More on Ground Loops

If you read this blog, you may have noticed many articles on the potential sources for ground loops. IMHO, proper grounding is one of the biggest causes of signal degradation, especially in audio systems. Proper electrical grounding at all points in your home entertainment system improves audio quality by lowering crosstalk (muted levels of nearby signals), lowering RFI and EMI effects (sporadic oscillations or hum), and literally cleaning up the grunge at very low audio levels such as when reverberations decay into the silence (smearing of clarity near the “noise floor”). Even if you have taken great pains to minimize the influences of such effects by installing quality line filters and assuring yourself of running all of your gear on the same electrical phase, grounding issues still creep into your system through other connected components.

The average home theater system today has numerous connections to it above and beyond the realm of RCA or balanced patch cords. Ethernet connections, antenna feeds, HDMI cables, and separate ground wires (such as from a turntable) all may be potential sources for grounding issues. Keeping everything straight is not that difficult IF you consider their influences as part of the entire system. Say for example you started with a stereo that grew to a surround sound system that grew to a cable television connection that then added a media streamer. Each time you added something to your system, did you just hook it up from the instructions or did you consider proper grounding? I suspect that the answer to this is the former since the emotion of the moment, the excitement to hear or see this new piece of gear in action, is what controlled your installation efforts.

And once you turned on your system, did you notice anything that wasn’t there before? Did the system perform admirably or was there a compromise noticed after time that made the sound change? If the sound adversely changed, it is almost certain that what you just added made this change. And it is almost certain that this change is due to how the new grounds within that new addition impacted the overall grounding scheme of the combined systems.

If you have ever been to an outdoor concert and heard hum coming from the PA system, you know how annoying major grounding issues can be. But in your home theater hopefully these types of major grounding issues are already resolved. If not, the easiest way to isolate the source of a grounding issue is to disconnect each piece one at a time from your system. When the problem goes away, you have identified the source. But then what? You know what is wrong but how do you know what to do about it?

Tracking down the source of the problem within the individual piece or added system takes time and thought, and a clear understanding of what a ground loop is. Basically, a ground loop is a path that electricity takes when there are multiple paths from which to choose. Like a lightning strike that has one main bolt and several branches like an inverted tree, electricity will always flow at the path of least resistance (the main bolt in a lightning flash or here the primary ground wire) but will also flow at any other possible path (the branches of a lightning flash or here the ground loop). You can also visually see this effect of you pour water into a bucket with one big hole and a much, much smaller hole. Not only will the water rush out the big hole but it will also trickle out the little hole and it is the little hole that provides a visual representation of the effects of a ground loop.

Lightning Takes Many Paths to Ground

So let’s get back to the effects of ground loops in the home theater. Below is a grounding diagram provided by TYCO Electronics to help computer network installers properly ground the newer CAT6a shielded network cables (using shielded twisted pairs or type STP). There are several sources of ground loops built into this wiring diagram, each detrimental to the overall noise in that system. See if you can tell where they are.

 The most obvious ground loop is through the power plugs of the workstation and the equipment in the network equipment rack through the new shielded CAT6a cable. If the ground of the CAT6a female jack on the workstation is connected to the same point as the ground in the power plug (and it most certainly will be), this is where the source of the problem occurs. Lifting the ground of the network equipment or workstation (such as by using a “cheater” plug that converts a 3-pin power connection to a 2-pin connection) will eliminate the ground loop but in doing so it will raise the risk of electrical shock or worse electrocution and is therefore not advised.

The most effective way to ground a shield is to ground it at the source and not the destination. Polarized RCA patch cords in audio systems already use this grounding method to help reduce ground loop effects introduced from the shields and the ground wires inside of the patch cords. The arrows on these cables indicate which end is connected to the destination (arrow points at the destination). In reality, this arrow tells you which end of the cable the shield is NOT connected to ground (shield is not connected to the outer case on this end).

