Help a monkey out - Schematic question (basic)

[t7mackie]

What are they asking for here??? To me it looks like a mono input with +9v on both the tip & shield. Doesn't seem right to me but I know I'm missing something. I've seen this on several schematics and searched the interweb to understand it to no avail.

Help a monkey out, please...

[Vivek]

Please be kind to post some of the official schematics from well known sources where you saw this Jack with the +9V connected to it in the manner shown.

Thanks !!!

[EBK]

That's a switched DC jack. (I think)

Looks drawn incorrectly.


Edit: I'm tired. Sorry. 

[duck_arse]

tip has a switch, which is closed normally. it is shown connecting tip to sleeve, which is connected to +9V, suggesting a positive ground circuit. insert a plug into the jack, and the plug tip will shift the tip dinger away from the switching contact. the swict is now open, tip goes off to somewhere useful, sleeve remains connecting to "+9V".

like so:

[iainpunk]

some germanium transistor PNP circuit??

i can't think of any other reason for this.

cheers, Iain

[idy]

If it is "positive ground" then it makes sense: The input is grounded when not in use to avoid noise when nothing is plugged in. Useful in a mixer for example. Hard to think why a PNP fuzz box would need this....

[iainpunk]

If it is "positive ground" then it makes sense: The input is grounded when not in use to avoid noise when nothing is plugged in. Useful in a mixer for example. Hard to think why a PNP fuzz box would need this....

to not have it make a bunch of unnecessary noise when you accidentally pull the plug out of the fuzz pedal in a gig... it happened to me with a fuzz that goes bezerk when there is nothing plugged in the front.
cheers, Iain

[Vivek]

That's correct !!!

The tip normally goes into the input of the circuit.

The switch grounds the input when there is no jack plugged in, so that no noise/RF in amplified

It's connected to +9 since its a positive ground circuit.

[ElectricDruid]

some germanium transistor PNP circuit??

i can't think of any other reason for this.

+1 agree. Looks like a positive ground circuit to me, so the input is connected to the "ground" when nothing is connected to prevent noise.

[t7mackie]

Please be kind to post some of the official schematics from well known sources where you saw this Jack with the +9V connected to it in the manner shown.

Thanks !!!

What is confusing me is that it appears that both the sleeve and tip are getting +9v. Am I crazy?

[idy]

In this circuit it is better to think of +9 as ground. So when nothing is plugged in, both tip and sleeve are grounded. When there plug is inserted, the tip is "lifted off the little upward arrow head, opening the switch so only the sleeve is grounded and the tip is a path for signal. You call this a NC or Normally closed switching jack.

If you are tripping out on positive ground, you can look that up. It is a weird idea mostly found in ancient fuzzes and *Range Masters*.

[Vivek]

https://www.electrosmash.com/dallas-rangemaster

[Vivek]

First thing, the schematic does not show positive ground!

Second, on most physical hardware, the sleeve is physically connected to ground. Unless insulated jacks are used, this schematic will lead to the jack shorting out the battery.

Maybe there is an error in the schematic ?

PS the electrosmash article talks about grounding issues of the range master.

[11-90-an]

There is no error in the schem. No shorts also. The article stated that the rangemaster is a *battery powered* circuit.

OP, check section 5 of the website, "Dallas Rangemaster Treble Booster Mods". I recommend you go the NPN route as the cheapest way without enclosure/grounding problems (if implemented well, of course)

[Vivek]

There is no error in the schem. No shorts also. The article stated that the rangemaster is a *battery powered* circuit.

Agree that its a Battery powered circuit

and agree that the schem, if used standalone on a breadboard, is just fine, though a bit quirky


But let us see what happens if we physically try to put the schem into an enclosure

A) Do you agree that the point marked Ground will be connected to the enclosure ?
Thats the negative of the battery

B) Do you agree that most hardware jacks are such that the sleeve is electrically connected to the enclosure ?
The schem asks for the positive of the battery to be connected to the sleeve and that automatically means connected to the enclosure.


If answer to both questions is Yes

Then both positive and negative of battery are connected to the enclosure in a real physical implementation.

Ie battery is shorted

QED

[ThermionicScott]

These schematics show shorting jacks, but I'm skeptical.  Original Dallas Rangemasters had a hard-wired output cable to a plug, so that's at least one end that wouldn't default to shorting out.

Regardless of the power supply, it doesn't make any sense to short it out when you don't have something plugged into the input, either, I would have used an open-circuit jack there.  Are we all going into the weeds because someone just used whatever symbols were available in their circuit-drawing software?   

[Phoenix]

Nothing wrong with the schematic, no short circuits, though it is drawn unconventionally, which seems to be throwing some people.

Enclosure is connected to +9V, it's a positive ground circuit. No need for isolated jacks.

The tip shorting is recommended to reduce noise if input is unplugged. If the input is left floating it will pick up whatever noise is floating through the air, and will often squeal. Better to have a quiet rather than noisy circuit if you accidentally tug your cord out of the pedal during a gig, right?

Here are two alternative ways to draw the circuit. Left is how I prefer to draw it (positive nodes at top, negative at bottom of schematic - this is the modern convention), and on the right is the way it is most commonly drawn (inverted from modern conventions).



EDIT: apologies to anyone who caught the first image I posted. In my haste I made some large errors when transcribing it. This speaks to the value of sticking to conventions when drawing schematics, as it greatly facilitates understanding.


Note, the circuit can also be built with conventional negative ground, to avoid daisy-chain/non-isolated PSU compatibility issues WITHOUT the need for a charge pump voltage inverter. RG has reported potential stability issues if doing so, but to my knowledge he is the only person to report such, and even he notes that it is an uncommon possibility. I personally have never experienced any problems in any new builds or conversions.

[PRR]

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.

[ElectricDruid]

First thing, the schematic does not show positive ground!

What do you mean by this comment, Vivek? I don't understand you, sorry.

The circuit looks to me like what is typically called a "positive ground" circuit, since points that would usually be connected to ground (e.g. negative side of the battery) are instead connected to the positive side of the battery. It's a Rangemaster. It's a famous example of this type of thing.

[Vivek]

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