balanced Xover

[Stefano]

One thing i've never seen is a balanced Xover, a really symmetrical circuit, not one with input or output connectors balanced, but one withthe two halves +/- equally amplified and crossed, have you ever seen? Any info?
Dreaming of a totally balanced audio chain...

[Stefano]

Obviously i mean active crossover...

[jackinnj]

TI's FilterPro software has "fully differential" filter design capability. You can download it from TI's website www.ti.com

[Stefano]

Tank you very much jackinnj, is exactly what i've in my mind!

[carlmart]

Originally posted by Stefano
One thing i've never seen is a balanced Xover, a really symmetrical circuit, not one with input or output connectors balanced, but one withthe two halves +/- equally amplified and crossed, have you ever seen? Any info?
Dreaming of a totally balanced audio chain...

It may not be that easy. Once I did some research, as I was looking for a balanced filter for microphones. The problem is that you would need at least two differential stages, input and output, plus the others in between to do the filtering.

The TI example shows a balanced chip driving an ADC, and TI probably designed both stages to work as one, because most input diff chips have little driving force.

The next thing is that parts have to be very precise for + and - halves, or CMMR will suffer. We are talking 0.1% precision here, which may not be that easy to get on caps.

IMHO you might be better doing the filtering non-balanced, with differential input and output stages.

It would be nice to know of other approaches.


Carlos

[jackinnj]

Originally posted by carlmart


The next thing is that parts have to be very precise for + and - halves, or CMMR will suffer. We are talking 0.1% precision here, which may not be that easy to get on caps.

If you download the TI software you will see that you can specify the tolerances -- E12, E24, E48, E96, E192 and Exact for resistors, E6, E12 and E24 for capacitors and model the performance. At any speed, smt resistors have very high acuracy, but I don't know if there are "audio quality" precision caps for filters in SMT.