PS Audio's Noise Harvester and Audioprism's Quietline are claimed to reduce the noise induced on mains power lines by electromagnetic interference and radio frequency interference. PS Audio does not publish specifications for the Noise Harvester. I found out that the Harvester operated in the 7 kHz to 15 kHz frequency range by searching the PS Audio Internet forum. Audioprism's published specification for the Quietline says it "operates from the middle of the audio band to several hundred megahertz".
The Noise Harvester is claimed to work by gathering and storing noise energy in a capacitor, which is then bled off by an LED. Therefore, electrical noise energy is converted to light. The faster the Noise Harvester's LED blinks, the greater the amount of noise that is being converted to light. It is priced at $99.95.
The Quietline is claimed to work by shunting noise energy from line to neutral. It is priced at $29.99.
Figure 1. Audioprism's Quietline and PS Audio Noise Harvester power line noise filters.
Figure 2. Single Noise Harvester plugged into kitchen counter receptacle.
Figure 3. Two Noise Harvesters plugged into kitchen counter receptacle.
Figure 4. Noise Harvester and Quietline plugged into kitchen counter receptacle.
The Fast Fourier Transform function of a Tektronix TDS 2012 did not show any changes in the powerline's noise spectrum with either the Noise Harvester or the Quietline plugged in. This was expected since the Harvester and Quietline operate far above the 60 Hz power line frequency. PS Audio claims that the more Noise Harvesters are used on an AC circuit, the more noise will be removed. The results from using one to four Noise Harvesters in two of my kitchen counter receptacles (two outlets per receptacle) on three different days are shown in table 1. My home is wired so that lights and receptacles are on different circuits. There are four receptacles on this particular AC circuit: three above the kitchen counter and one below the counter which serves the disposal. Nothing else was plugged into the receptacles other than the disposal, Harvesters and Quietline.
Blinks were counted for 1 minute and trials were timed with a digital topwatch. Each trial scenario was repeated five times over a 45 minute period on each day. There were differences in the amount of blinks recorded on different days, but the number of blinks recorded on successive trial scenarios during a 45 minute period on the same day were constant.
I expected to see the blinking rate decrease with each successive Noise Harvester plugged in. However, there was only a decrease in the blinking rate when going from one Harvester to two. Going from two to three or three to four Harvesters produced no further reduction in blink rate.
When a Quietline was plugged into the same receptacle as a Noise Harvester, the Harvester's blink rate increased.
Two Channel Audio System Listening Evaluations
Two musical selections were used for all listening trials:
A musical selection of average recording quality (clarity, detail, spatiality, dynamics): Track twelve ("When We Come Together") from Jakiem Joyner's "Lil Man Soul" CD. Specific "markers" that I use to judge sound quality as rendered on different equipment are the electric guitar crack at the very beginning, the high hat strike at 00:06, a low pitched scraping sound at 00:24, a high pitched scraping sound at 00:59, and the electric guitar notes at the right of the sound stage beginning at 04:24.
A musical selection of excellent recording quality (clarity, detail, spatiality, dynamics): Track two ("Lisa") from Stanley Clarke's "At the Movies" CD . It has a growling electric bass at the intro, sharp drum rim shots throughout, well recorded electric lead guitar transient notes, and airy background vocals, although it is primarily an instrumental song.
Listening evaluations were done with two different preamplifiers: a Pass Labs X0.2 and its next generation, and higher resolution, successor, the XP-30.
My two channel system is fed by three dedicated 20 amp AC circuits, which are terminated by PS Audio Soloist Premier SE in-wall passive power conditioners. Each monoblock power amp is on a separate circuit. The third circuit feeds a PS Audio P10 AC regenerator, which feeds the source components and line level and phono preamplifiers. A Noise Harvester or a Quietline was plugged into the upper outlet of each Soloist receptacle during specific trials.
Noise Harvester Trials With The X0.2 Preamp
Music sounded louder and clearer. I could stand next to the left speaker and hear the change in clarity of the drum rim shots as I plugged in and unplugged the Harvester from the receptacle feeding the left monoblock power amp. There was a little more fluidity and articulation in the electric bass notes.
Quietline Trials With The X0.2 Preamp
Music sounded louder and clearer than with the Harvesters. I could stand next to the left speaker and hear the change in clarity of the drum rim shots as I plugged in and unplugged the Quietline from the receptacle feeding the left monoblock power amp. The reverberent echos (in the left channel) of sounds in the right channel were easier to hear. There was also a small increase in tactile sensation, as felt through my armrests, that was not there with the Harvesters.
Noise Harvester and Quietline Trials With The XP-30 Preamp
The level of clarity and detail of the XP-30 without either the Harvesters or the Quietlines was greater than the clarity and detail of the X0.2 with the Harvesters and Quietlines. When the Harvesters were plugged in, I did not perceive a difference in clarity or detail, but there was a small increase in apparent loudness, which indicated a lowering of the noise floor. With the Quietlines plugged in, there was a greater increase in apparent loudness over the Harvesters. Pass Labs claims that the XP-30 has significantly better EMI shielding than the X0.2. Compared to the X0.2, it appeared that the XP-30 was not as sensitive to the types of noise that the Harvester and Quietline filter out.
The rate of Noise Harvester blinking was 600 blinks per minute at the left monoblock's AC receptacle, 150 blinks per minute at the right monoblock's AC receptacle, and 58 blinks per minute at the P10 AC regenerator's AC receptacle.
Home Theater Audio And Video Trials
My home theater system has high video resolution and moderate audio resolution.
I did not perceive any visual performance improvement from using either the Noise Harvesters or Quietlines on the two dedicated 20 amp AC circuits that feed the home theater system. Both AC circuits are terminated by a PS Audio Soloist Premier SE in-wall passive power conditioner. The video equipment is fed by a PS Audio P5 AC regenerator. Test patterns and the "Quantum of Solace" Blu-ray were used for video evaluations.
Both the Noise Harvester and Quietline caused an increase in apparent sound level and an increase in clarity and detail. For example, the MGM lion's roar prior to the start of "Quantum of Solace" was louder, heavier, more growly and more detailed with the Harvester and more so with the Quietline. The two CD's used in the two channel evaluation, as well as the "Quantum of Solace" Blu-ray, were used in the home theater audio evaluation. The audio equipment is fed by a PS Audio P10 AC regenerator.
Video evaluation was done at the viewing location and by comparing pixel level screen shots using the method shown in figures 6, 7, and 8 of this thread.
The rate of Noise Harvester blinking was 106 blinks per minute at the P5 AC regenerator's AC receptacle and 600 blinks per minute at the P10 AC regenerator's AC receptacle.
Figure 5. Quietlines plugged into two of three dedicated 20 amp AC circuits feeding my two channel audio
The Quietlines provided higher performance at one-third the cost of the Harvesters in my two channel audio and home theater systems. The Quietlines were retained and the Noise Harvesters were sent back. With a better EMI-shielded preamp (the XP-30 compared to the X0.2) in a high resolution two channel audio system, neither the Noise Harvester nor the Quietline provided an improvement in clarity and detail. Each of them did lower the noise floor which resulted in an apparent increase in sound level. Neither the Quietline nor the Harvester improved video performance in the home theater system, although small improvements in clarity, detail and the weight of sound were realized.
I expect that better results with the Harvesters may be realized in cases where several of them can be used on multiple receptacles on the same AC circuit. Of course, that is not an option with a dedicated circuit with only a single receptacle. The multiple unit performance advantage may also be true of the Quietlines.