Polarized RCA Interconnect Cables

This same practice would be beneficial with shielded network cables. Somewhere along this path, the ground must be lifted and the best place to do so is at the workstation CAT6a female jack (the destination). Doing so will retain the noise immunity provided by the use of a shielded network cable and eliminate the ground loop. Can this be done easily? Yes. Here, the shield-to-ground path must be literally disconnected but can you think of a way to do this? Here is the answer: use an unshielded CAT6a cable from the wall jack to the workstation.

If the new system you are connecting to your already quiet home entertainment system suddenly becomes noisy, it is easy to see that the source of the noise may not be a simple thing to eliminate although through elimination you have identified the source of that noise. Connecting any new component to your existing system can introduce ground loops and increase this undesired noise. My eBooks on getting more sound from your home entertainment system (see the Extreme Audio series below) discuss where to look for such potential sources for grounding issues at every point along the way in your home entertainment system. Using these eBooks, you may be able to identify where the three remaining sources of potential grounding issues are in the above TECO grounding diagram (yes, there are three other sources for potential problems).

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

My other titles include:

·  Extreme Audio 1: House Wiring	·  Build an Extreme Green Hot Water Solar Collector
·  Extreme Audio 2: Line Filtering	·  The Extreme Green Guide to Wind Turbines
·  Extreme Audio 3: Chassis Leakage	·  The Extreme Green Guide to Solar Electricity
·  Extreme Audio 4: Interconnect Cables	·  Meditation for Geeks (and other left-brained people)
·  Extreme Audio 5: Speaker Wires	·  Althea: A Story of Love
·  Extreme Green Guide to Improving Mileage	·  Build an Extreme Green Raised Bed Garden
·  Extreme Green Organic Gardening	·  Build an Extreme Green Rain Barrel
·  Extreme Green Organic Gardening 2012	·  Build an Extreme Green Squirrel-Proof Bird Feeder
·  Build an Extreme Green Composter	·  Extreme Green Appliance Buying Guide

Copyright © 2015 by Philip Rastocny. All rights reserved.

Bozak Rebuild Project - Part 9

A lot can be said about proper passive crossover network design in high-end loudspeakers and its direct contribution to improving or destroying the sound. Any loudspeaker's design is based on economics where a target selling price is set by marketing along with the target demographic, LF bass limit, size, etc. So a designer has her/his handsfull in making proper choices, the crossover network typically being a good place to compromise.  With a single esoteric capacitors rivaling the cost of their driver counterparts, it's no wonder that the crossover network is compromised the most when the final design is reached.

Historically speaking in early 2-way systems, woofers were permitted to roll off under the influence of the voice coil inductance and tweeters were used with simple first-order networks (BW-1). This kept efficiency high and phase distortion to a minimum and this approach is still used today in budget loudspeakers. But other highly undesirable effects rear their nasty little heads in too simple of a design and engineers initially opted for a passive network component on each driver to better limit the bandwidth of the driver.

The more sophisticated the network (second-order, third-order, etc.), the more power is "stolen" by the network itself (insertion loss) and the speaker's 1-Watt sensitivity is therefore reduced.  But the benefits outweighed the loss in efficiency and so began the evolution of "modern" crossover network design (I use this term loosely since there is great debate between what is and what is not the best crossover network design to use). Today, 2nd, 3rd, and 4th order networks are routinely used in well-designed speakers but each design corrects something while compromising something else.  In other words, there is no such thing as a free lunch.

Rudy Bozak did not like the sound of higher order crossover networks and as a result all of his systems used BW-1 designs. While such designs can be well implemented (and his was done pretty well considering its era where esoteric capacitor designs were in their infancy), knowledge about loudspeaker behavior is much better understood today than in Rudy's time. So with this understanding and with a wealth of new technology at my disposal, I decided to see what could and could not be done to improve this early design.

Others have upgraded the existing network, most notably Pat Tobin's work with his B-101T design. Here Pat attenuated the over-anxious B-200Y tweeter by -9dB and then bypassed the attenuator at the proper point (the 2.0uF capacitor) to recover the extreme HF content (above 8KHz). He also used the existing chokes although changed the value of the midrange component (selected the other available tap). Lastly, he lowered the midrange crossover point and as a result the speakers sounded much like the original but much more balanced. Below is the schematic for this modification to a stock N-10102 network.

