Blogs

Recent
Entries

Best
Entries

Best
Blogs

Blog List

Search Blogs

Home > Forums > Amplifiers
> Chip
Amps

Confused over various grounding methods and designs

[log out]
Welcome, dmfraser66.
You last visited: Today at 06:37 PM

Private
Messages: Unread 0, Total 0.

Home

Forums

Rules

Articles

The
diyAudio Store

Gallery

Wiki

Blogs

User CP

Donations

FAQ

Calendar

Community

Quick Links

Search

Chip Amps Amplifiers based on integrated
circuits

Community Links

Social Groups

Contacts & Friends

Members
List

Search Forums

Show
Threads   Show Posts

Advanced
Search

Google™ Search

Search Wiki

Advanced Search

Search Blogs

Advanced Search

Quick Links

Today's
Posts

Mark Forums Read

Open
Contacts Popup

Networking

Contacts & Friends

Social Groups

User
Control Panel

Edit Your Details

Edit Options

Miscellaneous

Private
Messages

Subscribed Threads

Your Profile

Who's
Online

Wiki Links

diyAudio.com Wiki (Page)

diyAudio.com Wiki (List)

Post New Article

Wiki Tools

Special pages

Books

Recent changes

Go to Page...

User Control
Panel

Private
Messages

Subscribed Threads

Edit Your Details

Edit Options

Miscellaneous

Your Profile

Please
consider donating to help us continue to serve you.

Ads
on/off / Custom Title / More PMs / More album space / Advanced printing
& mass image saving

Page 1 of 8

1

2

3

>

Last
»

Thread Tools

Search this Thread

Rate Thread

26th February 2015, 06:38 AM

#1

darklife

diyAudio Member

Join Date: Oct 2013

Confused over various grounding methods and designs

Sorry if this is not the right place but the
guitar amplifier I am designing around the LM3875 chip has me scratching
my head over what to do for the overall grounding scheme.

There is
a sensitive preamp circuit I designed which includes a clean/fuzz channel
switch, so even the smallest error in grounding inputs, outputs, pots,
main grounds and so on can mean the difference between a tame amplifier
and one that squeals from ground loops.

It is my understanding that
the idea is to not have more than one ground path to a circuit. As in the
input jack, speaker jack, headphone, and chassis should all be separated
in that they all receive their own ground connection to the overall star
ground.

This is really bugging me how the smallest change in ground
is making a night and day difference in this design.

So here is my
plan, and please tell me if I have something wrong here...

-Input
jack and speaker jack and headphone jacks all have their ground separated
from each other at the jack (no connection to faceplate metal) and each
goes to their respective ground on the circuit board via shielded
cables.

-Main amplifier board has everything star grounded just
like any other chipamp, then rectified filtered DC running to to that and
the positive connections.

-Preamp circuitry all having its own star
ground, that then connects to the main amps star ground on the circuit
board.

-Finally.. metal chassis itself connected to the ground on
AC outlet, and a resistor/capacitor from chassis to the main amplifiers
star ground.

Do I have this all correct?
This is quite confusing
to me because I am use to RF electronics where everything is a matter of
RF shielding on the same ground, or even antique electronics where all
jacks and controls and chassis were grounded to each other directly, even
sometimes with multiple grounds going to the same thing (example: volume
pot grounded to chassis, shielded cable going to volume pot with ground
also wired to chassis, aka: two ground paths).

So as I understand
it the rules are... No multiple ground paths to the same part either
through wires or chassis.
There are three separate grounds, chassis,
circuits, and input jacks, that all eventually connect together at one
point.

Sorry for the long post.
It is one thing to design an
amplifier with line inputs only, but when you add a sensitive preamplifier
and tone circuitry in the same unit, things get complex!

PS: If
anyone knows some good tutorials or documents I can read through about
this subject please link me. Sorry if this is a common question.

darklife

View Public Profile

Send a private message to darklife

Visit darklife's
homepage!

