Non-Phool jellybean audio-frequency JFET

Trying to pick a JFET that's still being made with reasonable low noise 
characteristics for simple audio preamp type duties. No golden-ear BS, 
just things that can be measured. Mic preamps, instrument pickup 
preamps, a FET to have in the junkbox for unknown things yet to be 
cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap 
would be even better ;-) Old-fashioned packaging would be nice, but its 
unlikely these days, I think.

Mouser has one item that comes up with Audio JFET (that's not a jfet 
input something else...) Audio FET gets a few more, but most are class D 
power devices.

Toshiba 2SK880 in "irritatingly tiny" package. Par for the course these 
days and I have adapted to soldering irritatingly tiny if I have no 
other choice in packaging. 43 cents for 1, $29.50 for 100 Looks to be 5 
years old judging by the datasheet date.

One that is mentioned in some older web circuits that's still marginally 
available (in the 150% larger SOT23 only) is the J201, which seems to 
have somewhat worse noise numbers. 23 cents for 1, $21.90 for 100, and 
all of its relatives in other packages are already obsolete, so it may 
not be long for this world, either?

Digi-key's search is as usual near useless (or it and I search 
differently), and Newark comes up with a bunch of class-D power fets 
that probably won't like non-switching use (If I have even a vaguely 
correct recollection of what "class D audio amp" means. Looks like I do 
per 5 seconds of checking my memory)

There are of course lots of RF parts that have no specs below 100Khz, or 
1 Mhz, or 1 Ghz, depending on part. Perhaps some of them work fine for 
audio. Anyone care to clue me in?

-- 
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Ecnerwal wrote:
> 
> Trying to pick a JFET that's still being made with reasonable low noise
> characteristics for simple audio preamp type duties. No golden-ear BS,
> just things that can be measured. Mic preamps, instrument pickup
> preamps, a FET to have in the junkbox for unknown things yet to be
> cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
> would be even better ;-) Old-fashioned packaging would be nice, but its
> unlikely these days, I think.
> 
> Mouser has one item that comes up with Audio JFET (that's not a jfet
> input something else...) Audio FET gets a few more, but most are class D
> power devices.
> 
> Toshiba 2SK880 in "irritatingly tiny" package. Par for the course these
> days and I have adapted to soldering irritatingly tiny if I have no
> other choice in packaging. 43 cents for 1, $29.50 for 100 Looks to be 5
> years old judging by the datasheet date.
> 
> One that is mentioned in some older web circuits that's still marginally
> available (in the 150% larger SOT23 only) is the J201, which seems to
> have somewhat worse noise numbers. 23 cents for 1, $21.90 for 100, and
> all of its relatives in other packages are already obsolete, so it may
> not be long for this world, either?
> 
> Digi-key's search is as usual near useless (or it and I search
> differently), and Newark comes up with a bunch of class-D power fets
> that probably won't like non-switching use (If I have even a vaguely
> correct recollection of what "class D audio amp" means. Looks like I do
> per 5 seconds of checking my memory)
> 
> There are of course lots of RF parts that have no specs below 100Khz, or
> 1 Mhz, or 1 Ghz, depending on part. Perhaps some of them work fine for
> audio. Anyone care to clue me in?
> 
> --
> Cats, coffee, chocolate...vices to live by
> Please don't feed the trolls. Killfile and ignore them so they will go away.

A few BF862s in parallel, for choice.  About 0.8 nV 1-Hz noise in the
flatband, 1/f corner around 1 kHz.

Cheers

Phil Hobbs
-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

On Aug 20, 12:33=A0pm, Ecnerwal
<MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> Trying to pick a JFET that's still being made with reasonable low noise
> characteristics for simple audio preamp type duties. No golden-ear BS,
> just things that can be measured. Mic preamps, instrument pickup
> preamps, a FET to have in the junkbox for unknown things yet to be
> cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
> would be even better ;-) Old-fashioned packaging would be nice, but its
> unlikely these days, I think.
>
> Mouser has one item that comes up with Audio JFET (that's not a jfet
> input something else...) Audio FET gets a few more, but most are class D
> power devices.
>
> Toshiba 2SK880 in "irritatingly tiny" package. Par for the course these
> days and I have adapted to soldering irritatingly tiny if I have no
> other choice in packaging. 43 cents for 1, $29.50 for 100 Looks to be 5
> years old judging by the datasheet date.
>
> One that is mentioned in some older web circuits that's still marginally
> available (in the 150% larger SOT23 only) is the J201, which seems to
> have somewhat worse noise numbers. 23 cents for 1, $21.90 for 100, and
> all of its relatives in other packages are already obsolete, so it may
> not be long for this world, either?
>
> Digi-key's search is as usual near useless (or it and I search
> differently), and Newark comes up with a bunch of class-D power fets
> that probably won't like non-switching use (If I have even a vaguely
> correct recollection of what "class D audio amp" means. Looks like I do
> per 5 seconds of checking my memory)
>
> There are of course lots of RF parts that have no specs below 100Khz, or
> 1 Mhz, or 1 Ghz, depending on part. Perhaps some of them work fine for
> audio. Anyone care to clue me in?
>
> --
> Cats, coffee, chocolate...vices to live by
> Please don't feed the trolls. Killfile and ignore them so they will go aw=
ay.

