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Old 3rd October 2008, 10:06 AM   #1
burbeck is offline burbeck  United Kingdom
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Default Another jfet buffer

hi all,
i have been using this John Linsley Hood line buffer stage for 15 years, recently modded it to use 2sk170 and 2sj74 and i am very impressed with the results. great volume control buffer.

any comment?
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File Type: zip jlh buffer mod.zip (2.2 KB, 1103 views)
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Old 3rd October 2008, 12:16 PM   #2
Bonsai is offline Bonsai  Taiwan
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Its good. I like it.
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Old 3rd October 2008, 01:00 PM   #3
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Very nice circuit, I was wondering when someone was gonna post The JLH buffer. Sounds very good too. Published ETI Apr92.
It can also be used similar as Pass F5 at higher power and is essentialy 2 cfps.
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Old 3rd October 2008, 03:53 PM   #4
EUVL is offline EUVL  Europe
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I don't quite understand why you would use this modified version compared to the simple complementary JFET follower from John Curl (Just 2SK170 / 2SJ74). Are you trying to drive more current with the BJTs than the JFETs can cope?

For the Pass F5, (or maybe even the original JLH circuit), the situation is different, as the first stage is just not capable of driving the intended load.

Maybe you care to explain ?


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Old 3rd October 2008, 05:28 PM   #5
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Yes thats the idea, the Jlh circuit as is can even drive my seinheisers which is a abot 150 ohm load with very little distortion. Try it with simple jfet buffer, high distortion, no go.
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Old 3rd October 2008, 05:42 PM   #6
CBS240 is offline CBS240  United States
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Hi

The 5457/5460 just doesn't have the transconductance required to supply enough current as source follower output. I like them and use them a lot, they are nice linear transistors with a small input capacitance but only good around the 100uA range, plenty of current to drive the base of a small signal BJT.
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Old 3rd October 2008, 08:28 PM   #7
burbeck is offline burbeck  United Kingdom
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hi
i use this circuit as a volume control buffer, it alows me to tack more or less anything on the output that i may have or be playing around with at the time, universal buffer is how i would describe it. good old JLH.

i was wondering if an improvment could be made by replacing the transistors with better types, and as i had the original made up, i did some sims, and replaced the transistors and altered the values around them, sounds nice.

i suppose losing the preset would would have some advantage, but it trims the offset nicely.

i think it is good that the buffer has a low impedance output makes it versitile. (drive capability etc)

in my non expert simulations the distortion is very low, mayby someone who is more expert could do the sims and compare with a simple compementary jfet follower, because in my world of fumbling around with sims it comes out better?? surely this cant be correct. this would be educational and give people a chance to understand a simple circuit. (including me)

ps thanks guys for the comments



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Old 3rd October 2008, 08:41 PM   #8
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Question Re: Another jfet buffer

Quote:
Originally posted by burbeck
hi all,
i have been using this John Linsley Hood line buffer stage for 15 years, recently modded it to use 2sk170 and 2sj74 and i am very impressed with the results. great volume control buffer.

any comment?
With what prgram do I open this file? Is it really a ZIP file?



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Old 3rd October 2008, 11:59 PM   #9
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by bear
Yes it is a zip file, but the image opens as some wierd file type.

Here is the jpeg save from that file...


_-_-bear

ya mean - here is gif ........
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File Type: gif jlh buffer mod.gif (7.8 KB, 2001 views)
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Old 4th October 2008, 12:03 AM   #10
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Default Re: Re: Another jfet buffer

Quote:
Originally posted by QSerraTico_Tico

With what prgram do I open this file? Is it really a ZIP file?
It is better not to post files with spaces in names.
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