Find More Posts by darklife

Add darklife to Your Contacts

26th February 2015, 06:41 AM

#2

darklife

diyAudio Member

Join Date: Oct 2013

One more quick question.. Am I correct in
assuming this all as modern electronics always separate the RCA and 1/4
plug inputs from the chassis body if metal using plastic jacks and plastic
nuts to hold them in place, whereas old electronics often had their
input/output jacks with metal ground threading touching metal
chassis?
What changed since times past?

darklife

View Public Profile

Send a private message to darklife

Visit darklife's
homepage!

Find More Posts by darklife

Add darklife to Your Contacts

26th February 2015, 12:24 PM

#3

AndrewT

diyAudio Member

Join Date: Jul 2004

Location: Scottish Borders

Number ONE in my book (don't worry, you're
safe from me! I will never become an author),
is give EVERY CIRCUIT
it's necessary FLOW and RETURN connection/s to the outside
world.

Then you will find that all your confusing "grounds" have
gone away to bother those other Members who continue to use this most
confusing of words in our DIY dictionary.

Once you have EVERY Flow
and Return identified, make sure this pair are close coupled along the
whole route from module to module.

Then, as an extra belt and
braces, try to twist every close coupled Flow and Return.

This
practice minimises the interference effects of aerials in our systems. The
receiving aerials and the transmitting aerials become very ineffective
when the two conductors are twisted pairs.
It is all about LOW LOOP
AREAS.

In an amplifier one often finds that the separate modules
need a common reference. This applies to opamps and Power Amps. The input
and the output NEED a common reference. I like to call this the "Main
Audio Ground" (MAG), because it does not get confused with all the other
Members' misused "ground" word.

__________________
regards Andrew T.

Last edited by AndrewT; 26th February 2015 at 12:28
PM.

AndrewT

View Public Profile

Send a private message to AndrewT

Find More Posts by AndrewT

Add AndrewT to Your Contacts

26th February 2015, 02:30 PM

#4

bentsnake

diyAudio Member

Join Date: Jul 2014

.
You'd probably expect that power
supplies and grounding would be mature technology, with all issues long
since settled. But this is partly true, and mostly not. There are gray
areas where judgment enters in, and this very much includes the subject of
grounding.

Before anything else, the #1 rule that everybody agrees
on is keeping the audio signal away from the relatively large power supply
voltages and currents. Obviously this is done to avoid distortion of the
audio signal. Not so obvious is that this rule applies as much to the
return side as the hot side.

The "audio separate from power" rule
applies to the return side because: a) ICs (integrated circuits) work on
very low voltages and currents, and: b) these voltages and currents are so
low that the real-world resistance of straight wires becomes a factor. A
straight wire has only milli- or micro- ohms of resistance, but with ICs
milli- and micro- volts and amps are involved, so E=IR becomes
significant.

Posted below is a succession of images, intended to
progress from the basic principle to real-world application.

Figure
1 is simply the usual schematic for a power supply. You're supposed to
look at it and admire the simplicity of the concept.

Figure 2 is
the same (literally) schematic, but with notes added that I hope are
self-explanatory.

Figure 3 is electrically identical to the first
two, but mechanically different because real-world wiring connections are
shown.

Figure 3 is where the various this-grounds and that-grounds
come in. All these different "grounds" seem to--and do--violate the rule
of "one ground point, and one only." I resolve this conflict by
referring to everything except the shown Point A as
"commons."

Figure 4 shows the chassis bond. This is also
called chassis ground, safety ground, and probably a dozen other
names.

Figure 5 brings everything together--I hope--showing how the
audio circuit connects to the power supply.

I'm not making this
stuff up. All of this is as suggested by audio gurus of serious
reputation, including the chip manufacturers themselves. However, I don't
present any of this as "the way you do it." As before, in the gray areas
there's room for judgment, so you pretty much pays yo'money and takes yo'
choice.

I should add that what I'm presenting here is the Cadillac
way of doing things. In contrast, when building just a small preamp,
stompbox, or similar, it's not uncommon to just hook all the
grounds/commons/returns together in the way that's most convenient. This
is the "ground bus" method, and it's likely to work just fine. However,
following the "audio separate from power" rule is always a wise.
.

