mrw wrote: > I think you may need to rethink what you mean by "colouring the sound". > The behaviour of the cartridge is determined by its mechanical and > electrical construction, and must be influenced by the electrical input > impedance of whatever it's connected to. "Coloration" is, therefore, > unavoidable, at least at a theoretical level, because what you record > will, of necessity, reflect this composite state of affairs.
This is an excellent point. Perhaps it would be more accurate to say that I'm trying to avoid any -additional- colo[u]ration. Until recently I used a hardware "re-equalizer" when digitizing 78s. It has a switch that allows the signal to simply pass through and the manufacturer swears that it's safe to leave inline when not being used because it does nothing. Unfortunately, despite that claim, it adds audible hiss. Not really a problem when the source material is a 78, but definitely not something I'd want to inject into a modern recording. That's part of what got me wondering if my phono pre-amp (which is definitely nothing fancy) is also potentially doing something undesireable, which in turn made me think about the possibility of simply not using one at all and "fixing it in post." mrw wrote: > Perhaps, also, you have have an adequate characterization of the actual > input impedance of your chosen input device. Then you might be able to > construct a digital filter that modifies your recorded input to reflect > what it would have been had your input device had the same impedance > that the manufacturer designed his cartridge to drive. Or any other > input impedance of your choosing. I have found a claim out there that the mic input impedance of my device (a Roland R-05) is 7,000 ohms. Phono cartridges generally want 47,000 ohms. It's nice to know that, but what I don't know is what the real-world ramifications of that mismatch are. Too many highs? Not enough highs? Something wildly non-linear that would be extremely difficult to fix via digital EQ? Unfortunately, while the EQ curves for RIAA and its predecessors are reasonably well-documented and easy to adjust, I have no clue where to begin to emulate additional impedance. I have no idea what the capacitance of that input is, though I deduce that higher capacitance = attenuated high frequencies. Back in the quadraphonic days it was important to have low-capacitance phono cables because CD-4 demodulation required absurdly high frequencies. In fact, it's also a desire to preserve some CD-4 records for potential maybe-some-day software decoding that makes me think about this project. I doubt my cheap phono pre-amp is passing 45kHz, though I suppose that I don't know that it isn't. Certainly my cartridge (an AT440MLa) is not rated for anything that crazy, but it actually will perfectly activate a CD-4 demodulator. Making it even more interesting, I've read (but have no idea if it's true) that impedance/capacitance can actually have a -mechanical- effect on the cartridge/stylus. If that's the case, I wonder if it's simply a bad idea to attempt to fix via software something that's traditionally done in hardware for a good reason. If I sound like I'm completely lost and am blindly theorizing about something I simply don't understand at all...well, I am! ------------------------------------------------------------------------ atrocity's Profile: http://forums.slimdevices.com/member.php?userid=16009 View this thread: http://forums.slimdevices.com/showthread.php?t=110295 _______________________________________________ ripping mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/ripping
