azaz44;574552 Wrote: > Why 75-100, is this volume SB3 control digital, thus reducing > resolution? The SB3 volume control is digital, but operates at 24 bit accuracy. This means that if your sources are 16 bit (eg. ripped from CDs), you can afford to apply 48dB of attenuation before losing any resolution in the digital domain. That would imply that you can use as much digital attenuation as you like (no need to worry about staying within the 75-100 range).
HOWEVER... the other effect of using digital attenuation is reduction of S/N ratio in the DAC. That is why many people recommend you keep the level fairly high, and why you should use attenuation such that with the SB3's volume control at 100, the music is as loud as you'll ever want. azaz44;574552 Wrote: > Maybe you can also explain me, how is it with impedance matching. I've > heard a lot of times, connecting power amp directly to the source using > passive attenuator is a good test for how the setup will sound, but an > active pre will make things much better because of proper impedance. > But as I see it, output impedance of active preamps and source are > similar. Is it a passive volume control which makes things wrong, or > how does it work. If I put a passive volume control in between, is it > like the output impedance of the source gets higher? Same with these > Rothwells? There are two reasons why you might care about impedance matching. One is to maximise the power transfer from source to load. In that case the output and input impedances should be the same. But in audio, we don't care about power transfer - what we're interested in is accurate voltage transfer across the frequency range. In that case, you ideally want to drive a high input impedance from a low output impedance. This is why source components such as SB3s, CD players and preamps have output impedances around the 100 - 1000 ohm mark, and power amps have input impedances of at least 10,000 ohms (usually more). If you add passive attenuation (in the form of a passive preamp, or simple resistor network such as the Rothwell devices), then you effectively increase the output impedance and lower the input impedance, thus narrowing the desirable gap between their values. But you'd have to do some pretty drastic attenuation before this would result in any audible effect on the frequency response. In my opinion the possible audible effects of passive attenuation are far far less than the distortions introduced by all but the very finest active preamps. Where people report that adding an active preamp has improved the sound, my money is on the preamp having added some euphonic distortions that the lisenter just happens to like. It's well understood that some mild to moderate even order harmonic distortion can give the impression of greater depth and "airyness" (hence some people's love of tube amps and vinyl records), but it's an illusion. -- cliveb Transporter -> ATC SCM100A ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=81664 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
