How was Your rehearsal last morning or night ?

[Franticsmurf]

Last night's rehearsal with a relatively new outfit (we've been together for about 8 weeks with 4 practices) was pretty good. After a two week hiatus, we arrived with 8 new songs to work through; 6 went reasonably well with just some light sanding and polish required (starts and endings, as you'd expect) and two will require some extra work to bring them up to speed. Two of the 6 good 'uns featured yours truly on lead vocals. I'm not a singer by nature or by choice but as all the others sing and I've been doing BVs for years, I thought I should make the effort. Listening to the recordings this morning and I'm not as bad as I thought.  I'll never be head hunted for a solo career, though. 😀

[tauzero]

Rehearsal with the originals band last night - third rehearsal for the three of us, and we've got a gig next Friday. Ran over the three songs we'd already got, then worked on the next three and started looking at BVs for both me and the drummer.

[tauzero]

Rehearsed with the covers band last night. I have a soft synth module (a Squishbox) in a metal enclosure that I use with a McMillen 12-Step for one song. Plugged the soft synth in with the 9V adaptor I use for it, then went to connect it to the mixer with a jack-jack cable and got a shock. Can't remember exactly what I did next but with the soft synth connected to the mixer, I touched the case and got a real zap. The studio owner had a look at the wiring but couldn't find anything wrong, and there was no tingle from touching microphones. We carried on without the soft synth as it's only for embellishment.

 

Anyroadup, my playing got sloppier and sloppier. A song that I'd been playing fine earlier in the evening was suddenly a complete cock-up. Then I went to the toilet which is along a fairly cool corridor and it felt freezing, and by the time I'd got back to the room I was shaking badly. Shock. We cut the rehearsal a little short and I managed to drive home, and went to bed soon afterwards. Had a bad night, nauseous and barely sleeping, almost unable to stand up to get out of bed, but feeling somewhat better today. Mrs Zero wanted me to go to A&E but 12 hours in A&E versus 12 hours in my own bed was no competition.

 

The studio owner messaged our drummer to ask after me and to say he'd checked the wiring and it was OK. He suggested I check the power adaptor - that's not the problem, I've checked the connections between the pins and also plugged it in and powered up the soft synth, which would have exploded if it had been fed mains power. I suspect the mixer.

[Stub Mandrel]

  On 17/03/2025 at 18:37, tauzero said:

, I've checked the connections between the pins and also plugged it in and powered up the soft synth, which would have exploded if it had been fed mains power. I suspect the mixer.

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Have you checked the plug pins are isolated from the output?

[tauzero]

  On 17/03/2025 at 19:59, Stub Mandrel said:

 

Have you checked the plug pins are isolated from the output?

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Yes. And there was no issue with it plugged in and powered up but the jack-jack not plugged in, plus this is a 9V adaptor supplying 9V to a 5V regulator which would have blown up had it got mains voltage, plus it's completely harmless at home using the same adaptor.

[Stub Mandrel]

  On 17/03/2025 at 23:01, tauzero said:

 

Yes. And there was no issue with it plugged in and powered up but the jack-jack not plugged in, plus this is a 9V adaptor supplying 9V to a 5V regulator which would have blown up had it got mains voltage, plus it's completely harmless at home using the same adaptor.

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Is thd output earthed?

[tauzero]

  On 17/03/2025 at 23:39, Stub Mandrel said:

 

Is thd output earthed?

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The jack sockets are metal chassis type, set directly in the metal case. The output is only earthed via whatever the soft synth is connected to - in this case, the mixer. There is no other connection from the soft synth to earth as it uses a guitar effects 9V power supply which doesn't have an earth connection.

 

9V DC power adaptor (Boss type) --- 2 core lead & barrel jack --- soft synth --- jack-jack cable --- mixer

 

The only way that the synth can be live is if the mixer instrument input ground is live. At home, using the same power adaptor, through the barrel jack which is isolated from the casing, the synth doesn't go live.

[Stub Mandrel]

  On 18/03/2025 at 11:28, tauzero said:

 

The jack sockets are metal chassis type, set directly in the metal case. The output is only earthed via whatever the soft synth is connected to - in this case, the mixer. There is no other connection from the soft synth to earth as it uses a guitar effects 9V power supply which doesn't have an earth connection.

 

9V DC power adaptor (Boss type) --- 2 core lead & barrel jack --- soft synth --- jack-jack cable --- mixer

 

The only way that the synth can be live is if the mixer instrument input ground is live. At home, using the same power adaptor, through the barrel jack which is isolated from the casing, the synth doesn't go live.

