Krell Current Audio Signal Transmission C.A.S.T. - Current mode Technology = CMT

[tiefbassuebertr]

Regarded Krell's very special connection technology I read this:

CAST (Current Audio Signal Transmission) is the name Krell has given to its novel analog connection scheme. In an ordinary audio system, signal is transmitted in the voltage domain and every component and connecting cable operates as a separate entity that interacts with the other system elements in its own peculiar way. Put as simply as possible, CAST takes advantage of Krell's Current Mode Technology (CMT) to transmit signal as current. This has several advantages -- for one thing, it causes the entire chain of CAST components to behave as if they were a single global circuit. Rather than dictating that the preamp's output be low and the power amplifier's impedance be high, which creates a situation where the interconnecting-cable's impedance can affect (even distort) the signal voltage operating the amplifier, CAST transfers current from a high-impedance source to a low-impedance load, minimizing (if not outright eliminating) the cable's effect on signal transmission. And, if you're using a CD player, the signal can be taken straight off the DACs without going through a I-to-V conversion stage. Krell claims CAST is responsible for a 6dB noise reduction alone.

For me it seems like high impedance output stages connected to low impedance input stages in common base resp. common gate - but what about the details?
Who knows more about the basic circuits concerning this connection in current mode?

[serraniruben]

Hi Tief,
I open my Krell KPS 25sc and see the board and cabling of the cast ouput.
Rubén

[scott wurcer]

Originally Posted by tiefbassuebertr

Regarded Krell's very special connection technology I read this:

CAST (Current Audio Signal Transmission) is the name Krell has given to its novel analog connection scheme. In an ordinary audio system, signal is transmitted in the voltage domain and every component and connecting cable operates as a separate entity that interacts with the other system elements in its own peculiar way. Put as simply as possible, CAST takes advantage of Krell's Current Mode Technology (CMT) to transmit signal as current. This has several advantages -- for one thing, it causes the entire chain of CAST components to behave as if they were a single global circuit. Rather than dictating that the preamp's output be low and the power amplifier's impedance be high, which creates a situation where the interconnecting-cable's impedance can affect (even distort) the signal voltage operating the amplifier, CAST transfers current from a high-impedance source to a low-impedance load, minimizing (if not outright eliminating) the cable's effect on signal transmission. And, if you're using a CD player, the signal can be taken straight off the DACs without going through a I-to-V conversion stage. Krell claims CAST is responsible for a 6dB noise reduction alone.

For me it seems like high impedance output stages connected to low impedance input stages in common base resp. common gate - but what about the details?
Who knows more about the basic circuits concerning this connection in current mode?

Standard industrial practice is to have a 4-20mA current loop for instrumentation in very noisy environments with long cable runs.

[knutn]

Many years ago I made what I called my active passive preamp. I moved my symmetrical JFET input transistors to an enclosure of their own (no power supply is needed!) and the connection to the power amp was done by XLR connections. So the result is high impedance drain output and low impedance common base input in a symmetrical manner. As suggested, the idea is not new; I think it was used in early data communication.

[ilimzn]

Hardly novel - Sony used it in it's first ES series (the 1980's one) with the name ACT, Audio Current Transfer. Essentially a current output with a resistor I-V conversion scheme at the input terminals.

[tiefbassuebertr]

Originally Posted by ilimzn

Hardly novel - Sony used it in it's first ES series (the 1980's one) with the name ACT, Audio Current Transfer. Essentially a current output with a resistor I-V conversion scheme at the input terminals.

That means, Krell did only invented the name for this newly.

But "Current Audio Signal Transmission" (C.A.S.T.) sounds more special in
advertisements than SONY's "Audio Current Transfer", which sounds rather commonly.

Independend of this - thanks to all for the advices.

Is this type of signal transfering in fact recommended ?
I have never check out this.

[carz]

Has anyone done a DIY Krell CAST cable ? I need to know the pin configuration, and the type of cable to use (cable characteristics and impedance)

By the way, the connector is made by Lemo (lemo.com)

[Telstar]

I have a very nice sounding krell cdp, which has among others a cast output which should be the current output of the dacs.
Which would be the best way to design a preamp input stage to take benefit from this?