Looking to buy Texas Instrument based amps - AVS Forum
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post #1 of 13 Old 04-20-2012, 10:48 PM - Thread Starter
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Guys, I'm looking to replace my old Panny XR-57 with amps based on these Texas Instrument chips:

TAS5631B
TAS5614A
TAS5612A

These are supposed to be the ultra noise "high definition" new chips from TI that replace all those old ones. Any cheap amp based on any of these would do. Please let me know if you come across any! Thanks!
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post #2 of 13 Old 04-21-2012, 04:07 AM
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Quote:
Originally Posted by Veda View Post

Guys, I'm looking to replace my old Panny XR-57 with amps based on these Texas Instrument chips:

TAS5631B
TAS5614A
TAS5612A

These are supposed to be the ultra noise "high definition" new chips from TI that replace all those old ones. Any cheap amp based on any of these would do. Please let me know if you come across any! Thanks!

http://www.mouser.com/Search/Refine....yword=TAS5631B


Have you done any reliable listening tests that found audible coloration in the power amps in your receiver? What about bench tests?
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post #3 of 13 Old 04-21-2012, 09:52 AM - Thread Starter
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Originally Posted by arnyk View Post

Have you done any reliable listening tests that found audible coloration in the power amps in your receiver? What about bench tests?

Yes I understood that with digitally controlled class d amps the freq response sucks. But these closed loop new chips are supposed to fix all that. Thus my interest. I'm looking to buy a finished amp though. Any leads?
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post #4 of 13 Old 04-21-2012, 11:53 AM
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Originally Posted by Veda View Post

Yes I understood that with digitally controlled class d amps the freq response sucks.

That's usually due to the output filter network being outside the feedback loop. Source impedances are high at 20 KHz - often around 2 ohms or more.

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But these closed loop new chips are supposed to fix all that. Thus my interest. I'm looking to buy a finished amp though. Any leads?

http://www.ti.com/lit/ds/symlink/tas5631b.pdf

shows no feedback loop from the output of the amp. The output inductors are still shown outside of any feedback loop that I can see.
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post #5 of 13 Old 04-21-2012, 04:27 PM
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Hi Veda,

I've been following the TAS5631 chip since the first datasheet was released back in 2009 (prior to the B version). But my interest was based on the low heat dissipation, not on audio quality. Low heat and power-consumption are the real advantages of class-D.

The problem with these chips is the poor THD+N at higher power. It is fine at 1 watt (0.03%), but skyrockets to 10% at full power. In my opinion, the high THD+N make them unusable for quality audio above around 60 watts. But up to that point, the specs are good.

The other issue with that chip is that it is just a driver. It needs a lot of support in front of it. Arny mentioned the output filter outside the feedback loop. That filter will behave differently with different speakers, so EQ would be required to get a flat frequency response. Combined with the fact that inputs are PWM, a DSP front-end is all but required for a quality system.

I see three applications for these chips (there are certainly more):

Automotive audio, where the low heat-dissipation would allow more power behind the dash, and THD+N is not as big a concern.

Portable audio, where the lower current consumption, smaller size and lower cost are advantages.

Low end AVRs, where the power is kept low enough so THD+N is not an issue, EQ is provided, and the low cost is an advantage.

The audio quality of class-D is not yet equal to the quality of class-A/B, so I don't think the home-audio manufacturers are embracing class-D, except at the low-end. There is also the possibility that class-D will be supplanted by class-H, which has similar heat and power advantages.
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post #6 of 13 Old 04-21-2012, 05:50 PM - Thread Starter
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LOL, yes guys I'm fully aware of the disadvantages and yes I'm waiting for a good Class H. I'm not looking to have a technical discussion and Arny I think we've had another discussion like this back in 1999. I'm simply asking around to buy the product. Do you know anyone who sells a complete amp for cheap?
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post #7 of 13 Old 04-22-2012, 04:22 AM
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Quote:
Originally Posted by MarkHotchkiss View Post

Arny mentioned the output filter outside the feedback loop. That filter will behave differently with different speakers, so EQ would be required to get a flat frequency response. Combined with the fact that inputs are PWM, a DSP front-end is all but required for a quality system.

I see three applications for these chips (there are certainly more):

Automotive audio, where the low heat-dissipation would allow more power behind the dash, and THD+N is not as big a concern.

Portable audio, where the lower current consumption, smaller size and lower cost are advantages.

Low end AVRs, where the power is kept low enough so THD+N is not an issue, EQ is provided, and the low cost is an advantage.

The audio quality of class-D is not yet equal to the quality of class-A/B, so I don't think the home-audio manufacturers are embracing class-D, except at the low-end. There is also the possibility that class-D will be supplanted by class-H, which has similar heat and power advantages.

I think that successful implementations of this chipset will be those that marry it with specific speaker drivers so that the frequency response de jour problem due to differences in speaker loads will be addressed by packaging the amplifier with the speaker.

