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AC Filtering, Grounding Boxes, Linear PSU and Balanced Power.


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I am building an AC Filtering device which has one inlet, several outlets, each along a filter path. This should help prevent some of the noise re-injected into the mains by some of the switching-mode power supplies from affecting the other components.

 

The design is rather simple:

 

Inlet + Inlet filters -> Rails -> separate Filters for each outlet

 

On researching and building this, however, a lot more questions cropped up not just about the AC Filtering, but about alternate approaches or additional devices, and general use.

 

1. I could use duplex outlets, but if I were to plug two devices in one of these, would one device be well isolated from the second one?

 

2. I believe I'll benefit by plugging the iMac into it, but I think I would need to build a new, properly shielded power cable for it to keep the benefits of the filter box.

 

3. If I plug my amp in the filter box, then the line sees a 'pre-filter' before heading into my amp's power supply. I believe this could potentially be good, but it could also be detrimental to dynamics.

 

4. If I use that filter box, will I still derive cumulative benefits if I install Linear PSUs? I think this is a 'yes'.

 

5. If I use balanced power (like Equi=Tech or an isolation transformer), do I get cumulative benefits with the filter box? With the filter box and LPSUs? Or could the installation of balanced power replace some of this arrangement?

 

6. Currently, in the arrangement for stereo, only the iMac is grounded:

External HDD -> iMac -> DAC -> Amp. Theoretically, this should be OK, but I do hear some high-frequency hash that diminishes timbral accuracy for cymbals and the like, and proves fatiguing in the long term.

 

During my recent readings, I was reminded of the importance of the Ground Plane in DIY Ham radio circuits. In equipment which has not been designed properly, this is not well implemented. Thus, we often find ourselves with a mix or properly and improperly designed equipment, each with their own grounding scheme, each with either a two-prong power cable or a 3-pronged one.

 

Could this be the explanation why some people report getting much better results using grounding boxes? Take for example two commercial products which are very expensive and out of my budget:

 

1. Tripoint Troy - Grounding box used for chassis grounding for all components of your playback chain. This connects through a Ground pin only to mains.

 

2. Entreq Tellus - Autonomous Grounding box initially reserved for grounding Signal returns (e.g. an RCA return from each of your components). This doesn't connect to any other ground or earth, it has its own internal ground.

 

Are our power lines, grounding schemes, power supply units are compromised in various ways and greatly spoiling our enjoyment of music?

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I use 2 heavy duty mains filter in the same case . One for supplying the LED backlighted TV, and the other for my normal audio gear. They are based on a design by Silicon Chip magazine. The only mains rubbish that I get through is due to DTV reception in this low signal area with Rabbit's Ears and a low noise MHA, when the fluoro in the toilet across the hallway gets turned on.

Fortunately, 230V AC 50HZ mains supplies don't appear to normally have problems anywhere near as bad as those with 115V AC 60HZ.

 

Thanks Alex. I think I could go with that type of setup: each outlet line is a separately filtered one, totally passive. The inlet-side rails has a common filtering.

 

For testing, I am restricting myself for now to a simple stereo playback chain.

 

If at one outlet I use a duplex instead do you think I could connect one external HDD and the iMac in there (just as an example) or it would be better than these are on two separate Duplex elements?

 

I do think when I was supplied with Euro-style 220-240V/50Hz the mains was cleaner. But that's before I moved to North America.

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Yashn

Normal mains filters may not be as efficient as a specially designed heavy duty filters that also take into account SMPS rubbish coming back the other way ?

 

Certainly, and I'm not trying to compete with commercial offerings here.

 

I'll definitely separate analog and digital and perhaps small power from big power.

 

Since each line in my filter box has its own filter, each component will have less opportunity of affecting the other components.

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If you are going to make several filters, the best place for a filter is at the component's chassis. With the filter touching the chassis if possible.

 

Thanks Speedskater, saw a few of your cool posts and references over at WBF.

 

That's an interesting idea as well. Do you have any link with an implementation? Do you think this is the same thing that the Tripoint Troy devices do?

 

Dual receptacle's can be split in to two circuits.

 

That would be ideal. Does this necessitates some mechanical work to enable or should I check how the duplexes are implemented? I thought they had common rails for each lead.

