In defense of 'star' grounding

[Eight_Stringer]

Am a long term TEM ( wave ) man meslf. Yes i know it is not obvious why that is relevant in these discussions. Maybe it is to some believers, grin.

[SGD Lutherie]

Originally Posted by warnergt

SGD Lutherie, you just don't get it. You're spreading tons of
misinformation here and don't even realize it. You are
performing a terrible disservice to the TB community. You're
on a one man crusade to rewrite the physics of noise. It's
time to stop.

Bullsh!t.

Like I said, take a 10 foot long unshelded wire and solder it to your ground at the output jack of your bass.

Did it create any noise? No. Why not? Because it's grounded. Now attach it to the hot. Lots of noise.

Now surround it with a grounded shield. No noise. Why? The shield shunts the noise to ground. Ground is at zero potential.

http://en.wikipedia.org/wiki/Ground_(electricity)
"Circuit ground versus earth
Voltage is a differential quantity. To measure the voltage of a single point, a reference point must be selected to measure against. This common reference point is called "ground" and considered to have zero voltage. This signal ground may not be connected to a power ground. A system where the system ground is not connected to another circuit or to earth (though there may still be AC coupling) is often referred to as a floating ground."

Does the shield on your cable between the bass and am produce noise? No.

"The shield acts as a Faraday cage to reduce electrical noise from affecting the signals"

http://en.wikipedia.org/wiki/Shielded_cable

http://en.wikipedia.org/wiki/Faraday_cage

"A Faraday cage's operation depends on the fact that an external static electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used, for example, to protect electronic equipment from lightning strikes and electrostatic discharges.
Faraday cages cannot block static and slowly varying magnetic fields"

"If the cage is grounded, the excess charges will go to the ground instead of the outer face, so the inner face and the inner charge will cancel each other out and the rest of the cage will retain a neutral charge."

So how do we block the slowly varying magnetic fields? Humbuckers.

This is what I keep saying. And there are some references for you.

Got it?

We aren't talking about cars. Spark plugs and the like cause lots of RF noise. Basses don't have spark plugs.

http://en.wikipedia.org/wiki/Spark-gap_transmitter

You have already shows you don't understand the physics behind it.

As far as my disservice, ask some of the people here who's problems I helped solve what they think. I'd be happy to share some of my emails.

And what have you done for them? Have you proven yet that star grounding eliminates any kind of noise that isn't already eliminated with regular electrostatic shielding? have you? No, just anecdotal stories about cars.

In fact, show us something you have designed and built.

[SGD Lutherie]

More on shielding and grounds:

http://www.newark.com/pdfs/techartic...haWire/USC.pdf

Understanding Shielded Cable

Industrial applications such as the factory floor are typically electrically noisy environments. Electrical noise, either radiated or conducted as electromagnetic interference (EMI), can seriously disrupt the proper operation of other equipment. Insulation protects a cable mechanically from scraps and abrasion and environmentally from moisture and spills. But insulation is transparent to electromagnetic energy and offers no protection.

Shielding is needed to combat the effects of EMI. Cables can be a main source of transfer for EMI, both as a source and receiver. As a source, the cable can either conduct noise to other equipment or act as an antenna radiating noise. As a receiver, the cable can pick up EMI radiated from other sources. A shield works on both.

The shield can act on EMI in two ways. First, it can reflect the energy. Second, it can pick up the noise and conduct it to ground. In either case, the EMI does not reach the conductors. In either case, some energy still passes through the shield, but it is so highly attenuated that it doesn’t cause interference.

The shield is grounded. The noise is conducted to ground. In none of these papers will it say the shield/ground causes noise.

And I mentioned about added wire and resistance:

Make sure the equipment that the cable is connected is properly grounded. Use an earth ground wherever possible and check the connection between the ground point and the equipment. Eliminating noise depends on a low resistance path to ground.

While I'm at it, I have mentioned in the past that one way to eliminate ground loops between two AC powered pieces of gear is to lift the ground on one side of the cable, since both pieces of gear are already grounded.

Ground the cable at one end. This eliminates the potential for noise inducing ground loops.

Now before people misinterpret this, this is assuming two pieces of AC powered equipment that are both grounded to the mains. Connecting the two grounds together forms a loop. The loop is:

AC ground->cable-> AC ground

So the two AC ground circuits are connected together.

