Recommended Audio System Tweaks: Part 1
by David Magnan, President of Magnan Cables, Inc.


I have found the following list of "tweaks" or adjustment/correction techniques to be essential for great sound. Individually and collectively these modifications have improved the sound of my system more than any component upgrades such as new amplifiers, preamps, etc. I believe my findings are applicable and useful to audiophiles in general, but of course I cannot guarantee the same results given the great variation in personal taste and component design.

A prerequisite is that your system already has to be good enough in terms of resolution, imaging, etc. for these techniques to be of benefit. Of course, closed-minded strictly by-the-book meter-reader engineer types who believe that the differences obvious to audiophiles between cables, amplifiers, use of "tweak" accessories, etc. are hype and illusion will not be interested, and need read no further.

This is just a partial and evolving list and only touches on a vast subject. One of the fascinations of audio is the complexity of the basic problem — attempting to reproduce recordings as realistically as possible in a home environment. The elements of the problem include electronics, psychoacoustics, acoustical engineering, mechanical engineering, physics (electromagnetics) and many other disciplines.


I believe that these measures work primarily through two interrelated mechanisms: by increasing the "time coherence" of the system, and by lowering the noise floor. In this context, to "improve time coherence" means to reduce the delay and smearing of sonic energy of a musical event over some period of time following the event. This "time smearing" phenomenon is inherent in the mechanical and electrical systems used for sound reproduction, and the ear-brain system is very sensitive to it. Electrical examples are skin effect or frequency-dependent phase shifting of signal current propagated through the interior of a wire and dielectric absorption in capacitors and cables. Mechanical / electrical examples are the time delayed and resonant behavior of speaker drivers and enclosures, flutter (rapid speed variations) in turntables and CD transports, and time smear induced in the phono cartridge output due to stylus contact-generated energy returned to the stylus after first being propagated into the tonearm and record. Interestingly, timing jitter in the CD playback serial digital data is caused both electrically and mechanically by vibration, and rapid speed variations in the transport drive mechanism.

Another example of vibration feedback-induced time smearing is the vibration of wires in cables due to sound pressures from the speakers and to electromotive forces induced by adjacent current-carrying wires.

Another form of mechanical vibration-induced time smearing is the fore-and-aft vibration of a speaker enclosure in response to forces on the driver voice coil. This is simply due to Newton’s law of action and reaction and occurs regardless of the rigidity and degree of damping of the enclosure. Simply placing a 15-20 pound lead weight on the top of the speaker improves clarity of sound considerably by reducing Doppler distortion due to the reactive fore-and-aft motion of the enclosure. Doppler distortion smears sonic energy over a range of frequencies (rather than time) and is inherent in all speaker designs. If a driver diaphragm is moving at both a low and a high frequency at the same time (say 50 and 5000 Hz), the higher frequency is modulated (distorted) by the lower frequency due to the Doppler effect. As the sound source approaches at some velocity its sound is shifted up in frequency proportionately to the speed of approach, and vice versa for the sound source moving away from the listener. This effect "frequency smears" the output of all speakers, with the effect worsening with decreasing efficiency, smaller radiating area and 2-way designs. Of course the weights also improve performance by increasing the damping of cabinet resonance.

The common effect of all these and many other time and frequency smearing mechanisms is a massive perceived blurring, smearing, flattening and veiling of the sonic "picture", along with various tonal imbalances such as overbrightness and bass boominess or looseness.

The items listed below are really more than tweaks — they partially correct fundamental problems such as time smear and RF induced noise that no new improved electronics or speakers can address. As a general observation, each of these techniques achieves unique improvements, which cannot be produced by other tweaks.

The following observations are very important and should be kept in mind when considering "tweaks". The less revealing or resolved the system already is, the less impact the addition of a single modification or tweak will make. Of course, "revealing" doesn’t mean expensive — the transparency, resolution and musical naturalness of a system are more dependent on the quality of setup and tweaking than expense of components. This means that the first few modifications may only slightly improve the sound, but as the system’s resolution gets better and better, subsequent "tweaks" become more and more dramatic in their effect. Basically, the ear/brain system can perceive very small amounts of time smear or incoherence. If a given system mod or "tweak" reduces time smear by x amount and the system initially has 10x time distortions, there is little improvement. If the system is better, with only 2x distortion, the same tweak transforms the sound because it doubles the resolution by halving the time distortion.

My overall tweak technique list keeps expanding, but this is it for now. It is hard to give a relative ranking of all those items, but I have found that as a group the AC power purification techniques make the greatest improvement. Your comments and questions are welcome.

