I have been helping a friend build a balanced pre amp to go with his new balanced output Dac. He seems pleased with the improvement.
The pre does balanced out and so we said we ought to try balanced power amps.
I see some amps such as my Aleph 30 can do balanced input but one of the signals just gets connected to ground. The I saw the XA252 schematic where both phases of the balanced signal get treated the same with the same input filtering and buffering.
What would these two topologies be known as out of interest and what are any benefits or otherwise. I also thought we could convert his balanced output from preamp into SE with transformers before his power amps, but this surely has no benefit over just using an SE pre>SE power.? And to recollect the Aleph that connects one phase to ground....what is the benefit of connecting a balanced pre to an Aleph using XLR?
Another question being can we use 2 SE power channels to create a true (bridged?) balanced power amp?
Thanks
Jim
The pre does balanced out and so we said we ought to try balanced power amps.
I see some amps such as my Aleph 30 can do balanced input but one of the signals just gets connected to ground. The I saw the XA252 schematic where both phases of the balanced signal get treated the same with the same input filtering and buffering.
What would these two topologies be known as out of interest and what are any benefits or otherwise. I also thought we could convert his balanced output from preamp into SE with transformers before his power amps, but this surely has no benefit over just using an SE pre>SE power.? And to recollect the Aleph that connects one phase to ground....what is the benefit of connecting a balanced pre to an Aleph using XLR?
Another question being can we use 2 SE power channels to create a true (bridged?) balanced power amp?
Thanks
Jim
It is no problem to connect one input to ground, provided the impedance from that input to ground is the same (R and C) as the other input.
The definition of balanced is that all source output and receiving input impedances are equal. The signal itself can be anywhere with respect to ground (although it must be within the power supply voltage range of course).
The idea of balanced lines is to minimize or cancel noise and EMI ingress which requires equal impedances but not signals.
If you want symmetrical signals, same level with respect to ground, but opposite phase in the two lines, that might help to increase dynamic range but in audio is almost never used or necessary, and in itself does nothing to minimize noise/EMI.
Jan
The definition of balanced is that all source output and receiving input impedances are equal. The signal itself can be anywhere with respect to ground (although it must be within the power supply voltage range of course).
The idea of balanced lines is to minimize or cancel noise and EMI ingress which requires equal impedances but not signals.
If you want symmetrical signals, same level with respect to ground, but opposite phase in the two lines, that might help to increase dynamic range but in audio is almost never used or necessary, and in itself does nothing to minimize noise/EMI.
Jan
Last edited:
