|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
71.131.194.128
In Reply to: Quantum field power conditioning posted by DHT 4 ME on February 10, 2007 at 18:35:09:
The TV in the bedroom on the other side of the wall from my audio system is one with a switching supply and it pollutes the sound from the audio system. The TiVo or replacement DVR along with it is even worse. I've had to build a fairly elaborate power filter for the video gear to restore the performance of my audio system.Interesting that a filter on your audio system does not undo the goodness, but the filter on the TV does. Perhaps there is another, stronger, noise source on your AC line and the TV in the 'off' state is absorbing some of that noise. You might want to try Alan Maher's Hammond 193L choke tweak. This is a power choke wired to a plug and used as a parallel filter to absorb noise on the AC line. You might also benefit from applying AC filters to suspect noise sources, such as your computer or any appliances with computers inside.
Follow Ups:
Just for grins I just plugged the tv ino the dedicated ac line for the audio system.
Yuck! it sounds compressed and makes a slight hum in the system. I don't know how it could do that as I have transformer coupled inputs to my preamp and amps.It is therefore not a ground loop.
Mabye the set is shunting some current somewhere and creating some emf.
Switching power supplies are becoming all too common in appliances. They make RF noise that appears in normal mode and common mode on the AC wiring. Some of this noise may also get onto the safety-earth ('ground'). Even if the appliance does not have a grounded plug, a filter somewhere else, such as in a surge-protected power strip, may couple the line noise to the ground wiring through the "Y" caps in the filter that connect line and neutral to ground.Your system is protected against ground-loop noise, but may be susceptible to normal mode, common mode, and ground noise, through parasitic capacitances in the power supplies.
If your audio system still sounds better with the TV plugged in to the convenience circuit, I suggest further experiments with shunt filters on that circuit, and elsewhere in your house. You may be able to get further audio improvement.
If you can DIY, you can make simple and cheap R-C filters for line-to-neutral that will tame some of the normal mode noise. R is about 120 ohms, one-half watt, and C is whatever "X" capacitors you can get your hands on, up to about 1 microfarad. Use care to contain the flame if the capacitor fails to a short: a non-flameproof resistor will go up like a kitchen match!
The better version of this filter is to use a series of caps of different sizes, down to the smallest "Y" cap you can find. Wire each with its own resistor and put them all in parallel.
This tweak can be combined with the iron-loss tweak by using a large, sloppy filament transformer with the R-C filter on the secondary. Use a resistor value that transforms to look like 120 ohms at the primary, and a series of caps with the largest one equivalent to 1 microfarad at the primary (transformers step impedances by the squares of the turns ratios). This will be better than either the R-C filter tweak or the Hammond choke tweak by themselves. The caps are protected against spikes by the transformer, and do not have to be "X" or "Y" rated.
Try the filters in different outlets. Some outlets will affect the audio system more than others.
I guess that the question now is does a little emf cause a system to sound more open.
I know that rf can cause oscillations in regulators that have wide bandwith.
I know that a power supply that is too tight will kill the sound of my DHT amps.
The tube guys are split but I am one that is in favor of the slightly underdamped puwer supply. The underdamped supply sings and the highly damped supply is muffled.
One of the artifacts is spurious treble, which makes a system indeed sound more 'open' and 'detailed.' However, careful listening with the ability to insert and remove the noise at will reveals that these are false, and that true information is being suppressed.Most of my tweaking for last couple of years has been focused on finding and removing RF noise artifacts. I still get misled from time to time when some tweak adds a little RF noise. Analytical listening is fatiguing, so it takes several sessions to be sure a minor change is actually improving resolution and reducing noise artifacts, instead of the opposite.
A more reliable guide is the midrange. RF noise causes a dryness in the midrange. One of the first casualties is the gorgeous warmth of well-recorded strings.
This post is made possible by the generous support of people like you and our sponsors: