Sound quality differences among RCA, Powerlink and WiSA

[Archm@ge]

Hi Buddies,

I am new,therefore dropping out some basic questions here 🙂

I plan to upgrade my BS2 to BL18, since i experienced better sound quality via line-in from external DAC + Pre-Amp on my BS2, therefore i’d like to re-use the DAC and Pre-amp for BL18, assuming the wired connection would provide better sound quality as well over wireless(WiSA) on BL18.

Since the there are both RCA inputs and Powerlink inputs on BL18, could like to know which inputs is better when it comes to sound quality? Or there is no difference at all?

Thanks in advacnce.

[geoffmartin]

Hi,

I might be able to offer a little information about this – but I need to know what a “BS2” is… I see this as a “Beosound 2” – but I’m pretty certain that this is not what you mean. 🙂

Or, if this IS what you mean, then what DAC + Preamp are you using?

[Archm@ge]

Hi geoffmartin,

What i meant ‘BS2’ is actually ‘Beosound 2’ 🙂

I am using SMSL M500 Mk2 DAC + Topping Pre-90 for this experiment 😉

[Stan]

Unlike Geoff, I wasn’t involved in designing these speakers, but I’ll give it my best guess.  I doubt if there are any differences between the RCA and PowerLink connections. These both accept analog signals, and each probably sends essential the same signal to the same internal circuits.  Any difference might be attributable to the cable being used.  That is, there are probably more bad RCA cables out there than PowerLink.  However, if either cable is decent quality, then there should be no difference.  Use whatever is more convenient.   I’m sure Geoff will correct me if my guessing is wrong.

One nice thing about PowerLink is that it carries both left and right signals so you can daisy-chain your speakers.  That is, instead of running a cable from your source to each speaker, with PL, you can run from your source to speaker 1, then from speaker 1 to speaker 2.  Sometimes this makes the cabling easier.

Also, note that the BL18s are “digital” speakers so the analog signal you send to them will be digitized and DSPd before being converted back into analog and sent to the drivers.  You can skip that initial digitization step if you use the TOSLink connection (which must be daisy chained) and send a digital signal to the speakers.  However, if you like the sound of your DAC, you may not hear this as an improvement.  Volume control can be an issue with the TOSlink connection (it depends on your whether you source device supports).

[Archm@ge]

Hi Stan,

Thanks for your reply, it is very informative, one follow-up question: do you think BS2 is also a ‘Digital’ speaker that will do similar things(Analog to Digital conversion) on its 3.5mm mini-jack line-in socket? My experiment has delivered better sound quality a bit(crisper highs, firm brass, broader sound stage) with external DAC+Pre-amp compare to Airplay to BS2. Do you think it is due to 3.5mm line-in goes via different path(Line-in to Power-amps to Drivers) than Airplay does(Airplay to Internal DAC to Power-amps to Drivers)?

🙂

[Stan]

Guessing here again, but I’m pretty sure the BS2 isn’t “digital” in the same way as the BL18.  It has no digital input so I would assume that the line-in signal takes a different path than a digital streaming signal.  AFAIK, all of the “digital speakers” like the BL18 have a digital input option.

I’m not very familiar with Airplay so I poked around on the web and found some discussions about Airplay2 requiring some non-obvious settings to get lossless transmission (https://audiophilestyle.com/ca/bits-and-bytes/apple-music-lossless-mess-part-2-airplay-r1026/).  Maybe this is what you ran into?

The BS2 is not a budget device so it is my understanding that it uses a quality DAC.  Therefore, I don’t think the internal DAC is the problem, but you never know.  We all hear differently.

[geoffmartin]

Hi again,

All Bang & Olufsen “Beolab” and “Beosound” loudspeakers are “digital” loudspeakers; meaning that any signal that comes in is converted to a digital signal for all processing, and then converted back to analogue signals which are sent to the amplifiers for the individual drivers. This is true whether the device has a digital input, an analogue input, or no input (meaning it only has “internal” sources).

In some cases, the Power Link input and the RCA (Line / Aux) input are essentially identical with respect to technical sound performance. In some cases, there is a difference in the maximum allowable input level (and therefore the sensitivity of the device: a measure of output level as a function of input level). In the specific cases of Beolab 5, Beolab 50 and Beolab 90, the  input sensitivity of the line inputs are user-adjustable.

IF your source / preamp has a high-enough maximum output, then it can overload the line input of the loudspeaker – but this is something that has to be specifically determined for the output and the input of the products in question.

Be careful making conclusions when comparing things like an analogue connection to a wireless digital connection. There are so many individual components in each of those two signal paths that may have an effect on sound “quality” that there’s no real way to know why they may be different, if they are. You certainly cannot conclude that “analogue wired is better/worse than digital/Airplay/Chromecast/Whatever” without doing an extensive amount of testing, including being able to measure the signals at points in the chain within (not between) devices. In other words, it’s not possible for a normal person without a lot of test gear to do this and arrive at a reliable conclusion. In addition, an overnight firmware update may make all of your conclusions irrelevant.

