Tas5630 Amplifier

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Firman Lamarre

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Aug 3, 2024, 5:51:53 PM8/3/24

to quebetcoaskat

Hi All,

The TAS5630 has quite noisy output. Doing an active monitor speaker is nearly not possible to drive the tweeter directly from TAS5630 - in quiet environment the noise from the tweeter is audible even in 1,5m-2m distance... Is any chance to decrease the TAS5630 output voltage noise level??? Would it be possible to decrease amplification factor? Is the noise this same in AD and BD modulation?

Best regards,
Tomasz

Also, can you try AC grounding TAS5630 inputs to see if the noise starts in TAS5630? Disconnect input caps to TAS5630 and connect them between TAS5630 inputs and ground. (If these are electrolytic caps please make sure to connect +terminals of the caps to TAS5630 inputs and -terminals to ground.)

There is not a problem with the TAS5630 signal source... My configuration is:

Input Stage -> Dig. Attenuator -> Buf -> SigmaDSP -> Buf -> TAS5630

The whole audio path is balanced.

Having my TAS5630 disconnected from the SigmaDSP with shorted input I can measure around 250V-255V RMS A-weighted output noise. The measurement is performed with NTi XL2 Audio Analyzer. TI specified the TAS5630 typical value as 270V RMS. So my application is fully in the TI spec.

- having connected with SigmaDSP (DSP output muted) I measure up to 260V
- having DSP unmuted but the attenuator set fully down I measure around 265V
- having the whole system connected together with attenuator set at 0dB and the open XLR input I measure up to 290V A-weighted noise, what shows that the rest of the system works OK.

My question is, could it be possible to decrease the specified TAS5630 residual noise anyhow ??? I guess the noise is coming from the TAS5630 input stage, so maybe decreasing the overall chip voltage gain could I decrease the output noise level ... but how to decrease the voltage gain ??? Is there any trick to decrease the voltage gain of TAS5630 ??? any additional external circuit ???

If the noise is really coming from the TAS5630 input stage it should be no difference in noise between AD and BD modes...

Thanks for your support!
Tomasz

Tomasz, TAS5611A in the Oasis family (the family for TAS5630 and TAS5613A) has slightly lower noise, 168uV typical, with lower power output but otherwise performance similar to performance of TAS5613A and TAS5630. Maybe it can deliver enough power for your tweeter. Of course it is pin-pin compatible with your PCB.

However, you must limit PVDD, to 34Vdc for TAS5611A and 38Vdc for TAS5613A. Maybe it is possible to add a series element for one or the other of these chips to drop PVDD enough? I know this will depend on your tweeter power requirement.

Hi Steve,

Thanks for your replay. I checked TAS5613A and TAS5611A specs and I've chosen the TAS5613A - I like the low overal voltage gain of the amplifier. However the whole PurePathHD is damn noisy ... I really like the chips, but with residual noise over 100V they have 'no go' to use in active speaker as direct tweeter driver.

Back to my amp I ordered directly some samples of TAS5613A and replaced the TAS5630. Today I performed some measurements and the TAS5613A noise performance looks way better than TAS5630 - I measured around 165-170V A-weighted RMS voltage noise on the output of my amplifier after changing the chips. Before I had like 255-260V. It is already great step ahead! The amplifier has to drive high grade active speaker, like a studio near field monitor, therefore the tweeter must be really quiet. To have the tweeter really quiet, using this amp, I still have to use a passive tweeter crossover with at least -3dB band attenuation. However, how I said, 170V is a really nice step ahead, because now, using classic tweeter crossover with band attenuation of -6bB (what is like normal for tweeter) the audible tweeter noise is really acceptable even for high grade product.

Cheers,
Tomasz

Steve,
Could you tell me what is the root cause of the residual output noise for the TAS5630/15/13/11 PurePathHD amplifier family? It looks for me like a analog input stage is casing the noise and it is overall amplifier gain depend...is it a technology limitation? It would be really perfect to have a class-D easy applicable chip amplifier with unclipped output power around 150W and residual noise of 50-70V...

I consider to use the fully digital amplifier in my next similar project but I do not really understand the noise issue using TAS5518 modulator. Different, however quite similar, applications using TAS5518 have sometimes completely different noise performance - from fantastic (TAS5518-5152K8EVM) to poor TAS5518+TAS5631, but I will try to discuss a little bit more about it in my other thread.

