RE: E30 amp wiring question

[Bob Hazelwood <woodyh@xxxxxxxxxxxxx>]

> From: tom.murphy@domain.elided
> Subject: RE: E30 amp wiring question
>
> Hello BMW Experts!       Thanks to Chris, Don, Felix, and Bob for
> the great advise they all offered.  <snip>
>      Unfortunately, my read of Bobs' reply finds his answer to be
> ambiguous.
> Will the fader work to a lesser degree, or not at all?

Well, here's an even more ambiguous reply: That depends on the actual amp you finally end up with.

In my '87, with the fader connected to an a/d/s/ 642ix crossover, it only attenuated the "off" side by about 6dB. Not very much at
all. This unit had a 10k-Ohm input impedance. This is pretty typical of most aftermarket amps. A lower impedance and the fader
will work better. Much over 10kOhm and it's action will be pretty much non-existant. As I mentioned, if you load down the fader
output you can get it to work virtually the same as it does now, but you lose the benefit of reducing the stock radio's distortion
that the higher amp input impedance provides.

> Can a nice Radio
> Shack (!)
> fader be used as a substitute?

Actually, yes. I am not up on Radio Shack's current offerings, but you could substitute a line level fader, often known as a
"dual-amp balancer" for the factory fader and get both benefits. Most car audio dealers will either have, or know where to get,
such a device. The only down-side is cosmetic. I have never seen one of these which was an exact match for the BMW thumbwheel.

One othere thing that may be worth considering is to juat replace the head unit with a newer model BMW head unit with built-in
fader that someone else has removed. You'll have to either run new wires for the rear channels, or run the wiring from the fader
output side direcly to the radio, but this will get you the fader operation combined with a factory look and anti-theft. You can
sell off your old radio to offset some of the cost and make the swap reasonably inexpensive.

Best regards,
Bob Hazelwood
'93 525i 5-sp, Sharked, BL/ss'd, Etc.
BMW CCA (Boston Chapter)

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