Bypassing Bose Amp?

Having started to look at a double din replacement for my Bose system (NC3.5), I thought I’d get a local car audio place to look as I’m not 100% confident on doing it myself.

They commented that they’d have to bypass the amp, which wasn’t a bad thing as (in their opinion) they often go wrong, something I’d not heard before. Is this correct, and is it the best thing to do? I’ve read something about that you need to be careful to connect the amp separately, but not to bypass altogether. I’m a bit confused :man_shrugging:

TVM :sunglasses:

The amp can fail though I’m not aware of an epidemic, there is a company in Edinburgh who offer an economic repair service with a lifetime guarantee so I wouldn’t worry too much about that aspect.

I have an NC1 with a double din Pioneer and Focal speakers. It doesn’t sound d as good as it should, and I reckon the Bose amp (along with the resister pack to lower the Pioneer’s output to the Bose input) is the problem. In short, if I were you I would be happy to let them bypass the Bose.

I’m in favour of still using the amp, mine sounds great. I wired my own head unit in, needed an extra cable, in my case, then find that lead to feed the amp power, the blue lead if I remember correctly.

Did you connect ‘pre-out’ to the amp, or like me use the highline (speaker level) outputs with a resistor pack to connect the amp?

Most of the wiring was already in the car, a previous head unit change from standard. I wasn’t getting any sound though. It needed an additional multi lead plus if I remember the blue amp lead coming from the new head units harness splicing in to blue or blue/white cable. Does that make sense?

Yes, sort of. The blue lead is the one that switches on the amp, without the amp on, no sound.

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So what does the amp do? If you can bypass it with no consequence, why have it in the first place? :man_shrugging:

I imagine the head unit either has no internal amp or it has a ‘pre-amp out’ take off that allows the built in power amp to be bypassed and the signal sent to a higher quality and more powerful amplifier.
I doubt the amp amplifies an already amplified signal as that is likely to degrade the sound quality.

Standard head unit has built in amp that power the speakers.

Bose head unit has no amplifier, so an external amp is necessary to provide a strong enough signal to power the speakers.

An external amp is a way to get bigger/better/more powerful sound as you have the space to fit the components in and the ability to dispose of excess heat. But it is also sometimes a bit of a marketing gimmick.

A third party head unit will usually have a built in amplifier that can connect directly to the speakers ; but in the case of a Bose headunit replacement the speaker cables don’t run from the head unit, they run from the (hard to get to) Bose amp. So what most people do (me included) is to use an adapter that connects the new head unit to the existing wiring which means the sound goes through an amplifier in the head unit, then a resister pack to reduce the signal and then through the Bose amp. This is generally said to be good enough, if not optimal.

Personally, I don’t like how mine sounds and am thinking about either using preout (low level unamplified signal) from the head unit through the Bose amp and see if that helps, and if it didn’t then I would remove the Bose amp and replace it with a third party amplifier.

Another option is to bypass the amp, use the output from the head unit’s amplifier through new speaker cables direct to the speakers.

Make sense?

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Pretty much as I suspected then.

As a lover of simplicity, I think I would be taking the last option. The idea of putting an amplified signal through a resistor to reduce it before amplifying it again to output to the speakers sounds horrible somehow.

Then again, with roof down at speed, the difference between all options may not be discernible.