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Puritan Audio PSM156 Review (AC Filter)

AndreaT

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It is always fun to watch how many are anxious to spend their money on totally useless audio electronic equipment and how many are walking the tight rope of discussing hypothetical benefits of useless (and often harmful) electronic equipment even after a thorough scientific testing by Amir.
 

NTK

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I want to say
I'm very embarrassed that ASR makes completely wrong measurements for such products every time.
To evaluate such a product, create a situation that actually causes disturbance such as noise and affects the audio equipment, and measure how the target product is attached and how it works at that time. If you don't, it doesn't mean anything.
It is natural that measuring it in a normal state without any obstacles has no effect. "No effect" is the correct answer. If there is any change in the audio signal, it means a defective product.
Such products are similar to car seat belts and lightning arresters, and only show their effects in the event of an accident. It usually looks like a useless and disturbing entity.
Do not measure such products in the same way as audio equipment. Evaluation of these products requires a completely different and advanced measurement environment.
These are the first 2 paragraphs from Puritan Audio Lab's product page:
http://www.puritanaudiolabs.com/products/master-purifiers/psm156/

The PSM156 builds upon the brilliance of the legendary PSM136 retaining the precision symmetrically balanced circuitry and 6 fully independent outputs. Increasing the number of independently tuned filter elements from 39 to 52 enables your system to deliver even greater delicacy and detail whilst enhancing dynamics and punch.

The PSM156 will lift your system into a new dimension. Definition takes an enormous stride forward, individual instruments gain air between them with their sound and timbre becoming believable, the sound-stage will move out of your speakers and into the room with gains in three dimensionality with clarity definition and space between the instruments for them to interrelate rather than muddle each other. Your listening will become a far more engaging and pleasurable experience.

I didn't see any wording that says the product is only beneficial if your AC is "bad". (And if it is only beneficial if you have "bad" AC, then give the detailed definitions of what "bad" AC means, so people can determine if this product is useful for them.) They claimed their product improves sound quality, which is disproved by Amirm's AP measurements. Why are Amir's measurements wrong when he is measuring against the manufacturer's claims?
 

bidn

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Oh @amirm
No matter how much money you put in this stuff and £1500 is not in the cheapo category, the result is always the same.
As French during the revolution:
I want to see a headless panther please !!


The guillotine got rusty and needs maintenance. There are too many snake oil manufacturers targetting gullible audiophooles, revolutionary Amir cut off too many heads these last times... Also, his wife is getting mad at him , his testing lab has become a gory, horror place, full of blood...
.
 
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tmtomh

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So much FUD in some of these comments, just like in the last power filter review/test. I live in a dense urban environment, with light dimmer switches, window ACs, old fridges, HVAC condensate pumps, tons of wi-fi networks including public ones, contractors and residents constantly using power tools plugged into AC, decades-old electrical wires strung above ground on poles, cable TV/internet lines strung everywhere, dense cell-tower infrastructure, and anything else you can think of. I’ve had 3 power amps, two preamps, 3 DAC/digital source components, a graphic equalizer, and two streaming devices in my system during the past 10 years. The only noise I’ve had was mechanical hum from the toroidal transformer in one of those power amps - precisely because my AC is dirty and has DC in the line. That problem was solved by a $150 DC blocker (a different, more specific tech that, unlike these alleged power cleaners, actually works).

My point is that I - like many others who could chime in here with similar situations - have never been able to produce the problem these cleaners claim to solve, even though I’ve had multiple items in the chain, Class AB amplification (including a used Adcom amp I got for $150), Class D amplification, a cheap computer streamer with a cheap PSU and unfiltered USB connection to my DAC, linear and switch-mode PSUs, unbalanced interconnects, etc. So what lengths is Amir supposed to go to in order to find this mythical Black Swan setup that would be so FUBAR with AC noise that it would benefit from a $1500 AC “cleaner”?

The objections raised here and in the other AC cleaner thread are nonsense. The device does not do what the manufacturer claims.
 
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groovybassist

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These are the first 2 paragraphs from Puritan Audio Lab's product page:
http://www.puritanaudiolabs.com/products/master-purifiers/psm156/

The PSM156 builds upon the brilliance of the legendary PSM136 retaining the precision symmetrically balanced circuitry and 6 fully independent outputs. Increasing the number of independently tuned filter elements from 39 to 52 enables your system to deliver even greater delicacy and detail whilst enhancing dynamics and punch.

The PSM156 will lift your system into a new dimension. Definition takes an enormous stride forward, individual instruments gain air between them with their sound and timbre becoming believable, the sound-stage will move out of your speakers and into the room with gains in three dimensionality with clarity definition and space between the instruments for them to interrelate rather than muddle each other. Your listening will become a far more engaging and pleasurable experience.

