Bluetooth vs Analog

**RunNgun** · 09-26-2011, 12:20 AM

I've been surfing the net trying to compare the two, but figured an actual car stereo forum would have the most real world opinions. So as the title states, what are your opinions of using Bluetooth A2DP vs wired analog connections to a head unit? The way I understand it bluetooth is digital, therefore the source audio to your head unit is 100% pure, no degradation. However using something like an aux-in connection via 3.5mm is converting the signal to analog stereo before your head unit can process it, and thus there is potential for quality loss.

Ultimately my goal is to build a tablet car with an excellent head unit for maximum audio fidelity. Initially I wanted the tablet to BE the head unit, but since a tablet isnt a receiver there is no real way to send a signal to an amp, short of converting 3.5mm to RCA which I imagine would have all sorts of issues. You still need the head unit to properly control the amp.

Since there arent really any direct interfaces for android/iOS to a head unit, there is no way to transpose the audio data between the two. Technically your best options are still to burn cd's or utilize a head unit which has on-board flash memory for loading mp3 tracklists. There are probably a few head units with dedicated iPod docks that an iPad could interface with just the same, but iPad's are too large for my dash so I'm hoping to find one of the many Android tablets that might have a better fitting form factor.

So is my synopsis correct? Does A2DP even support multi-channel encoding? Or would my head unit still be mux'ing the data to handle a 5 channel amp/sub? Even with a muxed signal, do you feel using bluetooth to head unit would be superior than using 3.5mm to head unit? This would also save some hassle on wiring allowing me to only worry about power and not power+audio.

**malcom2073** · 09-26-2011, 06:06 PM

Welcome to mp3car. You seem to have stumbled upon the wrong forum, as this is typically about installing a PC into a Car (EG: CarPC).

Very few, if any people here use headunits anymore, so we put our audio (be it mp3, flac, or whatever format you desire) directly on the PC and play it from there.

You would probably have better luck asking these questions on an Car stereo forum, since they likely actually use stock headunits.

Oh, and no headunit is superior, so give it up, get a carpc, and problem solved. Carry all your media with you in the carpc and you don't have to worry about quality between your ipod and your stereo

**soundman98** · 09-26-2011, 09:48 PM

hehe, most car audio forums aren't going to know much about a2dp...

for audio purity, bluetooth is horrible. it was really only developed for phone conversations, so it lacks the high bitrate to deal with the higher frequencies in audio files correctly. there have been plenty of members here that use it for basic audio setups, but no one uses it for the high-end stuff.

why can't you use the tablet as the hu? what is different about the audio signal that it outputs compared to a hu? other then the overall output level, there should not be any differences. sure, there are some differences in the parts used in the tablets d/a converter and audio output, but the actual audio signal is still just a sine wave with peaks and dips.

as for 'converting' the cables from 3.5mm to rca-- i have never heard of any problems with this 'conversion'. 3.5mm jacks and rca jacks are connection types, they do not dictate what type of signal, or how that signal travels across them.

for every connection, the signal does loose some of it's quality. but i have not met anyone that has been able to hear this difference, or tell me how many connections have degraded the signal.. it is only evident while using expensive equipment, and only on a very small scale.

just connect the tablet directly to the amps. if you have a issue with the output being too low, you can use a preamp to boost the signal-- i recommend the jl audio cl-rlc. it would allow for boosting the signal and also has a volume control.

**RunNgun** · 09-27-2011, 01:45 PM

Well I was under the impression that using the built in 3.5mm jack on the tablet was tantamount to using a cd-> cassette converter. Just a bunch of cheap parts with poor regulation. Obviously you are correct in regards to the signal, eventually even a digital source is converted to analog the moment it heads down a wire to a speaker. But only head units have the sophistication to balance that signal properly to each channel for the amp to get decent sound. A 3.5mm jack is carrying the entire sound signal down a single stereo wire. Since the amp doesnt really have any processing power I dont think anything is done to the signal. Speakers all get equal treatment, which is lousy for quality isnt it?

I guess I'm sort of relating it to comparing Component video to Digital video. Both are rated for the same resolutions in hi-def, but one actually tells the tv processor each pixel to light. The other just sends a signal and the processor must interpret this to decide which signal to light. It is less precise. I'm not audiophile but something tells me I could tell the difference between an iPod powering a home stereo vs a FLAC burned cd.