Hello guy,
I spent a lot of time to find the source of buzzing in my DIY aleph5 in this thread
Need help! Aleph5 buzzing when introduce preamp
Finally, I found that it is the EMI from the transformer which I actually not expect that because the torroidal suppose to irradiate less noise.
The first try, I put in the 1.2 mm thickness steel box cover the transformer, it work! buzzing is reduce a lot. but if I come close to the speaker I still can hear the buzzing sound.
So, I decide to put more shielding, but what is the most effective, practical, and wallet friendly to shield the EMI from toroidal transformer? I have search several thread and found some method that might be work ex.
- Put the thin sheet of copper around circumference of the toroidal like this
but I found this method with EI transformer. Is it work with toroidal?
- Or I just put more steel box in layer.
- What is the good material for shielding? steel which is quite cheap of copper /aluminium with higher cost?
one notification is my transformer generate buzzing sound that I can here from 2 m. it is not normal for sure. but it happen some time. What is it possible from? and does it relate to the EMI from transformer? The transformer is new, do you think it is fail?
Any suggestion would be appreciate
I spent a lot of time to find the source of buzzing in my DIY aleph5 in this thread
Need help! Aleph5 buzzing when introduce preamp
Finally, I found that it is the EMI from the transformer which I actually not expect that because the torroidal suppose to irradiate less noise.
The first try, I put in the 1.2 mm thickness steel box cover the transformer, it work! buzzing is reduce a lot. but if I come close to the speaker I still can hear the buzzing sound.
So, I decide to put more shielding, but what is the most effective, practical, and wallet friendly to shield the EMI from toroidal transformer? I have search several thread and found some method that might be work ex.
- Put the thin sheet of copper around circumference of the toroidal like this
but I found this method with EI transformer. Is it work with toroidal?
- Or I just put more steel box in layer.
- What is the good material for shielding? steel which is quite cheap of copper /aluminium with higher cost?
one notification is my transformer generate buzzing sound that I can here from 2 m. it is not normal for sure. but it happen some time. What is it possible from? and does it relate to the EMI from transformer? The transformer is new, do you think it is fail?
Any suggestion would be appreciate
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Have a look here to get an idea: Τ.Γιατράς Μετασχηματιστές - Toroidal Transformers
But it's hard to believe that EMI could be the reason itself.
Perhaps all that you need is a mains DC offset blocker Mains DC and Transformers
The intermittent buzzing sound could come from DC on the powerline. I have it sometimes for a few minutes, then it goes away again.
Though on my toroids it is not very loud, so I didn't bother with the DC blocker anymore.
You could try one of the circuits discussed here:
dc blocker test report
or here:
DC blocker diode/cap orientation
I think the "Bryston" one referenced in post #2 (or post #1 of the first thread linked above) works quite well.
Best regards, Claas
Though on my toroids it is not very loud, so I didn't bother with the DC blocker anymore.
You could try one of the circuits discussed here:
dc blocker test report
or here:
DC blocker diode/cap orientation
I think the "Bryston" one referenced in post #2 (or post #1 of the first thread linked above) works quite well.
Best regards, Claas
When I Picked up some transformers direct at a transformer factory I was told that thin steel does a very good job shielding against magnetic "noise". Thicker steel would be less efficient because of Eddy currents. The best solution is to have the transformer and bridge "far" away from the amp.
The bridge and the first filter capacitor because of the high pulse currents which can radiate noise from the wires (wires from transformer to bridge and from bridge to first filter capacitor). A 2nd filter capacitor is probably good to have in the amp chassis to have short wires from capacitor to amp circuit. It all depends…….
Yes, some put an e.g. 0.1 ohm resistor between the two filter capacitors to reduce the current pulses to the 2nd filter capacitor. Then the 2nd filter capacitor will define the Gnd for the amp. Layout of wires is also important. Good to twist wires. The size of the R in a CRC filter depends of how much current is needed…..how much voltage drop you can afford, how much ripple you can live with.....etc.
I have two mixing consoles in both of them there is a toroid inside and a metal sheet between them and the mixer up pcb enclosing the toroid. When I crank up the gains and master out there is a slight hum. When I lift the mixer boards up this hum gets quieter and if I move the board away from the case it dissapears completely towards hiss . What I've done was increasing the main supply capacitors which helped a lot. The hum is the same as You hear when You connect an 2m consumer RCA lead to an amplifier without source.
Try to isolate the problem by disconnect the PSU and loaded with a dummy (same impedance and wattage as your amp).
From that dummy, built a resistor divider with zener protection and connect it to your soundcard, use Any available soundcard spectrum analyzer, watch the FFT with power off, copy the spectrum as overlay, load that overlay and power on, copy both and post the photo here for further comments. If the spectrum of loaded PSU has 50Hz (60?) and its harmonics lesser than -70dB (-60, -70 is acceptable, -80, -90 excellent, -90 ...top notch...)
Almost all amps that I built never need a shield or enclosed container, with an exception, the latest one, a bi-circleton, does need a special shield.
Cheers and good luck
From that dummy, built a resistor divider with zener protection and connect it to your soundcard, use Any available soundcard spectrum analyzer, watch the FFT with power off, copy the spectrum as overlay, load that overlay and power on, copy both and post the photo here for further comments. If the spectrum of loaded PSU has 50Hz (60?) and its harmonics lesser than -70dB (-60, -70 is acceptable, -80, -90 excellent, -90 ...top notch...)
Almost all amps that I built never need a shield or enclosed container, with an exception, the latest one, a bi-circleton, does need a special shield.
Cheers and good luck
Thank you, It also surprise me that the problem is get a lot better by adding the steel box. I am thinking about the problem from transformer itself too, cause the loud buzzing directly from transformer.
So, I manage with the transformer supplier to sent transformer back to re-check the buzzing problem, but I really not sure, the problem is from the transformer or power line DC offset.
Do you have any idea,what should I suggest the supplier to check? I afraid that the problem may not show up in the testing at the lab.
Thank you, thinner steel sheet is better? or is it better to be multi layer? My transformer is mounting with the resin in the middle, bolt to the bottom plate, and floating at the top.
I afraid the my enclosure have not enough space already
So, I try to shield it.
That is what is want to try next, now the transformer wires are short. I will make it longer and try to rotate it. will see what happen.
I afraid that, I cannot find the same load as the power since my aleph5 draw 6A continuously. Is it possible to measure while I use power itself as a load?
I have also check the psu ripple. the ripple at the PSU out after CRC was less than 100 mV p-p. and the frequency was 100Hz.
An externally hosted image should be here but it was not working when we last tested it.
...So, I manage with the transformer supplier to sent transformer back to re-check the buzzing problem, but I really not sure, the problem is from the transformer or power line DC offset.
Do you have any idea,what should I suggest the supplier to check? I afraid that the problem may not show up in the testing at the lab.
Most probably the problem is mains DC offset. Building the recomended DC blocker is easy and will save money and time to have the transformer checked by the supplier who is unlikely to accept that as defective.
Now, the buzzing sound from transformer is heard all the time. Just different level each time. Is it from DC offset? I will build the dc blocker to see what happen. But for long term use, does it has an affect to sound quality or the reliability of the components in the dc blocker itself?
DC blocker won't affect sound and it will protect the transformer in the long term. Just read Rod Elliott's article and build it according his instructions.
Yes, just thin steel to shield against the magnetic field from the transformer. Mu-metal is very expensive so thin sheet steel should be a cheap alternative.
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