OPA2134?  ~$2 at the 100 quant.  8nV/rtHz, (only 8MHz)

George H.

On Aug 20, 12:33=A0pm, Ecnerwal
<MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> Trying to pick a JFET that's still being made with reasonable low noise
> characteristics for simple audio preamp type duties. No golden-ear BS,
> just things that can be measured. Mic preamps, instrument pickup
> preamps, a FET to have in the junkbox for unknown things yet to be
> cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
> would be even better ;-) Old-fashioned packaging would be nice, but its
> unlikely these days, I think.
>
> Mouser has one item that comes up with Audio JFET (that's not a jfet
> input something else...) Audio FET gets a few more, but most are class D
> power devices.
>
> Toshiba 2SK880 in "irritatingly tiny" package. Par for the course these
> days and I have adapted to soldering irritatingly tiny if I have no
> other choice in packaging. 43 cents for 1, $29.50 for 100 Looks to be 5
> years old judging by the datasheet date.
>
> One that is mentioned in some older web circuits that's still marginally
> available (in the 150% larger SOT23 only) is the J201, which seems to
> have somewhat worse noise numbers. 23 cents for 1, $21.90 for 100, and
> all of its relatives in other packages are already obsolete, so it may
> not be long for this world, either?
>
> Digi-key's search is as usual near useless (or it and I search
> differently), and Newark comes up with a bunch of class-D power fets
> that probably won't like non-switching use (If I have even a vaguely
> correct recollection of what "class D audio amp" means. Looks like I do
> per 5 seconds of checking my memory)
>
> There are of course lots of RF parts that have no specs below 100Khz, or
> 1 Mhz, or 1 Ghz, depending on part. Perhaps some of them work fine for
> audio. Anyone care to clue me in?
>
> --
> Cats, coffee, chocolate...vices to live by
> Please don't feed the trolls. Killfile and ignore them so they will go aw=
ay.

Hey, I was leafing through electronic design at lunch, and thought of
you when I saw an add for Jfets from linear systems.
(linearsystems.com)

George H.

George Herold wrote:
> 
> On Aug 20, 12:33 pm, Ecnerwal
> <MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> > Trying to pick a JFET that's still being made with reasonable low noise
> > characteristics for simple audio preamp type duties. No golden-ear BS,
> > just things that can be measured. Mic preamps, instrument pickup
> > preamps, a FET to have in the junkbox for unknown things yet to be
> > cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
> > would be even better ;-) Old-fashioned packaging would be nice, but its
> > unlikely these days, I think.
> >
> > Mouser has one item that comes up with Audio JFET (that's not a jfet
> > input something else...) Audio FET gets a few more, but most are class D
> > power devices.
> >
> > Toshiba 2SK880 in "irritatingly tiny" package. Par for the course these
> > days and I have adapted to soldering irritatingly tiny if I have no
> > other choice in packaging. 43 cents for 1, $29.50 for 100 Looks to be 5
> > years old judging by the datasheet date.
> >
> > One that is mentioned in some older web circuits that's still marginally
> > available (in the 150% larger SOT23 only) is the J201, which seems to
> > have somewhat worse noise numbers. 23 cents for 1, $21.90 for 100, and
> > all of its relatives in other packages are already obsolete, so it may
> > not be long for this world, either?
> >
> > Digi-key's search is as usual near useless (or it and I search
> > differently), and Newark comes up with a bunch of class-D power fets
> > that probably won't like non-switching use (If I have even a vaguely
> > correct recollection of what "class D audio amp" means. Looks like I do
> > per 5 seconds of checking my memory)
> >
> > There are of course lots of RF parts that have no specs below 100Khz, or
> > 1 Mhz, or 1 Ghz, depending on part. Perhaps some of them work fine for
> > audio. Anyone care to clue me in?
> >
> > --
> > Cats, coffee, chocolate...vices to live by
> > Please don't feed the trolls. Killfile and ignore them so they will go away.
> 
> Hey, I was leafing through electronic design at lunch, and thought of
> you when I saw an add for Jfets from linear systems.
> (linearsystems.com)
> 
> George H.

BF862s, really.  They're the cat's pajamas.