I didn't see any wording that says the product is only beneficial if your AC is "bad". (And if it is only beneficial if you have "bad" AC, then give the detailed definitions of what "bad" AC means, so people can determine if this product is useful for them.) They claimed their product improves sound quality, which is disproved by Amirm's AP measurements. Why are Amir's measurements wrong when he is measuring against the manufacturer's claims?

The text from Puritan’s website is a perfect example of “priming” - once you read those words, your brain is unconsciously biased to experience those results. The book Thinking Fast and Slow by Daniel Kahneman is a real eye opener on how our brain has evolved to fool us very often in modern day life. I spent decades on the purely subjective side of the fence, but funny thing is, the more I strip my system back to the basics, removing tweaks, expensive cables, etc., the better it sounds. I’m not criticizing people’s subjective beliefs, I’m simply encouraging people to understand more about how their brain works and draw their own conclusions.
 

GXAlan

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@amirm quick question.

THD involves a frequency range that you are looking at, right? Can you measure the THD from the DACs selectively from 1 kHz to 24 kHz instead of “everything”?

what if there is no difference when analyzed 20Hz-20kHz but in the areas that are filtered, there are differences?
 
D

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To both of you: your remarks are thoughtful and make a point.
Just how do you measure it "correctly" and does it "improve" the audio ?
The main measurement is FFT. There are more performance metrics like THD, harmonics, flicker. High-frequency such as EMI/RFI have even more metrics and slightly different measurement procedures (measurement with LISN) but it is largely irrelevant for audio.

To both of you: your remarks are thoughtful and make a point.
Why don't the AC filter "box" manufacturers measure it objectively rather than claiming subjective audio heaven ?
Because in 2021, any reasonable gear has the filters built in to behave well on any mains power that satisfies the power quality standards.
There are countries/areas that have issues with power quality. However, these filters are -by far- not enough to fix them. You'd be much better off with a UPS (a on-line model without bypass) in these cases.

To both of you: your remarks are thoughtful and make a point.
Wouldn't the best solution to get cleaner AC from the start using shielded mains from the electrical board and wire the gear with correct phase?
Not really. First, wiring a house with "shielded power cables" only makes sense if you put a isolation transformer + filters in the electrical board. Otherwise, the house shares the power (including all distortions) with the neighbors. Second, mains frequency is usually not radiating and power cables are grounded (somewhere, depends on the exact system) so they are poor antennas.

While the power system is not perfect, any imperfections are largely irrelevant. Today, any external/internal switched-mode power supply gives you fairly clean DC out. Then designers can add a linear/switched regulators to get to the precision needed.
To be frank, the bigger problem is that we use single-phase power at all - single-phase power has an extreme ripple with 2x (100Hz or 120Hz) ripple once rectified... but this is also solved
 

AudioSceptic

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No. Typical use is that you connect more components to the filter outlets and you interconnect them with signal cables. So you get loops when especially SE cables are sensitive to shield currents and add the voltage drop into the signal. Depending on EMI emitted by the components to the power net the filter may reduce the shield circulating currents and thus improve S/N. This is the goal with AC filter. Not to measure single component in a clinical laboratory AP setup with balanced l/0, possibly with floating outputs.
Is this an opportunity to suggest a measurement setup with schematic so that Amir, or someone else, can measure these devices in the situation where they have the best possible chance of proving their worth? Then there can be no more doubt.
 

tmtomh

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@amirm quick question.

THD involves a frequency range that you are looking at, right? Can you measure the THD from the DACs selectively from 1 kHz to 24 kHz instead of “everything”?

what if there is no difference when analyzed 20Hz-20kHz but in the areas that are filtered, there are differences?

There are differences: in the SINAD graphs one can clearly see that certain distortion spikes above about 3kHz are down 10-20dB with the AC cleaner in the chain - and @amirm repeatedly notes that it does indeed filter.

But when he measures an actual audio device there is no difference because the audio device already filters the AC by itself - which is another point Amir has made repeatedly across many threads.
 

GXAlan

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But when he measures an actual audio device there is no difference because the audio device already filters the AC by itself - which is another point Amir has made repeatedly across many threads.

Look at the 3 kHz spike off the D90. It is lower with the Puritan audio.
Look at the 5 kHz spike off the D90. It is higher with the Puritan audio.

