I have a test bed for testing amplifiers.
Its just a transformer, bridge rectifier and a couple of smoothing caps with crocodile clips on the leads.
The input is just a jack socket with a volume control.
I chose an old lateral mosfet amp to listen to.
For some reason it had quite a bit of hum.
I remember when I designed it started off with hum but then I decoupled the power rails to the front end with 100R and 100uf filter and that got rid of it.
I scoped the whole pcb and found a little hum getting in on the input but not on the power rails.
I couldn't work out where it was coming from.
In the end I noticed that the amp sits on a big old pcb above the transformer on top of the test rig case.
I moved the pcb over a little away from the transformer and the hum disappeared.
While this makes sense I haven't had the same problem with other amps I have tested. Very strange. Maybe this one was a bit more prone to noise due to pcb layout.
Its just a transformer, bridge rectifier and a couple of smoothing caps with crocodile clips on the leads.
The input is just a jack socket with a volume control.
I chose an old lateral mosfet amp to listen to.
For some reason it had quite a bit of hum.
I remember when I designed it started off with hum but then I decoupled the power rails to the front end with 100R and 100uf filter and that got rid of it.
I scoped the whole pcb and found a little hum getting in on the input but not on the power rails.
I couldn't work out where it was coming from.
In the end I noticed that the amp sits on a big old pcb above the transformer on top of the test rig case.
I moved the pcb over a little away from the transformer and the hum disappeared.
While this makes sense I haven't had the same problem with other amps I have tested. Very strange. Maybe this one was a bit more prone to noise due to pcb layout.
I bounce on what I just said about the NAP140 naim clone thread.
since I built this amp, I always do the same thing, that is, I assemble the power supply components with temporary wire, then I move the elements until I have no more noise / hum / buzz output hp.
I had a pair of pcb amp mosfet very simple (like Burning Amp) that I liked but had buzz and despite the change several times the transformer, the diode bridge and capacitors, I had never managed to shut him up until I tried to change the power supply topology and since then, we do not know if it is on or off.
since I built this amp, I always do the same thing, that is, I assemble the power supply components with temporary wire, then I move the elements until I have no more noise / hum / buzz output hp.
I had a pair of pcb amp mosfet very simple (like Burning Amp) that I liked but had buzz and despite the change several times the transformer, the diode bridge and capacitors, I had never managed to shut him up until I tried to change the power supply topology and since then, we do not know if it is on or off.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.