Wireless Audio (Via Bluetooth) What are the losses people?
Jul 15, 2008 at 2:04 PM Thread Starter Post #1 of 15

therock003

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I hope I'm posting on the correct subforum,cause i couldn't decide which one was the most fitting.

Anyway here goes.I have a couple of Bluetooth audio transmitters.They connect to a 3.5mm jack they take sound and transmit it via Bluetooth to any Bluetooth receiver device.Here is my setup.

My Transmitters

Code:

Code:
[left]http://www.jabra.com/Sites/Jabra/na-us/products/Pages/JabraA120s.aspx http://www.sonystyle.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10551&storeId=10151&langId=-1&productId=11035425[/left]

First one is Jabra A120s,uses Bluetooth v1.1 specification,but has it's own battery.

A120s_banner_EM_EN_299.jpg


Second is Sony HWS-BTA2W,works as both receiver and transmitter (transceiver),uses Bluetooth v2.0, but requires external power source.

HWSBTA2W.png


So anyway, at this stage we have audio that is on analog format,and I suppose it's being converted to digital so it can be sent via Bluetooth packets to the receiving device,and then the receiving device re-converts it to analog in order to output it to Headphones,speakers/amps or whatever.

My Receivers
A)IT could either be the Sony if i use Jabra as the transmitter,or
B)I also have an individual Sony Bluetooth Receiver Sony DRC-BT15

DRCBT15.png


Code:

Code:
[left]http://www.sonystyle.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10551&storeId=10151&langId=-1&productId=8198552921665400453[/left]

Transmitters work with every Device with a 3.5mm jack.Be it an output of a computer sound card,a stereo device output,a radio device,a TV audio output,everything.

Overall.Things To take under consideration:
-Since they take analog input that means that one way or the other the Sound is converted to an analog format so that's the first loss right there.I will need a strong DAC device,that will output an accurate sound to the transmitter.

-Then the transmitter will somehow convert this signal back to digital so it will send it to the receiver.This conversion is up to the Transmitter,I don't know what kind of dacs Jabra or Sony uses internally for this job,but that's not up to me.

-Also i don't know the DAC the Sony Receiver uses in order to convert the digitally transmitted audio via Bluetooth back to analog for headphone ouput.

What's my best bet here guys?
 
Jul 16, 2008 at 10:57 AM Post #2 of 15

therock003

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Seriously guys i would require your opinion on this one.


-How do such devices convert digital-to-analog and analog-to-digital sound?

-Plus Bluetooth operates on a 2.4ghz frequency,does that mean that the frequency modulation will modulate audio signal's frequency from 44.1-48khz -> 2.4Ghz?

-Is this an acceptable way to transfer sound wirelessly?
 
Jul 17, 2008 at 6:32 PM Post #3 of 15

miniduncan

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Quote:

Originally Posted by therock003 /img/forum/go_quote.gif
-Plus Bluetooth operates on a 2.4ghz frequency,does that mean that the frequency modulation will modulate audio signal's frequency from 44.1-48khz -> 2.4Ghz?



I can really only answer this, the 2.4Ghz is the frequency of the carrier signal that the bluetooth uses to send your data. The signals frequency of the music should remain unchanged.

I don't know too much about bluetooth but i'm assuming that the signal is modulated onto the microwave at 2.4Ghz in much the same way that a radio signal is modulated onto the carrier wave of 80-110Mhz for an FM radio.
 
Jul 18, 2008 at 8:41 AM Post #4 of 15

nghiasays

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Quote:

Originally Posted by therock003 /img/forum/go_quote.gif
Seriously guys i would require your opinion on this one.


-How do such devices convert digital-to-analog and analog-to-digital sound?

-Plus Bluetooth operates on a 2.4ghz frequency,does that mean that the frequency modulation will modulate audio signal's frequency from 44.1-48khz -> 2.4Ghz?

-Is this an acceptable way to transfer sound wirelessly?



From what I could gather from the A2DP v1.0 spec they must be using A2DP to transmit audio with 723kbps of bandwidth. The Sony likely converting to ATRAC though that may mean the receiver must also be a Sony product to decode as ATRAC is optional for A2DP devices. Mandatory is SBC, so all A2DP transmitters and receivers will support it. I don't know how good SBC encoding are. Bluetooth v1.2 (the Jabra) supports 1mbps bitrates the actual bitrate for the older devices is more like around 700kbps which means while around other 2.4GHz devices which create interference the bitrate may drop below the max 723kbps while the Sony would likely have an easier time achieving that. 723kbps though is more than enough for mp3s (also an optional encoding) and I'd guess for SBC too or otherwise this spec would be worthless. Some might complain about all the sampling, encoding, decoding, and conversion back to analog. It sure isn't full bandwidth. I'd also be concerned with the bitrates the Jabra can achieve while at the fringes of its transmission range.
 
Jul 18, 2008 at 1:07 PM Post #5 of 15

therock003

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Sony uses bluetooth v2.0.I'm not sure that it supports edr (Enhanced Data Rate) but i know for a fact that v2.0-2.1 with edr support achieve a new maximum of 2.1mbps.

