TAS5630 any one done listening tests? Also THD limiting techniques. - diyAudio
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Old 24th August 2014, 01:26 PM   #1
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Default TAS5630 any one done listening tests? Also THD limiting techniques.

This is my first post to DiyAudio although I've been reading for some time.
I'm considering a design using the TI chip TAS5630, so far I'm at the data reading and thinking stage.
Does anyone have listening test information on how these amps sound in a hi-fi environment with good quality monitor speakers, compared with class AB? They clearly should have no problems in subwoofer (THD not critical) and semi-portable/portable equipment (battery life important).

One issue I foresee is the need to add some sort of amplitude limiting to ensure that output doesn't enter the high THD area. TI cheerfully quote output at 10% THD and if this were applied to multiway speakers that would mean the tweeters would expereince perhaps 6 to 10v rms of mostly harmonics.
Fom my days working in loudspeaker companies I know that users running their amplifiers (then all class AB) into clipping were frequent tweeter destroyers for this reason. And here we have an amplifier that would not be limited by clipping in the same way as AB designs used to be!
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Old 24th August 2014, 05:08 PM   #2
DUG is offline DUG  Canada
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Quote:
Originally Posted by HappyBull View Post

...

And here we have an amplifier that would not be limited by clipping in the same way as AB designs used to be!
Not sure what you mean. I have rarely seen any amp with clipping limiting...A, AB, or D.

Not that there aren't any...just rarely seen by me in DIY.



TAS5630 has clip detect (open collector) but there are no notes in the data sheet. (that I could find)

There may be notes in an ap note on the device.
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Old 24th August 2014, 09:34 PM   #3
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Originally Posted by DUG View Post
Not sure what you mean. I have rarely seen any amp with clipping limiting...A, AB, or D.
What I mean is that this amplifier has a significant permitted operating region with high THD. With AB it just clips, you can't continue increasing the output power for another 100W or so! Onset of clipping is heard by the more discerning user and they (hopefully) decrease the output. I am not sure user response would be so definite in this case, and I anticipate the possibility of users continuing to operate at high THD level, with consequent tweeter risks.

I don't see this device's clip signal as something I could use as I have no control over the point at which it asserts.
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Old 24th August 2014, 09:59 PM   #4
DUG is offline DUG  Canada
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Quote:
Originally Posted by HappyBull View Post
What I mean is that this amplifier has a significant permitted operating region with high THD. With AB it just clips...
I may concede the point that class D may clip "harder" and AB "softer" but THD will appear in both and both will show an " increase" in power.

Compare data sheets for various D and AB amps, looking at 1% and 10% distortion power curves.

Quote:
Originally Posted by HappyBull View Post

...
Onset of clipping is heard by the more discerning user and they (hopefully) decrease the output. I am not sure user response would be so definite in this case, and I anticipate the possibility of users continuing to operate at high THD level, with consequent tweeter risks.

...
IMHO it will be more pronounced in class D and therefore more readily detected...though I would have to set up two similar amplifiers to prove that.

Quote:
Originally Posted by HappyBull View Post

...

I don't see this device's clip signal as something I could use as I have no control over the point at which it asserts.
You may be able to use it but I agree that the usefulness is limited because you do not have control over the settings.

You could build your own clipping detector by comparing the input and output signals and amplifying the difference, comparing that difference to a set level.

Or you could compare the peak of the output waveform to the supply and set a pre-clip detection circuit.

These are not new ideas and I have seen both used. (somewhere)

Have fun

Doug
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Old 25th August 2014, 08:21 AM   #5
Nisbeth is offline Nisbeth  Denmark
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I think maybe you need to consider your power requirements first. If you look at TIs THD vs. power curves you can see where the onset of (significant) clipping is and the question is if your application (by which I mean speaker sensitivity and listening distance together) actually mean you need more than that output power to achieve your desired SPL. If that shows you have significant headroom, the question is if you need to bother with any clipping monitoring/limiting.

If you do, there is a couple of rather good articles on the subject on Rod Elliot's site

/U.
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Old 25th August 2014, 09:31 AM   #6
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Originally Posted by DUG View Post
You could build your own clipping detector by comparing the input and output signals and amplifying the difference, comparing that difference to a set level.

Or you could compare the peak of the output waveform to the supply and set a pre-clip detection circuit.

These are not new ideas and I have seen both used. (somewhere)
I was intending to design the output limiter (not really a clipping detector as I want it to operate in the low THD region) to trigger at a set peak output voltage level, probably at about the point the distortion curve "turns the corner" in the data sheet. (That would be approx 100W into 8R BTL mode). The limiter would attenuate the analog input and generate a warning. As the design will also have a LED power bar-graph it is just an additional output to add there with a latch/delay/attenuator.

@ Nisbeth: I already know that I need about the same SPL as the AB amp currently in use which is about 100W/8R so I have already considered that issue. If it were just me using the system I could guarantee never to take it into the high THD region as you suggest. I want to protect against use by others too. Will check out Rod Elliot site as you suggest.
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Old 25th August 2014, 11:15 AM   #7
DUG is offline DUG  Canada
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Diff-single ended /10 IC:

ina143

http://www.ti.com/lit/ds/symlink/ina143.pdf

digikey

Just a suggestion

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