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Sea Shadow 24th September 2012 06:30 AM

Hello! - Jumping in feet first
Hello everyone!

My name is Alex and I have been a long time lurker on the forums. I have always loved tinkering with electronics and love to build things. I am a member of my local hackerspace, where I am always trying to build something new to apply what I learn.

Music has been a major part of my life as long as I can remember. While I have always had an appreciation for music, it was not until recently that I started to delve into just how the electronic circuitry behind it worked. Though I have played with digital circuits for a number of years.

I have built a number of basic chip amps using salvaged ICs from old car headunits, but now I feel like I want to move on to more substantial audio systems.

I have a number of projects I have started and a few more that I would like to start (once I can procure the necessary parts). Here is a quick list of my current projects that I am focusing on:

-Multi-channel car amplifier with SMPS-
This will take in 4 channels of audio and mix it out to 8+. Front, Mid, Rear, and subs for left and right. I am thinking about tri-amping the whole thing but that depends on how well my active crossover works. I have about 75% of the power supply done, and hope to take the oscilloscope to it in the next week or so.

-Restore Sansui QRX-8001 quadraphonic receiver-
This is my Dad's old receiver and was my first introduction to above average audio equipment. It is rather old, and is in need of serious work (one of the channels cuts out a lot). I will have to rework much of the internal circuitry and replace most of the caps and resistors to restore it to its former glory. But I am set on bringing this unit back to full function. I have yet to crack it open to see what exactly I am up against but I have pulled the service manual and looked at how others have restored theirs.

-Configurable active crossover-
About a year ago we had someone give a rather sizable donation to our hackerspace which included LOTS of audio paraphernalia including a small mountain of discreet components. The vast majority of which are of relatively high precision (1-3%). We sorted through the mess and finally got it organized only to find that most of the stuff wasn't really useful to us. So after a year I got permission to take a bunch of the parts. After doing a lot of searching around for projects to build, it dawned on me that these parts work great for filters. More specifically a large box full of 1% Panasonic ECQ-P polypropylene film capacitors, and large quantities of 1% 5 band resistors.

I played around with the formulas for Linkwitz-Riley 24db/octave filters and it turns out these components give me some really nice crossover frequencies. So I figured well why not build a pile of active crossovers and use them in all of my audio projects? So for the past week I have been pouring over forums and other sources of information trying to piece together a proper active crossover. So far I have a board that is currently 1.35"x4" and can be configured to act as a high pass/low pass, or band pass filter. Or it can even be configured as a dual high pass or dual low pass (for single board 2 channel applications). Obviously enough it would be trivial to add in any standard dual op-amps of choice. I have finished laying out the filters but am still working out the input and output buffers (trying to figure out how much gain I should put on the output stage). Oh and it is single ended with a dual rail power supply.

I dunno how many of these things I will be making but I estimate I have enough parts to build up to ~400 of them. Who knows if I will ever use them all :D

planet10 24th September 2012 06:44 AM

Welcome Alex


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