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Old 24th February 2009, 05:24 PM   #1
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Default A Visit To Aunt Corey's House

I am interested in the thinking & design behind the old-as-hills Stereophile "Aunt Corey's Passive Buffered Preamp" and I've read the related posts here at diy.


Obviously the BUF-03 used in the project is long out of production & according to Analog Devices (and a long perusal of their cut sheets) there is no direct replacement.

Has anyone re-visited this project recently? Is there a modern equivalent to the BUF that I'm missing? My local electronics outlet has some nice +/-15V PSUs which are just begging to go into a project such as this!

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Old 24th February 2009, 05:40 PM   #2
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Default buf replacement

I too am fascinated with corey's buffer design, came this close to building one when it first appeared in stereophile- ended up builing one around a circuit offered thru old colony (the morrey super buffer)based on an ne531 op amp- high slew rate-35vms- low cost and low power- having multiple isolated outputs-nice little piece of kit- It actually measures lower distortion figures than either the B-1 which I just built or the same card with a 5534
uncompensated-but life is not about specs its about the emotional response to listening which i hope to do over the next few weeks-
anyway I digress- I believe the current thinking is very wide bandwidth,fast video op amps made to drive long, low impedance cables would be the next step beyond the buff 03
just one guys opinion
by the by on my B-1 board i jumped from r1/l1 (input) to w/w with 25k of resistance and was successful in bypassing the 25k pot.-lost about 1% of the signal
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Old 24th February 2009, 05:50 PM   #3
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BUF634 and LT1010 will work in this design but probably not sound quite as good. There are many discrete buffers, some using just two fets which are a lot more tempting to use. A great commercial version of the same is the Mc Cormack SMC line stage.
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Old 24th February 2009, 05:52 PM   #4
Nisbeth is offline Nisbeth  Denmark
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Got a handful of the BUF03s off ebay a while ago, but unfortunately I haven't had time to build anything yet

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Old 24th February 2009, 05:55 PM   #5
PH104 is offline PH104  United States
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The TI BUF634 and Linear Technology LT1010 are popular buffers. Can't comment on sonics. BUF634 has lower input bias current and might be the better choice.
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Old 24th February 2009, 06:12 PM   #6
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Originally posted by analog_sa
There are many discrete buffers, some using just two fets which are a lot more tempting to use.
Can you share :-)

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Old 24th February 2009, 08:50 PM   #7
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Originally posted by philipbarrett

Can you share :-)

Nelson Pass's two fet buffer for the Lightspeed Attenuator.


Cheers George
Avatar : Production Lightspeed Attenuator
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Old 25th February 2009, 12:33 AM   #8
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Don't get hung up on unobtainable parts. Practical options abound:
1) Nelson's First Watt B1...http://www.passdiy.com/pdf/B1%20Buffer%20Preamp.pdf
2) My Line Drive (see the GR-25 thread)...similar to the Nelson's JFET buffer that George posted above, but with more current. Yes, reasonable parts substitutions are allowed.
3) Walt Jung has a clever bipolar buffer (he credits John Curl for helping, as I recall) on his website. No, I don't immediately recall what the article's called, but you could do worse than to stroll through his online offerings. The one you're looking for has two sets of push-pull bipolars. Conceptually, it's similar to Nelson's JFET buffer/my Line Drive, just redone to accommodate bipolar parts.
4) Any ol' tube cathode follower buffer.
5) And ol' solid state Source/emitter follower buffer. For added ain't-I-****-o'-th'-walk bragging rights, use something like the 2SK389/2SJ109. Given that they're out of production, you can afford to sneer at anyone who wants to build your buffer...unless, of course, they happen to have some 2SK389/2SJ109s of their own.
Etc. The point being that buffers aren't all that hard to find...even good ones.

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Old 25th February 2009, 01:36 AM   #9
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I'd been looking closely at Nelson's. There seem to be 2 distinct boards, the one on Pass' site (great deal, with JFETs for $40) and then this one (which I really like the layout of) on enjoythemusic.com but seemingly unavailable?

Does the B1 require a regulated/smoothed PSU? Looking at the schematic I say yes but having seen some builds on the web, folks are hitting the 18V rail directly with a xformer's secondry tap.
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Old 25th February 2009, 01:44 AM   #10
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You certainly can do it that way, but I like the fat RC network on
the power supply, since many commercial wall-warts and so on are
not very quiet and may even be unregulated.

The PassDIY board has provision for this.

You can in fact run directly off the wall-warts and such, but this is
a bit quieter, and I am charging real money for the product.

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