Your bass has one ground point which is at the output jack. It's connected to one grounded piece of equipment, your amp. If you have an AC powered stomp box in between your bass and amp, that can create a ground loop. So you just lift the ground on that piece of gear and it goes away.

So ground loops have nothing to do with star grounding.

These are known facts that have been published for a long time.

[Lowactnsatsfctn]

Originally Posted by warnergt

Anyone who installs car stereos will recognize these two
paragraphs of yours as total nonsense. And it fits the entire
theme of what you're spewing here. A car chassis ground is
fine for headlights and taillights and motors but, for audio, it
is complete noise.

From a CEA certified Audio installer,
Nissan And Toyota have mounted there Factory stereos to metal brackets, That connect to metal sub frames in the dash, which connect to the metal panels of the car, and then from a ring connector bolted to the inner fender to the Negative terminal of the battery.

There isn't an automotive manufacturer that runs a wire all the way from the battery to the radio for a ground aside from those with Fiberglass bodied vehicles and those with Pos. Grounds.

Whats complete noise is your post

[Eight_Stringer]

Worked inside a solid brass wall, ceiling and floor/door "Faraday Cage", in the 1980's. It was fabricated by some military orientated company in the UK, at the height of the cold war.... war and cage were cold as i can assure you. All services incoming ( electrical cables ) were "choked" VLF to Microwave. It sat on a well supported, wooden support plinth, was no "ground" connection to the earth we all stand upon. The entrance door was a work of art, all these non ferrous spring fingers filling any gap between entrance jamb frame and door. Massive locking mechanism, trick ventilation ducting. Worked 100% when we were testing transmitters. There was no ground, there was no ground as many here understand it.

Those Wiki based information articles can be a real worry at times. There is nothing like that information in the British Admiralty publications from ( 1910-20 from memory ), an era that meant in real terms, we transmit from "DC to Light", big grin. The things you find/found in book stores over the decades. Real books from real engineers from the beginning of Radio.

Regards.

[SGD Lutherie]

Originally Posted by Lowactnsatsfctn

From a CEA certified Audio installer,
Nissan And Toyota have mounted there Factory stereos to metal brackets, That connect to metal sub frames in the dash, which connect to the metal panels of the car, and then from a ring connector bolted to the inner fender to the Negative terminal of the battery.

There isn't an automotive manufacturer that runs a wire all the way from the battery to the radio for a ground aside from those with Fiberglass bodied vehicles and those with Pos. Grounds.

Whats complete noise is your post

And my ex wife's Nissan's radio is noise free.

I had a Bradley GT once. It didn't run the radio to the battery either. It used the frame as ground.

[SGD Lutherie]

Originally Posted by Eight_Stringer

Worked inside a solid brass wall, ceiling and floor/door "Faraday Cage", in the 1980's. It was fabricated by some military orientated company in the UK, at the height of the cold war.... war and cage were cold as i can assure you. All services incoming ( electrical cables ) were "choked" VLF to Microwave. It sat on a well supported, wooden support plinth, was no "ground" connection to the earth we all stand upon. The entrance door was a work of art, all these non ferrous spring fingers filling any gap between entrance jamb frame and door. Massive locking mechanism, trick ventilation ducting. Worked 100% when we were testing transmitters. There was no ground, there was no ground as many here understand it.

Those Wiki based information articles can be a real worry at times. There is nothing like that information in the British Admiralty publications from ( 1910-20 from memory ), an era that meant in real terms, we transmit from "DC to Light", big grin. The things you find/found in book stores over the decades. Real books from real engineers from the beginning of Radio.

Regards.

Wikipedia is a worry, but the technical articles are generally sound.

I worked in a Faraday Cage in the late 70s that was more like screening. It was grounded.

But any solid brass room with thick enough walls will pretty much shield out anything! Copper in general absorbs RFI.

I use brass "Faraday Cages" in my neo pickups, and solid copper shields in my sidewinders.

[Meddle]

Originally Posted by SGD Lutherie

Bullsh!t.

I'm surprised you bother with this forum. Between these weird personal attacks and that thread where people queue up to whine about waiting for their pickups to come through the mail I'm surprised you can stomach it all.

Its like a gradual decline back to the caves. In a few decades time bassists will be sitting in damp caves rocking backwards and forwards with handfulls of PIO capacitors, having replaced all learned information with gut feeling and 'I feel I'm right because...'