List of Techniques

Power line shunt or parallel filters

Do-it Yourself AC Filtering

Power conditioners

Dedicated earth ground

Ferrite RFI blockers

Turn Off and Unplug

Other Noise and Hum Reduction Techniques

Power Cables


Speaker Cables

Devices designed to correct CD digital errors

Component support and damping

Special component feet

Improved passive parts

Parallel RFI filtering at speaker input

Antistatic sprays

Power line shunt or parallel filters

These devices incorporate capacitors connected in parallel across the power line, and reduce noise reaching the equipment without imposing any inductive, maximum-current choking coils or inductors in the line.

Correctly applied, this major system modification or adjustment (really more than a "tweak") dramatically improves digital and to a lesser extent analog playback quality. Digital processing, especially the serial digital, is extremely sensitive to power line noise, probably due to the effect of noise on digital timing jitter.

There are two alternate approaches for this technique: either use commercially available plug-in filters, or build superior-sounding units yourself.

Commercial parallel-type plug-in AC filters


Audioprism Quiet Line plug-in filters (kit of 8). Audioprism, Inc. Tel. (206) 641- 7439

Rubycon NF-1 line filters, available from Michael Percy (415) 669-7181

Enacom plug-in power line filter, available from The Tweak Shop (707) 575-8626.

The Quiet Line and Enacom filters plug into the A/C socket. The Rubycon filters can be wired either into equipment power supplies or preferably into 3-prong AC plugs. The Quiet Line and Rubycon filters work together synergistically, producing a large reduction in background noise level, edginess, hardness, etc. The Enacom filter is more expensive, but also improves clarity, especially in the midrange, very much more than the Quiet Line and Rubycon units.

All three commercially available filter types employ small value (0.1 microfarad) capacitors. The Quiet Line and Rubycon units are primarily designed as RFI/EMI filters, with inexpensive, nonaudio-grade capacitors. The Rubycon has 3 caps, shunting RFI noise to earth ground from both AC and neutral, and from AC to neutral.

Ideally, most of the Quiet Lines and Rubycon units should be plugged only into other AC lines than the one used by the system, in the listening room and in other rooms in the house. The Enacom filters incorporate a much higher quality, better sounding capacitor and should be reserved for the outlet(s) powering the system. You need at least 2 to 3 Enacoms for the best performance. A single Enacom improves clarity and resolution over a relatively narrow band from the high frequencies through the upper midrange. Adding one, two, three, etc. Enacoms extends the improvement successively lower in audio frequency. Three together (total .3 microfarad) seem to extend fully through the midrange.

I find that the greatest sonic improvement to result from installing a combination of all 3 filters:

At least 16 Quiet Line filters plugged into other AC lines than the one used for the system, covering all the AC lines in the house if possible.

Two Rubycon NF-1 filters to each Quiet Line (total of 31), plugged into the same AC receptacles as the Quiet Lines.

Three Enacom line filters plugged into the power conditioner supplying the signal source component (CD player, phono/line stage preamp), or into the wall outlet used if there is no power conditioner.

This may seem excessive, but the effect of all the filters is cumulative. This one combined "tweak" accomplished a wonderful improvement to digital playback quality unobtainable in any other way than AC filtering. Of course, power line quality varies from location to location and the optimum number of filters certainly also varies with location and with the AC line noise susceptibility of the particular components.

I suggest the common sense approach of starting out with one of each type, increasing numbers of filters until the point of diminishing returns is reached.

A Do-it yourself approach to AC line filtering

This is only for the EXPERIENCED HOBBYIST who is familiar with a soldering iron and basic house electrical wiring practices. [Please note that Positive Feedback assumes no responsibility for injury, damage, or loss sustained by the DIYer — the reader proceeds AT HIS OR HER OWN RISK.] Inexpensive and simple AC filter adapters can be made using large-value metallized polypropylene film capacitors. There are no commercially available units equivalent to the designs suggested here. If correctly utilized, such hand-made plug-in filters have a huge, almost unbelievable effect in improving the sound of digital, an order of magnitude more than the commercially available units mentioned previously. Multiple plug-in capacitors are required for best performance improvement. About half of them should be connected from AC line to neutral, and the other half connected from neutral to earth ground. The more the total capacitance, the better the sound. The 120 VAC line to neutral capacitor adapters should of course be carefully insulated using tape and/or shrink tubing to thoroughly insulate the caps and wiring to the 2-prong plugs.

Care should be taken when removing one of the 120v AC line-connected capacitor plug-in units from the receptacle since the capacitors may be charged up to over 180 volts at the moment of removal. Always short out the plug prongs before handling. Alternatively, a 50,000 ohm 1/2 watt resistor can be soldered across the caps to automatically discharge the caps rapidly on removal from the receptacle.

The capacitors connected from AC line to neutral should be plugged in as close to the CD player (or DAC and transport) IEC power inlet(s) as possible. The largest improvement in smoothness, transparency, depth of image and lowered noise level is obtained using an adapter allowing the AC line to neutral plug-in caps to be placed near the CD player (DAC/transport IEC input receptacle). This short adapter has a female IEC at one end, a box containing the caps or a multiple ungrounded (two wire) AC receptacle for the caps, then a male IEC connector for the power cord.

