Ld1014d question about noise

woody · 8th January 2021, 11:47 AM

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???

BesPav · 8th January 2021, 03:30 PM

Quote:

Originally Posted by Presidentovich

Is this an amplifier for speakers???

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 · 04:22 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

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

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

8th January 2021, 11:47 AM	#1
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	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 ?

8th January 2021, 01:53 PM	#5
Presidentovich diyAudio Member Join Date: Dec 2017	Is this an amplifier for speakers??? __________________ I don't understand what I am doing, but everything people are telling me is wrong

8th January 2021, 04:19 PM	#8
MarcelvdG diyAudio Member Join Date: Mar 2003 Location: Haarlem, the Netherlands	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. Last edited by MarcelvdG; 8th January 2021 at 04:22 PM.

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8th January 2021, 12:59 PM	#2
BesPav diyAudio Member Join Date: May 2011 Location: Russia, Moscow	What signal swing are desired? In the --someVolt range i suppose noise will not be the problem.

8th January 2021, 01:36 PM	#3
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	I was thinking about 5v 50 ma at 15v drain to source with a 500 ohm input source resistance at 1k hrz.

8th January 2021, 01:49 PM	#4
BesPav diyAudio Member Join Date: May 2011 Location: Russia, Moscow	For ~100 Ohm headphones?

8th January 2021, 03:38 PM	#7
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Familiar with the Zen8? PassDiy