[1958Bassman]

Originally Posted by Lowactnsatsfctn

From a CEA certified Audio installer,
Nissan And Toyota have mounted there Factory stereos to metal brackets, That connect to metal sub frames in the dash, which connect to the metal panels of the car, and then from a ring connector bolted to the inner fender to the Negative terminal of the battery.

There isn't an automotive manufacturer that runs a wire all the way from the battery to the radio for a ground aside from those with Fiberglass bodied vehicles and those with Pos. Grounds.

Whats complete noise is your post

Only those two? Ever work on a '90s Honda/Acura or most other cars of that time? (I can't comment about cars after '97, when I stopped working on them) The fact that car radios are often mounted in plastic (FINALLY!) is because of the problems caused by multiple ground paths and shared grounds and because the mobile electronics industry did most of the troubleshooting for the auto industry unless they needed to solve a wide-spread warranty problem.

Re: the radio ground- what about the ground wire? That goes to the dash harness, which is usually grounded to the firewall or the metal behind the kick panel, using a bolt and star washer, or a large connector mounted on the firewall that mates with another connector on the other side. If connected to the body behind the kick panel, this metal is spot-welded to the belly pan, which is spot welded to the firewall and the rest of the body assembly. All of this is bonded to the frame, along with the engine and hood. Measure the resistance from the radio harness ground wire to the battery - post and see what you get- usually more than an Ohm on a new car, several Ohms on an older one. Now, install an amp in the rear of the car, grounding it to the trunk floor, connect everything and listen to the noise, especially if the amp is mounted directly to the body without some kind of panel to isolate it.

The lights and other devices in a car that are sharing a ground path can inject noise into a mobile audio circuit because the ground paths are shared. That's why amplifiers with no isolation for the mounting holes shouldn't be screwed directly to the body AND grounded to a different place. This was a really bad problem when an amp was mounted under the rear deck and grounded to the supports or the trunk floor, rather than finding a point that has no resistance when referenced to the battery - AND the radio.

You posted that you're CEA certified- is this for 12V audio, or something like CEDIA/ Two different worlds, with a few common problems/situations. The common problems have similar solutions, though.

[warnergt]

Originally Posted by Bassamatic

I can appreciate both sides of the argument. However, my genius audio engineer that knows everything about guitars and amps, tells me that star grounding is still effective due to the high impedances involved - that it is easy to induce currents in the wires.

Now he was an instrumentation engineer, designed electronics for electron microscopes, etc. before moving into audio, and now does tweak amp and guitar mods and repairs in SFO, for whatever that is worth.

Your genius audio engineer is right.
Any decent engineer with knowledge of low noise design would agree.
Don't let anyone here tell you any differently.

[warnergt]

Originally Posted by Lowactnsatsfctn

From a CEA certified Audio installer,
Nissan And Toyota have mounted there Factory stereos to metal brackets...

That's irrelevant. What they don't do is use chassis ground as
a return for the low level audio signals.

[1958Bassman]

Originally Posted by Eight_Stringer

Worked inside a solid brass wall, ceiling and floor/door "Faraday Cage", in the 1980's. It was fabricated by some military orientated company in the UK, at the height of the cold war.... war and cage were cold as i can assure you. All services incoming ( electrical cables ) were "choked" VLF to Microwave. It sat on a well supported, wooden support plinth, was no "ground" connection to the earth we all stand upon. The entrance door was a work of art, all these non ferrous spring fingers filling any gap between entrance jamb frame and door. Massive locking mechanism, trick ventilation ducting. Worked 100% when we were testing transmitters. There was no ground, there was no ground as many here understand it.

Those Wiki based information articles can be a real worry at times. There is nothing like that information in the British Admiralty publications from ( 1910-20 from memory ), an era that meant in real terms, we transmit from "DC to Light", big grin. The things you find/found in book stores over the decades. Real books from real engineers from the beginning of Radio.

Regards.

No "ground", but a path TO ground for RF, right?

Harley Davidson's main R&D facility is on the West Side of Milwaukee and I toured that not long after it opened. Among the areas is an RF bombardment room, where they test the bikes for resistance to disruption from strong RF sources. This room is anechoic, WRT RF. It looks like many anechoic chambers but, instead of acoustical absorption materials, they have copper screen, formed into wedges/pyramids that minimize reflection, mounted inside a Faraday Cage.

