IS this enough of a "D.I."

[Eddododo]

I can post a schematic if needed, but essentially I am thinking the AMZ mosfet booster more-or-less in 'buffer' mode using the phase-normal and inverted outputs of the fet, followed by an op-amp   buffer for each side.      I like the mosfet element because I find it to be super clean but to clip gracefully within reason. The op-amps are good ol' low impedance goodness. Perhaps two parallel buffers per 'side' a-la amz super-buffer.   What else should i squeeze in there for a solid d.i?    And can ground lift just be a spdt in series with ground, or does it take something more sophisticated?

I dont even need one, i was just bored thinking.

of course i have to consider dealing with phantom power and the likes

[bool]

you don't need opamp buffering. just use the fet as a phase-splitter. approx 2k2 in both drain and source will usually work from the get-go.

most probably you will ned a PAD (i.e. dual pad, each on the xlr outs) the outputs in 1:10 ratio.

a well chosen j-fet is going to yield lower noise than a mosfet ...

[Seljer]

Just take a dual opamp, run the first half as a non-inverting buffer (or make it add some amplification if you so desire), then use the second half as a inverting buffer, the input being taken from the output of the previous stage.
Add a couple of hundred ohms resistance on each output to mitigate and capacitive loading effects from long runs of cable, and slap on a big (++10uF) bipolar decoupling capacitor with an appropriate voltage rating (+60V) so you can't accidentally fry it with phantom power.

If you want to be add the ability to power it via phantom power this setup works fine: http://sound.westhost.com/project35.htm (the schematic at the bottom, but the way the opamps are used there make it more suitable for non-balanced low impedance signals or for taking the signal directly off a speaker)

[Eddododo]

you don't need opamp buffering. just use the fet as a phase-splitter. approx 2k2 in both drain and source will usually work from the get-go.

most probably you will ned a PAD (i.e. dual pad, each on the xlr outs) the outputs in 1:10 ratio.

a well chosen j-fet is going to yield lower noise than a mosfet ...

The idea was that op amps have much lower output impedance than fets.   You may be right about the jfets, especially at unity gain... ive some 2n5456 that make great buffers

Just take a dual opamp, run the first half as a non-inverting buffer (or make it add some amplification if you so desire), then use the second half as a inverting buffer, the input being taken from the output of the previous stage.
Add a couple of hundred ohms resistance on each output to mitigate and capacitive loading effects from long runs of cable, and slap on a big (++10uF) bipolar decoupling capacitor with an appropriate voltage rating (+60V) so you can't accidentally fry it with phantom power.

If you want to be add the ability to power it via phantom power this setup works fine: http://sound.westhost.com/project35.htm (the schematic at the bottom, but the way the opamps are used there make it more suitable for non-balanced low impedance signals or for taking the signal directly off a speaker)

Yea, I'm not a fan of opamp clipping,  and though I SHOULD be dealing with higher headroom than 9v but I still like the idea of any brand of fet clipping over op clipping,  worst case scenario.  Plus its more fun with fets

[Gus]

A sim idea I posted in the past, have not built it.

Just take a dual opamp, run the first half as a non-inverting buffer (or make it add some amplification if you so desire), then use the second half as a inverting buffer, the input being taken from the output of the previous stage.
Add a couple of hundred ohms resistance on each output to mitigate and capacitive loading effects from long runs of cable, and slap on a big (++10uF) bipolar decoupling capacitor with an appropriate voltage rating (+60V) so you can't accidentally fry it with phantom power.

If you want to be add the ability to power it via phantom power this setup works fine: http://sound.westhost.com/project35.htm (the schematic at the bottom, but the way the opamps are used there make it more suitable for non-balanced low impedance signals or for taking the signal directly off a speaker)

Is a good post

[bool]

at guitar level, you will most likely have to pad the outputs down, so the "lower output impedance with opamps" isn't much of a concern in this case anymore (a well proportioned pad will bring it down anyway). At least if you plan to DI into the mic inputs, which I took for granted.

If you planned to DI into the 10k line inputs, output impedance wouldn't be much of concern, but the output swing-ability would. Try to use some rail-to-rail opamps, like a TLC2272

A fet will sound more "organic" and have a better SN ratio in most cases (if you use a low-noise one). It will have slighltly less-than-half output swing-ability compared to an opamp, but usually good enough with guitar-level signals - at 9-12V supply.

[ashcat_lt]

Why would you have to pad down a guitar level input?  Especially on the "long" end of the cable?  Most microphone inputs have knobs that go at least down to unity, and no guitar signal is going to clip them.  I run line level signals into mic pres pretty regularly.

Honestly, the "true" balancing you're shooting for here might even be overkill.  You can usually "pseudo-balance" the output even more easily.  This way you don't even need a ground lift because the chassis aren't connected anyway.