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Old 22nd July 2004, 05:14 PM   #11
audioPT is offline audioPT  Portugal
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I think this would be enough:

ESP P51
or
ESP P87

Just convert the circuitry power from symetrical to assymetrical.
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Old 20th August 2004, 04:27 PM   #12
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Hey guys... I noticed this thread... I'm looking to do the same thing, but know little about the internal part of systems...

What's the simplest way to attenuate speaker outs from a stock stereo to be safe inputs to an amplifier?

Thanks!
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Old 20th August 2004, 05:13 PM   #13
ECM is offline ECM  United States
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the simplest way would be to buy a line level converter. what this will do is convert the speaker outputs to rca level outputs safe for an amplifier.
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Old 20th August 2004, 05:15 PM   #14
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Thank you! I realize that was a really dumb question for you pros....
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Old 20th August 2004, 05:34 PM   #15
ECM is offline ECM  United States
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you won't learn unless you ask questions......and i don't consider myself a pro, just a diyer.
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Old 21st August 2004, 01:47 AM   #16
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Quote:
What's the simplest way to attenuate speaker outs from a stock stereo to be safe inputs to an amplifier?
A series resistor on the RCA center conductor. The value should be about one to four times the amplifier's input resistance.

A voltage divider would be a better method, and may require capacitor coupling if the stock stereo is BTL.

Good line level adapters use audio transformers followed by voltage dividers.

A voltage divider followed by a differential amp would probably be about the best solution to be worth it's cost or effort.

Tim
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Old 24th August 2004, 04:20 AM   #17
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I've done both pre-amp input and output from a stock Toyota radio.

The input was done by removing the AM Stereo decoder chip, and substituting an op-amp in negative gain on an adapter board. (It was also reverse-phase, but I figured that was relatively unimportant.)

Output was realtively easy. I followed the signal path past the pre-amp to the tone/volume/balance/fader, and where it led back to the board was where the input coupling capacitor was located. I simply tapped into the 4 outputs after the fader control and ran them to RCA jacks using some 63 ohm resistors and cat5 network wire. (I found that the pre-amp would sometimes oscillate without the resistors, especially when changing inputs.) I'd guess signal level at that point was pretty close to 500mV, as the amplifiers treated it similar to an inexpensive aftermarket deck, in terms of gain settings.
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Old 24th August 2004, 04:45 AM   #18
ECM is offline ECM  United States
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that's what i plan on doing to my ford radio. i was just gonna tap off right before the power amp chip. i'll be sure to add some output resistors too.

as for the input, i used an adapter for the cd changer that allows me up to 3 inputs plus the changer itself.
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Old 1st September 2004, 10:42 PM   #19
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Default Yes, I do!

I have about a dozen boards coming in next week designed specifically for this very purpose. I have been doing custom line drivers for OEM radios for about 5 years, from simple two channel to others with aux inputs. The boards themselves are comprised of all SMD components, and utilize a BUF rail splitter (cleanest sound) for the OPA driver. I also include a half-second soft mute turn on circuit for those that need it. Each board is two channel, and must be installed by Envision Electronics...unless you REALLY know what you're doing and don't want a warranty. They are $110 each, installed...a bargain considering you retain factory cosmetics and seriously decrease your chances for getting it ripped out of the dash one night.

I will post more details and pics once the boards come in...

my site: www.envisionelectronics.com
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