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-   -   Ld1014d question about noise (https://www.diyaudio.com/forums/solid-state/365776-ld1014d-question-noise.html)

woody 8th January 2021 11:47 AM

Ld1014d question about noise
 
In looking at this high power jfet I wonder if it might be suitable for a small low impedance source follower in the 50 to 100ma range. Does anyone know if it would be very noisy when used like that with a 500 ohm source impedance ?

BesPav 8th January 2021 12:59 PM

What signal swing are desired?
In the --someVolt range i suppose noise will not be the problem.

woody 8th January 2021 01:36 PM

I was thinking about 5v 50 ma at 15v drain to source with a 500 ohm input source resistance at 1k hrz.

BesPav 8th January 2021 01:49 PM

For ~100 Ohm headphones?

Presidentovich 8th January 2021 01:53 PM

Is this an amplifier for speakers??? :confused:

BesPav 8th January 2021 03:30 PM

Quote:

Originally Posted by Presidentovich (https://www.diyaudio.com/forums/solid-state/365776-ld1014d-question-noise-post6480428.html#post6480428)
Is this an amplifier for speakers??? :confused:

No.
50 mA idle current follower can't provide enough current to drive speakers.

jackinnj 8th January 2021 03:38 PM

Familiar with the Zen8? PassDiy

MarcelvdG 8th January 2021 04:19 PM

It has a high transconductance and it must have a large die area, so chances are its equivalent input voltage noise level will be quite low. Current noise will be low(*) as long as you reverse bias the gate, which will happen automatically at 50 mA to 100 mA.

(*): Regarding noise current, a smaller JFET will be even better, but you will only notice that at very high source impedances, like those of condenser microphone capsules without built-in amplifier.

jackinnj 13th January 2021 07:58 PM

1 Attachment(s)
Here's the Zen9 "noise" -- to get flat frequency response (into a 6 ohm passive load) I had to increase Vds to 2.12, and lower the current to 1.6A. Gain is 21dB.

I've run the LU1014 on its own, not yet satisfied with the results.

jackinnj 14th January 2021 06:28 PM

1 Attachment(s)
Here's the LU1014D all by itself, powered by Groner's ultra low noise current source (400pA/RtHz), adjusted to 50mA:


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