Like to use a buffer on output of a R2R DAC.
BF861 SMD is an inexpensive, available, low-noise N-CH Jfet.
Are there any other variation beside what is in the attached pics?
Pics from Erno Borbely's JFET Frontier's articles.
I tried the B1 v1 in between the DAC and BA3-Pre and the sound was much better. Like to build something good for inside the DAC case and avoid the extra caps, pot, switch and interconnects.
Thanks,
Vince
Notes:
BF861 SMD is an inexpensive, available, low-noise N-CH Jfet.
Are there any other variation beside what is in the attached pics?
Pics from Erno Borbely's JFET Frontier's articles.
I tried the B1 v1 in between the DAC and BA3-Pre and the sound was much better. Like to build something good for inside the DAC case and avoid the extra caps, pot, switch and interconnects.
Thanks,
Vince
Notes:
Attachments
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I don't believe there is a complimentary P channel version of bf861/862. So pretty much all designs will use a coupling cap.
Are you going to use the DACs power supply? Is it single or dual? That will make a lot of the decisions for you. Also, most DACs use a lower voltage supply than most of these buffers.
B1 rev2 would be the smallest/easiest.
Are you going to use the DACs power supply? Is it single or dual? That will make a lot of the decisions for you. Also, most DACs use a lower voltage supply than most of these buffers.
B1 rev2 would be the smallest/easiest.
I'm not look for complimentary jfets.
This is the point of my post.
Just asking if there are any alternatives to what is posted in the pic, e.i., what Erno propsed.
Thx
V.
This is the point of my post.
Just asking if there are any alternatives to what is posted in the pic, e.i., what Erno propsed.
Thx
V.
With the 2SK170 / LSK170 you will find that 15 a,b,c will all work very well, and put
you in the .00x distortion category or better. The current source version is preferred,
and you don't need to use expensive Jfets for that. J113 will do the job nicely.
you in the .00x distortion category or better. The current source version is preferred,
and you don't need to use expensive Jfets for that. J113 will do the job nicely.
also some of it (plain buffer or Borbely's WCF) explained in opening post of tips 'n' tricks for B. M25 and SissySIT
with some SOT23 adapter pcbs and veroboard , you can do your own , including shunt reg
buy 100pcs of JFet I used and you're good for a decade , for peanuts , without any loss of performance (comparing to more expensive options)
🙂
Do 15 b and c both use current sources, one just a discrete current source and the other a JFET?
So in other words, use a 2sk170 for the buffer and use a J113 for the current source. No matching needed? Just use same Idss class?
J113 is JFet , internally connected as 2 pole
though , irrelevant - -use whatever CCS option you want ,taking care of TempCo (think DC offset) , according to your needs
though , irrelevant - -use whatever CCS option you want ,taking care of TempCo (think DC offset) , according to your needs
You should note that all of these plans will have some DC at the output. Unless you are comfortable feeding DC out the line to the next box (which may change!), an output DC blocking cap or other technique is wise.
15C has "potential" to be DC-free. If the two FETs are exactly matched the DC nulls. If they are a bit off-match, trimming the bottom resistor will null DC. At least for today, or this-hour. I had a Heathkit 'scope which used this plan as input buffer, and I found the DC drift annoying enough that I put a then-sexy chip in place.
15B would null if the two different parts happen to match, unlikely. 15A can be nulled by changing Rs, but it may need large change and will drift with temperature and rail voltage.
16A "could" be nulled if Rd were put down to its proper value (few dozen Ohms) and another couple resistors added, which modestly reduces its virtue in low-Z loads. 16B "would" null if you could match P- and N-types- unlikely without a barrel-full of FETs and an automated sorter, and tempco may not be totally compensated.
Stick a cap on the input, run the Gate resistor to a +/-1V trim, they all null today, with some residual drift.
Stick a cap on the output and DC is avoided. Cave-man, but effective. For typical hi-fi loads, I'd go for 15A, because it is simple, real-real clean despite not being "best", and the small curvature is not likely offensive.
15C has "potential" to be DC-free. If the two FETs are exactly matched the DC nulls. If they are a bit off-match, trimming the bottom resistor will null DC. At least for today, or this-hour. I had a Heathkit 'scope which used this plan as input buffer, and I found the DC drift annoying enough that I put a then-sexy chip in place.
15B would null if the two different parts happen to match, unlikely. 15A can be nulled by changing Rs, but it may need large change and will drift with temperature and rail voltage.
16A "could" be nulled if Rd were put down to its proper value (few dozen Ohms) and another couple resistors added, which modestly reduces its virtue in low-Z loads. 16B "would" null if you could match P- and N-types- unlikely without a barrel-full of FETs and an automated sorter, and tempco may not be totally compensated.
Stick a cap on the input, run the Gate resistor to a +/-1V trim, they all null today, with some residual drift.
Stick a cap on the output and DC is avoided. Cave-man, but effective. For typical hi-fi loads, I'd go for 15A, because it is simple, real-real clean despite not being "best", and the small curvature is not likely offensive.
Some other Source Follower Configurations
Posts #353, 457, 473.
Taylor Source Follower
NJFETs for Source Follower Applications
Patrick
Posts #353, 457, 473.
Taylor Source Follower
NJFETs for Source Follower Applications
Patrick
Hi,
the 'Calvin Buffer' is a improved and beefed-up version of circuit 16a.
Sonically it adds power and slam, which the simple JFET-only Buffers might slightly miss.
It works with several different but still available N-JFETs (the BF862 are already obsolete for a while now).
There are versions utilizing throughhole devices as well as all-SMD variants.
The search will lead You to the associated threads.
jauu
Calvin
the 'Calvin Buffer' is a improved and beefed-up version of circuit 16a.
Sonically it adds power and slam, which the simple JFET-only Buffers might slightly miss.
It works with several different but still available N-JFETs (the BF862 are already obsolete for a while now).
There are versions utilizing throughhole devices as well as all-SMD variants.
The search will lead You to the associated threads.
jauu
Calvin
but it's so much cheaper in 1000 quantities ... still looking for BL Idss?
If a person still has access to 2SK170 or LSK170 and doesn't have to go through the exercise of vero-board replacement (think - stack 3 sot-23 adapters into a single 3-pin footprint for drop in replacement), is there a good reason to do this other than the fun of experimenting? That's good enough reason for me 😀
> the 'Calvin Buffer' is a improved and beefed-up version of circuit 16a.
I have tried a few CFP with N-JFETs and PNPs.
They are sometimes a bit "nervious" for my taste.
But just my personal choice.
Cheers,
Patrick
I have tried a few CFP with N-JFETs and PNPs.
They are sometimes a bit "nervious" for my taste.
But just my personal choice.
Cheers,
Patrick
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