflicting this information by adjusting their beliefs to be compatible with such new information.

There is no way to help in this deconflicting process externally, until that time, if ever they do, such new information will be rejected regardless how much proof is provided.

Might as well shout at a wall. For disclosure, my Dad was a Psychologist with a most interesting set of fields of practice.

For another view on this see link where supplementing the "Earth connection" by means of parallel conductors is discussed with real world installation references. The focus of the article is screen connection at both ends but it all comes together.

https://www.emcstandards.co.uk/file...oise_for_emcj_may_02_pdf_version_4_may_02.pdf

Nice piece.

I observe that it already pushes 21 years. It's old enough to marry, drink, smoke and buy a semi-automatic gun!

Thor

 

[sahib]

tbf he hasn't claimed that the current disappears or ceases.
Just that voltage differential is low when the impedance between units is low.

For another view on this see link where supplementing the "Earth connection" by means of parallel conductors is discussed with real world installation references. The focus of the article is screen connection at both ends but it all comes together.

https://www.emcstandards.co.uk/file...oise_for_emcj_may_02_pdf_version_4_may_02.pdf

Just read the relevant bits. I will read the bits about their test methods/results etc.

However, what's in that paper is not what we are talking about here. First and most importantly it is about pro-audio application where you have large number of signal cables/connections.

Read here
"
[4] recommends directly bonding cable shields at both ends using 360o RF bonding techniques. It also recommends using a “Parallel Earth Conductor” (PEC) with a lower impedance than the shields, where necessary, to divert a large proportion of the power-frequency ground loop currents away from the shields and preventing them from overheating.

A PEC can be a dedicated conductor, or it can be new or existing metalwork, as long as it is bonded to the frame/chassis/enclosure of the equipment at both ends of the cables concerned (effectively in parallel with their shields).
"

I do not have to repeat what it says, but it is primarily referring to running a parallel low impedance path to take the stress from the shield.

It says nothing about the earth connection to the mains earth path or the signal ground connection to the mains earth within the equipment. Because it assumes that it is there. That's the basic requirement.

Even in this context if the mains earth has no bearing on diverting the noise currents, then the noise currents must be circulating within the system. The noise currents must flow into something. They can't just disappear in thin air.

Edit:

As I mentioned before, otherwise (if the noise currents are not flowing in to the mains earth path) you have to introduce discontinuity to the flow of the current. You can do that by either "cutting" the loop or introducing some filtering where the current is shorted.

 

[Newmarket]

I see no one positing that currents "disappear".

 

[thor.zmt]

The noise currents must flow into something. They can't just disappear.

They do not, of course.



For I noise 3 (noise current 3) to exist Vnoise (green) must exist.

For Vnoise to exist we must have Inoise 1 or Inoise 2 or both flowing. We also require a non-zero impedance in the audio cable. Many line cables can run a substantial fraction of an ohm per meter.

Getting very low ground resistance for line cables as remarked, is less easy than (for example) using a 10AWG (6mm^2) Earth connection mains cable is trivial.

According to Kirchoffs law Inoise 1 & Inoise 2 must flow out of the circuit somewhere, they "exit" via the cable to the distribution Panel. From there on they are of no further concern.

Technically speaking neither Inoise 1 or Inoise 2 are of concern either, ONLY Inoise 3 is of concern, because it is the only current that flows where it matters to the audio circuit.

One way for Inoise 3 to exist, we can for example interrupt the current loop for iNoise 1 or Inoise 2 by interrupting (lifting) the Earth, which will then redirect these currents to flow in the audio cable (which is precisely where we do not want it and where it causes noise).

The other is have a non-zero impedance earth connection in the power cords that will cause a the noise Voltage Vnoise to be non-zero and thus redirects a proportion of Inoise 1 & Inoise 2 through the audio cable ground as Inoise 3.

Inoise 3 will however not be affected in any manner whatsoever with any current flowing in the earth conductor exiting our sheet at the bottom or as noted before even a 1kV offset at that point (it's incredibly unsafe though).

Now we have another type of earth loop that indeed may require to break one current path, though it usually preferably to use a different solution.

In this case we actually have two separate circuits with separate spurs to the distribution panel or a ring mains with substantial distance between sockets and often substantial current flow from non audio appliances in either spur or through the ring mains.

This creates a substantial between the two earth pins of the two sockets which are usually at a substantial distance.

In a home environment this may be one or many powered subwoofers placed remote from the main amplifier and plugged into a convenient nearby outlet.

Lifting any of the earth is usually not permitted and the correct solution is to use long power cables on the subwoofers and to plug them into the distribution unit or outlet the Amplifier is plugged into. And again, using "fat mains cables" will produce lower noise than "thin mains cables".

Of course, most real systems tend to have more than two pieces of equipment interconnected and life gets a lot more interesting. As mentioned, SMPS type power solutions add their own challenges.

Having a low ground resistance in signal cables (as low as feasible) is obviously desirable, but I do not see anyone using line cables with 10AWG ground lines and massive connectors with very low resistance any time soon.

Having a separation between Audio Ground and Chassis/Earth is desirable but holds massive EMC challenges (you end up putting EMC capacitors between every connector ground and the case) and electrical safety regulation compliance challenges (the testing currents are VERY high, relatively speaking at 25A RMS), so it is not something seen commonly.

So we are back that easiest point to gain leverage is the mains cable.

QED (again) and now this coon has been well and truely chased up the tree and shot with buck shot from both barrels!

Thor

 

[sahib]

I see no one positing that currents "disappear".

I'll refresh.

Read Thor's post 141 at the beginning of this page. relating to the mains earth path.

Read the later posts carefully, he then makes the earth wires of both equipment zero impedance, applies Kirchhoff's law and states that the noise currents become zero. What does this look like to you?

However, I can see that he changed his mind on his last post. Now, currents flowing out of the system into the mains earth path.