Did you build it with 8 pairs of Jfets?
What would the reason be for having so many paralled Jfets?
Do you think there is a true sonic benefit from having so many paralleled devices?
I am wondering if to drive a regular premplifier, which in the worse case could present 20-30Kohm of impedance we require an output stage capable of 40-50mA?
Buffers are one of my hobbys you know so at the beginning of the MPP thread i published a lot of buffers and several people build various versions. The buffer you just posted won the listening contest.
This is now more then 2 years agao.
Yes, i build it with 5 pairs of Fets in parallel.
Do i think that this sounds better then only one pair ?
That depends on how much current we draw.
By the way i find the Paradise buffer transparent in most cases and as good as the
Hawksford.
This is now more then 2 years agao.
Yes, i build it with 5 pairs of Fets in parallel.
Do i think that this sounds better then only one pair ?
That depends on how much current we draw.
By the way i find the Paradise buffer transparent in most cases and as good as the
Hawksford.
It's either noise level, multiplying transconductance, or stacking current.
A buffer with high drive capability is never a bad thing, ime, even for phono duty (inbalance percentage of a V8 versus a 2-cylinder four-stroke)
Eight in parallel would be totally unstable, only works with BJT's.
(Accuphase manages 3 parallel J108/K370)
quoting from the other post:
John seems to like the type "A" circuit:
http://www.diyaudio.com/forums/anal...ch-preamplifier-part-ii-3746.html#post3431096
John seems to like the type "A" circuit:
http://www.diyaudio.com/forums/anal...ch-preamplifier-part-ii-3746.html#post3431096
It's just a simple FET buffer, nothing exceptional.
The specialty is the monolithic JFET number.
Matching numbers of the monolithics aren't that great, spread of the predecessors was tighter off-factory, but even those had to be hand-picked
It's much easier to get a good matching K170 pair, than a K389 with close Idss numbers, and cheaper.
At the going rate of a K389, bit of a shame for buffer duty, unless you have as many as me and also bought them for 2 quarters in bulk.
(main reason why I've accumulated such a huge number of parts over three decades. not just J74/K170 and J109/K389 by the hundreds, but also J72/J73/J75/K146/K147/K240/K246 in GR/BL/V, and every single/dual JFET made by NEC. I even match power-supply diodes for Vf, so I buy those by the thousand)
The specialty is the monolithic JFET number.
Matching numbers of the monolithics aren't that great, spread of the predecessors was tighter off-factory, but even those had to be hand-picked
It's much easier to get a good matching K170 pair, than a K389 with close Idss numbers, and cheaper.
At the going rate of a K389, bit of a shame for buffer duty, unless you have as many as me and also bought them for 2 quarters in bulk.
(main reason why I've accumulated such a huge number of parts over three decades. not just J74/K170 and J109/K389 by the hundreds, but also J72/J73/J75/K146/K147/K240/K246 in GR/BL/V, and every single/dual JFET made by NEC. I even match power-supply diodes for Vf, so I buy those by the thousand)
Oh my gosh!! What the heck do you do with all these parts?
I mean it is pretty amazing and truly I envy your stock!!
I am thinking how come 7-8 mA would not be enough to drive an input stage of a preamp which requires in the worse case few hundred uA to drive full out!!?
I understand the more the better... But not if transparency and or speed has to be traded off to have a little more muscle sound!
Simpler is the most elegant, but usually the most difficult.
Beauty of the monolithic JFETs is a close to ideal thermal coupling between the pair.
Single JFETs do not have that, there will always be thermal jetlag between a matched pair.
A single JFET differs, depending on it's location on a wafer.
Same deal with the monolithics, but with two JFETs on one substrate, twice as difficult.
No coupling cap & no DC-servo : usually only leaves manual hard labor.
Buy ten, have seven left. Buy hundred, hand pick thirty, have seventy left.
Ask yourself what an audio manufacturer, who buys a million, does with the left-overs after the automated selection process.
[3 decades ago on a limited budget, I figured I could build a decent stereo set myself. Phono pre-pre, preamplifier, monaural power amps, loudspeakers, Verdier turntable clone.
3 decades later I can pretty much buy what pleases me, but audio is the only activity that turns my head to zero mode. Dangerous hobby to get into. Reason I rather spend my time with the likes of Joachim & Martina, or an amusing gent from New Zealand, than with a bunch of fckng lawyers, doctors or corporate finance puttane]
Beauty of the monolithic JFETs is a close to ideal thermal coupling between the pair.
Single JFETs do not have that, there will always be thermal jetlag between a matched pair.
A single JFET differs, depending on it's location on a wafer.
Same deal with the monolithics, but with two JFETs on one substrate, twice as difficult.
No coupling cap & no DC-servo : usually only leaves manual hard labor.
Buy ten, have seven left. Buy hundred, hand pick thirty, have seventy left.
Ask yourself what an audio manufacturer, who buys a million, does with the left-overs after the automated selection process.
[3 decades ago on a limited budget, I figured I could build a decent stereo set myself. Phono pre-pre, preamplifier, monaural power amps, loudspeakers, Verdier turntable clone.
3 decades later I can pretty much buy what pleases me, but audio is the only activity that turns my head to zero mode. Dangerous hobby to get into. Reason I rather spend my time with the likes of Joachim & Martina, or an amusing gent from New Zealand, than with a bunch of fckng lawyers, doctors or corporate finance puttane]
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Well it makes perfect sene.
Just thought aside though: in this design there is a servo and whether the buffer is generating 1mV or 2mV output offset, really doesn't matter.
Now if this was just a buffer for line stage, then I would understand the importance of matching for perfect offset
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