Nobody's looked at the potential that I use all the time in my Susan blue boxes (active, with transformers, but a FET and two transistors rather than an op amp) of running on phantom power, and the option of a resistive ground as well as a total lift (for amps grounded locally) and solid ground through (for amps with no ground at all, keyboards with two pin power cords, and electric pickups going straight into the board, with no local amp. A 10 meg input impedance means it gives all the snap to bass pickups, or Fender Rhodes, and handles pietzo well, too (and can even be used with C-ducers ribbons). Whenever possible I try and reduce my dependence on batteries on stage.
Sounds comprehensive - what sort of transformers does it use? Given some of the previous posts I wouldn't dare ask if you had a schematic!
Well since this thread never seems to die I thought I might as well add some observations.
If you want some more detailed knowledge and circuits for MI or PA interfacing, there's nothing better than the Jensen site: JENSEN TRANSFORMERS, INC. - APPLICATION SCHEMATICS
To address chrispenycate's comment, here is an active DI box with all the bells and whistles (to defend my previous comment it is the 1st hit on a Google search):
at this site: Hansén Audio Gothenburg
If you want some more detailed knowledge and circuits for MI or PA interfacing, there's nothing better than the Jensen site: JENSEN TRANSFORMERS, INC. - APPLICATION SCHEMATICS
To address chrispenycate's comment, here is an active DI box with all the bells and whistles (to defend my previous comment it is the 1st hit on a Google search):
at this site: Hansén Audio Gothenburg
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The Jensen site has lots of goodies, this grabbed my attention:
http://www.jensen-transformers.com/as/as032.pdf
Wiring an ac wall wart to run 50mA ac through the ground circuit of equipment to test for internal grounding problems.
Plenty of other stuff too, what I've seen so far looks well written.
Nice one Leadbelly - thanks for shrinking the schematic too, or maybe my browser is just very slow.
http://www.jensen-transformers.com/as/as032.pdf
Wiring an ac wall wart to run 50mA ac through the ground circuit of equipment to test for internal grounding problems.
Plenty of other stuff too, what I've seen so far looks well written.
Nice one Leadbelly - thanks for shrinking the schematic too, or maybe my browser is just very slow.
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RF bypass of star earthing
Perhpas a bit tangential to DI boxes this, but one scheme I've seen suggested and used that seems to work well in guitar amps is as follows:
Use isolated sleeve input jack sockets (ie the usual plastic body ones). Connect the sleeve terminals of the jacks to the star point, but also to the chassis via 10 nF caps, thus avoiding ground loops inside the equipment, whilst minimising ingress of rf via the external cable screen.
Perhpas a bit tangential to DI boxes this, but one scheme I've seen suggested and used that seems to work well in guitar amps is as follows:
Use isolated sleeve input jack sockets (ie the usual plastic body ones). Connect the sleeve terminals of the jacks to the star point, but also to the chassis via 10 nF caps, thus avoiding ground loops inside the equipment, whilst minimising ingress of rf via the external cable screen.
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