I have a recapped 400a that has a light hum to it. It also hums a bit through the speaker tweeters/mids. It does not get louder or quieter with the adjustment of the preamp volume.
Any ideas?
Any ideas?
I don't know. It was my Dads amp. My uncle, who knows his stuff, recapped it. Sadly, he passed away a few months ago.
Sorry to hear... Would you think he made any modifications?
Check the ground connections, look if the caps + & - terminals are tightly fit. (discharge first!)
Check the ground connections, look if the caps + & - terminals are tightly fit. (discharge first!)
Ok, is this a low pitch hum, or more of a buzzing, similar to when the turntable ground wire is disconnected?
If your uncle is good, then the soldering should also be good.
How long ago was this work done, and how much was the amp used after that?
If your uncle is good, then the soldering should also be good.
How long ago was this work done, and how much was the amp used after that?
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I should have asked if you are a bit acquainted in fault finding.
If not, be aware that these amps are not working on a 5 or 12V supply. 😉
If not, be aware that these amps are not working on a 5 or 12V supply. 😉
Most commercial amps has a bit of hum if you have sensitive speakers. If you build your own amp(s) + PSU(s) you can build a PSU(s) that has most lower ripple than any commercial amp. For me DIY is the ability to build amps to a much higher standard that you can buy 🙂
If you go for max. 1 mV ripple on PSU.......you are almost there....... 🙂 .......filter chokes does a nice job.......
If you go for max. 1 mV ripple on PSU.......you are almost there....... 🙂 .......filter chokes does a nice job.......
try measuring the VAC coming off of the power supply caps. I don't think the PS is very sophisticated on these amps. As in, just a plain cap bank. Not even CRC. As mentioned, a little hum coming from the speakers is pretty normal. As in having to put your ear up to the speaker to hear it.