Attached Thumbnails

Last edited by bentsnake; 26th February 2015 at 02:42
PM.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

26th February 2015, 02:38 PM

#5

bentsnake

diyAudio Member

Join Date: Jul 2014

Quote:

Originally Posted by darklife

One more quick question.. Am I
correct in assuming this all as modern electronics always separate
the RCA and 1/4 plug inputs from the chassis body if metal using
plastic jacks and plastic nuts to hold them in place, whereas old
electronics often had their input/output jacks with metal ground
threading touching metal chassis?
What changed since times
past?

Nooo! Some jacks/connectors
might be internally bonded [to ground], others might not be. You have to
examine the specs. Often this means clicking through to the manufacturer's
spec sheet (sometimes given, sometimes not) and studying
that.

Usually a non-bonded jack/connector will be called
"insulated," but you can't depend on that one way or the other unless it's
clearly stated what "insulated" means.
.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

26th February 2015, 02:52 PM

#6

bentsnake

diyAudio Member

Join Date: Jul 2014

Quote:

Originally Posted by darklife

There is a sensitive preamp circuit
I designed which includes a clean/fuzz channel switch, so even the
smallest error in grounding inputs, outputs, pots, main grounds and
so on can mean the difference between a tame amplifier and one that
squeals from ground loops.

Ground
loops commonly produce hum, squeals are feedback. Do your circuits include
decoupling and/or bypass capacitors?

If your answer is "I don't
know," then they probably don't. But you'd have to post a schematic for
there to be any useful discussion.

However, if you're not already
following the rule of "audio separate from ground," then that might be the
solution to more than one problem.
.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

26th February 2015, 02:58 PM

#7

bentsnake

diyAudio Member

Join Date: Jul 2014

Quote:

Originally Posted by darklife

This is quite confusing to me
because I am use to RF electronics where everything is a matter of
RF shielding on the same ground, or even antique electronics where
all jacks and controls and chassis were grounded to each other
directly, even sometimes with multiple grounds going to the same
thing (example: volume pot grounded to chassis, shielded cable going
to volume pot with ground also wired to chassis, aka: two ground
paths).

Then these are tube/valve
circuits? Don't confuse yourself by directly comparing tubes/valves to
ICs. The hundreds of volts that tubes/valves work on are a whole different
world.

Also, antique devices had no third (bonding) conductor on
the wall plug. More opportunity for confusion.
.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

26th February 2015, 03:14 PM

#8

bentsnake

diyAudio Member

Join Date: Jul 2014

Quote:

Originally Posted by darklife

...metal chassis itself connected to
the ground on AC outlet, and a resistor/capacitor from chassis to
the main amplifiers star ground

The
"ground lift" method goes by various names. Some swear by it, others, such
as me, consider it a sloppy workaround that might be illegal where you
live, and dangerous to boot.

Call it whatever, ground lift
introduces an unknown by un-bonding the chassis. This can mean that you
have everything else right, but the ground lift itself is causing
hum.

I suggest that you remove the ground lift for troubleshooting
purposes, instead bonding the third conductor of the wall receptacle
directly to the chassis, which really is a bond. Then if all else fails
again resort to a ground lift.

Ummm...you have tried plugging
everything into the same wall receptacle? Using a power strip if
necessary, or much better, just a plain ol' multi-outlet extension
cord?
.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

26th February 2015, 03:32 PM

#9

bentsnake

diyAudio Member

Join Date: Jul 2014

Possibly a Root Cause

Quote:

Originally Posted by darklife

Preamp circuitry all having its own
star ground, that then connects to the main amps star ground on the
circuit board.

Reading along in your
post, this finally jumps out at me. Possibly your problem in the first
place (or possibly not).

I'm not certain of what you mean by
"preamp star ground" and "main amp star ground," but if I'm thinking right
I can see these being connected together as fatal. The small audio signals
in the preamp fall victim to the larger currents and voltages in the main
amp, and everything gets scrood.

Solution: referring to my own post
#4.

