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Gareth, try mounting your transformers back to back so the magnetic field around them cancels, it makes a world of difference killing any stray magnetic fields near sensitive circuits.
I tried to solve an "earth hum" in my amplifier that used two toroidal transformers for years only to find that mounting one up-side-down onto the other killed the hum dead.
I tried to solve an "earth hum" in my amplifier that used two toroidal transformers for years only to find that mounting one up-side-down onto the other killed the hum dead.
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My boards arrived - see post 662.
Unfortunately, I don't have any time to work on my DIY projects due to combination of looking after my house and two kids with an amazing workload in the day job with travel and visitors it goes on week after week.
But for sure the project will not be abandoned !
Unfortunately, I don't have any time to work on my DIY projects due to combination of looking after my house and two kids with an amazing workload in the day job with travel and visitors it goes on week after week.
But for sure the project will not be abandoned !
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Joined 2009
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I made a bit of progress on the power supply: http://www.diyaudio.com/forums/power-supplies/313228-tgm-external-psu-power-amp.html#post5207187
DC component of mains removal ( it was mentioned ). If you take a 35 or 50 amp bridge recticier where the + and - pins are joined you have a very cheap set of forward and reverse biased diode of circa 1.4 V kick in voltage. As they are back to back even a 100 PIV device could work as the most the diodes should see is 1V per diode. This is part one of the DC blocker.
Next take some non polar caps ( other people don't bother and take the risk of the low voltage being OK in reverse bias ). Use the ripple ratings. For example a 1000 uF 16V might be 800mA. I would tend to say 10 000uF regardless. These are connected across the spare rectifier terminals. The device is connected to the live feed ( or neutral would work ) as if a fuse in series with the transformer.
If you try to measure a voltage across the caps when in use I doubt you will if reasonably generous with uF. Using the big 600V 50 amp bridges can be no more expensive than 6 amp devices. ESP Audio show the how and why. It strikes me the phase shifts etc are likely to be worrying with some permutations. As yet any I built oversized to the recipe above seem to have worked. They are always for friends who could not live with the hum. Some technical explanations I read seem unlikely. The one I take as possible is Delta connected three phase supplies where neutal shifts to make a DC component are the cause. My feeling is most houses are supplied very near to the house via a transformer. This should remove any DC component. The one it can't is three phase imbalance.
Next take some non polar caps ( other people don't bother and take the risk of the low voltage being OK in reverse bias ). Use the ripple ratings. For example a 1000 uF 16V might be 800mA. I would tend to say 10 000uF regardless. These are connected across the spare rectifier terminals. The device is connected to the live feed ( or neutral would work ) as if a fuse in series with the transformer.
If you try to measure a voltage across the caps when in use I doubt you will if reasonably generous with uF. Using the big 600V 50 amp bridges can be no more expensive than 6 amp devices. ESP Audio show the how and why. It strikes me the phase shifts etc are likely to be worrying with some permutations. As yet any I built oversized to the recipe above seem to have worked. They are always for friends who could not live with the hum. Some technical explanations I read seem unlikely. The one I take as possible is Delta connected three phase supplies where neutal shifts to make a DC component are the cause. My feeling is most houses are supplied very near to the house via a transformer. This should remove any DC component. The one it can't is three phase imbalance.
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