Acoustic b260 mkII no DI

[nosaj]

Got an Acoustic b260 mkII with no DI. Not Finding a schematic anywhere on this.

Once I verify signal is going to the DI board and hitting the jrc4560d.

What I am supposed to see on the DI is 2 signals(one inverted) and a ground right?


Thanks,
nosaj

Also what protects a DI when it doesn't require the 48 phantom voltage? Input diodes

[J M Fahey]

Slightly confusing post

Got an Acoustic b260 mkII with no DI.

What does it mean: it has no DI output and youŽll build one or it has one which doesnŽt work?

Not Finding a schematic anywhere on this.
Once I verify signal is going to the DI board and hitting the jrc4560d.

Ok, supposing you do have a DI circuit (on its own miniboard?)youŽll have to check functionality.

Active DI are NOT true balanced and floating outputs which is what a transformer one does, but a simulation of it, sort of.

They are really one preamp out, maybe straight from preamp or going through an Op Amp, feeding pin 2; plus a unity gain inverting section, made out of an Op Amp connected as an inverter, with typically 10k and 10k NFB resistors, feeding XLR pin 3 .

So you have two Op Amp gain stages, one with gain=1 and the other with gain= -1 , feed signal and check how each one works on its own.

To begin with, each one must have 0V DC at its output pin.

Then if you feed it , say, 100mV RMS, you must find 100mV RMS at each output.
If not,trace signal path to see where itŽs lost.

Pin 1 may be directly grounded or separated from it with a switch called "Ground Lift", because ground is NOT required if device at other end is truly differential.

What I am supposed to see on the DI is 2 signals(one inverted) and a ground right?

See above: you must find original signal injected at each Op Amp output.
And of course nothing on ground.

If a sinewave, you wonŽt see "one is inverted", both will look like a plain sinewave.

Also what protects a DI when it doesn't require the 48 phantom voltage? Input diodes

??????
The balanced out stage does not *need* +48V 7mA , quite the contrary, but may fail or misbehave because of such voltage and current, so caps and resistors are essential, and diodes add protection.

[nosaj]

My apologies Juan. The DI was not outputting signal. They do recording with this amp so I thought it might be a possibility they connected the DI to a PA with phantom voltage engaged. But when I pulled the board out and started probing with the scope I found and electrolytic with a busted trace. Repaired trace and voila working DI now.

nosaj

[J M Fahey]

Oh, no need for apologies in any way.
Simply the first question was dubious and I asked for clarification.
Happy it works now