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Topping BC3 Review (Bluetooth Receiver) & BT CODECs

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amirm

amirm

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I had a Samsung S8, paired with the Sony XM3. Lot of frustration as the signal was garbage even at 20cm from the phone, in 990. I have now an S21, and the connection is solid all the time, thanks to the better bluetooth radio and dual antennas.
The larger S8+ I have must have room for a better BT antenna setup.
 
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amirm

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Any chance you could make a video explaining (on certain devices) why the left and the right channels are not the same when it comes to output. One for distortion values and another for volume. Why are they different and is it a manufacturing issue or just poor equipment from the getgo?
You mean small difference? If so, yes, it is manufacturing tolerances for so many components in signal path. If the difference is excessive, I do make a note of it. In one case Schiit sent me a new pre-amp when I complained about it and the new one was fine.
 
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amirm

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I have most music in AAC 320 kbit/s. Iif someone can give example of music where AAC 320 kbit/s is audibly different from loss-less I am all ears.
Do you know the encoding rate used for AAC over Bluetooth in iOS and Android?
 
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And can we hear the differenses between different codecs?
I did a casual test in my last review of BT receivers and I could tell the difference between SBC and AAC. This was sighted and not perfect test but if you are asking for an opinion, there it is. :) I guess someone with more time than me can use the Toslink output of BC3 and we could do some listening tests.
 

Thomas_A

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Do you know the encoding rate used for AAC over Bluetooth in iOS and Android?

What I've seen - max bitrate 264. But receiver device may have other spec.
 
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Mulder

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I did a casual test in my last review of BT receivers and I could tell the difference between SBC and AAC. This was sighted and not perfect test but if you are asking for an opinion, there it is. :)
In what way do they differ? I guess you found that SBC was better than ACC. But is the noise level lower or is the audio more transparent?
 

Thomas_A

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Interesting, So it does looks a bit better on Apple devices

Yes. But perhaps something extra compressed with the iPhones and BT codec, 160 kbps mono AAC gives basically flat to 19 kHz. Thats above my hearing range for sure.

aac%20vs%20wav.png
 

Bullwinkle J Moose

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Keep in mind that most OS, Browsers, and media players adapted to the Latency of the various Bluetooth Codecs by now. I don't know of Games, I don't play those, but for Video Playback, syncing image to audio is an issue of the past, I see very limited appeal to AptX LL nowadays.

Do you have any idea what your talking about?

OS, browsers and media players do not adapt to a bluetooth transmitters codec latency

latency remains the same for any source material whenever a bluetooth transmitter is added to any computer

If you are referring to "manual" adjustment for latency in VLC or any other player, then it's worthless to me

I need a plug and play - Low Latency system for everything I want to do from now on

AptX LL is the best there is for now, and it will only have limited appeal when something better comes along
 

Thomas_A

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Here is 20-24000 converted to AAC 160 kbps mono (aka 320 stereo) through my Marantz with BT, Airplay and analogue cable from Mac Mini to Marantz (-> pre out). The latter one is direct/pure direct mode so no DACs involved. Not sure here but I would say that both Airplay and BT has -2 dB at 19 kHz so I guess that is due to DAC filtering in the Marantz and not BT drop off. So BT with AAC 160 kbps mono is most likely linear to 19 kHz.



wifi-bt-cable%20aac.png
 

Nathan Raymond

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This is from a couple of years ago, but has some good info, like why synthetic tests aren't necessarily representative of a given codec's performance with actual music:

https://habr.com/en/post/456182/

Due to the fixed distribution of quantization bits, the codec cannot “transfer the bits” to frequencies that need them most. Unlike SBC, aptX will not “cut off” frequencies, but will add quantization noise to them, reducing the dynamic range of the audio.

We should not assume that using, for example, 2 bits for a band reduces the dynamic range to 12 dB: ADPCM allows up to 96 dB of dynamic range to be used, even with 2 quantization bits, but only with a certain type of signal.

ADPCM stores the difference between the current and the next value in numerical representation, instead of using the absolute value, as in PCM. This reduces the requirements for the number of bits needed to store the same (without loss) or almost the same (with relatively small rounding error) information. To reduce rounding errors, factor tables are applied.

When creating the codec, the authors calculated ADPCM coefficients on a set of music audio files. The closer audio signal is to the set of music on which the tables were built, the less quantization errors (noise) are generated by aptX.

Because of this, synthetic tests will always produce worse results than music.
 

PeteL

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Do you have any idea what your talking about?

OS, browsers and media players do not adapt to a bluetooth transmitters codec latency

latency remains the same for any source material whenever a bluetooth transmitter is added to any computer

If you are referring to "manual" adjustment for latency in VLC or any other player, then it's worthless to me

I need a plug and play - Low Latency system for everything I want to do from now on

AptX LL is the best there is for now, and it will only have limited appeal when something better comes along
Nope, sorry, In my setup, use AAC over Bluetooth and HDMI to my TV, Image and sound are perfectly in sync for Netflix, for youtube, VLC, etc. No manual adjustment needed. It was not the case a couple years ago. of course if you use a bluetooth transmitter from an analog or digital out of your TV or DAC to feed a BT headphone, the TV cannot possibly know that you hooked up something with a delay on it and it will be out of sync, but if audio and image is fed from a computer and sound is fed trough Bluetooth, it will know to delay the image to match the sound. Yes I know what I'm talking about, I developped a Bluetooth receiver in the past.
 
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Bullwinkle J Moose

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Nope, sorry, In my setup, use AAC over Bluetooth and HDMI to my TV, Image and sound are perfectly in sync for Netflix, for youtube, VLC, etc. No manual adjustment needed. It was not the case a couple years ago. of course if you use a bluetooth transmitter from an analog or digital out of your TV or DAC to feed a BT headphone, the TV cannot possibly know that you hooked up something with a delay on it and it will be out of sync, but if audio and image is fed from a computer and sound is fed trough Bluetooth, it will know to delay the image to match the sound. Yes I know what I'm talking about, I developped a Bluetooth receiver in the past.

Let me get this straight....

Your built in bluetooth transmitter has no delay ?

But there is a delay if you add an external bluetooth transmitter, correct ?

All of my bluetooth devices are external add-ons with intolerable delay unless using AptX LL

My audio and image is fed from a computer and sound is fed through "external" Bluetooth transmitters
The computer "DOES NOT" know to delay the image to match the sound
 

PeteL

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Let me get this straight....

Your built in bluetooth transmitter has no delay ?

But there is a delay if you add an external bluetooth transmitter, correct ?

All of my bluetooth devices are external add-ons with intolerable delay unless using AptX LL

My audio and image is fed from a computer and sound is fed through "external" Bluetooth transmitters
The computer "DOES NOT" know to delay the image to match the sound
Exactly, you understood right, yes if the bluetooth transmitter is not talking directly to the computer but just getting an input signal it can't be in sync. or in other words, Your audio output of your computer or smartphone is "Bluetooth". The transmitter can be a USB dongle tough, it doesn't have to be "internal", but it has to be recognized as a device by the OS.
 
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Daniel0

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The transmitter can be a USB dongle tough, it doesn't have to be "internal", but it has to be recognized as a device by the OS.
Interesting. I know android and iOS do some compensation for delay but it is news to me that computers do that too.

Do you know if it's OS dependent or application dependent specifically regarding Windows 10?
 
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