Help a monkey out - Schematic question (basic)

[ElectricDruid]

Does positive ground mean positive of battery is connected to ground ? I don't know the convention.

I'd say a better way to describe it is that the "ground" and "+V" symbols are reversed. The "ground" symbol still appears in the circuit diagram, and like on the power supply cap you posted, that obviously has to be the right way around.
But whereas the sleeve of a jack and similar places would ordinarily be considered as "ground", instead these points are connected to +V, hence "positive ground".

Phoenix's diagrams showing alternative ways of representing the same situation are nice. Both of those diagrams represent it with 0V and -9V, but the Electrosmash diagram shows 0V and +9V, so that's a third way of drawing the same thing. Nightmare.

But I completely agree, it really is only a convention, and it's pretty confusing and causes no end of trouble. In fact, here we are again!

[willienillie]

In my opinion, the Electrosmash schematic is drawn incorrectly and does short the battery.  They have a ground symbol where most people would put "-9V."  Then they have "+9V" connected to the jack sleeves.  Even if you isolate the jacks from the enclosure, the sleeves are going to connect to ground at some point.  It looks like 'Smash started to draw it as an "upside down" PNP circuit to be negative ground, but labeled the jacks for positive ground.  Hense, shorted battery.

[Phoenix]

Nothing wrong with the schematic, no short circuits, though it is drawn unconventionally, ...

So how do I turn it off? I do not see a power switch or a jack finger.

A fair criticism. I omitted power switching just like the original rendering of the schematic under discussion. It's fairly common for this information to be "implied" and left to the builder to intuit, which is hard to argue isn't just bad practice and laziness.

My comment was levelled at the concerns about the battery being shorted out. I think we can agree that it is *functional* as drawn (though unintuitive, leading to this discussion), but lacks the practical aspect of being able to turn off without disconnecting the battery.

EDITED: to add schematic with input jack power switching. Also removed output jack NC connection from Electrosmash rendering as it serves no purpose

[Vivek]

Phoenix,

Your drawings and descriptions are great !!!


I still do feel that there are "errors" in the schematics. That is not "Confusion created by convention" but real errors.

Error 1 :

In positive ground systems, the positive of the battery connects to ground. But the schematic shows the negative going to ground in the power section (Cap parallel to battery)




Error 2 :

There is a ground symbol shown on the top of the schematic but the +9 is written at the bottom. This means that the top is not at +9V. which means that the ground is not at +9 Volts.

Implied error 3 : There is a ground symbol shown on top. It has to be the negative terminal of the battery since the +9 is written at the bottom.

It is implied that ground is connected to enclosure. There is a +9 connected to the sleeve. Most jacks are not isolated, it means that the sleeve will touch the enclosure. That means that the battery will be sorted.





There is nothing wrong with the concept of positive ground since, for AC signals, both the terminals of a battery should be equivalent.

There is nothing wrong in convention 1 or convention 2 as long as they are consistent.

The schematic is the one that has errors.

[Vivek]

I made an attempt to rectify the Rangemaster schematic using my feeble brain. I hope I did not introduce even more errors

[bluebunny]

For fewer headaches, just change "+9V" to "-9V" (because that's exactly what it is).  Don't get hung up with the markings on a PP3.

[Vivek]

Does positive ground mean positive of battery is connected to ground ? I don't know the convention.

Phoenix's diagrams showing alternative ways of representing the same situation are nice. Both of those diagrams represent it with 0V and -9V, but the Electrosmash diagram shows 0V and +9V, so that's a third way of drawing the same thing. Nightmare.

I still do believe

Phoenix' drawings are correct

Electrosmash has an error. This is not "confusion due to convention",  it is plain error

In a positive ground system, the positive of the battery and the ground are the same thing. Phoenix shows it that way.

In the power supply section, Electrosmash shows that +9v and ground are two different things.

In the main circuit, if ground = +9V in positive ground section and the top rail is ground, it means top rail and bottom rail are at the same voltage. This is error. This is not "Confusion due to convention"

================
I stand corrected !

Please read https://www.diystompboxes.com/smfforum/index.php?topic=125770.msg1199569#msg1199569

[Phoenix]

Error 1: In positive ground systems, the positive of the battery connects to ground. But the schematic shows the negative going to ground in the power section (Cap parallel to battery)

Where you are tripping up is how you are interpreting the ground symbol used in the schematic. There are at least three most commonly used "ground" symbols

Signal/circuit ground is an arbitrary reference. It only denotes where all voltage measurements are taken from, but critically, it *does not* imply a chassis or protective earth connection. It is common to see circuit/chassis/earth ground connected, which is why this is throwing you for a loop, but it's important to know there are very important differences.

"Earth ground", as used in the Electrosmash schematic, is the tricky one. In a schematic with multiple different ground symbols, it denotes a connection to protective earth - almost always a safety critical connection. But, it is also often used in schematics in place of the circuit ground symbol, where it does not imply anything about a chassis or protective earth connection. As the "earth ground" symbol is used in isolation in the Electrosmash schematic, it's implied that it's only indicating circuit ground in this case.

Chassis ground is *only* used to denote chassis connections. The Electrosmash schematic does not specify this connection, but it is implied by the jack connections and other circuit details that if it were present, it would connect to +9V.

