yes, another problem. i just started another thread because i have a feeling someone in the future might have this problem, so instead of burying it in a 4-page thread, ill just make a new one for it.
anyways, here is the problem...
i got all the fets changed out and the preamp section tests well. the two voltage reference points are pretty close to perfect (+-1% or so). and, i got music. however, after completely finishing the faceplate, hooking up the LED's for what i thought would be the last time, now i get some buzzing and humming out of it.
i would normally assume ground loop or something like that, which i am familiar with and can fix. however, this is different. the amp belts out a loud buzz sound as soon as its turned on, and it slowly fades after maybe 5 seconds, and goes away. the amp isnt exactly dead quiet afterwards (its got some hiss and a SLIGHT hum) which increases with volume to a pretty loud buzz at full volume.
if i turn the amp on, wait until the buzz thing goes away, then turn it off and back on really quick, it doesnt happen again. so, its like it only happens when its "charging". thats just an explaination of how it feels, not a techincal explaination of what i think is happening.
also, im using a light bulb in series to check for shorts (ive tried without one, it does the same thing), and when the amp turns on, the light bulb light VERY brightly and dims in sync with the buzz. and the light bulb never completely goes off. it is always on just a little bit. it glows very dimly but is never off when the preamp is on.
the funny thing is, when i was testing the amp after i changed those resistor values that were wrong, i never noticed a hum at all. it sounded fine. the buzz is quite loud and it sounds like something is VERY VERY wrong at first, and then it slowly fades and goes away. but when it first comes on, you think the speakers are at risk or something is seriously in danger.
that doesnt seem like a good sign.
SO, i will conquer this, but i will definately think twice about building a preamp again! ill link the previous thread so you can figure out schematic and stuff if you havent been following my plight.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=60218
p.s. - this thing is drop-dead gorgeous with its final coats of lacquer though! and i didnt put anything against the backs of the LED's so they glow inside the case to let a tiny bit of blue light spill out of the top vents. yummy. now it just needs to work.
anyways, here is the problem...
i got all the fets changed out and the preamp section tests well. the two voltage reference points are pretty close to perfect (+-1% or so). and, i got music. however, after completely finishing the faceplate, hooking up the LED's for what i thought would be the last time, now i get some buzzing and humming out of it.
i would normally assume ground loop or something like that, which i am familiar with and can fix. however, this is different. the amp belts out a loud buzz sound as soon as its turned on, and it slowly fades after maybe 5 seconds, and goes away. the amp isnt exactly dead quiet afterwards (its got some hiss and a SLIGHT hum) which increases with volume to a pretty loud buzz at full volume.
if i turn the amp on, wait until the buzz thing goes away, then turn it off and back on really quick, it doesnt happen again. so, its like it only happens when its "charging". thats just an explaination of how it feels, not a techincal explaination of what i think is happening.
also, im using a light bulb in series to check for shorts (ive tried without one, it does the same thing), and when the amp turns on, the light bulb light VERY brightly and dims in sync with the buzz. and the light bulb never completely goes off. it is always on just a little bit. it glows very dimly but is never off when the preamp is on.
the funny thing is, when i was testing the amp after i changed those resistor values that were wrong, i never noticed a hum at all. it sounded fine. the buzz is quite loud and it sounds like something is VERY VERY wrong at first, and then it slowly fades and goes away. but when it first comes on, you think the speakers are at risk or something is seriously in danger.
that doesnt seem like a good sign.
SO, i will conquer this, but i will definately think twice about building a preamp again! ill link the previous thread so you can figure out schematic and stuff if you havent been following my plight.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=60218
p.s. - this thing is drop-dead gorgeous with its final coats of lacquer though! and i didnt put anything against the backs of the LED's so they glow inside the case to let a tiny bit of blue light spill out of the top vents. yummy. now it just needs to work.
You just seems to run into all sorts of problems, with that darn BosoZ
Check out your solderings in the supply, very carefully. If you shorten'd up the leads on the trafo; make sure you did clean up the ends until they are pure copper. This could sound like a cold solder point
Or a thousend other things