Assuming that I'm picturing correctly what you're doing, the
preamp star ground instead runs directly to what I call Point A, circuit
ground at the power supply, and the main amp star ground does the
same.

Of course, always keeping audio signals away from power
supply lines.

OK last post, I'm giving somebody else a chance.
.

Last edited by bentsnake; 26th February 2015 at 03:38
PM.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

26th February 2015, 04:27 PM

#10

bentsnake

diyAudio Member

Join Date: Jul 2014

Correction to Post #6

.
My post #6 says, "...if you're not
already following the rule of 'audio separate from ground,' then
that might be the solution to more than one problem.

Of course this
should be, "...if you're not already following the rule of 'audio separate
from power supply,' then that might be the solution to more than
one problem.

It's kind of inconvenient that posts can't be
edited.
.

bentsnake

View Public Profile

Send a private message to bentsnake

Find More Posts by bentsnake

Add bentsnake to Your Contacts

Page 1 of 8

1

2

3

>

Last
»

Message

Cancel
Changes

Quick Reply

The following errors occurred with your submission

Okay

Message:

Options

Quote message in reply?

Posting
Quick Reply - Please Wait

« Previous Thread | Next Thread »

Thread Tools

Enhanced Print View

Regular Print View

Email this Page

Subscribe to this Thread

Search this Thread

Advanced Search

Rate This Thread

Excellent

Good

Average

Bad

Terrible

Posting Rules

You may post new threads

You may post replies

You may post attachments

You may edit your posts

BB code is On

Smilies are On

[IMG] code is
On

HTML code is Off

Trackbacks are
Off

Pingbacks are
Off

Refbacks are
Off

Forum
Rules

Forum
Jump

User Control
Panel Private Messages
Subscriptions Who's Online Search
Forums Forums Home
Site
Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps
Class D
Power
Supplies
Headphone Systems Source
& Line
Analogue Source
Analog Line Level     Digital Source     Digital Line
Level     PC
Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems
Instruments and
Amps Design &
Build
Parts
Equipment & Tools     Construction Tips     Software Tools
General Interest     Car Audio     diyAudio.com
Articles
Music
Everything Else Member
Areas
Introductions
The Lounge     Clubs & Events The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio
Store
Vendor Forums
Vendor's Bazaar         Sonic
Craft
Apex Jr         Audio Sector

Acoustic Fun
Chipamp         DIY HiFi Supply

Elekit
Elektor         Mains Cables R Us

Parts Connexion
Planet 10 hifi         Quanghao
Audio Design
Siliconray Online Electronics
Store
Tubelab     Manufacturers         AKSA

Audio Poutine
Musicaltech         Aussie Amplifiers

CSS
exaDevices         Feastrex
GedLee
Head 'n' HiFi - Walter         Heatsink
USA
Markaudio
miniDSP         SITO Audio
Twin
Audio
Twisted Pear         Wild Burro Audio

Similar Threads

Thread

Thread Starter

Forum

Replies

Last Post

Methods
of Handling Various Devices and Grounding - Ground Loop Issues

mattwalston

Analog Line Level

7

10th January 2012 11:08 AM

Lions
and Tigers and Grounding Problems, Oh My! DoZ Grounding...

EchoWars

Solid State

37

3rd August 2008 08:50 AM

Bias
methods?

Psychobiker

Tubes / Valves

8

3rd April 2008 09:07 PM

LM3875
kit grounding, optimal grounding for separate amps and psu?

findog

Chip Amps

9

16th May 2005 09:27 PM

grounding
on pcb designs

FunkyStu

Solid State

4

12th March 2003 05:00 PM

New To Site?

Need Help?

Search

Privacy Statement

Contact
Us

Frequently Asked
Questions

Mark Forums Read

Log Out dmfraser66

All times are GMT. The time now is 08:43 PM.

Home - Contact
Us - Advertise - Rules
- Store - Sponsors - Archive - Privacy Statement - Terms of
Service - Top
- Opt-out policy

vBulletin
Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte
Technologies Ltd.
Copyright ©1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2