Good Class D amps ??

[opus101]

16 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 

 

This is an interesting point - the squarewave response with the stated 100pF load shows about 30% overshoot on the positive excursion, less on the negative. Not oscillation by any stretch of imagination (or denial!).

[sandyk]

9 minutes ago, March Audio said:

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. 

 

No. It also used a modified John Linsley Hood designed PSU add-on (A.K.A. "Ripple Eater in DIY Audio) for it's + and -15V supplies which has <4uV noise and a very low Output impedance with close to 2FARAD simulated capacitance..

[sandyk]

10 minutes ago, opus101 said:

 

This is an interesting point - the squarewave response with the stated 100pF load shows about 30% overshoot on the positive excursion, less on the negative. Not oscillation by any stretch of imagination (or denial!).

 

It is more likely to have been oscillating as I mentioned before , where it was reported to be oscillating at around 30MHZ, which is close to the 30MHZ maximum operating frequency of the original DECT handsets.

It may have been acting like a Regenerative receiver, thus demodulating the audio ?

[March Audio]

8 minutes ago, sandyk said:

 

It is more likely to have been oscillating as I mentioned before , where it was reported to be oscillating at around 30MHZ, which is close to the maximum operating frequency of the original DECT handsets.

It may have been acting like a Regenerative receiver, thus demodulating the audio ?

 it will oscillate due to poor phase margin and gain peaking. 

[March Audio]

15 minutes ago, sandyk said:

 

No. It also used a modified John Linsley Hood designed PSU add-on (A.K.A. "Ripple Eater in DIY Audio) for it's + and -15V supplies which has <4uV noise and a very low Output impedance with close to 2FARAD simulated capacitance..

 

The discussion opus pointed to suggests it was just picked up out of the air and not even related to psu noise.  Just looks like a bad design to me to do that.  

 

You clearly didn't have an issue and obviously nor do others. 

[opus101]

4 minutes ago, sandyk said:

...the 30MHZ maximum operating frequency of the original DECT handsets.

 

 

I had a quick look at Wikipedia on DECT, didn't see any mention of DECT going that low in frequency. In my understanding its >900MHz but you're a telecoms guy, feel free to educate me.

[sandyk]

Just now, March Audio said:

No it won't be oscillating due to that, it will be poor phase margin and gain peaking. 

 

 As I stated before, the symptoms were grainy sounding audio and the chip running very warm.

 I am not going to bother continue discussing this with you about this, or go looking for the Silicon Chip Errata.

 I will leave you both to slug it out.

[March Audio]

27 minutes ago, sandyk said:

 

 As I stated before, the symptoms were grainy sounding audio and the chip running very warm.

 I am not going to bother continue discussing this with you about this, or go looking for the Silicon Chip Errata.

 I will leave you both to slug it out.

Being hot is an indication of oscillating beyond the audio range. 

 

Opus is going on ignore when I find the relevant button in this forum settings. I have realised I have come across him previously as mentioned above.   There will be no more pointless discussion with him. Just take a look on ASR forum if curious. I think the posts may have been removed but he specialised in arguing semantics and pedantry instead of anything to do with the subject. 

 

The ti op amp stability video is worth watching. 

 

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

[sandyk]

8 minutes ago, opus101 said:

 

I had a quick look at Wikipedia on DECT, didn't see any mention of DECT going that low in frequency. In my understanding its >900MHz but you're a telecoms guy, feel free to educate me.

 You obviously didn't look hard enough, because the ones I used to have did, and the 30MHZmaximum that I mentioned was verified from the official Au requirements using Google just before I posted my reply

 

https://www.legislation.gov.au/Details/F2017L01079/Explanatory Statement/Text

[opus101]

2 minutes ago, sandyk said:

 You obviously didn't look hard enough

 

Well it is true I only scanned the Wikipedia article. But now I've had more time to look through it, I am seeing things like : 

 

Before 1.9 GHz band was approved by the FCC in 2005, DECT could only operate in unlicensed Region 2 2.4 GHz and 900 MHz ISM bands

 

A cite for your 30MHz claim would be useful.

[sandyk]

4 minutes ago, opus101 said:

 

Well it is true I only scanned the Wikipedia article. But now I've had more time to look through it, I am seeing things like : 

 

Before 1.9 GHz band was approved by the FCC in 2005, DECT could only operate in unlicensed Region 2 2.4 GHz and 900 MHz ISM bands

 

A cite for your 30MHz claim would be useful.

Look at my post immediately above yours.

 

3.                  The Radiocommunications (HF CB and Handphone Equipment) Standard 2008 (the sunsetting HF CB Standard).

The sunsetting HF CB Standard previously set out the applicable performance and testing requirements for High Frequency Citizen Band (HF CB) and Handphone equipment for the purposes of the Australian radiocommunications compliance and labelling regime.  The sunsetting HF CB Standard had adopted, with modifications, the industry standard ‘AS/NZS 4355:2006 (R2016) Radiocommunications equipment used in the handphone and citizen band radio services operating at frequencies not exceeding 30 MHz’.

[opus101]

I see no reference to DECT there. Handphones of course existed prior to the establishment of DECT standards.

[sandyk]

9 minutes ago, opus101 said:

I see no reference to DECT there. Handphones of course existed prior to the establishment of DECT standards.

  As I said previously, I used to have DECTs at that frequency too.

It should have been obvious that an LM4562 wouldn't have been able to demodulate at frequencies of 900MHZ !!!

 

The title of the link that I posted . I am out of this silly argument now .

 BYE !

