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Hypex NC1200: Quality of the implementations

March Audio

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4 mm or more
.

With this graph it is evident that 2 mm is insufficient if we are in an environment contaminated by radiofrequency. If it is not the case, with 1 mm will be enough, I say. But we have to foresee adverse situations.

Aluminum is expensive and it seeks to lower costs in production and transport.
Have you ever thought about how RF ingresses and egresses from a box? Do you realise it's not just through the box walls?
 

March Audio

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I understand his specs. I also don't disagree, in principle, with the idea that -90dB of PSRR is a desirable thing, and indeed I add LCR filtering to my SMPS units to drive a phono stage which are simulated/measured to achieve that performance and higher as the gain in the stage is very high- c. 4000 and the output SINAD has to be better than 75dB weighted with power supply artifacts included.
To illustrate this, at a closed loop gain of 100 an AD797 or OPA1612 only has, if my memory serves me well, about 40dB of PSRR at 20kHz and a signal level of c. 25mv for a MC cartridge, so for a PSU with say c. 2mv of noise you would like 30dB or more of extra supply rejection to be safe.
I use damped LC filters to achieve this.
However, the opamps cited all have similar PSRR rejection figures, so this is hardly a blind comparison.
My comments were in reply to Maty and his misplaced obsession with certain numbers without context.
 
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4 mm or more.

With this graph it is evident that 2 mm is insufficient if we are in an environment contaminated by radiofrequency. If it is not the case, with 1 mm will be enough, I say. But we have to foresee adverse situations.

Aluminum is expensive and it seeks to lower costs in production and transport.
I still don't get your point. Why did you post graphs for steel and copper?
Is there a specific targeted rejection/frequency profile that you are attempting to reach? If so, what is the nature of the aggressor that you are protecting against- what's the amplitude/frequency? What radio frequencies are of interest here?
Generally the range that you show is problematic for conducted RFI, whereas radiated RFI lies well above it and any of the choices for metal/thickness that we have discussed will suffice.
Again, I ask for a precise, if possible, definition of the goals of this exercise. What are you protecting against, and what level of protection is sufficient?

Why not use steel?
 

March Audio

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I still don't get your point. Why did you post graphs for steel and copper?
Is there a specific targeted rejection/frequency profile that you are attempting to reach? If so, what is the nature of the aggressor that you are protecting against- what's the amplitude/frequency? What radio frequencies are of interest here?
Generally the range that you show is problematic for conducted RFI, whereas radiated RFI lies well above it and any of the choices for metal/thickness that we have discussed will suffice.
Again, I ask for a precise, if possible, definition of the goals of this exercise. What are you protecting against, and what level of protection is sufficient?

Why not use steel?
This is precisely the point I have been trying to get across to maty. Just using 4mm aluminium or galvanised steel doesn't mean you have solved any problem. Especially when he doesn't even know what problem he is trying to solve, or if it exists.
 
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DonH56

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It's a class-D amp with a big SMPS in the box... Internal noise coupling (physical or radiated) is likely a bigger problem than RFI getting through the box. And as @March Audio and @wynpalmer would perhaps agree, ingress is usually through the input and output cables, not the chassis, at least IME.
 

maty

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About OPA1611/12, Hypex HPR12 and HNR12 ±12 V regulators,... just now:

https://www.diyaudio.com/forums/chip-amps/267802-modulus-86-build-thread-post5844043.html

[ One of my commercial clients has often asked about the various "discrete opamps", including many of those mentioned by Tio. Thus, I've examined their data sheets quite a bit and measured a few samples. I remain skeptical of "discrete opamps" for a number of reasons:
  1. They don't provide any better performance than I can get with an OPA1611/12 (based both on their data sheets and on lab measurements).
  2. The "discrete opamps" are 30+ dB more expensive than the OPA1611/12 and closer to 40 dB more expensive than the LME49720.
  3. Many of the "discrete opamps" have a 2nd order loop gain response, i.e. -40 dB/dec rolloff from their dominant poles. They then have a phase compensation network to make them unity gain stable. Such an amp will work well as a buffer, but will oscillate in a gain stage unless you add an external compensation network. They're not plug-n-play replacements for an actual opamp.
That said, quality opamps like the OPA1611/12 don't offer the bling that the "discrete opamps" do. No blinding red LEDs. No significant power dissipation... ]
 
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tomchr

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I never thought I'd live to see the day where I'd be quoted by the Honourable Maty... ;) How this quote fits in with the rest of this thread is anybody's guess. Thanks for providing a link to the DIY Audio thread so people can see my comments in context.

The emphasis (bold) in above was added by Maty, and is not mine. I'm not generally opposed to "discrete opamps". I just don't think you get much value from them that you can't get from an OPA1611/12 at a much lower cost. I also encourage designers who wish to use "discrete opamps" to use caution, as some of them are advertised as "unity-gain stable" even if they are only stable near/at unity gain. Commonly, "unity-gain stable" is interpreted as "stable at all gains, including unity gain". That's not the case with an opamp that has a 2nd order response, such as many "discrete opamps".

