Is String Grounding Necessary?

[Mike Sulzer]

The thing about balanced cable though is that both conductors need to have equal impedance to ground. Plus then you'd need a bal/un transformer at the amp (or the first effects pedal) unless you're making a wholly balanced rig. Which would be impressive and commendable!

A separate conductor for the low side of the signal does not imply an attempt to make a balanced system. It is just good grounding practice.

[Leo_Gnardo]

You'd think a company like Fender, that produces at least one product somewhere along the entire signal chain, could introduce something like a balanced guitar rig more readily than anyone else, and exploit the selling point.

Gibson had some Les Paul guitars & basses with balanced outputs. Never caught on much. Still needed a transformer at the amp end. And if "going direct" guess what's in the mix console, just on the other side of those balanced inputs. A transformer again. It's a bit disheartening to see all those studio gadgets with balanced inputs, each and every one processes signals in a "one sided" circuit so there's transformers or the op amp equivalent at inputs & outputs. There was a notion for a long time "get the iron out of the signal path" - no transformers please - but in actuality practically all the recorded music we enjoy has passed thru many of them. And somehow we still manage to enjoy it.

Can you imagine the size and expense of a pedal board where all the effects have balanced ins & outs? All to no good effect really, just makes everything bigger and raises the price a lot. I'm sure there are some people for whom that would be an attraction.

[J M Fahey]

I wish, but no, it was across the bay from Tokyo in the Port of Chiba where ...

the sky above the port was the color of television, tuned to a dead channel.

Please tell us the truth, the guitar hum was just an excuse, you were shopping for illegal synthetic body parts

FWIW I´d be interested in an aftermarket pancreas

[rjb]

There is a way around this, in principle, although I have not tried it. It involves using a stereo jack for the guitar and amp and two conductor shielded cable. You then have two signal leads, call them high and low. The high signal is what it is, and it goes to the tip. The low signal is what people usually call ground, but you have to make sure that no actual shield is connected to it, and it goes to the ring. So all the copper foil, pot cases, etc. connect to the shield of the cable and at the other end it goes to the chassis of the amp. The low side of the signal runs directly to the bottom of the cathode biasing resistor of the first stage. (Yes, that point is at "ground" potential, but it is signal ground rather than chassis ground, and they can be a bit different.)

Question:
Say you harness a guitar as outlined, but do not modify the amplifier.
Build an instrument cable with TRS on one end, TS on the other (SIG- and SHD tied together).
Plug the TRS end into the guitar, TS end into the amp.
Would (might) this configuration offer some advantage over using a mono cable?
If the answer is "it depends", what are the considerations?

-rb

EDIT:
My guess is that hum induced in the cable and guitar shields would be largely eliminated from the signal, but hum induced on the amp chassis would remain.

[salvarsan]

Please tell us the truth, the guitar hum was just an excuse, you were shopping for illegal synthetic body parts

working title: "Neuromantic Lyttony"

Fortified wines from Portugal are named accordingly -- port. Inside Texas, a port is only a fortified wine when export sales are involved. Sometimes, a port-style vinified in Texas or 'Tejas' is euphemistically called "portejas" and seldom leaves the state.

Enoch's Stomp's first harvest was Texas Black Spanish or Lenoir grapes, known to thrive despite threat of Pierce's Disease in the weather extremes of East Texas. The Lenoir must, they fermented, fortified, and aged in barrel for 4 years. It waited another 4 years in bottles labeled "Dark Portejas". Upon release, it won double gold and Grand Star at the 2015 Lone Star International. Competing well in the $$$ category, it is inexplicably underpriced at $40/btl.

Dark Portejas, a rare and fine thing, is available only over the winery's tasting room counter.

When I finally arrived at Enoch's for a tasting, the day was dusk, warm, and wet. Electing to enjoy the weather on the patio, I carried the Portejas snifter outside, sank into a chair beneath an umbrella. I filled my head with the wine's cloyed cedar-and-oak aroma and reflected on the weather.

A dark sky met the darker horizon while outdoor lights obliquely lit the gentle rain to give the air a chrome-and-black speckle like monochrome video noise. On a whim, I lifted my snifter to eye level and brought the dark wine meniscus even with the black horizon.