 

The real experts on this topic are:

Keith Armstrong

Ralph Morrison

Henry W. Ott

But none are easy reading, nor convenient.

 

Heard about Morrison and Ott: Ott from reading and researching a couple of years ago about ground planes, and recently saw Morrison mentioned as a very accesible read.

 

More accessible are papers by (but they still require some studying) :

Jim Brown

Bill Whitlock

Middle Atlantic

 

I think I have these saved on my HDD for future reading sessions, together with a couple of Ott texts.

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I was reading some interesting texts from the Equi=Tech website. They make Balanced Power devices:

 

What is wrong with grounding? The answer is simple. As a rule, the grounding circuit is not meant to carry any type of current except for rare occasions when there is a short circuit, and then only momentarily. However, Underwriters' Laboratories standards are somewhat lax in this respect. “Objectionable ground current" is loosely defined in every area except for hospital operating rooms. Outside of hospitals, “objectionable ground current” is gauged more closely to shock hazard levels (about 3.5 milliamps). It seems that this standard has backfired. Data corruption, disk crashes and simple hum noise cost time and money -- sometimes a lot. Clearly, UL standards that define "objectionable ground current" are inadequate by today's standards. On the other hand, UL is not responsible for re-engineering audio equipment and AC systems. Normally, performance standards are left up to manufacturers and the marketplace. The basic problem is that when loaded, all differential mode 120-volt AC circuits create noise in the ground reference. Noise problems occur in audio signal circuits due to an unclean ground. The old Edison circuit (where a 240-volt circuit is split into two 120-volt circuits) is still used today as a standard means of 120-volt power distribution. Standard power is unbalanced. Even when a high quality 120-volt isolation transformer is installed, one side is grounded (made neutral) which is really not much different at all. The way the AC voltage phase is referenced and carried by the circuit has everything to do with electrical interference in a grounding system. If any aspect of the circuit is applied or loaded in an unbalanced manner, noise will appear in the ground.

 

 

The system was built full of ground loops, but grounding currents and chassis potentials were nowhere to be found. This is how it should be. Star grounding and linear signal reference grids are nothing more than "Band-aids" that, at best, can only marginally mask over some of the noise. To be free of noise problems, grounding circuits must remain clean -- that's all there is to it. If they're not, a hundred ground rods won't help.

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Now, the interesting thing is that Equi=Tech mentions that using balanced power resolves the issues.

 

On the other hand, people like spiritofmusic over at WBF have benefited from using the Entreq Signal plane grounding even after using Balanced Power.

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Dual receptacle's can be split in to two circuits.

 

I think this is how, right?

 

[h=2]How To Wire Split Outlets... Step #6: Remove Hot Tab on the Outlet[/h]

 

 

 

pliers-removing-outlet-tab.jpg

 

 

 

Remove the Hot Tab to Split the Outlet. Photo Credit: Timothy Thiele

 

There is a tab on the hot wire connection side of the outlet called the hot tab. Locate the side of the outlet where the brass screws are located. Between the two screws and the face of the outlet, you'll notice a small brass piece of metal (called a tab)connecting the hot feeds. Simply break it off by inserting a screw driver under it and bend it back and forth. You can also use long nosed pliers to break it loose. Once remove, the common bond is broken.

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I also use shielded power cables.

 

I found by step 4 the diminishing returns had hit hard as far as sound quality improvements went.

 

If I could just have one type of device it would be the Balanced Power Transformer.

2nd choice would be the Linear PSU.

Others much more knowledgeable than me suggest having the Isolation Transformer before the Balanced Power Supply.

 

I find that once you provide better power to your system ... the next big challenge is to stop each device from adversely affecting each other.

 

I made my own AC cable for the amp using separate shielded single core: it's better than the stock cable.

 

Interesting thought about the iso transformer before the balanced power.

 

As for stopping each device affecting the other, this is precisely what my AC filter is planned for: since each component has its own filter line, it is very difficult for one component to affect another one.

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Here is on almost readable Keith Armstrong article. The interesting part is well down the page.

 

"Fundamentals of EMC Design: Our Products Are Trying To Help Us"

 

Thanks for the additional links, Speedskater, very cool info in there.

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As it was nearly impossible to solder wires to the previous single plugs I bought, today I got some more normal-looking duplex units: one white duplex, one ivory and one black.

