Passively splitting a pickup's signal output?

[peskywinnets]

but at just 20mA output ability, that's not enough current delivery for a dual rail power amp :-( it might just get away supplying a headphone amp - but nothing with a speaker connected (which will be the end of the signal chain)

[cbarrow7625]

OK, that clarifies what you are trying to accomplish. Thanks. So, in whatever you are trying to do, why would 90 degrees of phase shift make a difference? Do the circuits after the guitar signal is split have the exact same phase response? Is there a practical problem with the small phase shift (i.e., outputs would not sum as planned) or a philosophical one (i.e., eliminating any phase shift must be "better" and an "improvement")?

[Steve Conner]

If phase shift across the coupling cap is a problem, just make the cap bigger until it isn't a problem. If you make the 3dB breakpoint a factor of 10 lower than the lowest frequency of interest, then the phase shift at that frequency will be 5 degrees, IIRC.

Transformers have phase shift too: the transformer's magnetizing inductance forms a L-R highpass filter with the source impedance, directly analogous to the R-C highpass filter you get with a DC block cap and the load impedance.

It's more expensive to reduce a transformer's phase shift, because you need a bigger core of more boutique material, as opposed to just buying a bigger capacitor.

[David Schwab]

Since the pickups are going to feed an active circuit anyway, I don't see the point it wanting to do this passively. You will have a single input to the active splitter, and the two outputs will be in the phase.

As far as DC blocking caps, if there is DC present at the input of the circuit, you don't want that going to your guitar.

[Rick Turner]

Look into "DC Coupled" circuits in which the power supply is servo controlled. That automatically takes any DC offset to zero by correcting the plus or minus rails based on monitoring the output. My pal Bob Wolstein has done some amazing DC coupled circuits, and if you then play through a truly fully DC coupled system (think stupidly expensive audiophile stuff...), you can get frequency response down to the sub 10 Hz range...or lower. Of course most of the stuff under 30 Hz is expensive noise (think ridiculous non-musical cone excursions!), but it's very illuminating to have the experience of playing through such a system.

[Rick Turner]

One other observation...

This passive vs. active thing is a false debate. If you're playing an electric guitar or bass, you're active. The only issues are where you have your first active stage (basically which end of the cable it's to be found) and how much trouble the passive side is giving you in terms of impedance matching. It IS possible to preserve what you like about passive circuits without being tied to their disadvantages. It just takes good clean buffering and a knowledge of what load impedance(s) you'd like your pickup(s) to "see".

[Rick Turner]

And one more...

With the Alembic's and then the Dead's PA system, all mics and the few direct boxes we used were set up with high quality transformer splitters so we could send the same signal to the recording truck as went to the PA. No problem.

BTW, we also met a guy who did a lot of live big band recording who actually ran several pairs of dynamic mics in series so he could have more mics than inputs to his 1" eight track tape machine. Worked amazingly well...

[David Schwab]

If you're playing an electric guitar or bass, you're active. The only issues are where you have your first active stage...

I've quoted you saying that for a while now when people start talking about how passive instruments are more "organic" sounding. I never understood how an electronic guitar or bass would be passive, or organic sounding.