The future of preamps

@ Atmasphere, Hi, I do apoligize for my post, However, I am correct with the pre-amps of krell, I am only saying what they told me on phone, on their site, it only gives out put over load specs of all the current pre-amps of 8 to 16 volts out-put, regarless, because of the gain a pre-amp gives, I believe I need a pre-amp to drive my Krell 700cx to full capacity!, I enjoy your post, and appreciate your input here,I run balanced, so the 16 volts out-put is over load, thats why krell told me pending on an older pre-amp or newer, 6 to 8 volts out-put is the norm for a krell pre-amp balanced out put, thankyou.

@ Atmasphere, Hi, your name would not happen to be Ralph would it?, Are you in relation to the atmas-phere audio company?, pending on the answers here, if you are, I do have many questions I hope you take the time to help me with., cheers.

12-13-13: Audiolabyrinth
@ Atmasphere, Hi, your name would not happen to be Ralph would it?, Are you in relation to the atmas-phere audio company?

LOL! Yes, Keith, meet Ralph Karsten, Founder and Owner of Atma-Sphere music systems.

Audiolabyrinth, Krell states that the gain of their amps is only about 25db. FWIW that is quite unusual (I had assumed their gain to be a more typical 30db), so in a high power amplifier you would indeed need more than 4 volts to full output. The spec on your amp is 3.58 volts for full output, so your amp probably makes right around 500 watts, assuming a similar gain structure.

The industry standard is 1 volt FWIW; that standard is really eroded at this point. However, most audiophiles do not push their amps to full output all the time- you still have to knock down the signal from a digital source if you want to use it. So a preamp is still useful.

The specs indicated in the manual for the Krell 700cx are 3.58 volt sensitivity (for its balanced input), 26.4 db gain, 700/1400/2800 watts into 8/4/2 ohms respectively.

26.4 db is a voltage gain of 20.89, based on db = 20log(Vout/Vin).
20.89 x 3.58 = 74.79 volts.
(74.79 squared)/8 = 699 watts into 8 ohms, corresponding almost exactly to the 700 watt rating.
Double that into 4 ohms (= 1398 watts), and double it again into 2 ohms (= 2796 watts). The results again correspond almost exactly to the rated power capabilities.

Ralph, I think you were right in the first place!

Concerning Keith's reference to "3.58 volts min," that is probably the result of a miscommunication. Sensitivity specs are usually neither min nor max, they are simply the (approximate) input voltage required to drive an amp to its rated maximum output power. And based on these calculations, that certainly appears to be the case here.

Regards,
-- Al