distortion channel doesn't sound right.

[timmyriot]

for awhile the distortion channel on my concert bass sounded GREAT. smooth overdrive...loved it. a couple days ago i thought i blew the speaker in my cab because i got that distinct crackly sound. well i troubleshooted the night away and found that it was the distortion channel giving me the shitty sound, not the speaker.

is there usually a culprit for this? i know my way around electronics pretty well so if its a certain component in the distortion channel that could be causing this i would be able to replace it.

[JoeArthur]

Well first, there is no distortion channel.

The distort works by increasing the gain of the second FET in the preamplifier. With higher gain, this stage is easily overdriven. With the exception of higher gain, the signal path through the amp is the same with or without distort.

If you are getting crackly noises with the distort functioning, my first suspect would be the footswitch, cable, or footswitch connection to the amp. The footswitch grounds a connection which allows a source bypass capacitor to affect the second stage.

I would first eliminate the footswitch by connecting an RCA plug directly to the footswitch jack and shorting the ends together.

If this removes the crackle, then the footswitch or cable is the likely suspect. If the crackle remains, then I would look closely at the amp's footswitch RCA jack (crud or loose "tip") and it's wire connection to the circuit board.

The crackle could be coming from a dirty distort control, so I would make sure I gave it a good cleaning as well.

[Robbie Nuke]

I suffered the same symptom with mine. Try the easier fixes first, they may be the culprit. I had to open my unit up and just reflow the solder joints on the circuit board, especially where the leads from the Distortion control pot enter the board.

Add a little flux to help the process, but be sure to clean it all off when your done. It seem a lot of flex stress occurs over the years at these points (or they were improperly cleaned prior to assembly) and you may be able to see some minute seperation of the solder from the leads, as I noticed.

I could also wiggle the pot and make the symptom come and go, but it was fine after I reflowed it. Don't forget to unplug amp when soldering on it!

[timmyriot]

i first thought it was the footswitch. i made the footswitch myself so i figured i made a mistake somewhere in building it but when i plugged rca cables with their ends shorted i still got the crackle.

i'll look at the distort pot and where the rca jacks are soldered in. could be a shitty connection there too. thanks!