The future of preamps

Audiolab, what Atmasphere said about voltage levels is essentially correct (given my subsequent clarification), although his comment is most probably not applicable to the proprietary CAST interface that is provided on your amplifier.

For conventional (non-CAST) preamp outputs, the max output spec that for most high-end preamps is much greater than 4 volts represents the maximum output voltage they are CAPABLE of providing. That number SHOULD be much greater than the maximum output voltage they will ever be called upon to provide under reasonable input voltage conditions, in order to provide margin and assure good distortion performance.

For the non-CAST balanced input of your amp, the 3.58 volt sensitivity spec represents the approximate amount of input voltage that would cause the amp to put out its maximum rated output power (700/1400/2800 watts in this case(!), into 8/4/2 ohms respectively), assuming that spec is defined in the same manner that nearly all other amp manufacturers define it.

Most amps will be driven to their maximum rated power by inputs in the range of about 0.5 to 2.5 volts for unbalanced inputs, or around twice those numbers for balanced inputs. If you research the specs for amps from various manufacturers you will see that.

I have no knowledge of the voltage levels that the current-mode CAST interface operates at; perhaps the 18 volt figure you mentioned relates to that.

Regards,
-- Al

Hi Al, take a look at this link on DIYaudio:

http://www.diyaudio.com/forums/solid-state/161371-krell-current-audio-signal-transmission-c-s-t-current-mode-technology-cmt.html

Scroll down a little and you will see something very similar. I rather doubt that such a setup would see much in the way of voltage swing- current mode suggests that the current of the driver is being drawn through the interconnect cable from the receiver.

I agree that phonostages are here to stay. But it seems to me that digital sources with volume control, and various types of all-in-one products (including integrated amps) could marginalize the role of the preamp. The loss of transparency introduced by the preamp needs to be counterbalanced by other sonic benefits. Otherwise, the preamp is little more than a fancy switchbox.

I hope my preamp doesn't get wind of this conversation...nobody needs an angry component.

The loss of transparency introduced by the preamp needs to be counterbalanced by other sonic benefits.

Actually if the preamp is working right, most people experience an increase in transparency, not a loss. I have already mentioned one reason why; an additional one is that many digital controls don't work that well. So the digital device works better if run at full volume, run through an active line section and the preamp's volume control is used instead.