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If the 9V adaptor is not earthed, it is possible for it to 'float' well above earth potential.  This can be made worse if their is tracking or some other fault that allows live potential on to its outputs.

 

But... if the mixer was plugged in and earthed the synth case SHOULD be at earth potential unless there was a significant fault.

 

If you got a shock ftom the case that suggests it was live and not earthed and you provided a route to earth (e.g. via another bit of kit) OR something else was live and the synth/mixer were just routes to earth.

 

 

I wonder if there was an earth lift somewhere in the chain that allowed some kit to rise away from earth potential.

 

Hope you can sort this.

[mrtcat]

Last rehearsal we had was in 2023. Can't remember if it was good or bad but we're still gigging weekly so can't have been bad.

[tauzero]

  On 18/03/2025 at 13:16, Stub Mandrel said:

 

If the 9V adaptor is not earthed, it is possible for it to 'float' well above earth potential.  This can be made worse if their is tracking or some other fault that allows live potential on to its outputs.

 

But... if the mixer was plugged in and earthed the synth case SHOULD be at earth potential unless there was a significant fault.

 

If you got a shock ftom the case that suggests it was live and not earthed and you provided a route to earth (e.g. via another bit of kit) OR something else was live and the synth/mixer were just routes to earth.

 

 

I wonder if there was an earth lift somewhere in the chain that allowed some kit to rise away from earth potential.

 

Hope you can sort this.

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There isn't any route for live to the synth via the power adaptor. Conversely, there's no route to earth from the synth via the power adaptor. The livened up earth had to be from the mixer via the jack lead (as it only happened when I touched the metal-cased jack plugs or plugged in the jack lead and touched the case). Inside the synth case there is a bridge rectifier to allow power supplies of either polarity to be used followed by a 5V regulator to supply the Raspberry Pi. I don't think that there's anything I can do to sort this, it's the studio wiring or the mixer. 

[nilorius]

Just went back from my bands rehearsal. It was cool - we went through our 26.03.2025 gig repertoire and asked a rehearsals place manager to take 3 videos with sound with his iphone of our 3 songs.

[Stub Mandrel]

  On 18/03/2025 at 13:52, tauzero said:

There isn't any route for live to the synth via the power adaptor.

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An interesting discussion of a similar problem here:

https://www.diystompboxes.com/smfforum/index.php?topic=118696.0

 

Another possibility is that the PSU was plugged into a different phase than the mixer. Unlikely in a properly wired studio, but possible.

[tauzero]

  On 18/03/2025 at 22:20, Stub Mandrel said:

 

An interesting discussion of a similar problem here:

https://www.diystompboxes.com/smfforum/index.php?topic=118696.0

 

Another possibility is that the PSU was plugged into a different phase than the mixer. Unlikely in a properly wired studio, but possible.

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Why would the PSU being plugged into a different phase than the mixer have any effect when, as I have reiterated several times, the mains is completely isolated from the DC side of the PSU? I doubt that there is any AC leakage as the DC voltage is 9V, the AC voltage is 5mV. The sockets are on the same cable run anyway - adjacent double sockets separated by a metre or so.

 

I should add that the jack plugs on the jack-jack lead are these Neutrik ones

 

 

and I had very little contact with the metal part as I pushed it in by pushing on the plastic part - when I pulled the plug back out of the mixer after getting (I think) the second shock from the synth case, I held it by the plastic part. Had it been a fully metal plug, I think I'd have got the shock a lot earlier, before the synth was connected to it.

[Stub Mandrel]

I'm not arguing for the sake of it... I am genuinely trying to help. Having had a few close calls I sympathise.

 

My point is don't assume a low voltage supply is safe and isolated from the mains just because it is supposed to be. They can and do fail from time to time. You can't stop leakage by doubting it (and yes I have had a belt due to things like carbon tracking on a pcb allowing mains to trickle into the low voltage side... as it's "completely isolated" this doesn't trip the board...)

 

The phase issue sometimes occurs in large buildings where a three phase 440V supply is split to power more than one 240V ring main.  It's rare, but if happens.  If two items are powered from different phases you can get high differential voltages between them in the case of a fault.

 

Very low levels of leakage can build up enough charge to give you a belt without necessarily tripping an rcd. This seems to be what has happened here, suspect everything until the cause is found.

 

Also it may be the combination of different things that combine to make the problem.

 

Final thought... is there anything else that could have charged you up so the jack just provided a route to earth? Were you holding a bass or other instrument? I'll shut up now, after saying "don't assume anything is safe as there's a fault somewhere".

[MacDaddy]

Have you tried turning it off then turning it on again?

[mikebass456]

Sorry to interrupt! 