The Famous Pat Tobin Crossover Network Modification

Applying this modification to my own Bozak crossover network (mine is a slightly different version of a standard B-302A) yielded the following RTA measurement. A Zobel network is used on the woofer and a 2nd order network on the midrange LPF. (it measured a significant contribution above the designed crossover point with the 1st order network). Much like Mr. Tobin, I decided to try to use the existing inductors where possible. Note that instead of the usual two-tweeter arrangement, three tweeters were used changing the acoustic output in that band and therefore further attenuation was required. Also added was a VIFA BC25SC55-08 super tweeter to attempt to recover the top octave. The problem with matching an audiophile grade super tweeter to the Bozak system is that the Bozaks are highly efficient (98dB/W/m or more for the bigger Bozak designs). Even with this super tweeter the top octave still sounded quite weak compared to the rest of the spectrum.

Tobin Modified Network Design in my 3-tweeter System

Note that while taking the RTA measurement, the Peak dBFS scale somehow messed up (estimated to be about -20dBFS).

While interesting to listen to and very pleasant while retaining much of the original character of Rudy's design, they still sounded mediocre.  The transients were superb but there was just too much subjectively perceived IM distortion clouding the sound stage and making it quite two dimensional. Even changing polarities and hand-matching components did not help to make it that big sound I suspected it could deliver.  I believed that this network just did not permit the drivers to perform to their full potential. The original idea of using the existing inductors had to go in order to change the crossover points and to move to a 2nd order network..

For the past 18 months, I have redesigned, tested, retested, removed, replaced, repaired, reworked, and rethought about every aspect of a second-order Bessel design I could for these drivers. Giving up on the VIFA super tweeter, I turned my gaze to the professional market in hopes of a reasonable marriage between efficiency and sensitivity. Two drivers caught my attention, the Peavey RD1.6 and the Fountek Neo Pro 5i. Both drivers showed promise and I settled on the Peavey since musicians themselves reviewed that it sounded more like a home speaker than a PA speaker (I thought this was a good thing).

The latest design uses a 2nd order Bessel on the midrange LPF and HPF, a Zobel on the woofer and midrange, and a 2nd order Bessel on the Peavey super tweeter. This is NOT a finalized design; I plan to also swap out the tweeter network to a 2nd order LPF and HPF Bessel and see what can be done to encourage more from the B-200Y's 8KHz wall. Below is the last RTA of the system.

2nd Order LPF and HPF Bessel Network on Midrange

Now the sound stage is H-U-G-E, deep, wide, and tall.  As you can see, the top octave is back but the Bozak B-200Y tweeter is still dying near the 7KHz crossover point. Removing the tweeter LPF causes zero difference in the RTA measurement (sigh).

This is a network that has a nice wife acceptance factor (WAF) where before she thought it sounded good but now she thinks it's great! Ambiance and room resonances in live recordings are much more revealed with the return of the top octave and the 2nd order Bessel seems to have tightened up the midrange driver's sound. Vocals are more distinct such as Enya's Watermark album was blurred now background voices are as clear as hers. Details in this album's noise floor are readily revealed and nuances in piano soundboards are also more evident.

Putting a 1.5uF kicker capacitor on the tweeter helps the RTA graph look better (much like the 2.0uF capacitor used by Tobin) but ruins the sound raising vocal and instrumental textures to a near tizzy state.

So the next round of mods will address the tweeter. Foil chokes are on order and should arrive in house in a week or so. I plan also to change the woofer LPF also to a 2nd order Bessel in the near future and that should round out the network mods. So stay tuned and see what pops up out of my head next in Part 10.

