Headphone/PA with defined Ro

[mediatechnology]

Your defined Ro would need to compensate for deal that.

I'm still marveling over the complete lack of grammar. Ok, it was early...

There are a few more tricks that might be available.
2X 1646 in parallel provides a nice internal 12.5 Ohm build-out/current sense resistor.

I would look at a possible method of using one sense pin for CM drive and the second to sum feedback into the input.
There is a 10 pF to ground at that node which might be bothersome.
The absolute value of the resistances in the sense lines vary significantly, though they match closely. I don't know if they are trimmed or not.

[ricardo]

I'm still marveling over the complete lack of grammar. Ok, it was early...

Waddya expect from Rebel Colonial Yanks!

I'm looking at Gary Herbert's AES preprint to try & figure out what's inside 1600/1646.

The obvious comparison is with Benchmark Media's "0-Ohm" amp. http://www.benchmarkmedia.com/discuss/f ... dphone-amp

The Sony MDR-V6 example they use is actually one which would probably benefit a lot from current drive. It's supposed to be nominal 60R and their tests show 75Hz 0.6dB peak with Ro=30R. This should translate to a 1.9dB peak with current drive. The 300Hz & 3kHz impedance peaks will be about 0.6dB high with current drive.

I expect measured distortion of the Sony to be less overall and a lot better at 150Hz and 1.1kHz with current drive.

Another factor is the impedance suggests a lot(??) of electromagnetic damping on the Sony so it is likely, bass shy. Current drive would give more bass.

If a resonance is so bad that it shows an impedance peak of more than 1dB, current drive would be worse, simply cos you are driving the phones harder at those frequencies. Such a resonance would buzz/rattle even on a voltage sine sweep and indeed the impedance curve is the basis of one production test for buzz/rattle.

On the Sennheiser, I'd expect distortion to be less below 1kHz with current drive but it's likely the Sennheiser is lower distortion anyway, even with voltage drive.

Even more interesting would be to repeat his listening tests with current drive.

[mediatechnology]

Ricardo: Did you see how Rosalfonso used positive feedback (into a power op amp) to eliminate the current shunt monitor? That's the circuit I've seen over-and-over in the Design Ideas sections of EDN and Electronic Design for a high side grounded load current driver.

[ricardo]

Ricardo: Did you see how Rosalfonso used positive feedback (into a power op amp) to eliminate the current shunt monitor? That's the circuit I've seen over-and-over in the Design Ideas sections of EDN and Electronic Design for a high side grounded load current driver.

Yes I did. I'm only sorry I kun't reed ingish let alone Portuguese. I'm scratching my head to see how this can be converted to a defined Ro.