Sean R.

What I really want to know is what is the net effect of sending a speaker level out to the rear speakers in the concert system - massive distortion or can the factory rear amp handle it?

James R.

You're right the concert head outputs speaker level outputs to the front speakers and line level out to the rear. You'll find the rear amplifier attached to the rear left speaker...it's driven by line level signals from the head unit...there is also a remote line.

Lemme guess...you want to replace the concert head with an aftermarket unit which has an integrated amp...but you want to keep the rear speakers...so you just figure you'll use the rear output from the new unit (speaker level) to drive the line level inputs of the stock Audi rear amplifer with the speaker level outs from the new head??? While this may work...there is a good chance it won't. Here's why...most aftermarket heads which claim around 10 Watts per channel or more will more than likely have a BTL output stage (Balanced Transformerless) if you try to connect this to a single ended input (possibly like the Audi amp) you'll effectively be shorting one phase of the amps output to ground.

The idea behind BTL is that you can place 2 times the voltage across the load as you could with a single ended output (groud referenced)stage...this equates to a 4 fold increase in power V^2 / R = P basic stuff...so if you double the voltage...you'll quadruple the power because the Voltage term is squared.

Anyhow I guess I'm getting off the track...point is you need to find out if the input of the Audi amp is single ended or balanced. You can figure this out by measuring the resistance between each of the input leads of the amp to the chassis of the car...if one of the leads (on each input channel) has a low impedance to ground then chances are it's single ended and you're going to need some electroincs to make this work. If you measure a high impedance on both legs (should be equall) then you probably had a balanced input and it may work...but you need to watch the input voltage you subject the input to...a lot of these amplifier IC's have fairly limited input voltage ranges...and you can damage them by overdriving the inputs. You could measure the voltage while playing a test CD and determine what kind of voltage levels are seen coming from the concert head...then based on that you can decide if the head unit you're proposing to use will overdrive the input of the stock rear amp.

If you need more help contact me directly...I'll be happy to help you out...

Regards,

James R.

99 1.8TMS (Neuspeed K04, K&N Filter, S4 Wheel Well Liner Mod, Remus Exhaust, Neuspeed Sport Springs, Neuspeed Front Anti Sway, Bilstein Sport Shocks, Brembo Rotors, Mintex Red Box, Ronal R28's 17", Euro Corners, Clear Sides, Full Tint...and some other stuff I probably forgot)

Sean R.

Now that I think about it though, can't I just use the rear line out channels from the head and wire them to the stock speakers, and just let the stock rear amp take care of the amplification? Or is there more to it than that?

James R.

Yeah sounds like a plan to me...I assume your new head has line level outs for the front and rear..so simply patch those (rear) line level outputs into the existing line level wiring for the rear speakers and you should be ready to go.

This will be much easier than all the other crap I described doing...and should ultimately sound better...you may have to twiddle the fader a bit to get the levels right...but that's the case with just about any setup.

Good Luck,

James R.

99 1.8TMS (Neuspeed K04, K&N Filter, S4 Wheel Well Liner Mod, Remus Exhaust, Neuspeed Sport Springs, Neuspeed Front Anti Sway, Bilstein Sport Shocks, Brembo Rotors, Mintex Red Box, Ronal R28's 17", Euro Corners, Clear Sides, Full Tint...and some other stuff I probably forgot)

James R.

otherwise you'll wonder why your battery is running low all the time. The rear amp has remote enable disable built in...there is a wire for this...all of the wires are called out in the diagram on the top of the radio (when you pull it out)

Regards,

James R.

99 1.8TMS (Neuspeed K04, K&N Filter, S4 Wheel Well Liner Mod, Remus Exhaust, Neuspeed Sport Springs, Neuspeed Front Anti Sway, Bilstein Sport Shocks, Brembo Rotors, Mintex Red Box, Ronal R28's 17", Euro Corners, Clear Sides, Full Tint...and some other stuff I probably forgot)

Sean R.

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