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What resisters for inverting op-amp should I use?

Other Parts Discussed in Thread: TL071

I am not an electrical engineer by any means so go easy on me here. I am simply experimenting with a speaker amplifier.

My situation: I have a Clarion xc1410 4-channel amplifier with a 10k input resistance that is non-bridgeable. They are powering two 4 ohm speakers. The amp is capable up to 2 ohms.

My goal: I want to bridge the amp to create 2 channels producing twice the power. My understanding is if I invert the input signal on 2 channels I can bridge those channels with the non-inverted channels.

My setup: I have a couple TI TL071 op amps for my inverting setup.

My Question: I'm not 100% sure what resistors to use as my input resistor and my feedback resistor to match this ideally with my 10k input resistance on the Clarion amp. If I use 10k resistors for both will that suffice or should I use 5k resistors as they add up to 10k to align with my Clarion input resistance? Am I even on the right track? This is what my test circuit looks like:http://www.learningaboutelectronics.com/images/Inverting-op-amp-circuit-breadboard-schematic.png

As I said I am just a hobbyist, not an electrical engineer so this might seem like child's play to you but any genuine help will be greatly appreciated!

Also, if you have a simpler, easier way of doing this (aside from just buying a bridgable amp) let me know too!

  • Regan,

    I took a quick look the the Clarion Amp, all four outputs are already bridged. The black striped colored speaker wires are not grounds. Both speaker wires are driven.

    The input common mode range for TL071 must be at least 4V higher than VCC- pin. The bread board image shows non inverting input at pin 4 level. Input voltage must be higher. Use capacitor at input and output to block DC if needed.

    10k for both resistors is fine. there is no need to match input resistance.
  • I tested the black striped wires and they all were grounded (0 ohms) to the chassis.
    The common mode range is new to me. I don't know how I would get at least 4v higher at the input as it is run off an mp3 rca jack which isn't even putting out 1 full volt.
    Also, I am starting to think a single supply op amp would be better so I can run it off the car battery? However, I really am clueless here. 
    I'm wondering if I bit off more than I can chew with this project? I was really hoping it would be just as simple as soldering my op amp to a board with an input and feedback resistor and connect it to an rca in and rca out and my 12v battery. 

  • Regan,

    Try this external site that I found with a simple image search.
    www.electronics-radio.com/.../inverting-amplifier.php
    Scroll down to this section: Inverting amplifier single ended operation
    All resistors 10k and caps 10uF should be fine.