Finally, be careful to not confuse the terms DAC (Digital-to-Analogue Converter) with ADC (Analogue-to-Digital Converter), which appears to be happening above… 🙂

 

[Archm@ge]

Hi geoffmartin,

Thanks a lot for your answer, that is a lot to digest, the diffs I noticed between Line-in and Airplay might be too objective or an effect of my brain filters 🙂

 

[Archm@ge]

Hi Stan,

Thanks for your reply and the link provided 🙂

[geoffmartin]

@Archm@ge: There’s definitely a difference – but which is better (= which you’ll prefer) is impossible to predict. And, it might be different for audio files with different sampling rates (for example…) Anything can go wrong in many different places…

Cheers
-geoff

[Archm@ge]

@geoffmartin, to me the Apple Music Lossless via Airplay from iphone13 to BS2 sounds a bit blurry to me in comparison to Wired through DAC+Pre-amp, it might be the issues described in the page provided by Stan wrt Bit Perfect issue over Airplay(https://audiophilestyle.com/ca/bits-and-bytes/apple-music-lossless-mess-part-2-airplay-r1026/), my BS2 is a 2017 made version, not sure it is a Airplay1 or Airplay2 version.

The easiest way to examine whether it is due to Bit In-perfect issue over Airplay is to compare the sound(still objectively since i only have my ears :)) between Build-in Deezer steaming over WIFI and Deezer app on Iphone13 over Airplay 🙂

[geoffmartin]

Hi,

Sorry – the only way to find out if something is bit perfect is to actually measure it, bit for bit. And, as I said before, there are so many other things going on that you can’t trust your ears…

Even a 1 dB difference in output levels will skew opinions when there are no other differences.

[Archm@ge]

Gottcha, thanks a lot! Wish you a nice day!

[geoffmartin]

You too!

FYI: I just read what I wrote above – I said “you can’t trust your ears” – but to be perfectly clear: I don’t trust my ears either. Ears are notoriously untrustworthy – they’ll blindly believe anything they hear! 😀

[Archm@ge]

Morning greetings! Have been putting a lot of time reading/studying through articles on your blogger today 🙂

When talking about ears are untrustworthy, do you think different power cable will make BS2 sound differently, since I seemed to notice some differences(better sound quality, meaning punchier Bass and brighter Highs) by switching the power cable from BS2 original to AudioQuest NRG-X2 🙂

[Glitch]

geoffmartin wrote:

Ears are notoriously untrustworthy – they’ll blindly believe anything they hear! ?

Isn’t the problem actually the brain? (i.e. Psychoacoustics) 😉

Glitch

[geoffmartin]

Archm@ge wrote:

When talking about ears are untrustworthy, do you think different power cable will make BS2 sound differently, since I seemed to notice some differences(better sound quality, meaning punchier Bass and brighter Highs) by switching the power cable from BS2 original to AudioQuest NRG-X2 ?

Definitely not. The only difference a fancy new power cable will make is on the weight of your wallet. 🙂 You’ll get the same effect by keeping the original power cable and turning up the volume by 1 or 2 steps.

Glitch wrote:

Isn’t the problem actually the brain? (i.e. Psychoacoustics) ? Glitch

The brain is half of the problem – so one has to be very specific about exactly which psychoacoustic effect one is talking about in order to decide whether the issue is psycho or acoustic.

[Archm@ge]

Hi geoffmartin,

Thanks! BTW,  any diff wrt sound quality between Wired(Powerlink) and Wireless(WiSA), thanks.

[wanc1]

Hey Geoff,

There is a noticeable difference in the amount of bass when I switch from power link to optical from Beosound Core to Beolab 50. The power link sounds more bass heavy, while the optical sounds more balanced. What causes this difference?

 

[geoffmartin]

Archm@ge wrote:

Hi geoffmartin, Thanks! BTW, any diff wrt sound quality between Wired(Powerlink) and Wireless(WiSA), thanks.

Yes, but the differences are not easily explained in one sentence.

Power Link is an analogue connection, so you have the addition of the noise floor of both the DAC (Digital to Analogue Converter) of the source device and the ADC (Analogue to Digital Converter) of the input device. Typically, the noise floor of an ADC is higher than that of a DAC (a good rule of thumb as you go through life…).

Wireless Power Link is a digital connection, so the noise floor is defined by the word length of the signal that is being sent (and possibly the sampling rate converter of the transmission and/or receiving device). In the case of the word length, it’s a 24-bit signal, which puts the noise floor at about 141 dB below the maximum – which is well below the noise floor of the rest of the system. However, any low-latency wireless audio transmission can/will have errors caused by anything ranging from a cat walking between the transmitter and the receiver antennae and a police car driving by using a radar. As with most/all other low-latency wireless audio systems, WPL uses error concealment (rather than error correction – there’s no time for that…) to recover from those errors.

My last test of WPL involved putting a transmitter and a receiver 1 m apart, and sending a signal through it, checking that the bits that came out were the ones I put in. This test ran for 24 hours a day for 11 days and I got 0 bit errors in that time. However, if I waved my hand between the two antennae, I could see the error rate go up. NOTE however, that this does not mean that you can hear those errors – this is dependent on how bad the error is (which, in turn is a result of what caused it) – but they exist.

When you ask about “sound quality” there are too many aspects / dimensions to say which is better or worse, because we’re talking about which you prefer. If you never listen at a high enough volume setting to make the noise floor of the Power Link signal audible, then this is a non-issue. IF you live in a densely-populated apartment building with a lot of RF noise (e.g. microwave ovens, numerous WiFi networks, and a high crime rate with lots of police presence and ambulances) then maybe WPL is not the best solution for you…

Which means that the answer to your question is “it depends”, which is not terribly helpful, but honest.

 

[Author]

Posts