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.
http://www.stereophile.com/amplificationreviews/54/index.html
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!
PB
http://www.stereophile.com/amplificationreviews/54/index.html
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!
PB
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
r
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
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
r
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
philipbarrett said:
Can you share
PB
Nelson Pass's two fet buffer for the Lightspeed Attenuator.
http://www.diyaudio.com/forums/showthread.php?postid=1521697#post1521697
Cheers George
Don't get hung up on unobtainable parts. Practical options abound:
1) Nelson's First Watt B1...http://www.passdiy.com/pdf/B1 Buffer Preamp.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.
Grey
1) Nelson's First Watt B1...http://www.passdiy.com/pdf/B1 Buffer Preamp.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.
Grey
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.
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.
Attachments
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.
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.
+15V rails sound fine to me, but if you intend to start with a 15V wall-wart, it doesn't leave much room for regulation. I'd suggest starting with a higher voltage and regulating it down to +15V or thereabouts.
I don't trust wall-warts. Given that nearly all of them are sealed units, you're buying a pig in a poke; there's no telling what's in there. True, you can buy an example of each of 99 different units and chop them up to see which one is suitable, but I would rather build something from scratch so as to know precisely what's in it. In the long run it will be the cheaper (and probably better sounding) option.
Grey
I don't trust wall-warts. Given that nearly all of them are sealed units, you're buying a pig in a poke; there's no telling what's in there. True, you can buy an example of each of 99 different units and chop them up to see which one is suitable, but I would rather build something from scratch so as to know precisely what's in it. In the long run it will be the cheaper (and probably better sounding) option.
Grey
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