A proper head scratcher...

Bridgehouse

Ok, I'm stuck. Hmm. @ICBM might be a likely candidate..

So - Shuker fretless. Twin pickup system. In essence magnetic pickup wired to volume pot. Volume pot wired to Delano active preamp with mid pot and 3 band switch, and then treble/bass stacked pot. 

Output from preamp goes into a Ghost Acoustiphonic preamp for the bridge piezo pickups. Output from Ghost goes to a switchcraft TRS socket. It's wired as per Graphtech's diagram for a TRS:

http://www.graphtech.com/docs/default-document-library/trs-jack.pdf?sfvrsn=2

In that diagram my Delano sits in-between the volume hot out and the MAG input on the ghost. The Delano is powered from the Aux power out for active mag systems. 

Plug a normal cable in - silent. Plug my smooth hound in and I get a bit of wireless interference from time to time, but not much.

However - I just got a Boss WL20 today - plug that in, and I get a high-pitched whining (plus normal audio output too) - which according to internet wisdom is probably a ground being lifted somewhere which allows the digital clock to demodulate onto the audio line. 

Now, my suspicion is that as the Boss system has power supplied to it for charging via the ring on the plug, it's getting a grounding issue when plugged in to the TRS socket on the bass as it's wired to have the 18v ground onto Ring. The ghost system appears to work by having ring go to ground from the acoustiphonic (as per the diagram) to force mono mode, and then the battery on ring which allows it to be powered on and off when a jack is inserted. 

Now, apparently this is common with the Line 6 G10 - which uses a similar TRS jack and the ring is used for charging - the common fix there seems to be either a TRS male to TS female adapter or swap over ring and ground. I can't swap them as the graph tech doesn't like this.. 

The question is - 1. Would a 4 pole switchcraft help so I could wire it as per:

http://www.graphtech.com/docs/default-document-library/switched-barrel-jack.pdf?sfvrsn=2

which would separate ring and ground. However, the battery neg is still going to the jack - in the standard install to a standard stereo jack it goes to a lifted ground on the ghost board which is controlled by a FET and is connected to ground when a jack is inserted.

Or should I try something else? Frankly - I'm well confused now! 

axisus

Sorry, two sentences in and my head exploded. 

octatonic

Bridgehouse

Yeah I suspected my ramblings might be incoherent. 

Bridgehouse

axisus said:

Sorry, two sentences in and my head exploded. 

Pretty much like mine...

Bridgehouse

octatonic said:

Is that 9v or 18v?

octatonic

Bridgehouse said:

octatonic said:

Is that 9v or 18v?

I can make it 230v if you like.

Bridgehouse

octatonic said:

Bridgehouse said:

octatonic said:

Is that 9v or 18v?

I can make it 230v if you like.

Might need it at this rate - going to rip the whole electrics setup out and get it on the bench - though I doubt I’ll be able to spot the issue anyway

Funkfingers

To unpick this one, even ICBM is going to need photographs of the actual wiring in your actual bass.

Bridgehouse

Funkfingers said:

To unpick this one, even ICBM is going to need photographs of the actual wiring in your actual bass.

Yes. Going to take it all out and photograph in a bit

Funkfingers

Bridgehouse

Funkfingers said:

Well it *was* going to be

Bridgehouse

Ok. Pics time for the benefit of @funkfingers @ICBM @SteveRobinson and anyone else who might fancy a gander at my crap work!!

All innards removed - all that remains are the piezo wires going to a Summing board and the string ground which attaches to the others with a screw into the shield and body..



Heres the graphtech board for the labels:



And heres the actual loom labelled..

PhilKing

I'd be tempted to run the magnetic pickup to the jack without going through the Ghost.  Put the switch out of it too.  Then you only have to worry about the Piezo to ring wiring.

Bridgehouse

PhilKing said:

I'd be tempted to run the magnetic pickup to the jack without going through the Ghost.  Put the switch out of it too.  Then you only have to worry about the Piezo to ring wiring.

I did think about trying that and wiring a switch beforehand. I’m going to try with just Ghost first to see if it still does it so I can at least isolate which bit is the issue

Paul_C

One or two questions/suggestions; Can you test (or have you already tested) the mag/pre separately from the piezo to check they both work ?
Sometimes shielding can cause unexpected earths, though if it doesn't work taped to the desk then the shielding probably isn't the problem
What is the switch on the "mag vol" pot doing ? Is it wired right, or back to front?
What is the switch on the "piezo vol" pot doing? Is it wired right, or back to front?
I assume you've checked the batteries ?
Are you sure power is getting to both the preamps ?
What does that trim pot do ?
I assume both preamps like 18v?

The one thing I would do is test the magnetic pickup/pre first - you might be able to run them separately if needed using the on/on/on switch, running the out to the jack socket. .

Bridgehouse

Paul_C said:

One or two questions/suggestions; Can you test (or have you already tested) the mag/pre separately from the piezo to check they both work ?
Sometimes shielding can cause unexpected earths, though if it doesn't work taped to the desk then the shielding probably isn't the problem
What is the switch on the "mag vol" pot doing ? Is it wired right, or back to front?
What is the switch on the "piezo vol" pot doing? Is it wired right, or back to front?
I assume you've checked the batteries ?
Are you sure power is getting to both the preamps ?
What does that trim pot do ?
I assume both preamps like 18v?

The one thing I would do is test the magnetic pickup/pre first - you might be able to run them separately if needed using the on/on/on switch, running the out to the jack socket. .

Switch on mag/vol is active passive - works fine
Piezo vol switch is dark/bright - works fine
Batteries checked
Power def getting to both
Trim pot on ghost board just adjusts gain - no difference if trimmed
Both preamps confirmed as liking 18v

I've just removed the mag circuit completely so it's just ghost, vol, switch, and 18v and it still does the high pitched frequency whine - so it's the ghost and the wiring to the socket.

Bridgehouse

Interestingly if I hold the plastic body of the boss receiver, or the shield of the socket, it goes away.....

ICBM

Sorry, (you won't like this) I am very much of the opinion that all this sort of complexity and trying to get multiple incompatible active systems to work together is just a pain in the arse, and essentially what octatonic said pictorially...

But - does the Boss have a TRS plug on it? If so, do NOT put that into an active instrument which uses the jack ring to turn on the power - otherwise you're essentially connecting the two power supplies together, and depending on the voltages that could damage one of them as well as causing other problems. If it does, you will need a different type of jack with an electrically isolated switch to connect the battery circuit - a plain TRS power-switching jack must only be used with a mono plug.

Bridgehouse

ICBM said:

Sorry, (you won't like this) I am very much of the opinion that all this sort of complexity and trying to get multiple incompatible active systems to work together is just a pain in the arse, and essentially what octatonic said pictorially...

But - does the Boss have a TRS plug on it? If so, do NOT put that into an active instrument which uses the jack ring to turn on the power - otherwise you're essentially connecting the two power supplies together, and depending on the voltages that could damage one of them as well as causing other problems. If it does, you will need a different type of jack with an electrically isolated switch to connect the battery circuit - a plain TRS power-switching jack must only be used with a mono plug.

Yes that makes sense. Does the 4 prong switchcraft style barrel (which is essentially tip, ring, switch, shield) give an isolation or do I need an actual switch to isolate?

Bridgehouse

Just to answer your point about the multiple actives - the ghost is designed to work with others - and now I've removed it I'm still getting the issue - so it's def. the connection to ring that is the issue.