idrivetoofast

Just installed a new Blaupunkt Los Angeles MP74, in my TT, replacing Audi Concert (with Bose). I'm using the factory Bose speakers. I get a loud pop from all the speakers when I turn the unit on or off, muting on or off and changing stations. Any possible solutions? The head unit is properly grounded.

Merkin

the unit it self is defective, but how did you make it work with bose speakers?

Audi Logic

are you using the line outs or speaker outs?

MacSub

The Audi HU's don't use industry standard noise suppression when the HU does something electrically noisy like changing trackings on a CD. Aftermarket HU's kill/earth the RCA output to prevent the noise getting amplified. Unfortunately the Bose amp has a wierd array of capacitors on the front stage to filter such noises so when your BP HU grounds the RCA it discharges the capacitors very quickly and thus the pop!
Only way round it is to use a speaker out wiring adapter (rather than the RCA/line out one you've currently got). Unfortunately this will give you inferior sound and may introduce other noise/interference.
Better route is to upgrade the puny Bose speakers and run them directly from the HU or via a decent amp. Unfortunately you can't run the Bose speakers off anything but the Bose amp as they are 2 ohm impedance.
You can buy delay relays that delay the amp turning on but this only cures the initial pop when you first turn the unit on.
Or better still

idrivetoofast

But yes, I did get the Bose speakers to work with thenew head unit. I cut the existing wires to install RCA wires and used line level outputs from the head unit.

idrivetoofast

Line out, cause you have to when using stock Bose speakers.

idrivetoofast

that make it sound so plausible. I hate you.

1) I'm gonna try plugging in some regular speakers to amplified out from head unit to see it it still happens.

2) If I still get popping, I'll take the unit back to the shop and have them test it.

Grrr! In case u are correct, I gotta do a search for some kinda so I don't have to run new wires all over the car for new speakers. Grrrrrr!

MacSub

and I've also experienced it trying to retrofit a Bose amp on an aftermarket HU.
For an easy life I would give the speaker input adapter a go, that's just a straight swap for the RCA adapter you currently have. Pull the HU out and you'll find an adapter plugged into the RCA outs of the HU going to the mini ISO socket on the Audi loom. Disconnect it, then plug in the speaker input adapter and connect the speaker wires from the HU to the speaker in wires on the adapter. TBH the Bose system is pretty average quality anyway the drop in SQ by using the line level converter in this adapter shouldn't make much difference.

MacSub

All you are doing is getting a line level/RCA signal to the Bose 4ch amp. If you use the RCA's on the HU which is the purist way to do it, then you will get the popping. The other way is to use a line level converter to take the speaker outs from the new HU and convert them back down to line level for the Bose amp. Both adapters should be available from where you sourced the original kit. You need to swap the RCA adapter for the speaker input adapter

idrivetoofast

Dude at Bestbuy swore up and down it wouldn't help. "If it's popping from the line levels, it'll still pop from speaker level. I don't care what anyone says, I guaranty it'll still pop." Proved him wrong. It doesn't sound bad. There's noticeable noise (hissing, not engine noise) when the volume is all the way down, but I'll never have the vol all the way down anyway.

What a costly HU swap. $340 for head unit, $52 for adaptors. Sheesh.

Thanks very much for your help!!