Tomasz

I believe the source of output noise is the input stage in both TAS5630 and TAS5613. Input stage noise performance was chosen to provide the 100dB signal-noise performance of the devices, really quite good. However, I think your application uses a tweeter with unusually high efficiency, and that makes the difference.

Steve,

Yes, somehow the design made one step ahead. I still didn't shared this results with the end-customer, who was really unsatisfied with the noise performance. I hope having the improvement we can go one step ahead with the project - start building the first pre-series.

You right, the 100dB signal to noise performance is good. My application is quite special and this is why I would probably need something like 115 dB or 120dB SNR to ba fully satisfied.

Tomasz

I'am a little confused about your power ratings of the TAS5630 audio amplifier. Taking a look at the datasheet, the 5630 gives you 300W per channel at a real 4 Ohm load. Quick calculation 50V Input is round about 36V rms for the audio signal. P = U^2 / R gives you theoretical 325W of sweet loundness. So far so good but I wan't more, so I configured the TAS5630 in PBTL mode and here I'am getting confused. According to the datasheet the PBTL mode gives you 600W for a 2 Ohm load. But why am I supposed to lower the load when bridging the IC? Ok the math says so, if you keep the voltage and cut the resistance in half you get two times the power, but than again why should I bridge the channels for that result? If I just could reduce the resistance of my loudspeaker chassis I would do so. So the only thing that comes to my mind is that you don't mean a real resistance of 2 Ohm for the chassis in PTBL mode but instead 4 Ohm which are divided virtually by the number of linked channels. But this brings up the question how the 5630 achieves the 600 watts of output power. If I got it right the TAS5630 has a full bridge per channel linking them wouldn't result in a higher output voltage so you must instead increase the current through the chassis. But if the TAS would measure the current through each channel and do some limiting this would mean that I could connect any load without damaging the IC. You see I'am really confused in the matter. So please TI tell me what resistance should my loudspeaker chassis have when I went to my dealer and tell the salesman: "I need a speaker with xxx Ohm" for getting the theoretical 600W out of the TAS5630? And if you could spare the time a little explanation about how the 5630 produces the 600W would be really appreciated. Does it increase the output Voltage or the current? Is the load seen by each channel cut in half or do you have to buy a new chassis for more power?

There are cases in which loads include more than one speaker, placed in parallel, and in these cases the net load can easily be 2ohms. Placing 2 - 4ohm speakers in parallel will produce this, of course. This is often done in bass boxes and in extended systems. Of course, TAS5630 voltage cannot be increased beyond what is permitted in the data sheet (maximum PVDD is 52.5Vdc, from data sheet SLES220B, page 4, RECOMMENDED OPERATING CONDITIONS).

thank you for your reply. What I want to do, is to use the TAS5630 to power a PA bass. The bass chassis has a nominal resistance of 4 Ohms. Now if you use a conventional analog power amplifier you can often bridge the channels to archive a greater output power on the same load. For example an amp has 2 channels with 2 x 170W @ 4ohm in single mode and 1 x 660W @ 4 ohm in bridge mode. That I would have expected to be the same for the PBTL mode of the TAS5630. Now what is confusing me is the fact that TI says 600W in PBTL mode for a 2 Ohm load, while 2 x 300 Watts @ 4 Ohm in BTL mode. I mean if I have an amplifier with two channels capable of delivering 300W into a 4 Ohm load and I got the same output power on a bridged channel and still 4 Ohm, what can I gain by using the PBTL mode?

However, it is not possible to produce more voltage from a TAS5630 than is available with BTL mode - it is already a bridged output (Bridge-Tied-Load). Output voltage can swing only between PVDD and Ground, and PBTL can only place outputs in parallel - there is no way to place channels in series to get more voltage. The only way to increase output power is to produce more current, and that requires reducing load Z.

What is the bass chassis configuration? Does it include multiple speakers? If it included a pair of 8ohm speakers, would it possible to replace them with 4ohm speakers with equivalent performance? That could provide the increased power you seem to be seeking.

NOTE: DO NOT power the amplifier board when there's signal input, or the chip will be burnt out.
It is suggested to plug RCA jack first, stop signal input and then power the amplifier board.
Finally, begin signal input after 1 second.

Just one look at the power input terminals and you will know that this amplifier board means business! A Class D TAS5630 with enabled integrated feedback is used to deliver 300W to two channels, effortlessly and efficiently. This amplifier board works amazingly well with both low sensitivity speakers and subwoofers.