rmorris

Copper or aluminium shielding won't really help with 50 Hz mains interference. But can help with harmonics resulting from its rectification - 100 Hz, 200Hz etc. And that is a lot of the mains hum you hear.

yeah - this stuff isn't easy if it's not your thing. And the sort of "half-information" eg in the Epiphan piece (I found it on their website) really doesn't help. There's a lot to unpack with Hi-Z / Lo-Z / Balanced / Unbalanced etc. I'm not going to do a full treatment here 🙂 But if you want technically excellent info I'd suggest looking up the work of Bill Whitlock (associated with Jensen transformers and THAT semiconductors). But a few quick points: Balanced audio can be any level. Obvs if going into a mic pre it needs to be fairly low level (or padded down at the input) to avoid clipping. Higher Impedance connections are more susceptible to external interference - so it is often worth trading level for a lower impedance (as with a DI transformer that presents a high Z to the source and a low Z to the mixing desk input etc). Contrary to what the article says - it is not necessary for a balanced connection to drive the two legs in anti-phase. Impedance matching on each leg is what matters wrt noise rejection (CMRR)

Yes. Commonly used on AC and DC outputs (it's termed a "DC Power Plug" but there's no actual electrical polarity to the plug itself).

Some nonsense here tbh. "when the cord length is under 10 feet, unbalanced cables actually have a stronger signal than balanced cables." What does that even mean ? What does "stronger" mean here ? level ? lower impedance (So lower susceptibility to interference) This is because at this length, any distortion is unlikely, and the simplicity of unbalanced cables can work wonders when there’s no detriment coming from potential distortion. For instance, mastering studios typically use unbalanced cables ranging between three and ten feet in length.".........."If you’re using a longer unbalanced cable on a loud device like a guitar, there won’t be a difference at all (vs balanced)" Witness #2 " most people have the impression that a balanced connection is superior because it is more resistant to external signal noise sources. While this is true, it does not necessarily mean that the balanced line is "better" than a single-ended cable"......"Under 10 feet unbalanced cables actually have a stronger signal than balanced cables. Great for low-level/gain signals like instruments"....(unbalanced is) effective at cable lengths up to 20-25 feet" By "distortion" I guess really talking about interference ? The mastering studio point is a mixed bag. I know some do but others do not. And if they do they have a very careful and thought out "Ground" scheme applied to a relatively simple audio setup.. Unlike what you get at any live gig type event. Level does not depend on cable type. "Under 10 feet unbalanced cables actually have a stronger signal than balanced cables." Errr...no in any sense 🙄

Yes. But I can see that it might be preferred to have a uniform thickness under the scratchplate for mechanical reasons so that it can sit true to the body. Whether significant depends on the thickness of the aluminium (in the Fender case illustrated).

It would be better to have the 'inside' of the area around the controls filled with the copper tape. Since otherwise it's a bit "open top". But the screening iun place should help a lot and you may think it's not a problem. But may as well fill it imo. Better is better.

Yes. The copper shielding needs continuity to the Screen (Ground) connection on the output jack. The bridge should already be connected to the jack socket screen connection (check it anyway with a continuity tester / DMM). So cavity to jack socket or to bridge will have same effect in practice. Without a connection the copper screen is just 'floating' electrically and effects are unpredictable.

I'd suggest that a good epoxy resin type adhesive / filler might be a better bet. "JB Weld" works well on metals. https://www.jbweld.co.uk/

phonos to 3.5mm jack cables are common.

Not necessarily. The kit may be designed to switch on/ off etc on successive momentary switch events. Eg most fx pedals use a momentary switch which toggles the fx on/off via a bit of hardware logic. See a schematic of eg a boss fx pedal.

Yes. But from a quick look it seems designed to work with other bits of Digitech kit. And there seem to be options on how you set those up to operate with the footswitch. ...And I see BigRedx and fleabag have commented alongg similar lines while I had to go do something else.