1) Is this reproducible run to run?
2) What is there a difference if you looked a HD in this region instead of THD 20Hz-20kHz

(I am sure this is below the threshold of audibility but it would be nice to quantify it in the same way we poo-poo gear with 96 dB SINAD versus 120 dB SINAD even though 96 dB is probably good enough.)
 
D

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It is impractical to build filters that go much lower. They would become large and expensive.
This is true for passive filters; active filters can do this even at current prices of audiophilia power conditions. However, it is pointless for the reasons that you state:
But no, it would not do any good. The incredible performance you see from Topping 90 is with my 'dirty' power. The limits there are not how clean the AC power is. We are down to just the noise a resistor produces and such.
 

David_M

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Haven’t you read the review where @amirm displays the dirty mains?

There are other forms of impairments/distortions such as under or overvoltage that this device needs to be tested for. These are far more common and problematic than the harmonics from the mains power supply. Actually performing a 1 kHz FFT which is in the region where no filtering happens is not useful. I'd like to see the effects (if any) on a 10kHz FFT before and after the conditioner.

Even better would be simulation high-frequency noise on the mains. I lived in an apartment where AM radio stations bled through my audio system. FM radio stations also bled through but that due to the long speaker cables that I had to meticulously re-arrange on the floor to minimize the bleedthrough. Frustrating that I'd approach the speaker wire to move it and the station 'disappears', only to re-appear if I moved away.

Now, we know that AC is converted to DC inside the audio device and further filtered to provide clean DC power to the rest of the circuitry. But this DC filtering may not be enough to eliminate AM radio frequencies (~500kHz - 1700kHz) depending on the design of the audio device. These are then rectified to DC or some lower frequency which may be visible on a DC-20kHz FFT spectrum. This is where this Puritan line conditioner could be useful.
 

phoenixdogfan

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The lesson I've learned as an audiophile to 47 years is to always spend your money on that which will do the most good. Obviously, that's not on a 1449 GBP AC filter.
 

pkane

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Actually performing a 1 kHz FFT which is in the region where no filtering happens is not useful. I'd like to see the effects (if any) on a 10kHz FFT before and after the conditioner.

I’m not familiar with an FFT that’s limited to just one frequency, nor do I see one in Amir’s measurements.
 
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sarumbear

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abdo123

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This is true for passive filters; active filters can do this even at current prices of audiophilia power conditions. However, it is pointless for the reasons that you state:

I'm really curious if anyone is willing to send Amir a DC iPurifier2

https://ifi-audio.com/products/dc-ipurifier2/

it's supposed to be exactly what you just mentioned, an active noise cancellation device for DC power.
 

David_M

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I’m not familiar with an FFT that’s limited to just one frequency, nor do I see one in Amir’s measurements.

So, where does the 1 kHz FFT he always performs in his tests come from ??? The AP sends out a clean SINGLE frequency at the set rate and said AP measures the response of the device under test (DUT). This would include the original 1 kHz signal plus a whole lot of distortion artifacts, mainly related to the original frequency and some not so much, e.g. powerline harmonics.

So, let's try this again ... Amir sets the AP to send out a SINGLE 10 kHz signal to the DUT and we measure its response, while said DUT is being fed AC mains mixed in with high-frequency AM and FM noise.
 

pkane

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So, where does the 1 kHz FFT he always performs in his tests come from ??? The AP sends out a clean SINGLE frequency at the set rate and said AP measures the response of the device under test (DUT). This would include the original 1 kHz signal plus a whole lot of distortion artifacts, mainly related to the original frequency and some not so much, e.g. powerline harmonics.

So, let's try this again ... Amir sets the AP to send out a SINGLE 10 kHz signal to the DUT and we measure its response, while said DUT is being fed AC mains mixed in with high-frequency AM and FM noise.

FFT measures a range of frequencies. Amir's measurements show spectrum from 0 to 20kHz. What does it matter what frequency test signal you're feeding the DAC? That signal isn't coming from the AC/mains, is it? The FFT shows all frequencies in the range, 1kHz and 10kHz included.

Any RF or FM noise affecting audible range would be captured in the 0-20kHz range if the filter has any effect on the DAC or preamp.
 
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David_M

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FFT measures a range of frequencies. Amir's measurements show spectrum from 0 to 20kHz. What does it matter what frequency test signal you're feeding the DAC? That signal isn't coming from the AC/mains, is it? The FFT shows all frequencies in the range, 1kHz and 10kHz included.

Yes, the test frequency matters. a 10kHz (or greater) FFT would be more telling since its harmonics are within the attenuation region of the line conditioner. Comparing the 10 kHz FFT before and after the conditioner (while HF AM/FM noise is injected on the mains) would let us know if this device works as designed (though not as claimed).
 
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