Good Class D amps ??

[opus101]

1 minute ago, March Audio said:

 

Considering it is not a problem I have seen with this op amp, even with specific RF testing, then my conclusion is that it isnt sensitive to RF in the way you are claiming when normal design considerations are made.

 

'in the way you are claiming' - I'm just pointing to other people's findings. Are you taking issue with them? Or saying they're mistaken or perhaps deceitful?

 

'normal design considerations' - you're saying the DIYA guys didn't employ them?

[March Audio]

34 minutes ago, opus101 said:

 

'in the way you are claiming' - I'm just pointing to other people's findings. Are you taking issue with them? Or saying they're mistaken or perhaps deceitful?

 

'normal design considerations' - you're saying the DIYA guys didn't employ them?

 

Im not saying anything, apart from Im quite confident you dont understand or have knowledge of the issues.  Plus Im not going to play your silly word games. 

 

I just have no interest in chasing dragons.

[opus101]

'Never underestimate the power of denial'.

[March Audio]

3 minutes ago, opus101 said:

'Never underestimate the power of denial'.

 

How could I be denying the potential for RF problems when I have implemented RF counter measures and tested for their efficacy?

 

Try harder

[opus101]

Let's see the results of the tests ? Also the measured response of the input LPF, not just a SPICE sim?

[March Audio]

20 minutes ago, opus101 said:

Let's see the results of the tests ? Also the measured response of the input LPF, not just a SPICE sim?

 

When I get the N9320 back in the office, or more appropriately the VNA, sure.

 

Do you really doubt that RF can be filtered?

 

Keep trying

[opus101]

Keep up the denial! Its going well so far!

[March Audio]

5 minutes ago, opus101 said:

Keep up the denial! Its going well so far!

 

There is no denial, I have fully acknowledged the potential for RF issues.  See above.

 

What is it you dont understand here?

 

I have just not had the problems, whatever they might be, that you are referring to by proxy. Do you know or understand the problems to which you are referring?  Why dont you provide a technical summary?

 

 

[opus101]

1 minute ago, March Audio said:

There is no denial, I have fully acknowledged the potential for RF issues.

 

 

It wouldn't be denial if you accepted it, would it? 😎

[March Audio]

4 minutes ago, opus101 said:

 

It wouldn't be denial if you accepted it, would it? 😎

 

Eh?  Thats precisely my point.  You clearly dont understand what has been said above.  Normal mitigations, no problem seen.

 

Would you like to provide your technical summary?  Thought not.  Its obviously not an area you have understanding of.

 

As such I think you are one for the ignore button.

[opus101]

Just now, March Audio said:

 

I think you are one for the ignore button.

 

QED

[mocenigo]

6 hours ago, March Audio said:

 

Just stumbled across this.

 

When you say "better" what do you mean or like to see?  The LM4652 is an exceptionally good buffer.  If you feel that a component with 0.00003% THD + Noise (-130dB), IMD of 0.00005%, voltage noise density of 2.7nV etc is somehow lacking, then you need to explain why.

 

Subjectively better. Or with a "preferred" sound signature. It is not a secret that Hypex-based Class D amps became more popular after solutions with better buffer boards and alternative op-amps came out. Maybe it is just because of the buffer boards (the original buffer boards for evaluation were notoriously quit bad, and also noisy). Music reproduction is not only measurement, and the monoblocks I have (with Sonic Imagery 994 opamps, and regulated power supplies) have "converted" many a friend  that thought Class D always "sucked".

 

 Roberto

 

[mocenigo]

On 6/19/2019 at 12:46 PM, Matias said:

No, it uses the standard opamps and regulators that Hypex provides.

 

More info and pics here

 

https://www.audiosciencereview.com/forum/index.php?threads/march-audio-p701-mono-block-power-amp.6862/post-185443

 

Perfect. And it is a good price indeed.

[March Audio]

34 minutes ago, mocenigo said:

 

Subjectively better. Or with a "preferred" sound signature. It is not a secret that Hypex-based Class D amps became more popular after solutions with better buffer boards and alternative op-amps came out. Maybe it is just because of the buffer boards (the original buffer boards for evaluation were notoriously quit bad, and also noisy). Music reproduction is not only measurement, and the monoblocks I have (with Sonic Imagery 994 opamps, and regulated power supplies) have "converted" many a friend  that thought Class D always "sucked".

 

 Roberto

 

 

With respect thats a massive leap.  Its a conclusion without basis.

 

Maybe its just the ineffectiveness of sighted uncontrolled and biased listening and the seemingly inexorable desire of so many audiophiles to fiddle and "hear" benefits. 