 

I intend to separate the filter lines for analogue, digital and amp/high-current.

 

But even prior to getting the duplex units, we did a really small and incomplete test last night with a single filter line (the two other lines did not hold...).

 

I chose the iMac as the component to connect, and we were both asking ourselves separately and silently at the time "How could this sound even better, I don't see how?".

 

The reasons for these were because I had already floated and tested the speakers as well as the HDD on a ball-and-cup arrangement, to isolate from horizontal vibrations and rotations and we noticed great improvements in soundstage, a reduction of bass bloat, and a clarity in the mid-range up to the very high-frequencies.

 

Knowing that ideally, I should also filter at least the external HDD (right?) and the amp, and that I really should do another cable for the iMac to keep the filter benefits to the max, I wasn't really expecting much.

 

Well, were we both surprised!

 

Even more space in the soundstage, well-defined mid-range, hearing soft rhythms play out, people preparing to play their instruments and involuntarily making sounds when touching them, lips before singing, a holographic effect as if the backing vocalists were in tow arcs in the room, etc...

 

So that great experience prompted me to get the additional hardware to try and finish a complete prototype with at least 3 or 4 lines (normally 6 with the three duplex units that I manage to separate into 6 independent ones, but here I need to check combined amperage).

 

I removed the flaky connections, re-did the new ones with the duplex units and the wires strongly screwed down this time, but hit a couple of snags before finally getting it to work.

 

On listening, we found something really odd: all native DSD recordings were very rolled-off, but Redbook up-converted to DSD128 sounded fine.

 

Took me some time to realise I had accidentally turned my amp to "Front Speakers A - Low Impedance".

 

I though the filter line used was the culprit, but it could be just that impedance mismatch which ruined the test tonight.

 

Hence, tomorrow, in between floating the computer and the DAC properly as well as making a new lighter USB cable, some new listening tests are in order for the filter.

 

Judging by the tests last night, this should be very promising.

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1500W Balanced Power Supply > 300W Isolation Transformer > 100W Linear PSU > DC Reservoir

 

1. Balanced Power Transformer ... this provides the bulk of the benefits, though I plug a TV (SMPS) into it.

2. Isolation Transformer ... outlets not isolated ... even though both devices attached to this isolation transformer use Linear PSU ... one of them (OppoMod PSU) did not have an EMI filter so recently put in a Furutech EMI Filter into the Oppo BDP-103 (though thinking of getting another one which is designed specifically for this Oppo), HD-Plex also attached.

3. Linear PSU ... for Regen, hub

4. DC Reservoir ... not really a real term, not sure what to call it ... just what was mentioned in the TBI OFR-1 manual, attached to the 19V rail of my HD-Plex, to feed my headphone dac/amp. Has 25 Joules of energy.

 

I also use shielded power cables.

 

I found by step 4 the diminishing returns had hit hard as far as sound quality improvements went.

 

If I could just have one type of device it would be the Balanced Power Transformer.

2nd choice would be the Linear PSU.

Others much more knowledgeable than me suggest having the Isolation Transformer before the Balanced Power Supply.

 

That was part of my questioning: i.e. if there were overlaps with say the AC filtering and balanced power, and additionally, if I start with Balanced Power, do I really need an isolation transformer as well, and do I also need linear power supply. I wanted to avoid going overboard with several devices when possibly a single more fundamental change would provide 80% of the benefits for 20% of the efforts.

 

But I think your experience echoes a little of what I read by spiritofmusic on the WBF forum (I think he's in UK), that is, large benefits with balanced power, but he additionally found great results in his rig by using the Entreq signal isolation products.

 

Though putting the EMI Filter into the Oppo was worthwhile (the OppoMod Linear PSU that I have does not come with a filter and it was putting some noise back into the Isolation Transformer).

 

I don't know if you've come across Coris and Rasmussen on diyaudio.com: they both have some cool mods for Oppo BDPs.

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The PS itself is likely the most important aspect.

 

One could also improve each component's PS individually, but I don't have sufficient knowledge yet to go and mod my amp's PS or the iMac's.

 

It would seem that some think that simply using a non-smps is the key when output impedance and freq response are typically king.