Cheers

Phil Hobbs
-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

On 8/22/2012 1:45 PM, Phil Hobbs wrote:
> George Herold wrote:
>>
>> On Aug 20, 12:33 pm, Ecnerwal
>> <MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
>>> Trying to pick a JFET that's still being made with reasonable low noise
>>> characteristics for simple audio preamp type duties. No golden-ear BS,
>>> just things that can be measured. Mic preamps, instrument pickup
>>> preamps, a FET to have in the junkbox for unknown things yet to be
>>> cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
>>> would be even better ;-) Old-fashioned packaging would be nice, but its
>>> unlikely these days, I think.


>
> BF862s, really.  They're the cat's pajamas.
>
> Cheers
>
> Phil Hobbs
>

   Just because I was curious I searched BF862 preamp and found a
high performance phono stage that uses 8 parallel BF862s.

http://www.synaesthesia.ca/LNschematics.html

3/4 downpage

I'm clueless as to whether it is a good circuit.

           Mikek

amdx wrote:
> 
> On 8/22/2012 1:45 PM, Phil Hobbs wrote:
> > George Herold wrote:
> >>
> >> On Aug 20, 12:33 pm, Ecnerwal
> >> <MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> >>> Trying to pick a JFET that's still being made with reasonable low noise
> >>> characteristics for simple audio preamp type duties. No golden-ear BS,
> >>> just things that can be measured. Mic preamps, instrument pickup
> >>> preamps, a FET to have in the junkbox for unknown things yet to be
> >>> cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
> >>> would be even better ;-) Old-fashioned packaging would be nice, but its
> >>> unlikely these days, I think.
> 
> >
> > BF862s, really.  They're the cat's pajamas.
> >
> > Cheers
> >
> > Phil Hobbs
> >
> 
>    Just because I was curious I searched BF862 preamp and found a
> high performance phono stage that uses 8 parallel BF862s.
> 
> http://www.synaesthesia.ca/LNschematics.html
> 
> 3/4 downpage
> 
> I'm clueless as to whether it is a good circuit.
> 
>            Mikek

BF862s parallel just fine.   But for audio, even just one is better than
good enough.  There's no need for subnanovolt noise in audio.

Cheers

Phil Hobbs
-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

On Aug 22, 2:45=A0pm, Phil Hobbs
<pcdhSpamMeSensel...@electrooptical.net> wrote:
> George Herold wrote:
>
> > On Aug 20, 12:33 pm, Ecnerwal
> > <MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> > > Trying to pick a JFET that's still being made with reasonable low noi=
se
> > > characteristics for simple audio preamp type duties. No golden-ear BS=
,
> > > just things that can be measured. Mic preamps, instrument pickup
> > > preamps, a FET to have in the junkbox for unknown things yet to be
> > > cobbled in the small-signal audio range. Cheap is also good. Jeorg ch=
eap
> > > would be even better ;-) Old-fashioned packaging would be nice, but i=
ts
> > > unlikely these days, I think.
>
> > > Mouser has one item that comes up with Audio JFET (that's not a jfet
> > > input something else...) Audio FET gets a few more, but most are clas=
s D
> > > power devices.
>
> > > Toshiba 2SK880 in "irritatingly tiny" package. Par for the course the=
se
> > > days and I have adapted to soldering irritatingly tiny if I have no
> > > other choice in packaging. 43 cents for 1, $29.50 for 100 Looks to be=
 5
> > > years old judging by the datasheet date.
>
> > > One that is mentioned in some older web circuits that's still margina=
lly
> > > available (in the 150% larger SOT23 only) is the J201, which seems to
> > > have somewhat worse noise numbers. 23 cents for 1, $21.90 for 100, an=
d
> > > all of its relatives in other packages are already obsolete, so it ma=
y
> > > not be long for this world, either?
>
> > > Digi-key's search is as usual near useless (or it and I search
> > > differently), and Newark comes up with a bunch of class-D power fets
> > > that probably won't like non-switching use (If I have even a vaguely
> > > correct recollection of what "class D audio amp" means. Looks like I =
do
> > > per 5 seconds of checking my memory)
>
> > > There are of course lots of RF parts that have no specs below 100Khz,=
 or
> > > 1 Mhz, or 1 Ghz, depending on part. Perhaps some of them work fine fo=
r
> > > audio. Anyone care to clue me in?
>
> > > --
> > > Cats, coffee, chocolate...vices to live by
> > > Please don't feed the trolls. Killfile and ignore them so they will g=
o away.
>
> > Hey, I was leafing through electronic design at lunch, and thought of
> > you when I saw an add for Jfets from linear systems.
> > (linearsystems.com)
>
> > George H.
>
> BF862s, really. =A0They're the cat's pajamas.
>
> Cheers
>
> Phil Hobbs
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC
> Optics, Electro-optics, Photonics, Analog Electronics
>
> 160 North State Road #203
> Briarcliff Manor NY 10510
> 845-480-2058
>
> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted tex=
t -
>
> - Show quoted text -

Geesh Phil, I don't know.  Mostly I can't tell the difference between
a Jfet and a J stroke.