Bandwidth is not my concern though.Well it was when i used my bleuttoth dongle to transfer sound,cause when i combined it with my bluetooth mouse,the sound was being cut off and mouse pointer was choppy,but with this bluetooth dedicated solution i can use my mouse with bluetooth dongle and have the transmitters take up the audio challenge.

Although using a transmitter the sound leaves and comes off as digital and the only conversion happens at the receiver,whichever of my sonys may that be.
 
Jul 20, 2008 at 12:37 PM Post #6 of 15

therock003

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Is there any way to get specifics on the devices as far as the signal conversion goes?Is there any sony dedicated forums where they might know the specifics of this device and point out how the dacs are being achieved?
 
Jul 24, 2008 at 4:16 PM Post #7 of 15

infinitesymphony

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No matter what, this setup is a bad idea if you care about sound quality. If the transmitters only have analog inputs, here's what will happen to the signal, with significant losses at every stage:

D/A -> A/D -> possible compression -> D/A

The quality of the D/A conversion at the start (i.e. your source) will not matter simply because the signal will be mangled by the time it reaches the (probably awful) D/A section of the receiving device. The only wireless transmission method that makes sense is something like the Squeezebox system, where the signal stays in the digital domain until the receiving device does D/A or it sends the digital signal along to another DAC via S/PDIF output.
 
Jul 26, 2008 at 10:12 PM Post #8 of 15

therock003

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I see what you mean,but since i mostly use this method for watching video files i dont seem to be bothered with the sound.

Although there is some annoying hissing,but that's a result of the sound cards output since i get it when i hook the phones directly to the source.

But although theoretically this looks like a nightmare with all these conversions and a possible compression the result so far is nothing noticeable,except for the result hissing of my bad integrated sound card.
 
Jul 27, 2008 at 3:31 PM Post #9 of 15

sonq

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My office has one of these stereo BT connected to the dept hifi.
WiMe - Love Your Music
Buy a WiMe Kurve Bluetooth Stereo Adapter, #KURVE - eXpansys UK

It sounded pretty good and just need a single button pairing on 1st use. We have a pretty decent office system with Rotel amp and wall mounted KEFs - most of us uses office issued Sony Ericsson P1i to DJ wireless to the system.

There's a headphone jack but I've never tried it, so no comment.
 
Jul 29, 2008 at 2:19 AM Post #11 of 15

infinitesymphony

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Quote:

Originally Posted by therock003 /img/forum/go_quote.gif
Guys i also gotta to ask you.Is it worth it using a DAC via this method?

And if so will i place the DAC on the before the transmitter or after the receiver,which would be better?



If the receiver has a digital output, then the answer is that yes, you may benefit from an external DAC, though not as much if it turns out that your audio was compressed for wireless transmission.

If the receiver only has analog outputs, then you would have to place the DAC before the transmitter. In that case, it is not worthwhile.
 
Jul 29, 2008 at 4:09 PM Post #12 of 15

therock003

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Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif
If the receiver has a digital output, then the answer is that yes, you may benefit from an external DAC, though not as much if it turns out that your audio was compressed for wireless transmission.


Not th receiver has only got the 3.5 jack output.I was wandering if i should hook the receiver output to a DAC 3.5 input and hook the IEMs the the DAC 3.5 output?

Quote:

If the receiver only has analog outputs, then you would have to place the DAC before the transmitter. In that case, it is not worthwhile.


What do you mean it is not worthwhile,cause it seems that this is the case.
 
Jul 29, 2008 at 4:32 PM Post #13 of 15

nghiasays

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Since the receiver only has an analog output the DAC could not be used after the receiver. So the DACs output would go to the transmitter which would then convert it back to digital and compress in order to transmit. While sending a better analog signal to the transmitter can't hurt, I think the benefit is lost with the conversion by the internal DAC on the receiver side if not in the transmitter's analog to digital conversion or compression.
 
Jul 29, 2008 at 4:37 PM Post #14 of 15

therock003

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Y can it not be used?DACs other than USB input they have 3.5 input if i'm not mistaken?

Well since it's a PC we're talking about and not some other source, you can even transmit sound directly from a bluetooth dongle with no conversions/compressions taking place.

But how could it be received on a DAC wirelessly?
 
Jul 29, 2008 at 5:58 PM Post #15 of 15

infinitesymphony

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Quote:

Originally Posted by therock003 /img/forum/go_quote.gif
Y can it not be used?DACs other than USB input they have 3.5 input if i'm not mistaken?


I've never seen a DAC with a 3.5mm digital input. RCA and TOSlink are the most common connector types.

Quote:

Originally Posted by therock003
Well since it's a PC we're talking about and not some other source, you can even transmit sound directly from a bluetooth dongle with no conversions/compressions taking place.

But how could it be received on a DAC wirelessly?



If you use a Bluetooth transmitter then you'll need a Bluetooth receiver. In order to send the signal to a DAC on the receiving end, the receiver needs to have a digital output. The receiver you have only has an analog output. The other problem is that your transmitter does not have a digital input.

The Slim Devices Squeezebox is probably the most popular solution for what you're trying to do. It receives audio over an 802.11g wireless connection and has both analog and digital outputs.
 

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