Our rehearsal last night went very well - just two more before the next gig on 5th April (day before singers birthday, so it could get a bit messy.....)

Finalised the setlist out, and ran through the ones most likely to trip one of us up, including the 2 newest ones not yet gigged (Stay Free by the Clash, and I'm Stranded by The Saints).

Usual gear - custom made shortscale LP  junior double cutaway and Orange Terror 500 with twin 2x10 and 2x 12 cabs 😎👍 

[tauzero]

Despite what people may think, I'm not arguing for the sake of it either. I want to find out what the problem is because I don't want a repeat, but there seems to be an insistence (not just by you) on focussing on the power adaptor which apparently works perfectly and has never generated a shock for me, and is also (and I think that this is crucial) electrically isolated from the chassis of the synth, whereas the mixer (an Alto) is connected to the mains with a 3-core lead. I can't remember the exact sequence of events though and I don't know whether the jack lead was live when it wasn't connected to the synth as I was handling the plug largely by the plastic part.

 

This is the synth innards - top left is the power socket. Both sides of the socket are insulated from the case - I made the mistake of using an uninsulated one once where the outer (+V in Boss power supply world) was thus connected to the chassis (0V in effects world), so I've never used that type again. Immediately inboard is a bridge rectifier, and then a DC-DC step-down regulator feeding the red and black wires leading to the PCB (just out of shot). The jack sockets are on the right - their grounds are connected to the chassis.

 

 

Next time we go, I'll take a mains integrity checker. The studio owner checked the sockets but AFAIK (certainly when I was there) only focussed on the socket that the power adaptor was plugged into, not the mixer.

 

I was holding a bass, but mains electricity doesn't travel over wireless links.

[Stub Mandrel]

  On 19/03/2025 at 18:20, tauzero said:

the power adaptor which apparently works perfectly and has never generated a shock for me, and is also (and I think that this is crucial) electrically isolated from the chassis of the synth ...
 Immediately inboard is a bridge rectifier, and then a DC-DC step-down regulator feeding the red and black wires leading to the PCB (just out of shot). The jack sockets are on the right - their grounds are connected to the chassis.

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Surely the psu is connected to the case of the synth via a continuous chain through circuit ground to the jack sockets to the case...?

[tauzero]

  On 19/03/2025 at 21:19, Stub Mandrel said:

 

Surely the psu is connected to the case of the synth via a continuous chain through circuit ground to the jack sockets to the case...?

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PSU -> bridge rectifier -> step-down DC-DC converter -> Raspberry Pi -> DAC -> jack sockets/case

 

I did continuity checking between all the pins on the PSU and both 9V and 0V on the power connector, and all were open circuit.

Edited March 20 by tauzero

[FretsOnFire]

Second rehearsal as a band yesterday and wow! That rush of jamming with others is like a drug and I want more

 

 

[Bagman]

Very good fun thanks 

[Franticsmurf]

5th knock with the new band - name as yet undecided - and it's still sounding good. We've run up a set list which varies from 'Does Your Mother Know' to 'Born To Be Wild' with side tracks to 'Superstition' and 'Games People Play' amongst others. The line up is drums, electric guitar, acoustic guitar and yours truly on bass. We all sing - them much better than me - so the potential is there for nice vocal harmonies. So far we've concentrated on getting familiar with each other's styles, finding the right mix of songs and, in the case of the acoustic guitarist, getting used to playing in a band (he's only ever played solo and then only a couple of times). We rehearse silently through a mixer and headphones and the recordings have been a great way to listen back in the cold light. So far, so good.

 

Next steps are to fix the arrangements and get a couple of rehearsals at full volume with backline etc at a local hall. Then it's gig time! 😀

[Rosie C]

I was invited to join an established folk band for a rehearsal last night, with a view to joining them. I've not played upright properly for a few months, and just before I found the G string has failed in some annoying buzzy way (notes on the G string buzz horribly, the same notes played on the D string are fine). Anyway, I was about first there, and set up with my trusty Crush 25B amp. There was accordion, violin, octave mandolin, clarinet, bodhran and washboard. The set list was a mixture of Morris dance tunes, Irish folk tunes and Klezmar. All went well - I kept it simple, mostly improvising, root-5'ing the chords with an occasional run on chord changes. 

[NoRhino]

  On 19/03/2025 at 11:01, mikebass456 said:

Sorry to interrupt! 

 

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Brilliant bass player humour. Made me smirk. 

[Mottlefeeder]

Reading the synth/mixer/shock sub thread, I wonder if the mixer connection was by jack or XLR, and whether the shock could have been caused by phantom power being connected to the signal lead in some way?

David