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Topping BC3 Review (Bluetooth Receiver) & BT CODECs

amirm

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This is a review and detailed measurements of the Topping BC3 Bluetooth receiver and headphone amplifier. It was sent to me by the online seller, Yaoyaotiger HIFI Audio Store and costs US $69. This is a follow up to our previous tests of Bluetooth receivers and investigating performance of various codecs supported within.

The shiny plastic and slick design sets the BC3 apart for the typical Topping desktop products:

Topping BC3 Review Bluetooth LDAC Receiver.jpg


The touch screen buttons are pretty but with no tactile feedback, they are kind of inconvenient to use. There is a lock button to deactivate them which is nice:

Topping BC3 Review Bluetooth Toslink Digital LDAC Receiver.jpg


Nice to see both headphone amplifier and digital/analog line outs. There is a convenient Toslink mini to full size adapter in the box which I used for my testing. The unit has battery built-in so you can charge it and use it on the go (car, commute, etc.). I did all of my testing while I powered it through USB-C from my computer monitor's hub (same port I use for all of my DAC testing).

Topping BC3 Digital Measurements
This is the first Bluetooth receiver we are testing that has digital output. This is exciting because we can see the true performance of the various codecs without the performance of the DAC getting in the way. The source for the stream was my Samsung S8+ phone running Roon player with Android developer options enabled so I could select the Bluetooth codec. Prior to this test, I was not successful in getting LDAC to work. I figured out the issue here. Turns out in their infinite wisdom, whoever did this work decided that you must enable LDAC both in the developer options and Bluetooth settings!

Let's start with aptX:

Topping BC3 Measurements Bluetooth Aptx.png


We immediate see the signature of aptX with that stepped down response in frequencies above 5 kHz. The higher frequencies are more "random" (have higher entropy) so harder to compress. By lowering their levels or truncating them, there is less for the codec to do.

Switching to AAC shows the poor quality we have seen which I am guessing is due to Android implementation of AAC encoder (meant to test this with an iPhone but forgot -- will do so later):

Topping BC3 Measurements Bluetooth AAC.png


We get a big boost in SINAD but I am not happy about all the artifacts. In my prior testing I found SBC to actually sound better:

Topping BC3 Measurements Bluetooth SBC.png


So our previous conclusions more or less hold with the codecs being the limiting factor not the DACs. However, now we have a new kid on the block, namely the Sony LDAC codec. Is it as good as its hype? Let's start showing its performance with 16 bit setting of the codec (source is still 24 bits):

Topping BC3 Measurements Bluetooth 16 bit LDAC.png


Performance jump quite a bit showing a SINAD which is the limit of 16 bit bit depth. Switching to 24 bit mode is this tester gets a big smile:
Topping BC3 Measurements Bluetooth LDAC.png


Wow! What an improvement. Then again, all the other codecs should have done excellently with this simple sine wave that is dead easy to encode. But they didn't so LDAC in 24-bit mode wins big time. Even in 16 bit more it leaves the other codecs behind.

All of these measurements are in digital domain. Let's fee the Toslink to a Topping D30 Pro and measure its analog output using LDAC:
Topping BC3 Measurements Toslink to Topping D30 Pro Bluetooth LDAC.png


Hallelujah! We get state of the art analog reproduction despite using a wireless connection that started life for just voice.

Topping BC3 Analog Output Measurements
The DAC here is not a heroic implementation so we are going to get decent but not state of the art fidelity when using LDAC:

Topping BC3 Measurements Analog Line Out Bluetooth LDAC.png


Dynamic range is basically representative of 16 bit format:

Topping BC3 Dynamic Range Measurements Analog Bluetooth LDAC.png


Headphone out is essentially the same as line out:

Topping BC3 Measurements Analog Bluetooth LDAC.png


Edit: A couple more measurements:

Here is an asynchronous frequency sweep comparing pairs of codecs:

Topping BC3 Frequency Response Measurements LDAC and SBC Bluetooth LDAC.png


That is one nice and flat response for LDAC. SBC on the other hand is filtering above 14.5 kHz. This is done because high frequencies are much harder to encode due to their high speed variations (in sample value)/noise.

I was surprised that AAC was also filters above 15 kHz:
Topping BC3 Frequency Response Measurements AAC and aptX Bluetooth LDAC.png


aptX as we saw earlier plays some serious games in treble.

This type of sweep also generates THD+N relative to frequency:
Topping BC3 Measurements Bluetooth Aptx LDAC SBC AAC THD+N vs frequency.png


We see that LDAC continues to be the cleanest codec by far. Note that this is a dynamic sweep signal so more complex than a single tone that dashboard uses. The other codecs trade places in different parts of the spectrum and are generally a mess. aptX by the fact that it chops off high frequencies does better at very low frequencies.