In addition, more plug-in AC line to neutral-connected capacitors should be placed in the same or adjoining wall receptacle that the system is plugged into. These capacitors drastically improve the sound by greatly reducing digital timing jitter through their AC line noise reducing effect, and also supplement the CD player/DAC/transport power supply capacitors during the short rectifier diode conduction periods (120 times per second) by acting as supplementary instantaneous current sources derived from their stored electrical charge.

The plug-in filter capacitors connected from neutral to earth ground reduce noise on neutral by bypassing or shunting it to earth ground, and improve the sound of digital even more than the AC line-to-neutral connected capacitors. The neutral to earth ground-connected capacitors must be wired to 3-prong AC plugs. For factory-terminated molded plugs, connection is from the white or blue wire (neutral) to green wire (earth ground).

These plug-in filters should be inserted in wall AC receptacles wired to each of the AC lines in the house, except the line the stereo system is plugged into. This is necessary because large neutral to earth ground connected capacitors usually cause ground loop hum and buzz if plugged into the audio system AC line.

Each of the non-audio system-connected power lines should have at least one capacitive filter on neutral because noise-induced on the neutral lines by appliances, digital, and RF devices in the house all sums at the common neutral tie point in the breaker box to be transferred to the audio system-connected lines. As many separate receptacles on each line as possible should have plug-in filters, for the best results.

Recommended capacitor type and values for a single plug-in unit for wiring either as an AC line to neutral or neutral to ground adapter: One to four 4-10 microfarad 400-600 volts DC metallized polypropylene film caps, connected in parallel and bypassed by at least one .47 microfarad and one .01 microfarad 400-600 volts metallized polypropylene cap.

Similarly to when connected directly in the audio signal path, the powerline capacitors have different sounds or sonic signatures when connected one way versus reversed. For the absolutely best results, the capacitor types used should be tested to determine the best sounding orientation or polarity, before wiring into the connectors.

Recommended capacitor brands and sources (inexpensive and good-sounding):

GE Series 41L, 10 microfarad/400VDC metallized polypropylene caps. Source: Madisound Speaker Components (608) 831-3433.

Xicon .47 and .01/630V metallized polypropylene film capacitors. Source: Mouser (800) 346-6873, part numbers 1429-6474 (.47), 1429-6103 (.01)

A number of other capacitor manufacturers also make as good or even better-sounding units in the same values, but at somewhat higher prices. Examples are Reliable and Axon. Reliable: (PPMF type) (562) 946-8577; Axon: recommend only the 20 microfarad/1200v: (602) 272-6696.

Power conditioners

Power conditioners are generally much more expensive than the single parallel (shunt) units recommended above, though the cost of a good

power conditioner can be comparable to the total cost of the multiple set of parallel AC filters. The sonic improvement due to most power conditioners is much less than from either recommended set of parallel type filters and is therefore not as cost effective. I have found that many high-end audio power conditioners are marginal or negative in their effect. This seems to be associated with the current-limiting isolation transformers and inductors used in the series filter type conditioners.

The Bybee Technology devices are a major exception to this. Though moderately expensive, they improve the quality of digital playback nearly as much and in the same ways as the recommended handmade AC filter approach. The two actually are additive in their sonic improvement.

Recommended: Bybee Technologies Signature Quantum Line Conditioner and Quantum Charger — Bybee Technologies (408) 257-0961. These units employ the unique Bybee Block quantum mechanical conduction-noise filters. The line conditioner also includes RFI parallel filtering. The Bybee filter greatly improves the sound of low line current components such as CD players and preamps, but does not seem to work well with power amps. The Quantum charger plugs in at the CD player, DAC, etc. IEC AC input connector. The Bybee block technology was originally available in the TAD Power Purifier, which is no longer being manufactured.

Turn Off and Unplug

The foregoing techniques clean up AC to some extent depending on how many capacitors and types of filters are used, but do so basically after noise of various kinds has already been injected into the power lines by all the plug-in devices in the house. Virtually all household appliances, TVs, radios, computers, burglar alarm systems, lawn sprinkler control systems, etc., etc. further pollute the already noisy AC power reaching the system. As many of these units as possible should be either switched off or preferably, unplugged for any listening sessions.

Some may think this is ridiculous, but unplugging the TV, lawn sprinkler system and burglar alarm, for instance, makes a really big difference comparable to some parallel capacitive AC filtering. Doing this is well worth the inconvenience to an audiophile perfectionist. For more convenience, external power switches and mechanical timers can be added. Such external switches should interrupt both AC and neutral. Of course, this issue is greatly subject to the obvious constraints imposed by practicality, and the power of your spouse to impose some degree of sanity.