From not my work - seems uses diode logic to signal 3 x switch states https://www.pinterest.co.uk/pin/353884483200361260/

Understood. But it seems the unit was faulty. In bypass it shouldn't have a "sound". It's simply a high impedance op amp buffer direct to a balanced output circuit in parallel with an unbalanced output.Assuming output taken from XLR then there shouldn't be a problem unless it is connected to an unbalanced input (due to the topology of the output stage where one leg gets tied to 0V albeit via a build out resistor). Alternatively the internal jfet switching might have been faulty.

Was the sound / noise a problem with the BDI21 in bypass ? What was it plugged into ?

Old thread - but since you've chipped in now - what is the output stage detail. Buffered - so presumably low impedance - but is it impedance balanced. This is so simple to implement that it should be standard in a high quality product. It offers real advantages wrt CMRR.

Okay. I missed the date of the original post. Doh 🙄

Have to say that this topic seems to have become a tad overcomplicated. The OP has the "sound" required so just needs to translate it to a "balanced" (there are several 'flavours' of this) and possible attenuated low impedance output to feed a mixing desk or interface. The most accurate and likely least expensive way to do this is with an active DI solution. Many available. It's basically just a flat response circuit with some form of balanced output. Passive transformer solutions are also suitable but might get expensive if going for highest fidelity. But the inexpensive solutions will likely be fine if they have enough low frequency response. They will 'colour' the sound further but you may like that or not. They may also offer better CMRR but that is unlikely to be an issue unless you are running long signals in high noise environments eg OB truck etc. You could likely implement an effective impedance balanced output inside a (larger eg Neutrik) jack socket body by wiring in a resistor and optionally a capacitor). But if not into DIY then a commercial solution is a good option. For bass guitar top end isn't a thing. You don't really need to go to the expense of a Sowter / Jensen / Lundahl transformer based solution. Also look at the (UK based) Orchid Electronics DI options. I don't have personal experience but hear from reliable sources that they are very helpful.

What DI was the problematic active one ? was it set to flat / bypass ? A flat response clean active DI is one of the easiest circuits to implement tbh so seems something wrong there. Was it feeding a balanced mic or line input ?

Are you asking about cable from the power block to individual effects ? 1A is a lot of current for a single device ime.

There are mods to switch in/out both the mids cut and the "cab sim" elements of the BDI21. But what I'm suggesting is that the OP can simply use it in bypass. Used like this it's simply a clean DI. That seems comparable with the passive DI option being considered.

Not seeing the problem with the BDI21. Simply use it bypassed and you have an effective clean DI. As you would with a passive transformer DI. Except the input impedance will be more like your amp or pedal input. If you find it noisy like that then probably a fault or noisy power or gain staging problem. I have both the BDI21 and the Sansamp BDDI (older model). Apart from the less robust build, odd foot switch and lack of ability to run off P48 there's not much in it.

Yes.

The noise happens when your thumb is resting / brushing on the screw ? Sounds like that screw is not connected to the guitar's 'Ground'. I'm not familiar with that pickup / design in particular so don't know if it meant to be 'grounded' by design. But it's not uncommon to get scratching / brushing / rustling noises from isolated screws eg scratchplate screws. More typically more noticeable with electric guitars due to higher gain used. Similar can happen with plastic/nylon scratchplates over time where they get 'shiny' from wear and this causes static charges when touched. If you can make some contact from the pickup screws to 'ground' then the problem should go away. Alternatively you can try to reinstate the protection that the film was providing by coating with eg clear nail varnish or similar.

Yes. There's some element of shielding there. But it's mainly an issue of avoiding static noise when it gets "shiny" or you touch the screws. My basses tend not to have them but I often get this problem with Fender style guitars. High gain makes it a big problem. Have it in a nice Harley Benton atm. Need to shield and "ground" it.

No. Simply the client didn't know their technical stuff and didn't realise that they needed to use tape with a conductive adhesive if they weren't soldering the joints / seams.