How to clean the DC at mains. And ripple too.

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maty

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Re: How to clean the DC at mains. And ripple too.
« Reply #120 on: 21 Dec 2018, 05:35 pm »
After reading a private email (from other forum), I think it is convenient to leave in writing:

I do not sell any audio device and I do not receive any commission from any vendor.

If someone knows of a better or equivalent product, I would ask you to comment on the thread, because I am the first interested in the search for excellence, in audio or in any other field.

Every time I find it harder to participate in the open Internet :(

maty

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Re: How to clean the DC at mains. And ripple too.
« Reply #121 on: 2 Jan 2019, 04:03 pm »
Informative reading about SMPS noise or 'conducted ripple'.

SMPS for Hi-Fi?

by Eva #4

https://www.diyaudio.com/forums/power-supplies/45589-smps-hi-fi-post510829.html

Quote
'Noise' is a classic misconception about SMPS

Speaking properly, there is no noise in SMPS, since noise by definition is a signal of random nature and what SMPS produce on their output is periodic 'ripple' as any 50/60Hz supply. We could call this 'conducted ripple'

This ripple is usually a sawtooth waveform and it may have some RF ringing on transients [on the peak and valley of the sawtooth cycle]. There's not much difference from 50/60Hz supplies, except the ripple frequency is about 1000 times higher.

As in 50/60Hz supplies, ripple is easily filtered with pi filters and it may be attenuated as desired [even below noise floor], but with the advantage of size since 100Khz pi filters are much smaller and cheaper than 100Hz pi filters...

Note: Eva designs class D amplifiers to professional audio.

maty

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Re: How to clean the DC at mains. And ripple too.
« Reply #122 on: 17 Feb 2019, 06:18 pm »
I think what I just wrote in other forums (The diyAudio First Watt M2x) is relevant in this thread as well. There for the Mumetal and here for the toroidal transformers.

Audio Transformers by Bill Whitlock

[PDF] http://www.jensen-transformers.com/wp-content/uploads/2014/09/Audio-Transformers-Chapter.pdf

Page 9

Quote
The effectiveness of magnetic shielding is generally rated in dB. The transformer is placed in an external magnetic field of known strength, generally at 60 Hz. Its output without and with the shield is then compared. For example, a housing of 1/8" thick cast-iron reduces pickup by about 12 dB and a Mumetal can by about 30 dB. Where low-level transformers operate near strong magnetic fields, several progressively smaller shield cans can be nested around the transformer. Two or three Mumetal cans can provide 60 dB and 90 dB of shielding respectively. In very strong fields, because high-permeability materials might saturate, an iron or steel outer can is sometimes used.
   
Toroidal power transformers can have a weaker radiated magnetic field than other types. Using them can be an advantage if audio transformers must be located near them. However, a toroidal transformer must be otherwise well designed to produce a low external field. For example, every winding must completely cover the full periphery of the core. The attachment points of the transformer lead wires are frequently a problem in this regard. To gain size and cost advantages, most commercial power transformers of any kind are designed to operate on the verge of magnetic saturation of the core. When saturation occurs in any transformer, magnetic field essentially squirts out of the core. Power transformers designed to operate at low flux density will prevent this. Often a standard commercial transformer, when operated at reduced primary voltage, will have a very low external field.