The sky above the port was the color of television, tuned to a dead channel.

[rjb]

working title: "Neuromantic Lyttony"....
The sky above the port was the color of television, tuned to a dead channel.

It appears this forum needs a new category: "Writer's Colony".

[Richard]

Question:
Say you harness a guitar as outlined, but do not modify the amplifier.
Build an instrument cable with TRS on one end, TS on the other (SIG- and SHD tied together).
Plug the TRS end into the guitar, TS end into the amp.
Would (might) this configuration offer some advantage over using a mono cable?
If the answer is "it depends", what are the considerations?

-rb

EDIT:
My guess is that hum induced on the cable shield would be largely eliminated from the signal, but hum induced on the amp chassis would remain.

You can just connect the shield at the amp end provided you have 2 conductor cable. I've done this but didn't notice a difference. I suppose the RFI is "further" from the amp input by whatever the resistance of you conductor (would we call it ground still?) is but with 5+K of pickup impedance, I dont thing that half ohm is much of a factor. I swapped ends and didn't notice a difference.

[J M Fahey]

Is that yours?

VERY good !!!!!!!

[rjb]

You can just connect the shield at the amp end provided you have 2 conductor cable.... I swapped ends and didn't notice a difference.

I'm not sure we're understanding each other.
I assumed it obvious that a TRS to TS cable would use 2 conductor shielded cable.

The guitar's innards would be wired as Mike outlined.
The cable connections would be:

Guitar End
T - SIG+
R - SIG-
S - SHD

Amp End
T - SIG+
S - SIG- and GND

If you swapped cable ends, you would tie SIG- to SHD at the guitar's TRS jack, defeating the separation of "signal ground" from shield.

If you used a two-conductor TRS-to-TRS cable and plugged it into an unmodified amp, SIG- from the guitar would float at the amp's mono input jack.

Again, I'm not sure what you're saying.
Did you wire the guitar with a TRS jack (as Mike outlined), connect the guitar to an unmodified amp with a TRS-TS cable, and find no difference when you swapped cable ends?
I'm not questioning your observation- just confirming we're on the same page.

Thanks,
-rb

[salvarsan]

It appears this forum needs a new category: "Writer's Colony".

Hey! That quip about "Perdido Street Station" started it.

The "Lyttony" in the title should have clued you to its aggressive competition in bad writing, i.e., the Bulwer-Lytton Fiction Contest in which contestants compete against the original "it was a dark and stormy night . . ."

So, if there's a writing category, it should explicitly be "Bad Writing".

You mooks, fix the damn guitar ground awreddy. That horse is dead and rotting.

[salvarsan]

Is that yours?

Yes. It's a documentary, accurate but for the last sentence.

Enoch's Stomp Dark Portejas is real, good enough that you shouldn't leave the bottle unattended among company. (*sigh!*)

[rjb]

You mooks, fix the damn guitar ground awreddy. That horse is dead and rotting.

But how can we know we've chosen the best fix, without exhausting all possibilities?

Seriously, as a concrete-skulled ignoramus, I can sometimes benefit from being told "Don't waste your time trying that. It won't work because yadda, yadda, yadda."

-rb

[salvarsan]

A good reference is Ralph Morrison's laconic 146 page "Grounding and Shielding Techniques in Instrumentation, Second Edition", published 1977, ISBN-13: 978-0471029922.

It's practical physics written for electrical engineering types. Used hardcover copies are about $5 shipped but later editions are stupid money expensive.

[rjb]

A good reference is Ralph Morrison's laconic 146 page "Grounding and Shielding Techniques in Instrumentation, Second Edition"

Laconic sounds good. 146 pages may exceed my attention span.
Maybe I'll warm up with this.
(Haven't read it in a few years. Maybe more will sink in this time).
It's only 12 pages, and even has a cartoon illustration.
http://www.rane.com/pdf/ranenotes/Gr...io_Devices.pdf

-rb

[John Kolbeck]

I had google "why does the bridge have to be grounded?", and I got a different answer for every guitar forum that came up in the results, and yet I bet that book has the single, correct answer somewhere within its pages. It's funny that in the age of the Internet and self-publishing, quality information is suddenly so hard to find, while wild guesses aplenty are at our fingertips. It's like The Great Dumbening is upon us.