[warnergt]

Originally Posted by SGD Lutherie

he shield is grounded. The noise is conducted to ground. In none of these papers will it say the shield/ground causes noise.

You're talking about something completely different here. This
is why I say you just don't get it.

Your shielded cable does not shield magnetic fields. So, both
the inner conductor and the shield are picking up noise. The
redeeming virtue of a shielded cable (and even an unshielded
pair) is that the inner and outer conductors pick up equal
amounts which cancel each other out when you look at the
differential voltage at the end of the cable.

Your ground plane (in a guitar or in a car) has no such
redeeming virtue. It picks up noise and the noise is there.
Only good design techniques (like single-point grounds --
a.k.a. "star grounds") can reduce the effect of those noises.

[eukatheude]

What do you mean by star grounding? What i do is ground pups to the pot casings, then connect them one another and go to the jack.

[Stealth]

Originally Posted by eukatheude

What do you mean by star grounding? What i do is ground pups to the pot casings, then connect them one another and go to the jack.

Star grounding would mean you ground each pot casing and the cavity shield directly to the jack, with one wire coming from each part you want connected to the common ground lug on the output jack.

What you described is daisy-chaining them. I prefer that method, as well, and it's worked fine so far.

[eukatheude]

Originally Posted by Stealth

Star grounding would mean you ground each pot casing and the cavity shield directly to the jack, with one wire coming from each part you want connected to the common ground lug on the output jack.

What you described is daisy-chaining them. I prefer that method, as well, and it's worked fine so far.

I don't understand the difference, i still ground all cases.

[Lowactnsatsfctn]

Originally Posted by 1958Bassman

Only those two?

Re: the radio ground- what about the ground wire?

And older Isuzu and some Mitsubishi.
The ones I listed don't even have ground wires in the stereo Harness.

Originally Posted by warnergt

That's irrelevant. What they don't do is use chassis ground as
a return for the low level audio signals.

occassionaly they do.
Take a factory stereo from a new Toyota/ Scion for instance, one of the only Factory installed stereos with RCA out puts


The out side of the RCA (low level audio) is connected directly to the Frame of the stereo, which is bolted to metal that connects to the battery.

[SGD Lutherie]

Originally Posted by Meddle

I'm surprised you bother with this forum. Between these weird personal attacks and that thread where people queue up to whine about waiting for their pickups to come through the mail I'm surprised you can stomach it all.

I like this place, and I like helping people. I've been messing around with basses and electronics since I was a kid. It's nice to share what you know instead of keeping it to yourself.

There's always a few dissidents. You either stand your ground or run away. In this case I have facts on my side. The rest of the argument is being taken out of context. Star grounding is important in certain situations. Inside your bass it's not very important.

And while a lot of hand waving is going on, no one has demonstrated that it makes the bass quieter than a well shielded bass with standard wiring. The rest of the argument, that grounds produce noise, well that's just noise. If it were true, all our shielding would not work.

Its like a gradual decline back to the caves. In a few decades time bassists will be sitting in damp caves rocking backwards and forwards with handfulls of PIO capacitors, having replaced all learned information with gut feeling and 'I feel I'm right because...'

We are all devo! The part that bugs me about the whole retro knee-jerk thing is that we have it better now than we ever did. You can get great basses for cheap, and nice small powerful clean sounding amps.

I started playing bass in 1969. We still have many of the same basses from that time, and they are still good. But we also have much better amplifiers and other gear. It wasn't that long ago when there were no effect pedals made just for bass. I used to play through a Maestro fuzztone. It was fun, but wasn't really made to work with bass. Many of the amps back then were underpowered, and bass players struggled to be taken seriously. That seems odd these days, but the bass wasn't seen as a serious instrument. It was a vague thump in the background in a lot of recordings. There were no bass sections in music stores, as paltry as they still are. We have options now!

Yeah, a lot of old records are great, and I even like a lot of the old bass tones with flats and everything. But even then, the strings didn't play in tune well, and amps used to break up before that was fashionable. Roundwounds came about when John Entwistle was trying to get strings that would play in tune well. Ironically as they made better flats, they also lost that old sound.

Active basses came along because it was something a lot of players wanted. Bass players used to really be into cutting edge stuff, while the guitarist kept playing their 50 year old gear.

