rmorris

Yes - used for "normalling" in patchbays - ie the 'normal' signal route exists with no plug inserted and the signal routing is modified when you plug in to put another piece of kit in the chain. And in headphone / speaker automatic switching etc. On an amplifier input the switched contacts are 'normally' connected to 0V so that the amp is quiet when no cable plugged in. Otherwise the high impedance of the input would pick up noise. Plugging a cable in replaces 0V with the signal from the guitar. The contact nearest the front of the socket would usually connect to 0V anyway so the switching on that contact may have no effect (although the designer might do something not straightforward with the 0V / Screen connection) but those sockets are mass produced like that.

It's 2021. We need Bluetooth connectivity, Retina Recognition and GPS on all basses at a minimum. Oh hold on - that's mobile phones. I'll go with the push-pull pot switch...

Mmmm...this is getting proper complex now. And you'd need to reliably sense the bass being played - take a signal direct from a pickup ? MEMS device ? At this rate I'll be suggesting Phantom Power 🙂

Yeah - why didn't I think of that option ! I had thought about the rear cavity cover option if the bass allows it. But this is better imo. Excellent stuff. Make it pull out to power off so you won't accidentally turn it off mid solo ! Now, of course there'll be the question of a suitable value / taper / mechanical size / shaft size and type...

Excellent stuff. I knew someone in Sussex would be able to do it 🙂 Could maybe use a larger jack body - Neutrik or Switchcraft ? I think Neutrik make one for speaker cable sized cable - it might be bigger internally. Not sure. and a cutout in the metal shell for the switch ?

Does the bass have a 'Passive' option - as opposed to being either active(powered) or no sound ? In any case the electronics is relatively simple. I'm thinking physically fitting the switch and led would be the biggest thing to sort ?

I know what you mean. I've previously used a switch on the bass to switch on/off rather than the jack socket. But I had a spare switch position after changing the pickup to one that didn't have series/parallel switching. I don't suppose you really want to fit an extra switch to the bass ?

Basically what nekomatic said. The jack socket in the bass has three terminals - TRS - and so using a 2core + screen cable (ie a standard 'balanced' cable) you can effectively extend those connections and so be able to connect / disconnect the R+S connections to power (or not) the electronics. I can see a possible issue in that you can't afaik get the 'low noise' type cable usually used for connection to passive instruments with Hi-Z pickups in a 2core/twisted pair format. This wouldn't be connecting to a passive instrument so it might not be a problem but the output impedance of an active bass might not be as low as we would want - depending on the electronics detail.

True for a standard guitar jack plug is a TS. But if you use a TRS 'Stereo/Balanced' jack plug you can move the switching outside the guitar. I do think it's a bit inelegant though.

Assuming you don't want to fit a switch to the bass itself: the connection is made by the sleeve connection of the TS jack plug. If you had a TRS jack plug at the instrument end you could look at fitting a switch between the 'R' and 'S' connections. Might be a bit trick / cumbersome though depending on your priorities. And I suppose you could build a box to do the same thing by running the TRS cable to it and switch there. With cable to amp running from the switch box to amp. Is it worth the bother ?

Yes - but tbf wiring the power to a 'digital' pedal (not forgetting that analogue delay pedals still have clock edges) more directly back to the power source (in this case the battery) will minimise the problem by reducing the common impedance. Just don't try daisy chaining a KORG G5 ! Of course, it all depends on how critical you are with this stuff - or how critical your sound / recording engineer is. In the past I've spent a fair amount of time in pro-audio development and lots of time with instrumentation/noise/EMC issues in general so I might be more "fussy" than some ! Speaking of which I should really go and do some work 🙂

Point taken about it being powered by a battery and not AC mains via transformer. But a "ground loop" doesn't rely on there being ac or a transformer involved in powering the system. That supply will help in that the individual outputs make the system wiring more like a 'star' topology as opposed to a 'daisy chain' (assuming one power cable pair is taken directly to one fx unit only. So the ability of the ground reference of one fx to be modulated by another is reduced. And with a typical daisy chain with 'linear analogue' pedals the results are likely fine - at least for live / rehearsal use if possibly not studio work depending on the context - we have taken mains related noise out of the equation and with typical Hi-Z instrument pickups they are the dominant source of noise. The obvious problems can come up when using fx that have clocks and/or microprocessors etc. Yes - different fx will have different characteristics here depending on the circuit and filtering (I'm considering conducted noise here) but there is always some that gets out and particularly common mode noise. But in addition you have the susceptibility of a loop to have noise induced into it from an external source. eg Thyristor Dimmed Lighting. Since you have two ground connections to/from each pedal - power cable 0V and the signal cable screen then you have a loop by definition. Minimising the loop cross sectional area minimises susceptibility so this points to running power connections as close to signal connections as practicable. And/or placing 'ground loop breaker' components in your patch leads but that's not the easiest thing to implement physically esp with small jack plugs and maybe not realistic at all with the flat 'pancake' jacks plugs. I opt to make life easy and go with electrically isolated supplies.

No. In that you're never working with only DC. A "noisy ground" has AC on it by definition else it wouldn't be noisy. One of the problems in talking about this stuff is that the term "Ground Loop" is used to describe several different, if related, scenarios. The presence of a "Ground Loop" does not require an association with an AC Mains Supply or any connection to the planet Earth. eg Unbalanced connections, relatively high impedances and clock signals (eg from a Digital Delay pedal) add up to a likely noise problem with power supplies that share a common "Ground". Not my original but useful : "Ground is a concept not a voltage node".

Yes. They won't avoid "Ground Loops" and so may give rise to noise problems esp with "Digital" pedals. It's not always obvious. Eg the Thomann "Powerplant Junior" is galvanically isolated while the larger "Powerplant" is not.

Just a note to say that if you put batteries in parallel for higher current capability you might want to put small resistors (say 10 Ohm) from each to a common output point. This limits the amount of current from one to the other due to differences in the individual voltages of each. Whether necessary depends on the batteries themselves and particularly their chemistry type - eg Lithium Ion / NiMH etc etc.