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B1 buffer with different fet
B1 buffer with different fet
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Old 9th November 2018, 04:03 PM   #1
cygnus x1 is offline cygnus x1  United States
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Default B1 buffer with different fet

Hi all, I hope this isn't a silly question, but can a B1 style buffer be built with different fets? I got a box full of J201 which are typically used as a low noise fet in guitar pedals. Not as quiet as the 2SK170 but respectable. The one thing I question is the lowish Idss of .2 to 1ma? The J203 is closer the K170, but the J201 is what I have to work with.
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Old 9th November 2018, 07:16 PM   #2
TungstenAudio is offline TungstenAudio  United States
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Not a silly question
However, the J201 has an Idss far too low to be of practical use in the B1 buffer circuit. Some parts you might try instead would be the 2N3819, J111, J112, or even the NTE452, NTE312 or NTE458. All of these parts have Idss ranges that are more in line with the 'B' series 2SK170, and also have reasonably low noise performance. You'll probably want to buy 10 or more of any given part to perform some Idss sorting.

Doing component substitution in the B1 will probably be best approached as a journey, rather than a quick solution. I would recommend finding a 3-pin socket that fits in the component footprint of the PCB. Once you have done some basic Idss matching, then your ears will need to be the final judge of performance.

The good news is that any of the parts I just listed also work fine in guitar pedals, depending somewhat on what kind of effect you're going for. Building effects pedals is another hobby of mine, and I've had good results especially with the NTE452 and NTE312.

Last edited by TungstenAudio; 9th November 2018 at 07:22 PM.
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Old 9th November 2018, 07:32 PM   #3
adason is offline adason  United States
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paralleling jfets should increase the Idss...
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Old Today, 01:57 PM   #4
cygnus x1 is offline cygnus x1  United States
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I've tried the NTE sub for the K170 (NTE 458 low noise) in a Salas preamp design, and they worked well. I did find some 2N5458 ( n ch depletion mode) and 2N5462 (p ch) in my junk box, so may give them a try. Not real sure of the changes needed... not a SS guy, I mostly build tube designs...lets see a tube B1 design!?!
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Old Today, 02:08 PM   #5
Zen Mod is offline Zen Mod  Serbia
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B1 buffer with different fet
half of tube constructions are predecessors of B1

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