LDAC Codec Licensing
Searching for LDAC lands you on the English translate of a site that is likely hosted by Sony Japan. In there we see the comforting mention of Topping as proper licensee of the codec:

Sony LDAC Supported Companies.png


Earlier it mentions that the source code for LDAC is part of the Android Open Source. Don't confuse this with it being fee. You still need to license the underlying patents from Sony or they can come after you. What is involved in said licensing? Sony is unusually transparent about that:

Sony LDAC Licensing.png


Predictably they expect you to spend months negotiating the NDA and actual license. Having been on both sides of such licensing, I can attest to this process being long and drawn out because the agreements likely start very one sided which you then kill yourself across countless conference calls to try to soften. Typical clauses are "covenant not to sue" meaning once you license this technology, then you can't sue Sony or their other licensees over any patents you may own. I don't know if such a provision is in there but I am guessing it would be. On NDA front you likely want to have a residuals clause meaning what you remember can't be unremembered. They will say you have to have a button to erase your memory if NDA is terminated.

And oh, after all the above you have to pay the license fee. I see no provision for RAND licensing (Reasonable and Non-discriminator Licensing), meaning everyone pays the same fee. Without it, a competitor to Sony could be charged much more money than a friend and thereby keeping a competitive advantage.

Did someone complain about MQA being bad? Welcome to the world of audio licensing! :)

LDAC Codec Range
I did most of my testing with the phone being a few feet from the BC3 receiver. I did however test to see if I could get performance to drop but could not even after I moved my phone some 20 to 25 feet (7 to 8 meters) away. I had the codec in adaptive mode by the way so it could have switched encoding rates but I saw no glitches to indicate it did so. Your mileage may vary of course depending on the implementation of Bluetooth transmitter in your device.

Conclusions
The previous Bluetooth receivers we tested suffered both from codec losses and less than optimal implementation of output DAC. Topping has the same limitation as far as codecs but since it supports LDAC, for simple signals at least, it eliminates that bottleneck. Its DAC implementation is what you expect: "good enough for 16 bit content." Fortunately with digital output you can connect it to your favorite DAC with balanced out and by using LDAC, you have a superb input path for Bluetooth.

I have not yet tested enough Bluetooth receivers to have a good calibration for what is good and what is great. Still, I was very pleased with the performance of the Topping BC3 and am putting it on my recommended list.

EDIT: video review just posted:


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As always, questions, comments, recommendations, etc. are welcome.

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MarsianC#

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Stunning performance. I'll buy a container full and sell them with a CNC'd case for $$$!
How much power is on tap for headphones?
 

stevenswall

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If this worked with Chromecast, I'd use the optical out and buy 3 of them. Need more multi-room dongles, fewer that are basic bluetooth like this.
 

3125b

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That new panther is a good visual representation of "missing the mark" ... and also my cooking skills :)

The performance of this receiver (DAC and headphone out) is about what could reasonably be expected, it's not that expensive and just about clears the 16-bit hurdle, wich is the maximum of what most people are gonna ask of it. Compared to the other bluetooth receivers tested so far it seems like the best.
 
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amirm

amirm

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Stunning performance. I'll buy a container full and sell them with a CNC'd case for $$$!
How much power is on tap for headphones?
It has 2 volt output so should be good. I can't do sweeps and such with Bluetooth.
 
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amirm

amirm

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Fantastic! Thank you, more of these, please…
Thanks. It was fun for me too discovering new things. I have another Bluetooth receiver to test as well.
 

daftcombo

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So, is this a good alternative to Chromecast Audio?
 

stevenswall

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Great review!

Looking forward for the iPhone AAC test because that is all what us Apple bleeps get to use.

Seems like they may fix that soon. I'll bet they make an proprietary codec for their new lossless streaming capabilities and re-release their headphones and earphones at a markup.
 

stevenswall

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So, is this a good alternative to Chromecast Audio?

This is a bluetooth receiver and doesn't do any wifi/multi-room stuff like the Chromecast audio does.
 

faheem

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Thanks for the write up, great to see you testing more BT devices and getting to discover these codecs implementation and limitation.

I own a Topping BC3, It's a unique and well thought out , brilliant little device. Toslink , fantastic battery life, good reception.

I use mine exclusively connected to an ifi Diablo via toslink, using LDAC through Deezer on mobile and APTX LL for tv / movie watching.
 
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