Examples of where you might see circuit ground and chassis ground *not* connected include audio products with ground-loop isolation through the use of bypassed diodes, floating power supplies, etc.

Error 2: There is a ground symbol shown on the top of the schematic but the +9 is written at the bottom. This means that the top is not at +9V. which means that the ground is not at +9 Volts.

Further confusion is caused by the schematic being inconsistent with top-to-bottom polarity. The schematic is drawn almost entirely with negative potentials at the top and postive at the bottom, with the glaring exception of reservoir capacitor C4. Modern convention has postive potentials at the top of schematics, but remember it is only a convention to aid in understanding. If the clarity of a schematic is aided by inverting top-to-bottom polarity, even if just for a section of an otherwise conventionally drawn schematic (like if a large number of crossing wires would be required to maintain absolute consistency), then that is preferred. These conventions only exist to aid in clarity, if they work against this aim then they can and *should* be ignored.

I do agree that the Electrosmash schematic is a particularly poor example, but it does *not* contain any short-circuit errors.

It is implied that ground is connected to enclosure.

This is the root of your misunderstanding.

[Phoenix]

Here's a reference from National Instruments noting the differences between "ground" symbols.

Pay particular attention to the following section:
"Note that none of these grounds are necessarily equivalent. Ground is a point of reference from which a potential (voltage) may be measured. Different grounds will have voltages between them that we must take into account when connecting equipment together and making measurements."

[Vivek]

Thanks Phoenix !!!

[willienillie]

^^^ You may be right, but I kinda doubt Electrosmash was thinking in the same way, I think they screwed up an attempt at negative-ground PNP.  They may be a good source for circuit function explanations, but MOST of the schematics I've seen from them contain errors.  If I'm wrong, they should stick with more conventional labeling of circuit portions, to avoid sewing confusion among the newbs they exist to assist.  In my overly-simplified understanding of guitar electronics, ground is ground, and it connects to cable shield, guitar bridge, amp chassis, etc.  We don't stick a ground symbol on Vref in a Tube Screamer, and specify all voltages relative to that point, put "-4.5V" on the jack sleeve, etc.  That would just cause unnecessary confusion, for no benefit.

(Vivek posted as I was typing, but I'm replying to Phoenix' post up a couple)

[Vivek]

What is the convention here if one makes a post,

and then gets wiser and corrected after reading other posts ?

Do you edit the earlier post ? or just let it be ?

[iainpunk]

^^^ You may be right, but I kinda doubt Electrosmash was thinking in the same way, I think they screwed up an attempt at negative-ground PNP.  They may be a good source for circuit function explanations, but MOST of the schematics I've seen from them contain errors.  If I'm wrong, they should stick with more conventional labeling of circuit portions, to avoid sewing confusion among the newbs they exist to assist.  In my overly-simplified understanding of guitar electronics, ground is ground, and it connects to cable shield, guitar bridge, amp chassis, etc.  We don't stick a ground symbol on Vref in a Tube Screamer, and specify all voltages relative to that point, put "-4.5V" on the jack sleeve, etc.  That would just cause unnecessary confusion, for no benefit.

(Vivek posted as I was typing, but I'm replying to Phoenix' post up a couple)

yeah, i'd dis-recommend electrosmash for beginners in general, they tend to over simplify and i guess they have no proofreader either because its riddled with mistakes. i'd never use one of their schematics to build anything. i wonder who's behind that website. i guess its a hobbyist without formal training.

nice new profile pic.

cheers, Iain

edit:

What is the convention here if one makes a post,

and then gets wiser and corrected after reading other posts ?

Do you edit the earlier post ? or just let it be ?

i always like to edit underneath my ''cheers, Iain" signoff, like this "edit: bla bla bla", i think its at least polite to let people know you learned something with an edit.

[duck_arse]

What is the convention here if one makes a post,

and then gets wiser and corrected after reading other posts ?

Do you edit the earlier post ? or just let it be ?

one common method, that doesn't make the thread loose it's -erm- thread, is to go back to your troublesome post and use the strikeout formatting. [that's how it looks in the Prince ... theme.] you only get 24 hours from when you posted for correctings, tho.

[PRR]

There is no "ground". Play in a rubber-tire car. Play the Space Station.

There are "COMMONS". Not topologically essential but super-practical. Signal common. Power common. And shielding.

[willienillie]

Signal common. Power common. And shielding.

In the vast majority of guitar gear, all of these are connected, and referred to collectively (if only by me) as "ground."  Maybe slightly more correct to say "all points at the same potential as earth ground."  And in my own setup, surely most others, it does all run outside to actual dirt via the third prong on the amp's power cord.  Not so with a battery-powered amp, of course.

[PRR]

> referred to collectively ...as "ground."

An oversimplification that sometimes leads us astray.

> it does all run outside to actual dirt via the third prong on the amp's power cord

It does; but this is frequently irrelevant. It gives "dirt" an exalted image it can't fill.

Working around utility AC, it "IS" useful to reference audio common to power common. Even with battery amps, which are never quite hum-free inside a room. Play in an airplane: you want to reference the plane power (not some ground 8 miles low). Play in an airship without electric power, "grounding" is not needed.

I grew up with Ge PNP and + "ground". These concepts do not disturb me unless a draftsperson mangles the drawing. (Yes, even in 1958 that happened often enough.)