tapping rear outputs
 

Maybe someone can clear this up for me. I've seen several threads that stated that the signal from the HU to the rear Bose amp is differential. I've also seen several threads of people who tapped the signal before the rear amp without doing anything special and seemed to not have any problems. And I've seen one thread that suggested that tapping the outputs before the amp was responsible for a fried HU.

Here are the questions:
- Is the signal to the rear amp differential?

- What is the best place to tap the rear outputs, pre-Bose-amp or post? I know another poster claimed that the amp was full-range, but I've also seen several people claim there is a subjective sound difference between pre and post amp, with the pre-amp signal sounding better. Obviously the post-amp signal is hotter (speaker-level) so a LOC would be needed.

- If one was to tap a differential output, what is the proper way to covert the signal to a normal, unbalanced signal? I would think that leaving the inverted signal unconnected and connecting the RCA ring to ground would work, although you would lose the benefits of the balanced signal. Does this risk damaging the head unit? Are there aftermarket boxes that will do this and actually perform the noise cancelation? I've seen one online, but it recommended installation behind the head unit; is that really necessary?

Thanks in advance.

yeah I actually tapped the pre-amp wires going to the bose with the wiring diagram I found here but the sound from my speakers was REALLY low and almost not noticable. Then I read the HU only puts out about 1V. So I tapped the speaker level wire going to the rear 6x9's and now everything is great. Still have to turn the HU to about 25 to have the speakers play loud but that may be due to my gain settings on my amp. I do not have balance ability since I spliced 2 channels (6x9) to a 4 channel amp but I never used balance anyways, still have fader though.

Hope this helps.

I used a peripheral components SVEN.2.
Do a search - you'll find it.
Spent many hours researching and trying to find an inexpensive interface between the BOSE headunit and the rear amp.
This was the best I could come up with.

After all my phone calls I came to the conclusion that most tech support people in the industry don't know jack. Use terms balanced differential and your met with "Speaker Level input". Ask about input impedence, and gain and you get "huh?"

I must say - kudos go out to JL audio for Stellar support. Earthquake Audio was up there as well!

The other option was an Audio-Control product - but at 4X the price.

Works well - although my gain on the amp is all the way up.
Plenty loud though.

I tapped the speaker outputs close to the rear speakers as my amp had speaker level inputs, combined with a bass boost adjustment up front. Dynamat in the trunk. It's not the most powerful bass I have heard but I've been enjoying the ride since Aug '03.

Same here, some amps come with speaker inputs.
Makes it very easy!

get a Ssoundgate LOCB.2, it is the only way to tap the signal before the bose amp. I have it and works 1000 times better and cleaner then a line converter after the bose amp.

Rotary Rasp,

That is interesting about the soundgate - I was going to use it - but the price was too high, and I didn't feel comfortable with their tech support's answers about whether it would work with the BOSE differential input. A local retailer wanted $180CDN for the unit - he was out of his mind. I picked up the SVEN.2 for under $60CDN after all expenses shipped to my door. For $180 - I would have gone with an audio control product cross-over

So I went with the peripheral components SVEN.2 - works well - I tap both the pre-amp signals, and the 12V trigger from the rear amp.

What trigger? I thought it sensed the RCA signal to trigger the amp. I had a line conver hooked after the Bose amp for a while and it work fine, but, the sound was muddy and boomy. So I emailed Soundgate and asked if it wounld work with our 8's. They said it was not listed as teated car, but, it should work fine. So I bought it and as they said, it worked fine. The sound a MUCH better, I have a feeling the bose amp has a EQ in it which is the reason for the boomy sound.

If there is a trigger wire, PLEASE fill me in. I'd love to take my amp off the ignition switch.

I got the LOCB.2 online for 90 USD.

I like my $60CDN for the SVEN2 over your $90USD.
Mine is with all taxes and delivery costs as well :p .
My only complaint is the gain isn't too great. I'll have to see what the sound is like when I get my front speakers hooked up.

Anyway - The trigger? You really need to visit the miata site for information on the radios - very helpful. MAZDA BOSE Audio pinouts

Look at the diagram - you will see 2A W/R from the battery. Just tap off this for the 12V amplifier trigger.

Just be sure you understand the colour code references

B Black
O Orange
BR Brown
P Pink
G Green
R Red
GY Gray
V Violet
L Blue
W White
LB Light Blue
Y Yellow
LG Light Green

which amps????? :) it would be nice to have a plug and play setup after I just tore apart half the car installing a modded xbox on the nav, I'm getting tired just thinking about it :P

maybe someone with "know-how" could post i DIY with pics for us. i'm just one of those that does better with the see one, do one, teach one method. : )

I concur. :D

Look for :
Line Level/Speaker Level Input: The amplifier includes a pair gold-plated RCA stereo line input jacks. For a speaker level input, you must use the supplied harness. The harness has a pair of male gold-plated RCA plugs on one end, a resistor circuit in the middle, and bare wire on the other end.

when you buy or select your amp.
I got mine from:
http://www.crutchfield.com/S-w8CfGRj...o&i=500MRDM301

The size of the amp was perfect for the space....
All wires are behind the seat and makes for a clean install.

By the way, the Soundgate LOCB.2 has a built in line driver which would solve your gain issue. :D Also, does that trigger go on with head uinit or with the key?