So using tone caps from the 1950s isn't a time machine and won't make your bass sound different. But you will hear a lot of out of context arguments for paper in oil caps, and these silly videos on YouTube, which while every cap sounds the same, people are getting all hot under the collar defending what they perceive as a golden tone. it doesn't help that in a large font the cap is announced before the guy starts strumming. Ah, nothing like a little confirmation bias.

Interestingly some scientist feel humans are getting dumber because we don't have to think to survive anymore.

http://www.popsci.com/science/articl...cist-thinks-so

[SGD Lutherie]

Originally Posted by warnergt

You're talking about something completely different here. This
is why I say you just don't get it.

I get it just fine. Earlier I differentiated between magnetic and electrical field noise.

Your shielded cable does not shield magnetic fields. So, both
the inner conductor and the shield are picking up noise. The
redeeming virtue of a shielded cable (and even an unshielded
pair) is that the inner and outer conductors pick up equal
amounts which cancel each other out when you look at the
differential voltage at the end of the cable.

We have hum canceling pickups to get rid of magnetic field noise. So are you saying that star grounding gets rid of magnetic field noise? It doesn't. If it did, you would have no need for hum canceling pickups.

The hum bucking concept has been around for a very long time, far longer than when it was used in guitar pickups. Engineers did that to get rid of magnetic field noise in things like chokes.

Your ground plane (in a guitar or in a car) has no such
redeeming virtue. It picks up noise and the noise is there.
Only good design techniques (like single-point grounds --
a.k.a. "star grounds") can reduce the effect of those noises.

That's nonsense. You have a single ground point in your bass at the output jack. That connects to the shield in your cable. So if shields are ineffectual for magnetic field noise, the cable would undo everything you are talking about. Yet they don't pick up that magnetic field noise you are talking about.

Pickups do because they are inductive devices.

And you keep going back to car audio. Shut the engine off and the noise goes away. We don't have spark plugs in the bass generating that RFI. And as many people here have shown, car makers ground the audio gear to the chassis ground. Where the noise often gets into your car stereo is through the (+) end of the power supply. They use filter caps to help with that.

And basses are grounded to your amp's chassis (unless it's a floating ground design, and then it uses a virtual ground).

So I'm sorry, your argument hasn't proved anything. It really sounds like you have partial information that you are taking out of context. Others here seem to agree with me.

But feel free to make a demonstration showing how star grounding in your bass is solving any real problem.

That's how science works. You need to set up a repeatable demonstration showing the same bass, in the same situation, where the only thing changed is start grounding, or standard wiring, and prove that the bass is measurably quieter with star grounding.

You are making claims, now you have to back it up.

[grendle]

Originally Posted by SGD Lutherie

See, this is the problem. You are making the assumption that one end a grounded wire is not grounded, and it's leading to ground. This is wrong. The whole wire is at ground potential. On a car the whole cassis is also ground, which is why ground connections are made to it. When those connections get flakey, as on an old car (like the 1980 BMW I used to have), then current will find the next lowest potential, which is often not ground.

So if a ground wire is grounded, how is it an antenna for noise? It that were true, then your grounded shields (like on your coax cable) and strings would also pick up noise. But they don't when they are grounded. That's why they are shields. If you unground them, they will be an antenna for noise.

Once again, in tube amps and similar situations, you have a lot of high voltages which are causing ground loops. The star grounding is to eliminate ground loops. But this discussion is mixing a lot of metaphors on what star grounding is for. It's not to cut down on RF/EMI pickup. That's what shields are for.

What I'm waiting for is a controlled test with a before and after demonstration showing how star grounding is cutting down on noise in a bass. In the test nothing else would be changed but the ground paths. This has not been done yet. All we have is anecdotal stories about two different basses, or people's experiences in fields that have nothing to do with bass guitars, or incomplete electronics theory.

I've been wiring up guitars and basses for about 41 years. I have tried all different ways of doing it, including star grounding. In my opinion based on my own tests, I find no benefit in doing it. I got the exact same results with a fully shielded control cavity and pickups, and the control cavity grounds connected to the closet point, with a single or sometimes dual ground wire running to the output jack. This has created basses so immune from noise that I often disconnected the bridge ground wire.

that +100

in 20 yrs i have never had a noisy bass. what shielding? solder well, and pay attention to what your doing.