(They've got BF862's at newark for ~$0.30/100)
... I might have a use for a 0.8nV Fet.   Where's the 1/f knee?
At the moment it's a ~10kHz resonace, but I could move that up, some.

George H.

On Aug 22, 4:39=A0pm, Phil Hobbs
<pcdhSpamMeSensel...@electrooptical.net> wrote:
> amdx wrote:
>
> > On 8/22/2012 1:45 PM, Phil Hobbs wrote:
> > > George Herold wrote:
>
> > >> On Aug 20, 12:33 pm, Ecnerwal
> > >> <MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> > >>> Trying to pick a JFET that's still being made with reasonable low n=
oise
> > >>> characteristics for simple audio preamp type duties. No golden-ear =
BS,
> > >>> just things that can be measured. Mic preamps, instrument pickup
> > >>> preamps, a FET to have in the junkbox for unknown things yet to be
> > >>> cobbled in the small-signal audio range. Cheap is also good. Jeorg =
cheap
> > >>> would be even better ;-) Old-fashioned packaging would be nice, but=
 its
> > >>> unlikely these days, I think.
>
> > > BF862s, really. =A0They're the cat's pajamas.
>
> > > Cheers
>
> > > Phil Hobbs
>
> > =A0 =A0Just because I was curious I searched BF862 preamp and found a
> > high performance phono stage that uses 8 parallel BF862s.
>
> >http://www.synaesthesia.ca/LNschematics.html
>
> > 3/4 downpage
>
> > I'm clueless as to whether it is a good circuit.
>
> > =A0 =A0 =A0 =A0 =A0 =A0Mikek
>
> BF862s parallel just fine. =A0 But for audio, even just one is better tha=
n
> good enough. =A0There's no need for subnanovolt noise in audio.
>
> Cheers
>
> Phil Hobbs
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC
> Optics, Electro-optics, Photonics, Analog Electronics
>
> 160 North State Road #203
> Briarcliff Manor NY 10510
> 845-480-2058
>
> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted tex=
t -
>
> - Show quoted text -

You 'pay' 10pF of input C for each one.

(According to the 'one' npx spec sheet I looked at.)

George H.

George Herold wrote:
> 
> On Aug 22, 4:39 pm, Phil Hobbs
> <pcdhSpamMeSensel...@electrooptical.net> wrote:
> > amdx wrote:
> >
> > > On 8/22/2012 1:45 PM, Phil Hobbs wrote:
> > > > George Herold wrote:
> >
> > > >> On Aug 20, 12:33 pm, Ecnerwal
> > > >> <MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:
> > > >>> Trying to pick a JFET that's still being made with reasonable low noise
> > > >>> characteristics for simple audio preamp type duties. No golden-ear BS,
> > > >>> just things that can be measured. Mic preamps, instrument pickup
> > > >>> preamps, a FET to have in the junkbox for unknown things yet to be
> > > >>> cobbled in the small-signal audio range. Cheap is also good. Jeorg cheap
> > > >>> would be even better ;-) Old-fashioned packaging would be nice, but its
> > > >>> unlikely these days, I think.
> >
> > > > BF862s, really.  They're the cat's pajamas.
> >
> > > > Cheers
> >
> > > > Phil Hobbs
> >
> > >    Just because I was curious I searched BF862 preamp and found a
> > > high performance phono stage that uses 8 parallel BF862s.
> >
> > >http://www.synaesthesia.ca/LNschematics.html
> >
> > > 3/4 downpage
> >
> > > I'm clueless as to whether it is a good circuit.
> >
> > >            Mikek
> >
> > BF862s parallel just fine.   But for audio, even just one is better than
> > good enough.  There's no need for subnanovolt noise in audio.

> You 'pay' 10pF of input C for each one.
> 
> (According to the 'one' npx spec sheet I looked at.)
> 
> George H.

Right, but this is audio after all.  I use them in boatloads to make
photodiode bootstraps that work up to ~20 MHz.  You put a good-quality
current source in the sources, which gets rid of Cgs pretty well, and
then bootstrap the drains to get rid of Cdg and Cds.   You still get the
voltage noise differentiated by Cdiode+Cin, but since they're so quiet,
that's still a big win.

I'm experimenting with using BF862/pHEMT combos with diplexers to get
low 1/f noise and extreme bandwidth.

Cheers

Phil Hobbs
-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net