See also Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, and Part 8

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

My other titles include:

·  Extreme Audio 1: House Wiring	·  Build an Extreme Green Hot Water Solar Collector
·  Extreme Audio 2: Line Filtering	·  The Extreme Green Guide to Wind Turbines
·  Extreme Audio 3: Chassis Leakage	·  The Extreme Green Guide to Solar Electricity
·  Extreme Audio 4: Interconnect Cables	·  Meditation for Geeks (and other left-brained people)
·  Extreme Audio 5: Speaker Wires	·  Althea: A Story of Love
·  Extreme Green Guide to Improving Mileage	·  Build an Extreme Green Raised Bed Garden
·  Extreme Green Organic Gardening	·  Build an Extreme Green Rain Barrel
·  Extreme Green Organic Gardening 2012	·  Build an Extreme Green Squirrel-Proof Bird Feeder
·  Build an Extreme Green Composter	·  Extreme Green Appliance Buying Guide

Copyright © 2015 by Philip Rastocny. All rights reserved.

Samsung UN65F8000 Review

After auditioning two different Samsung UN64F8500 plasma TVs each of which had absolutely superb images, the annoying issue with plasma RF interference and my high-end electronics made me move to a non-plasma choice. Know that it was NOT the Samsung brand of plasma TVs that caused me to eliminate this display technology from my home theater, but rather the plasma technology itself. I love the visual results this technology yields but I hate what it does to my audio system.

While providing a stellar picture superior to that of an LED, our choice of  an LED TV was a compromise just like anything regardless of what you are considering to add to your system.  For the plasma technology, there were two strikes against it: 1) the RF noise (I spend a lot of time and money assuring that this is eliminated from my system), and 2) potential health issues from prolonged exposure to high levels of RFI (although there is little scientific evidence that humans are adversely affected by such exposure, risking my health by believing those in authority on this matter is not who  I choose to trust). IMHO, anyone putting a plasma TV into their high-end theater (or owning any kind of plasma display device for that matter) is woefully uninformed.

With that said, there are a few very good choices for high-tech LED models and we decided on the Samsung UN65F8000 3D LED model as our next resident in our home theater room. With a very narrow frame, thin profile, and reasonably light weight for such a large screen, this Samsung fit right in to our needs. Replacing a 52" LCD, the newest black technology for this screen boasted plasma-like blacks and - well, read on to find out.

Samsung UN65F8000

This TV is pretty large, above average in display size but not altogether that heavy. Compared to the 5-year old LCD it replaced, this unit was a little lighter so mounting it in place on the existing stand was not an issue. The I/O cables are on the RH side (as seen from the front) and on the LH side on the old set, so interconnects were rerouted accordingly. The power cord enters in the LH side of the set and I put a toroidal core on it to help eliminate any stray RF interference (double loop of the cord through the core bonded closed with cable ties). These cores are also on all other pieces of equipment in my rig.

Toriodal Core on Power Cord

This TV has a lot of built-in processing ability. The calibration settings out-of-the-box are fair but lead to over-driven whites and exaggerated reds, and with a bit of patience and the HD Basics calibration disk , I adjusted the levels to meet our viewing preferences. My settings are listed below.

Picture Menu

Picture Mode	Movie
	Backlight	16
	Contrast	90
	Brightness	46
	Sharpness	20 (rec. 3)
	Color	49
	Tint	G51/R49
	Picture Size	16:9
	3D	3D Mode	Off
		3D Auto View	On
	PIP	Off
	Advanced Settings	Dynamic Contrast	Off
		Black Tone	Off
		Flesh Tone	0
		Color Space	Auto
		White Balance	R-Offset	24
			G-Offset	25
			B-Offset	25
			R-Gain	23
			G-Gain	26
			B-Gain	25
		10p White Balance	Interval	R	G	B
			1	-3	-1	-4
			2	0	0	-1
			3	0	0	-1
			4	-3	-3	-5
			5	-3	-5	-8
			6	-4	-7	-10
			7	-5	-8	-10
			8	-3	-6	-10
			9	0	-3	-6
			10	-6	0	-8
		Gamma	0
		Expert Pattern	Off
		Motion Lighting	Grayed out
	Picture Options	Color Tone	Warm2
		Digital Clean View	Auto
		MPEG Noise Filter	Off
		HDMI Black Level	(grayed out) Low
		Film Mode	(grayed out) Off
		AutoMotion Plus	Standard (Rec. On)
			Blur Reduction	10
			Judder	0
			LED Clear Motion	Off
		Smart LED	Standard
		Cinema Black	Off
	Picture Off	N/A
	Apply Picture Mode	All Sources

