My thoughts on the Vibelink Amp
- Thread starter onlyoneme
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- wiim vibelink amp
Ah, so you have measured that in the vibelink ? Thruth is you do loose some power when using PFFB.
Lowest distortion without PFFB with a single tpa3255 is at 34V according to some measurements done at diyforum.
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lol...
first stage of an class d amp: digitize signal....
Class-D amplifier - Wikipedia
Texas Instruments who produce the TPA3255 that the Vibelink uses describe it as a “315-W stereo, 600-W mono, 18- to 53.5-V supply, analog input Class-D audio amplifier”. Do you want to tell them they’re wrong?lol...
first stage of an class d amp: digitize signal....
Class-D amplifier - Wikipedia
en.wikipedia.org
TPA3255 data sheet, product information and support | TI.com
TI’s TPA3255 is a 315-W stereo, 600-W mono, 18- to 53.5-V supply, analog input Class-D audio amplifier. Find parameters, ordering and quality information
www.ti.com
slartibartfast
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The link in post #103 also shows an analog inputTexas Instruments who produce the TPA3255 that the Vibelink uses describe it as a “315-W stereo, 600-W mono, 18- to 53.5-V supply, analog input Class-D audio amplifier”. Do you want to tell them they’re wrong?
TPA3255 data sheet, product information and support | TI.com
TI’s TPA3255 is a 315-W stereo, 600-W mono, 18- to 53.5-V supply, analog input Class-D audio amplifier. Find parameters, ordering and quality informationwww.ti.com
hgo58
Major Contributor
First step in the class D amplifier is a PWD encoding of the analog input. Not really a digitized (binary) signal but a kind of. It's this pulse signal that drives output stage.Texas Instruments who produce the TPA3255 that the Vibelink uses describe it as a “315-W stereo, 600-W mono, 18- to 53.5-V supply, analog input Class-D audio amplifier”. Do you want to tell them they’re wrong?
TPA3255 data sheet, product information and support | TI.com
TI’s TPA3255 is a 315-W stereo, 600-W mono, 18- to 53.5-V supply, analog input Class-D audio amplifier. Find parameters, ordering and quality informationwww.ti.com
And?lol...
first stage of an class d amp: digitize signal....
Class-D amplifier - Wikipedia
i just don't get you first use-case for testing; "how to make sure that the analog inputs are not digitized?"
why bother really?
- the ESS is a D/A converter, not an A/D converter. WIIM does not mention any A/D converter being implemented (besides the class-D-amp itself)
- WIIM would be silly to include more components the necessary (as it increases cost)
- as I stated; de D-class amplifier is a form of digitized-signal-amplifier-by-design. so the answer to your question is; i can assure that they are... otherwise the amp would not work
you might question; do we hear induced noise by the D/A pre-stage when using the analog inputs of the amp?
that would be a probable 'no'; with an S/N of the chip of about 130DB you wont hear it. (welll, actuallyonly when WIIM messes up the supporting components or bad design (grounding and such) )
if we want cutting edge questions....why does WIIM convert the digital signal back tot analog using the ESS at all?
why not convert it to the needed PWD stream for amplification directly?
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I think you are getting it too serious. It was just a funny test to verify if an ADC was used or not. BTW, WiiM didn't mention that 2 DACs were used in the WiiM Amp.i just don't get you first use-case for testing; "how to make sure that the analog inputs are not digitized?"
why bother really?
- the ESS is a D/A converter, not an A/D converter. WIIM does not mention any A/D converter being implemented
- WIIM would be silly to include more components the necessary (as it increases cost)
- as I stated; de D-class amplifier is a form of digitized-signal-amplifier-by-design. so the answer to your question is; i can assure that they are... otherwise the amp would not work
you might question; do we hear induced noise by the D/A pre-stage when using the analog inputs of the amp?
that would be a probable 'no'; with an S/N of the chip of about 130DB you wont hear it. (welll, actuallyonly when WIIM messes up the supporting components or bad design (grounding and such) )
if we want cutting edge questions....why does WIIM convert the digital signal back tot analog using the ESS at all?
why not convert it to the needed PWD stream for amplification directly?
If I remember correctly 3255 does not accept the digital signal directly, so some sort of the external conversion is needed anyway. If the "true digital" amp is planned,
Edit: my mistake, AX5689 is not from Infineon.
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hgo58
Major Contributor
Probably because direct conversion of a 24-bit PCM sample to PWM would require a PWM clock frequency many times higher than the audio sampling rate (at 192kHz that could be 50MHz) and there may then be problems with noise shaping. Using the well known (and cheap) components for D/A conversion and Class D amplifier instead, makes the design robust.why not convert it to the needed PWD stream for amplification directly?
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ok maybe I took that too serious indeed
nah...would need a different design indeed, way to costly. can't be done at this price point (yet)
at current price, design seems solid
hgo58
Major Contributor
You will also have the analog feedback from the amplifier output that needs to be compared with an analog input (HHS Loop). So by design the DAC is needed.ok maybe I took that too serious indeed
nah...would need a different design indeed, way to costly. can't be done at this price point (yet)
at current price, design seems solid
You mean an ADC in this case?
hgo58
Major Contributor
No. The analog output of the amplifier is compared to its analog input, that is the output of the DAC.
What type of amplifier are we talking here? I thought it was about digitally controlled Class D amps.
If it is the classical analogue input Class D amp, then output and input signal are both analogue already. What would we need a DAC for? We just feed back a (filtered).portion of the output signal to the input comparator.
hgo58
Major Contributor
The DAC is for the analog input to the amp. The initial question was why it was not implemented to go directly from PCM data to PWM, without the use of a DAC.What type of amplifier are we talking here? I thought it was about digitally controlled Class D amps.
If it is the classical analogue input Class D amp, then output and input signal are both analogue already. What would we need a DAC for? We just feed back a (filtered).portion of the output signal to the input comparator.
Well, yes. But the need for a DAC is not directly related to feedback. It stems from the fact that the amplifier module in use here doesn't have a digital input (which is not a bad thing).
Feedback really is an issue of concern with digitally controlled Class D amps. Direct PCM to PWM conversion is mostly suitable to low performance, high efficiency applications. The famous TacT Millenium was able to reach good (but not exceptional) technical characteristics with no feedback at all. Other, newer designs are designed with analogue to digital feedback implementations, which is pretty hard to do.
EddNog
Major Contributor
From what I have seen, "true digital," power amps (frequently called, "power DACs") cannot be designed with feedback, so that rules out PFFB and also rules out load-independent-frequency-response.
-Ed
hgo58
Major Contributor
Abd as the WiiM AMP Ultra has PFFB it must have a DAC.
So thats the answer to the question.
EddNog
Major Contributor
Well it's also known that WiiM Amp, Amp Pro, and Amp Ultra all utilize Texas Instruments' TPA3225 amplification chip, which is designed specifically with an analog input circuit, so those specifically need a DAC if the source does not have analog outputs.
-Ed