 

So why is the 994 you mention sold on the basis improved technical performance?  If you look at its datasheet the performance its certainly no better than the 4562.

 

From elsewhere, the results of some op amp rolling in a real circuit.

 

[sandyk]

5 hours ago, opus101 said:

 

Quite. So the fact that the DECT 'signature' was visible at the output is itself quite remarkable. How could an opamp be designed to be so incredibly sensitive to such low levels of RF? Inquiring minds want to know.

 

 Several years ago, members of a U.K. based forum constructed my modified version of a Silicon Chip magazine designed headphone amplifier  (Studio Series Headphone Amplifier} which used an LM4562. Out of more than 300 constructed worldwide , not a single forum member reported any susceptibility to RF/EMI issues .

 

[sandyk]

48 minutes ago, sandyk said:

not a single forum member reported any susceptibility to RF/EMI issues .

 

I just had my memory jogged. When using a LM4562 in another Studio Series design, several constructors reported instability issues.

It doesn't like driving capacitive loads, and in this case it was connected via a cable into the remote volume control PCB. The symptoms were grainy sounding audio and being excessively warm . It was reported to be oscillating at around 30MHZ. This may have resulted in it demodulating RF around that frequency.

It needs something like a 100 ohm series resistor at it's output for guaranteed stability into capacitive loads. 

 

Alex

[opus101]

Here are Pavel Macura's findings with LM4562 : https://www.diyaudio.com/forums/analog-line-level/308415-ne5532-buffer-post5097962.html

 

If anyone's interested in further anorak-y stuff concerning LM4562, there's also this thread on TI's support forum which might raise the odd eyebrow : https://e2e.ti.com/support/audio/f/6/t/415907

[sandyk]

 

BTW, the metal can LM4562HA /LME49720HA did sound better in the HAs that were constructed.

[March Audio]

1 hour ago, sandyk said:

 

I just had my memory jogged. When using a LM4562 in another Studio Series design, several constructors reported instability issues.

It doesn't like driving capacitive loads, and in this case it was connected via a cable into the remote volume control PCB. The symptoms were grainy sounding audio and being excessively warm . It was reported to be oscillating at around 30MHZ. This may have resulted in it demodulating RF around that frequency.

It needs something like a 100 ohm series resistor at it's output for guaranteed stability into capacitive loads. 

 

Alex

 

And that's nothing unusual. 

[March Audio]

1 hour ago, opus101 said:

Here are Pavel Macura's findings with LM4562 : https://www.diyaudio.com/forums/analog-line-level/308415-ne5532-buffer-post5097962.html

 

If anyone's interested in further anorak-y stuff concerning LM4562, there's also this thread on TI's support forum which might raise the odd eyebrow : https://e2e.ti.com/support/audio/f/6/t/415907

 

And yet these problems don't show up in the measurements of the nc1200 module........... 

 

If you think getting this is in any way normal in a design, you are wrong. 

 

 

 

Do you actually think all op amps come out the factory with the same performance? 😀

 

Haven't you noticed that the datasheets have lower, typical and limit columns in the spec. 

[opus101]

Keep on playing that denial card, its working a treat!

[sandyk]

14 minutes ago, March Audio said:

 

And that's nothing unusual. 

In this case the length of the cable would have had <100pf capacitance.

It is when the Data sheets show a graph with Small-Signal Transient Response AV = 1, CL = 100pF

 LM4562.pdf

[March Audio]

15 minutes ago, opus101 said:

Keep on playing that denial card, its working a treat!

Why do keep saying that, it's totally non sensical? It just demonstrates your ignorance of the subject. 

 

@sandyk did your LM4562 project have mains pick up at such ludicrously high levels as shown above? It's - 90dBFS,  sorry the picture came out tiny when I copied it. 

[March Audio]

22 minutes ago, sandyk said:

In this case the length of the cable would have had <100pf capacitance.

It is when the Data sheets show a graph with Small-Signal Transient Response AV = 1, CL = 100pF

 

Sounds like There may have been some significant gain peaking due to the specific circuit design. 

 

Just for interest

 

https://training.ti.com/ti-precision-labs-op-amps-stability-1

[opus101]

1 minute ago, March Audio said:

Why do keep saying that, it's totally non senscal?

 

Of course it won't make any sense to you that I note your textbook denial behaviour. Coz from your point of view, there isn't any denial. But the defense mechanisms you display are textbook ones. Perhaps acquaint yourself with some of Anna Freud's work? I think there may well be free downloads.