Smart Features Menu

Apps Settings	Auto Ticker	Off
	Push Notification Settings	N/A
	Channel-Bound Apps	N/A
	Properties	N/A
Social Settings	N/A
Voice Recognition	Off
Motion Control	Off
Remove Viewing History	History	N/A
Photos, Videos & Music	N/A
Samsung Account	N/A
Notifications	N/A
Open Smart Hub	N/A
Terms & Policy	N/A
Smart Hub Reset	N/A

System Menu

Eco Solution	Energy Saving	Off
	Eco Sensor	On
	Min Backlight	3
	No Signal Power Of	15
	Auto Power Off	Off
Auto Protection Timer	4 hours
General	Game Mode	Off
	BD Wise	Off
	Menu Transparency	Medium
	Sound Feedback	Low
	Panel Lock	Off
	Boot Logo	Off
	Light Effect	Off
Anynet + (HDMI-CEC)	On
Auto Turn Off	Yes
DivX Video On Demand	N/A

With the menu settings administered as above, the lip-sync was way off compared to the old LCD. Setting the AV Delay in my OPPO BDP-105 at +70 yields very good audio-video synchronization (aka lip-sync).

What's WRONG with It?

• Picture quality. Any LED picture is definitely not up to the same video quality as a high quality plasma TV but this one is closer to plasma quality than most. Blacks are very black for an LED set but again not as good as the best plasmas on the market. As a result, the richness of deep colors is just not there - close but no cigar.
• The screw holes for mounting the thin profile to a wall bracket are incredibly short (only about 10mm deep) so most mounting hardware must be tossed for much shorter M8 screws. 
• The 3D technology uses the active shutter method and I am not a fan of quickly blinking battery-powered glasses (if you have a medical condition where you are sensitive to rapidly-flashing lights, you may not be able to use this technology in your home). More on this in a bit.
• 3D ghosting was still visible in some (but not all) high-contrast scenes. 
• Dynamic color tracking (shifts in shades as color intensity rises and falls) is pretty good under most conditions but plasmas are constantly better.
• Minor uneven color intensity in large areas of dark color (e.g., deep blue skies have minor rises and falls of color hue)
• Viewing more than 30 degrees off center makes the picture wash out.
• And like all flat panel sets, the built-in speakers suck.  

But that is about all I can say that I would fix with this set. Now on to the good things.

What's RIGHT with It?

This is beautiful television set with some of the most accurate colors I have ever seen, even in ultra HQ plasma sets. While still lacking the deep richness of the best plasmas, the color accuracy of this set was actually superior to them in many other regards. Discrete shades of blue are one example.

For example, videos of surf curling into a tube appeared more natural and less greenish-pastel-like as some plasmas lean toward, and color accuracy is solid across the entire screen – completely edge-to-edge.  Even 3D mode has some amazing abilities.  Where the Samsung F8500 plasma showed great separation in medium distance films (e.g., a typical Avatar dialog scene), the F8000 created greater dimensionality and believability.  Scenes appeared more natural and less staged. The Cousteau Ocean Wonderland created realism where sharks seemed to swim in a space just behind the screen as if I were peering through glass in an aquarium.

Clarity, even with only 30 hours on the set, was fantastic. One of the things LED sets have over plasmas is a characteristic color temperature difference that my eye is more sensitive to than that of the plasma sets. My eye is more blue sensitive and my wife’s is more red sensitive. Between the two of us, we both judged the clarity to both of our eyes as stellar. When low-resolution videos or commercials pop up, there is a sigh of disappointment heard from both of our prime viewing positions knowing what is possible but not what was being displayed. Just as it is when your stereo becomes sufficiently refined are you selective about the source material you wish to hear, so it is with a high quality television where you only want to watch those images that demonstrate the capabilities of the television. There are a few dozen favorite well-recorded audio tracks with which I am intimately familiar I use as a reference when auditioning equipment. So it is with HD video where most movies look like MP3 tracks sound – compressed, weak, masked, and thin. Add video terms like blurred, over driven, color biased, and grainy and you get a good idea of the number of reference videos in my personal collection.