 

I think it's really difficult to make an excellent SMPS PSU and these are usually prone to creating a lot of noise or EMI/RFI compared to linear ones.

 

If one does not want to pay in cash for say a JS-2, they would be well served to build some and experiment.

 

One future project would be to build a small linear PSU to experiment with overall sound, perhaps for the DAC, but it already has a battery. If that works, maybe I can even re-build a special USB cable without the power line.

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New tests today, making sure the "Low Imp" is turned off.

 

I am using the DAC with the 'Measure' Filter mode. Initially, the sound appeared to still have some roll-off at the top end for native DSD, but it seems to be improving along the day.

 

Another thing we noticed with the AC filter on the iMac is that when using Display Mirroring on the HDTV, the screen is clearer: the fonts more defined. Fun.

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In the stereo setup, I have the external HDD (one, and sometimes two), the iMac and the amp, and perhaps later the turntable and the Tube Amp (it already has its own filter).

 

It is said to be necessary to separate digital and analogue, and separate high-current from low-current, so I think I could put the HDD and the iMac at one end of the distribution, and the amp at the other extreme. Is considering the HDD as 'digital' the correct way here?

 

For now, only one filter line is active.

 

For surround, I will have another sound card (external USB), one active subwoofer, and one active centre channel.

 

That makes two additional amps, so I think I might need another AC filter box rather than put all these within my first one.

 

Further down the line, I may need one for the TV, Apple TV and Blu-Ray too.

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To avoid cross contamination between components is not that simple, since an audio component will provide a different spectrum. The injection mains side spectrum from an amplifier is different to a CD player or computer, so the filter should be tuned individually. You can add standard EMC filters PLUS use the balanced supply, since the filters work better on a symmetrical supply, rather than one side grounded if you still wanted to keep the filters.

The balanced transformer does a great job of providing an effective cross pollution from other components on its own. Having several filters in parallel could cause a surprise in that there could be a resonance condition, but not likely.

 

Hi One and a half,

 

and thanks for the excellent info about Balanced Power and Iso transformers. I have read a few of your AC conditioner related posts in past threads, thoroughly interesting as well.

 

I probably cannot take on a balanced power project currently, but the AC filter is coming along nicely: there are a few different configurations in different lines that I can use to test a single component and see what happens.

 

Totally agree with having to tune the filter lines according to the type of component. For the amp, which is high-current, a lower number of turns in the common-mode choke is good, right? The possible reduction in dynamics with improper values is definitely a concern here.

 

Then, I guess that for the troublesome digital components (I am considering the iMac, and the router, the Wi->Fi router, the HDD in those), I would need more aggressive filtering as these components' PSUs inject a lot back into the mains.

 

Now, one question that arose today was that I remember the focus on Ground plane noise, from John Swenson's posts and other reads. But, in my filter arrangements, the outlet GNDs are all connected together, there is only some filtering at the inlet, where E-L-N have a cap between each couple of leads.

 

Thus, I am wondering if there's a necessary enhancement for GND line filtering that I should add here. Otherwise, it appears to me that ground plane noise from one component can still go from one component to another one (there's no such direct connection at outlets for L-N from one component to L-N to another component).

 

Furthermore, if I do add some filtering on the GND lines, am not impacting the impedance of the ground line, especially at higher frequencies where the noisy currents are?

 

Here is the link to an schem of Jon Risch's original AC filter line.

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Initially, Lukasz, of Lampizator fame tested Risch's design, and posted some of his impressions and revisions over at Audio Asylum. I think he posted a couple of revisions but which, overall were quite close to Jon's schematics.

 

However, the last design by Lukasz, as posted in the Lampizator archive section is quite different:

 

silk220.JPG

 

On this one, there is an inductor on the Ground lead, and coming from the inlet, the caps between Ground and L and N are after the inductor.

 

Additionally, the L2 and L3 ferrite rods are omitted for the amp outlet.

 

Lukasz mentioned on AA around 2000 that he had some great feedback on his latest filter incarnation. Whether this is the same as the 'last design' above isn't known, but his filter appears better than what I am doing currently, which seems a hybrid closer to Jon's design.

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@ YashN ...Will check out Rasmussen (at least he is local, believe Sydney based) though I believe he focus on clocks for the Oppo (which is another current interest of mine, still trying to work out if it is worth it). He seems a bit more expensive, though his modded oppo's do seem to get snapped up very quickly on the local market.

