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Puritan Audio PSM156 Review (AC Filter)

pkane

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solderdude

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Yes, of course. At the very least you need to limit inrush currents and peak-to-RMS current ratio (relates to power factor and reduces efficiency if extreme).
Inrush current can also trigger your breakers..
This is before looking at any IEC, IEEE, or GB/T standards, which you have to do as well if you want to sell in these territories.

Only needed for (high) power amps. Those that really need it have this already. Nothing new. Is being applied for decades already.
This has nothing to do with the discussed filter/conditioner b.t.w.
What's the point with respect to this review ?
 
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Only needed for (high) power amps. Those that really need it have this already. Nothing new. Is being applied for decades already.
This has nothing to do with the discussed filter/conditioner b.t.w.
What's the point with respect to this review ?
Grid interface quality is described by many metrics including flicker, voltage/current harmonics, leakage current, and EMI. A power conditioner can improve any of these metrics and claim to improve grid quality. However, using such devices is equivalent to a user trying to "fix" shortcomings of a power supply design of a hifi device. However, (i) there is no unique "fix" for power supply metrics; (ii) power supplies make assumptions on what the grid is, so it is at least possible that a power conditioner makes things even worse, e.g. amplify some harmonics due to poor damping or partial collapse of the DC output voltage during transients due to too heavy filtering; and (iii) designs that I have seen tend to use typically third order filters with heavy resistive damping that consumes power (reduces efficiency).

Anyhow, your post suggested that rectifier current waveforms (= low order current harmonics) are a key metric to look at. This is not true in general because it rarely affects another device on the same circuit = no need for power conditioning beyond what the device itself has already built in. Just routing power and signal at reasonable distances from each other (inches; recommended also for digital signals) should be sufficient for pretty much any hifi use case and becomes more important for long cable runs.
 
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David_M

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The rather bizzare and passionate timbre of this thread amuses me very much ...all because of an AC powerline filter that does filter the mains but possibly has negligible effects on the audio devices it's targeted for.

13 pages and counting :-:)
 

solderdude

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your post suggested that rectifier current waveforms (= low order current harmonics) are a key metric to look at.

No I don't suggest that at all. I merely explained that current drawn from the mains are just short peaks and that the 500Hz filter frequency was well chosen.
This discussion reminds me of earlier discussions with @b4nt.
I regularly do test my designs (railway related analog measuring equipment) for EMC so am quite familiar with it and what it takes to pass those tests with flying colors.
 
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No I don't suggest that at all. I merely explained that current drawn from the mains are just short peaks and that the 500Hz filter frequency was well chosen.
This discussion reminds me of earlier discussions with @b4nt.
I regularly do test my designs (railway related analog measuring equipment) for EMC so am quite familiar with it and what it takes to pass those tests with flying colors.
What tests do you need to pass and why?
 

solderdude

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Several ones depending on which ones are required by the customer in order to be able to install the systems.
This, however, is not related to this thread.
 
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Several ones depending on which ones are required by the customer in order to be able to install the systems.
This, however, is not related to this thread.

This discussion is running in circles.

You provide no proof and little explanation, why according to your own statements
- a 500Hz external filter is a good choice
- shape of the AC current waveform is relevant in this context
- if rectifiers need any filtering or not (you flip flop on the topic)
- anything EMC related that you just brought up
I think you know what you are doing. However, your statements are at times vague, at times not on point what matters, and at times not particularly useful.

Just say what _matters_ according to you for a power supply in audio and what (if anything) an AC filter can bring to the table.
Then we can discuss and, maybe, figure out relevant test cases that may be of interest to @amirm
 

beefkabob

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It would probably also be fun to test a home with Tesla power walls. Coming to the SF bay area anytime soon? We could even see if there's a difference between one, two, three and four walls supplying power.
 
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amirm

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It would probably also be fun to test a home with Tesla power walls.
Speaking of which, what all is that status of power walls these days? I remember when it got announced you had to be a virgin born on some tropical island to get dealership for it. :) Was it a big success? Are people lining up with reservations to get one?
 

MZKM

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Speaking of which, what all is that status of power walls these days? I remember when it got announced you had to be a virgin born on some tropical island to get dealership for it. :) Was it a big success? Are people lining up with reservations to get one?
All I know is I keep getting YouTube pre-roll ads by dealers hyping it up.
 

solderdude

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- a 500Hz external filter is a good choice

Did you see the harmonic contents of the current pulses ?
To what frequency does that extend ?
I have more measurements, different currents, none really go any higher than 500Hz.
Why not filter AC from 500Hz ? The filter can be simple (40dB/decade) yet have good suppression up to about 10kHz where most transformers stop working properly.

- shape of the AC current waveform is relevant in this context

You are the professor in this field. What would happen if you were to filter at 100Hz ? Why doesn't anyone filter AC at just above 60Hz ?
Would there be enough power transfer into the smoothing caps ?
If one were to filter at 1kHz or 10kHz or 100kHz would that help with recharging the power caps?
Why would the current shape be not relevant when it is the current that charges the reservoir caps ?

- if rectifiers need any filtering or not (you flip flop on the topic)

Did I mention they did or did not ? Did I go into details about snubbering ? Did I address regulators (of different sorts ?)
This is about the mains side not what happens after the rectifier.

- anything EMC related that you just brought up
EMC is a wide subject. The discussed filter (that's what were taliking about) adresses various aspects of EMC of which only a small portion of differential mode is discussed which is not as important/impactful as common mode issues.
But if you read the thread and my and other comments you would have known this.


I think you know what you are doing.

The more you learn the more you realize you know next to nothing.

However, your statements are at times vague, at times not on point what matters, and at times not particularly useful.

And yours are ?


Just say what _matters_ according to you for a power supply in audio and what (if anything) an AC filter can bring to the table.

This is NOT a thread about power supplies this is a review of a mains power supply filter that has some of its aspects measured (not by me).
When you have comments about the review then post them.
 

beefkabob

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Speaking of which, what all is that status of power walls these days? I remember when it got announced you had to be a virgin born on some tropical island to get dealership for it. :) Was it a big success? Are people lining up with reservations to get one?

I've had them for a couple years so I don't know. Tesla installed them for me. I think they sell all the powerwalls they want to sell and then some. But I bet the wait is long.
 

solderdude

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Unfortunately, to infinity. Depends only on dynamic range of the spectrum analysis used.

At some point a transformer becomes a capacitor again and passes on RF garbage but common mode not differential mode.
In differential mode the bandwidth is kind of limited.
Measured a bunch of mains transformers when building electrostats and only found one that reached 16kHz, the rest stopped somewhere between 5 and 10kHz. Of course this was in 'reversed' conditions (audio amp feeding 24V windings) and primary loaded with a capacitance only.
So not comparable to normal situations.
 

solderdude

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And you get a display to boot including a bunch of features !
 

MC_RME

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More info and a look inside:

 

solderdude

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hmm and you get cheap capacitors in the internal SMPS...
Lesson learned... you need audiophile capacitors.
 

Yevhen

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I think you'll be surprised how "pure" that sine wave is from the audiophile point of view :). Something like a sine after 2- or in best case 4-bit DAC

lrg-2676-SDS00001__1_.png
 
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