I should also add that I have found a "discrete opamp" that provides as good performance as the OPA1611/12, so it is possible for a "discrete opamp" to perform well. It was still 30 dB more expensive, but at least it didn't wreck the performance. I forget the brand and part number. I recall it being one of those that had a solid data sheet (which showed performance as good as the OPA1611/12), so that should get you in the right direction should you wish to track it down.

Tom
 

maty

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A somewhat text is best read with a bit of rich editing and more in this era when everything is rushed and many are only reported from a small screen. It is true that sometimes I overdo it.

I always try to put the link to the source.


Off topic

The other day I sent a link with an excerpt to relatives, of an interview with a French philosopher on French, European and Western political reality. Surely they accessed from the mobile, saw how long it was and the density of the language and had to close. The most interesting reading that day in the Spanish media and I just verified that he only has fourteen comments.
 

tomchr

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A somewhat text is best read with a bit of rich editing and more in this era when everything is rushed and many are only reported from a small screen. It is true that sometimes I overdo it.
That may be. You do have to make sure you don't twist the original text into saying something that wasn't intended, though. If you just read the bolded parts of what you quoted, it says something rather different than if you read the entire text in context.

Tom
 

tomchr

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I've swapped out a number of older duals with them as a number of specs are clearly superior to the LME4562 and similar to the LME49720
The LM4562 and LME49720 are the same chip. Same die. Same package. The LM4562 was developed around the time National went from LM to the current 3-letter format (LME = audio, LMV = general purpose opamp, LMP = precision opamp, etc.)

I agree that the OPA1612 has better specs than the LME49720. Lower THD among other things. The differences are mostly of academic interest, but they are measurable.

- lower noise, lower distortion- and the replaced duals were NE5532. I don't have specifics at hand, but it seemed worthwhile at the time.
The NE5532 is 40 (forty!) years old now. I would certainly hope that swapping in a modern opamp would result in an improvement.

Tom
 
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The LM4562 and LME49720 are the same chip. Same die. Same package. The LM4562 was developed around the time National went from LM to the current 3-letter format (LME = audio, LMV = general purpose opamp, LMP = precision opamp, etc.)

I agree that the OPA1612 has better specs than the LME49720. Lower THD among other things. The differences are mostly of academic interest, but they are measurable.


The NE5532 is 40 (forty!) years old now. I would certainly hope that swapping in a modern opamp would result in an improvement.

Tom
Thanks Tom, I stated it in a pretty clumsy way, but my point was that the OPA1612 was better than the LM4562 and the LME49720 which had similar specs. I didn't know that the die for those two parts were identical, although I had read "rumours" to that effect.
Yes, I know that the NE5532 is that old, and yet it persists. The parts I replaced were in audio gear from the 1980/1990 era.
 

March Audio

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- lower noise, lower distortion- and the replaced duals were NE5532. I don't have specifics at hand, but it seemed worthwhile at the time.
Yes They will provide better technical performance than a 5532, although the 5532 isn't the poor performer many seem to think it is.

My general point about this op amp rolling is that rarely provides any genuine benefit. If you have a properly designed circuit swapping out a good op amp for another good op amp will show little measured difference. This has been demonstrated with Amir's measurements and the additional measurements that Maty has extracted from manufacturers and posted in this thread.

Then of course we have some examples here where these swap out op amps are absolute dogs.

Then we have the problem that people hear differences that aren't there because they have compared sighted and without controls. Mind you those bad performers shown earlier may possibly sound different.
 

tomchr

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Yes They will provide better technical performance than a 5532, although the 5532 isn't the poor performer many seem to think it is.
It's a quite decent opamp - especially considering its age. Same can be said for the OPA134/2134/4134.

Tom
 

maty

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Rouge Alauda MB3 mono, optimized

Picture updated

View attachment 28983
Those heavy cables can break or disconnect their connectors which moved around. They all need to be securely fastened to the chassis. The one on the left has screws on the bottom already. Shame they didn't put a clamp half-way in the middle. Hate to see that cause a break with mains wiring during shipping.
Francesco tells me

- top and bottom cover are 2mm thick
- we use alu mounting plate 1.6mm thick
- rear and front panel are 3mm thick
- the ac internal cable supra lorad mkII is fixed very well: fastons soldered on iec inlet; the cable is fixed with screw near the socket of hypex smps
 
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Wombat

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There are not my words.

I only extracted it because it was striking.

As I have said before, it will depend on the best or worst implementation of the op-amps. If the buffer is expressly developed for the OPA1622 it is expected that the measurements are very good.
Be more clear in posting, mebbee.
 
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