Special audio preamp circuit
I have a chrysler with the infinity head unit and amp. I found that the amp works much like a normal audio amp, only it seems to take a slightly higher power input than just a line out.
Past suggestions included line drivers, preamps, and headphone amps. I am looking for a more simple solutions, and I would like everyone's input.
I opened my headunit, and found the connection where the HU feeds the audio signal into a small preamp, and through the volume control, out to the amp (in the trunk). I spliced in my lineout signal and ran it through the preamp in the head unit. Aside from a great deal of noise (i think i had bad grounding and onboard sound, buzz and fuzz), the sound seems to be at about the right level.
I would like to build a small audio amp circuit VERY similar to the one in the head unit, but there a few more problems. First, i have yet to design and build a circuit from the ground up. Obviously, this can be a problem. Second, the volume control is not as it seemed. It is a digial knob (turn to the left acts like a vol down button being pushed, and same for turning right and vol up). With the head unit's audio signal unpluged, and the computers linout signal in it's place, the volume control did not work. Instead, turning the knob did NOTHING, until i turned it very low, at which point it would mute the output. So with my signal, it was either 1 volume, or mute.
Does anyone have any suggestions about design and building a small preamp with similar specs and a volume control?? (I would REALLY LIKE to try to include a digital vol control, b/c i do not want to send the audio signal all the way up to the dash and back. I would like to keep everything in the trunk).
PLEASE HELP! I have pics of the circuit boards, and I can collect any other info. I would even be willing to pay someone to make something i can use.