Powered speakers, which are successful in the professional audio realm, but still languish except for consumer subwoofers, seem to be an obvious application.
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post #8 of 13 Old 04-22-2012, 09:16 AM
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Quote:
Originally Posted by MarkHotchkiss View Post

The audio quality of class-D is not yet equal to the quality of class-A/B, so I don't think the home-audio manufacturers are embracing class-D, except at the low-end. There is also the possibility that class-D will be supplanted by class-H, which has similar heat and power advantages.

Levinson's latest high end monoblock is a switcher, Bel Canto offers several AFAIK, Rowland Research, Audio Research, and others all offer switching amps in home audio at the higher end.

Class H (or is that class G??) as been around for a while too, not as much in consumer amps but some Yamahas such as the M-80, I believe, had this back in the 80s. Lots in pro audio as you're probably aware. I'd say there probably won't be much expansion of class H/G with class D here. In the pro arena I'm not sure that Crown even makes a "big iron" amp any more. All their big stuff is switching.

Just because there is a knob doesn't mean you should turn it.
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post #9 of 13 Old 04-22-2012, 03:52 PM
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Quote:
Originally Posted by arnyk View Post

I think that successful implementations of this chipset will be those that marry it with specific speaker drivers so that the frequency response de jour problem due to differences in speaker loads will be addressed by packaging the amplifier with the speaker.

Powered speakers, which are successful in the professional audio realm, but still languish except for consumer subwoofers, seem to be an obvious application.

Hi Arny,

Yes, and that "integrated" approach is the application I was looking at when I first considered these chips. It is also what makes them useful for portable and auto applications (where speakers are included). However, in my application, I wanted to put an amp in each speaker, and these chips had four amps (although you would PBTL them into one amp) making them a little more difficult and a little more expensive.

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Originally Posted by whoaru99 View Post

Levinson's latest high end monoblock is a switcher, Bel Canto offers several AFAIK, Rowland Research, Audio Research, and others all offer switching amps in home audio at the higher end.

Hi WhoAreYou,

I did not know that. That shows that you can indeed get a quality output from class-D. I suspect that they weren't low-cost implementations, however.

Quote:


Class H (or is that class G??) as been around for a while too, not as much in consumer amps but some Yamahas such as the M-80, I believe, had this back in the 80s. Lots in pro audio as you're probably aware. I'd say there probably won't be much expansion of class H/G with class D here. In the pro arena I'm not sure that Crown even makes a "big iron" amp any more. All their big stuff is switching.

Class-G and class-H are similar in that both control the power rails to class A/B output stages. Class-G switches different rails in as needed, whereas in class-H the rails are continuously varied. ICs that implement class-H for the battery-powered player market are now available.

The reason that I think that class-H can supplant class-D is that it is easier. The output stages are trusted class-A/B, and the switching, instead of being included in each amp (x2 for stereo, x5 for 5.1), is in the power-supply (x1). All the filtering is at the power-supply output, where it doesn't effect frequency response. The control is more difficult, but that is just additional firmware in the DSP.

I could be wrong about that, but if I was designing a high-powered amp, that's the route I might go.
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post #10 of 13 Old 04-23-2012, 04:25 AM
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Originally Posted by MarkHotchkiss View Post


Class-G and class-H are similar in that both control the power rails to class A/B output stages. Class-G switches different rails in as needed, whereas in class-H the rails are continuously varied. ICs that implement class-H for the battery-powered player market are now available.

The reason that I think that class-H can supplant class-D is that it is easier. The output stages are trusted class-A/B, and the switching, instead of being included in each amp (x2 for stereo, x5 for 5.1), is in the power-supply (x1). All the filtering is at the power-supply output, where it doesn't effect frequency response. The control is more difficult, but that is just additional firmware in the DSP.

I could be wrong about that, but if I was designing a high-powered amp, that's the route I might go.

Both Class G and recently Class D power amps are becoming popular for pro audio. Class G implemented with switchmode power supplies has been very popular indeed with Crown, QSC, Behringer and others piling on. Crown and Behringer are also promoting Class D power amps.

Since user speaker equalization is generally used in pro audio, the sensitivity of switchmode amps to speaker impedance curves is not so much of a problem.
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post #11 of 13 Old 04-24-2012, 09:30 AM - Thread Starter
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In other words, nobody knows who make an amp based on that chip for cheap?
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post #12 of 13 Old 04-24-2012, 10:13 AM
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Originally Posted by Veda View Post

In other words, nobody knows who make an amp based on that chip for cheap?

If someone is doing it, they are keeping their mouths shut about it!

Looking at the cost of the required chips, it would take a big price break from TI for such a thing to exist.
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post #13 of 13 Old 04-24-2012, 01:40 PM
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These guys are building amps (I assume they're relatively cheap) based on the TAS5630 -the analog input version of the TI Purepath HD chips.
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