What strikes me most is walking into the room and being surprised by this television’s clarity and accuracy. When entering any of my friends video rooms, there is a moment of adjustment where I “recalibrate” my senses to the “oh yes, this is a television and not real life” moment; not the case for this Samsung. Sudden glances like live baseball games (the 6-8-13 Angels at Boston game on FOX) draw me into the action and my senses scream “WOW! This is amazing!” The carriage ride in the 3D Alice in Wonderland where Alice and her mother are talking before arriving at the party, you can see the glass in the carriage windows is beveled at the edges and the images actually track the bevels. Watching the live Indy Car series on ESPN shows more detail in night lighting reflections off of the suspension arms just as it appears live at the track. Stand blur and stair-step distortions are hard to find as the camera tracks the car and your eyes scan the stands.

In summary, have no hesitations about buying this set. It is pretty close to doing everything a HD television set should do and the 3D mode is excellent, better than most movie theaters. While the active glasses burn batteries and off-center viewing is limited, you will be pleasantly surprised by all of what this set does well. This set is a keeper and one that will be in our family for a long time.

UPDATE 6-24

With the set with now well over 100 hours on it, images have stabilized and minor adjustments to the calibration were made. These changes are: GAMMA = -1, BACKLIGHT = 15, BRIGHTNESS = 47.

Colors are still rich, deep and very accurate, difficult for an LED set at any price range to achieve. Still slightly favoring reds, this television picture continues to capture my attention as I walk into the room regardless of what is showing. It may be the fact that the wall behind the set is chocolate brown that caused the white level to appear a bit too strong, but for whatever reason turning the gamma down just a notch helped make the daytime levels more appealing. At night, the colors are equally as impressive and subtle details are amazing. Seeing the weave of sweaters and shadow content in low lighting conditions will impress even the most avid plasma fans.

Minor changes in video processing (along with a firmware update to my OPPO BDP-105) also changed the lip-sync delay. The OPPO's AV DELAY setting now averages +70 or +80 for most source material (this setting changes and is something I have just learned to live with - HOPEFULLY this will be addressed and resolved in the 4K format). 

UPDATE 12-19

Reportedly, there is a problem with the video settings file in the original post. So here is a link to the PDF for my current settings. Note that the new BIOS to the OPPO BDP-105 changed the delay most of the time to +40 and at others to +60. I have a real issue with this digital delay issue and I understand why it cannot be "standardized" but hey, that's what sync pulses are for, right? Hope this gets straightened out in the 4K format. I really get tired of adjusting it to watch CNN, and then again to watch movies, and then again...well you get the idea.

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

My other titles include:

·  Extreme Audio 1: House Wiring	·  Build an Extreme Green Hot Water Solar Collector
·  Extreme Audio 2: Line Filtering	·  The Extreme Green Guide to Wind Turbines
·  Extreme Audio 3: Chassis Leakage	·  The Extreme Green Guide to Solar Electricity
·  Extreme Audio 4: Interconnect Cables	·  Meditation for Geeks (and other left-brained people)
·  Extreme Audio 5: Speaker Wires	·  Althea: A Story of Love
·  Extreme Green Guide to Improving Mileage	·  Build an Extreme Green Raised Bed Garden
·  Extreme Green Organic Gardening	·  Build an Extreme Green Rain Barrel
·  Extreme Green Organic Gardening 2012	·  Build an Extreme Green Squirrel-Proof Bird Feeder
·  Build an Extreme Green Composter	·  Extreme Green Appliance Buying Guide

Copyright © 2015 by Philip Rastocny. All rights reserved.