Originally Posted by justanoldmuso
sounds like jfets are the way to go.
so for jfet circuits is bipolar power needed ?
just curious.
One of the handy things about JFETs is that, like valves, they're essentially self-biassing, because the gate (like grid on a valve/tube) can be at 0V and the source (like cathode on a valve/tube) rises until the voltage on the source causes the 0V on the gate to settle at the point where the gate starts to turn off the device. In both the FETHead and Cloudlifter CL-1 circuits, that's exactly how they bias. They both just use the +48V that already exists on the signal wires and they both use the current-limit resistors at their loads.

No special arrangements for power.

Where the circuits differ markedly is that the FETHead uses 50V parts and just drives the current-limit resistors directly, using two JFETs in parallel to reduce the noise a little more. The Cloudlifter in contrast uses a 40V JFET, so has to control the voltage on the drains, so uses a configuration usually known as cascade, where it stacks one JFET on top of another. That reduces the Voltage on the upper JFET's drain to 36V on a 48V system. Both circuits are therefore with their ratings on phantom power at 48V. One slight concern is that if the phantom is at the (allowed) 52V, both circuits go out of spec., however I rather doubt anyone now uses 52V.

FWIW, the Cloudlifter uses slightly noisier JFETs than the FETHead and whilst the FETHead parallels two to reduce the noise, I suspect((*) that the cascode arrangement does not do that. The cascode arrangement might, though, make the Cloudlifter slightly lower distortion, as it offers some negative feedback.

(*)I'd have to check or test and I'm not sure I could be bothered. I reckon the FETHead is 'typically' about 1dB quieter.

There is allegedly a DIY version of the Cloudlifter out there. I couldn't possibly comment.

Jazz relative beginner, starting at a much older age than was helpful.
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