 

Rasmussen has a lot of knowledge and mods and construction. Another thread you might be interesting in over that forum, but which is off-topic for this one is about the 'Rasmussen effect'. Generated some controversy and sidelining as usual, but Coris and another member who tried it with their DACs reported great results. Never got to try that myself.

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'YashN' you do not want an inductor nor a switch in the Safety Ground/Protective Earth conductor. Some experts write that capacitors from the Hot & Neutral to the SG/PE are not the best of ideas, as the caps just dump noise on to the SG/PE.

 

There is neither an inductor nor a switch on the ground line in my current build. I don't plan to integrate the latter either - I think Lukasz thought it a good way at the time to easily prevent ground loops if hums occur, but if I had to put a switch it would never be on that line...

 

As for the caps from L, N to G (or H, N to SG/PE so long as we understand each other), I think the dumping of noise is precisely the goal, but solely for high frequency noise.

 

So I believe the diversion to ground is deliberate, but that's also why I was asking earlier about how to properly implement the inter-component contamination isolation as currently, there doesn't seem to be anything to prevent the noise along the GND line from one component from going to the next one.

 

How would you do it?

 

Managed to do some additional building and testing tonight - see below - including a very controversial finding (for many).

 

To get real information on power line filters, you might look to the Henry W. Ott 850 page book "Electromagnetic Compatibility Engineering".

EMC Books

 

Thanks for the reference info, speedskater. I have Ott, Brown/Muncy lined up for further reading/research and already watched two of Armstrong's videos on Youtube, the earlier ones have bad sound, but the content is useful.

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During this week-end, before testing a single filter line with the iMac, we had decided to up-convert (AIFF to DS128) Lionel Richie's Greatest Hits collection to listen to it and also test. 'All Night Long' is a great test track for percussions and rhythms.

 

The thought of testing up-conversion with the same tracks but with the AC filter connected occurred to me (not unlike sandyk's recurrent urging to rip with linear PSUs for better sound).

 

Didn't think much about it until this afternoon when I tried to finalise the two other duplexes (only 3 filter lines connected for now although all 3 duplexes are separated into 2 outlets each).

 

So I up-converted 'All Night Long' and 'Say You Say Me' again, with only the computer connected to its filter line.

 

[warning: the following is controversial, and I am not trying to convince anyone here, your mileage may vary, I can speak only for my system and our 4 ears]

 

I didn't expect any difference, but we found there were more punch to the percussions, and a clearer sound from mid-high (there's a type of tambourine-like sound which appears twice at the beginning) in the version up-converted with the filter on as compared to the one with the filter not connected.

 

It isn't a huge difference, but it was sufficiently important to make the 'filter on' up-converted version more compelling: you feel the rhythm better, the kick drum and other drums startle you more compared with the previously up-converted version which sounds a little flatter. Once you describe the changes verbally, one version cannot be mistaken for the other. We both heard the differences.

 

Now, bear in mind both these DSD128 files were up-converted from the same rip.

 

I shudder at the thought of doing a rip again with the filter on, then up-converting with the filter on, and finding out I can't live without doing that because I hear important differences...

 

Ultimately, I will certainly want to do that test.

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I thought I had managed to wire up all three lines properly for tonight's testing, but we found out only 2 lines functioned after nearly a full hour of build. So, in the end, we didn't have much time to test tonight as it's already too late, but we did a few track extract with the iMac on one line and the amp on a second one.

 

The 3rd was supposed to be the external HDD, but that showed no sign of life there (the HDD is fine).

 

This means I will have to re-build the inlet distribution section as it's too flaky. I re-used the rails from a nondescript power distributor. It will be much better to use proper screw-on rails.

 

Results from the short testing tonight with the help of Diana Krall, David Bowie, Peter Gabriel, Tina Turner, Vangelis, Billy Idol and more:

 

I got the impression of a darker background: the music springs forth un-announced with great power. We recovered the feeling of 'they're here', punchy sound for percussions, but especially a very large height of the soundstage.

 

The notion of 'presence' was very well exemplified by David Bowie's 'Bring Me The Disco King', Thom Yorke's 'Street Spirit (Fade Out)', and eerily so with Cassandra Wilson's 'Harvest Moon', a cover of Young's song.