 

https://www.legislation.gov.au/Details/F2017L01079/Explanatory Statement/Text

Radiocommunications (Digital Cordless Communications Devices — DECT Devices) Standard 2017

• - F2017L01079
• In force - Latest Version
• View Series

[opus101]

4 minutes ago, sandyk said:

 

It should have been obvious that an LM4562 wouldn't have been able to demodulate at frequencies of 900MHZ !!!

 

Clearly this document's going to come in above your pay-grade but others might find it relevant : http://www.ti.com/lit/an/snoa497b/snoa497b.pdf

[sandyk]

5 minutes ago, opus101 said:

 

Clearly this document's going to come in above your pay-grade but others might find it relevant : http://www.ti.com/lit/an/snoa497b/snoa497b.pdf

 If you think that a mere radiated 10mW max signal can be demodulated without some kind of amplification to increase it's level first then you are delusional. In this case , it's not anywhere near that, as it is a radiated signal received at a far lower level , and picked up by poor wiring.

 You can continue your silly arguments without me !!!

[opus101]

Just now, sandyk said:

 

 You can continue your silly arguments without me !!!

 

For some reason I can't quite believe that claim.

[mocenigo]

7 hours ago, March Audio said:

7 hours ago, March Audio said:

 

 

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. 

 

 

Well, I *did* say subjective.

 

Also, the results of opamp rolling on other circuits prove (scientifically) nothing as well.

 

At the and I bought an amplifier that has great measurements and, most importantly, an absolutely fantastic sound to my ears, and I paid honestly quite little (about 1.2K EUR per channel including shipping).  I even had folks with amps that cost 10x as much come to my place and leave with envy (FWIW).

 

 Roberto

[firedog]

Maybe opus101 and march audio can just agree to stop the argument? It isn't really interesting to the rest of us at this point, nor really on topic. 

[DuckToller]

4 hours ago, March Audio said:

Opus is going on ignore when I find the relevant button in this forum settings.

Upper right corner, general menu, submenu Account-> Ignored Users (last one)

[March Audio]

5 hours ago, DuckToller said:

Upper right corner, general menu, submenu Account-> Ignored Users (last one)

Thank you ducktoller, job done. 

 

Now perhaps we can all discuss class d without the unhelpful noise. 

 

 

[March Audio]

6 hours ago, firedog said:

Maybe opus101 and march audio can just agree to stop the argument? It isn't really interesting to the rest of us at this point, nor really on topic. 

 

Thank you firedog, I have been trying to put the noise on ignore.  Now done. However someone arguing from an uninformed position does need to be corrected. 

 

In any case it is actually a relevant and interesting subject, that of the merits of various input buffers. I'm also not sure why you think you speak for "the rest of" us. 

[March Audio]

7 hours ago, mocenigo said:

 

 

Well, I *did* say subjective.

 

Also, the results of opamp rolling on other circuits prove (scientifically) nothing as well.

 

At the and I bought an amplifier that has great measurements and, most importantly, an absolutely fantastic sound to my ears, and I paid honestly quite little (about 1.2K EUR per channel including shipping).  I even had folks with amps that cost 10x as much come to my place and leave with envy (FWIW).

 

 Roberto

 

That's quite wrong.  It scientifically demonstrates performance differences which will potentially have impact on the sound.  As I mentioned the manufacturers of your op amps use the same data technical and scientific data to sell the product on, so I'm not sure why you are dismissing it as somehow not important.  Would you choose an amp with high distortion and noise levels? 

 

I have never said your amp doesn't sound good..  Hiwever I have also got plenty of feedback telling me the standard op amp on the nc1200 sounds fantastic. You can look at it on my website and read it if you like. So where does that leave us?  Your uncontrolled subject opinion v someone else's. With respect, that's of little use to anyone because by that standard anything goes, just so long as you personally like it.  That's fine in itself but we all may as well pack up and go home and not bother with the discussion in that case. 

 

My only point is to counter the earlier incorrect implication that different buffers necessarily offer improved technical performance or sound, or indeed that there is something deficient with what's already there in the nc1200. 

[March Audio]

5 hours ago, sandyk said:

The intolerant resident policeman does NOT speak for the rest of the members.

 

 While I do not believe that a 10mW DECT handset at a normal operating distance would be capable of doing this, I do have first hand experience of 200MHZ Analogue TV transmissions from nearby Channel 9 in Sydney causing audible Frame Buzz to LM3886 Gainclone amplifiers.

 The RF was getting into the negative feedback circuit via the speaker leads, and the cure was to put a couple of turns of the leads through a large RF toroid.

 

Absolutely, this stuff happens and counter measures need to be taken. As you allude to the difference in power between the 2 examples is immense. 

 

The current Sydney digital TV tx is around 50kW, so the now defunct analogue would have been 100s of kW. 

[opus101]

Since the topic of input filtering has already come up on this thread, here's something about aliasing from OOB input signals : https://www.diyaudio.com/forums/class-d/321632-hypex-ncore-nc400-input-anti-alias-filter.html

[firedog]

11 hours ago, March Audio said:

 

Thank you firedog, I have been trying to put the noise on ignore.  Now done. However someone arguing from an uninformed position does need to be corrected. 

 

In any case it is actually a relevant and interesting subject, that of the merits of various input buffers. I'm also not sure why you think you speak for "the rest of" us. 

It was relevant till it became more about the argument than the actual topic.
At a certain level of detail it's no longer about "good class d amps", but about something much more limited and technical, that I assure you most readers don't want to get to that level of tech detail. Such a discussion is for a it's own thread, as I see it.
The argument back and forth, with somewhat personal comments also isn't on topic.