Audio circuit round #3

"Today I have debugged the sound system (Lost a channel of audio, pulled the whole thing apart and later found it was the wire snapped off its solder on the audio circuit, and was stuck in place with the plastic so I couldn't tell it had snapped), got the 240V wiring done, and finialized the audio circuits." - Nat Allan, Jan 24, 2010.

Audio finalized? Bwahaha, what a idiot.

Over the last 3 days I have struggled with the audio stuff more. I had massive trouble extending out the potentiometer for the volume control... When I did so, the voulme got jammed at maximum and moving the volume knob just tuned RADIO STATIONS. Immensely frustrating, even if i did manage to get the footy scores.

Of course, not only did the potentiometer turn out to be broken, but some moron who will remain nameless used single wires from a roll he had to extend the volume pot, not sheilded audio cable he specifically bought for that exact purpose.


Braided single core wire mixed with audio = fail.

At jaycar, I bought (Amogst other stuff I didnt specifically need of course) a A10K Double-Gang potentiometer. The old one was linear (B10k) but I decided to try out a logrithmic pot, as they are supposed to be 'correct' for hearing (as human hearing works on a log scale as well). Unfortunatly, ive found this computer speaker amp hits a comfortably loud volume at 1K ohms, so having a 10K pot is overkill anyway.


Working temporary rig with cannobalized 50k pot from spare parts. The Project was playing a random SNES advertisment at the time, and as i took the pic it summised my feelings on finially getting it working.


Working log scale double-gang pot. Hooked it up temporarily with alligator clips to ensure I had it marginally right.

Above, you can see ive purchased spare alligator clips (Sooooo handy). When I was trialing with the pots earlier,l i only had 2 alligator clips, so i spend hours soldering and unsoldering when it didnt work. Big pack of alligator clips pre-made at Jaycar for $11 bucks has already saved me hours.


In non-audio news, ive also wired up the 80mm case fan mounted in the top of the box (to help remove heat from the monitor/sound adaptor. This has been directly wired into the DC input of the audio board (dammit, go away audio). I thought this would be a terrible idea in terms of noise on the audio's power line, but it makes no audiable difference. I did have to wire in two 100ohm resisters into the cable however to trim back the fan speed as it was two loud. These i wired in parallel to get a resistance of 50ohm (I think thats how the maths goes) as i couldn't be bothered finding a 50ohm resistor in my spare box when i had two 100's in front of me. Below the resistors are spliced in-line under the green shrink-tube.


Two 100ohm resistors wired in parallel on the top fan's power to bring down the speed to keep it nice and quiet.