Discrete DI mod

[uncle]

Can this schematic be modified to work on single +48V?

It is from seventh circle audio web site

 

[s2udio]

48v what ? single to split rail or are you adding phantom power ?
Why do you need to ?

 

[ppa]

yes,

 

[uncle]

I want to build it in external small box and connect it to whatever preamp I want. So it would be nice to power via +48V from preamp. I'm not shure how to mod it to work with single +48V rail.

 

[abbey road d enfer]

It is somewhat possible to make it work more or less, but performance would not be very good.
You would need to adress the power consumption problem, and modify the power rail arrangement, and one side of the output stage would need modification. All this for a less than satisfactory result.
You'd be better off starting with the so-called Schoeps circuit, used in many condenser mics, which provides high input Z and low-Z balanced output.

 

[ppa]

yes, the currents should be reduced, it's possible use a single resistor between the trasistors' emitter to reduce the main quiescent current. But the problem might be the power on's spike at the di's outs that might generate an excessive current to the preamp's input trasformer charging the decupling caps on di outs. This current might magnetize this transformer. These decupling caps should be added to couple the existent di's outs to the di's out connector to avoid that the +48V goes into the bjt emitters. Infact, when the +48V goes in on state these caps are charged, but since the charging currents are different in these caps than there is a current in the input trasformer's primary and, this current, if high, might magnetize the trasformer.