 

Incredible! This sound is going to be very, very addictive.

 

I'd really like to enhance inter-component isolation now, and then perhaps even plug in all the troublesome appliances like the cable modem and Wi-Fi router.

 

There is some serious quality lurking in clean AC power if you can do it right, and I've only done embryonic steps, really.

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I would try to reduce the resistance/impedance from one chassis to the next. Because the higher this impedance is, the more the noise currents will try to use your interconnects as a path back to their voltage sources. Bill Whitlock gets into this problem in some of his papers.

So from component to component, heavy short SG/PE conductors are best.

 

Very interesting, Speedskater, as I had planned to also implement a chassis-grounding system in my box.

 

Let me see if I understand this correctly: you're saying that to help with inter-component isolation within the mains, I should do chassis-grounding because in reality, the chassis are not at equi-potential and thus the stray currents will affect signal integrity by using the IC shield as return paths.

 

I think I agree with that latter premise.

 

However, what about the noise re-injected to the mains by each component's power supply?

 

If we do the chassis grounding well, are we providing an alternate, easier way for the power supply noise to be routed and hence aiding the AC line?

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How is a isolation transformer (and a balanced xformer) different then a Line Stabilizer/Conditioner ? I have a old Tripp Lite LS-604 that used to protect previous computer systems.

 

I don't know if I missed these explanations, but...

 

They all do different things and based on the experience of audiophiles with much better gear than me, can be used together with benefits (system synergy is of course very important):

 

1. Here is some general info on an isolation transformer. The first time I heard about them was from my friend Alexander who was going to use one inside his DIY tube amp in lieu of a capacitor (the latter which allegedly adds coloration to the sound). Therefore, they're quite versatile and can be used not just in tubes but for AC power clean-up as well.

 

2. The FAQ from Equi=Tech has a lot of info on Balanced Power.

 

3. The Wikipedia page on power conditioners may make for interesting reading.

 

Ultimately, I think 1 and 2 provide more fundamental changes, so that if these are implemented first and properly, the need for 3 may be less (doesn't mean eliminated completely as conditioners can sometimes have a lot of combined features)

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A couple of interesting reads last night in the light of speedkater's observations and my questions:

 

1. MIT Cables: Power-line noise - How Series Filters Work (and sometimes don't)

 

A very good overview of series filtering architecture, but also its shortcomings, and MIT's alternative, which is parallel filtering, thus not impacting current spike needs of amps.

 

It might be interesting for me to try a parallel filter line implementation dedicated to the amp and see what happens.

 

2. Thorsten Loesch (AMR/iFi) over at TNT-Audio appears to have posted a parallel filter as well.

m-filter.jpg

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On the circuit diagram you posted, they have a some caps specified as "100n". From my days in DIY electronics there were 'uF', and 'pF' (micro farad and picofarad) caps, but I don't know what a 'n' cap is about ? Can you educate me ?

 

It's obviously n for nano, and since it's a cap it's nanoFarad.

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'YashN' what I was attempting to describe is a small effort to what may be called.

 

Ralph Morrison:

STGP :: Signal Transport Ground Plane

ZSRG :: Zero Signal Reference Grid

 

Henry W. Ott:

ZSRP :: Zero Signal Reference Plane

 

Keith Armstrong:

Conductive Structure

 

Thanks Speedskater, these acronyms and references will come in handy for reading and research.

 

The more I think about this, the more I think many manufacturers have somehow forgotten about the utility of the ground plane, and what we now do is try and find solutions to that overlooked implementation post system setup...

 

What do you think of the Tripoint Troy devices?

 

TTS10.jpg

 

 

  • Dedicated EMI/RFI passive filtration component with proprietary modules made with classified composite materials
     
  • Proprietary Pure Silver Grounding Cables
     
     
  • No transformers, circuit boards, caps, op-amps, ferrites, coils, chips, plastics, LED’s or degrading parts that would create any electronic signature to the sound
     
  • Eliminates ground loop
     
  • Provides impedance ground match for all your components
     
     
  • Vibration control tuning. Through resonance control and implementation of the right materials we can tune your Tripoint system to match your personal preferences
     
  • Copper binding post provided to ground your components
     

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