[Steven Everett]

Possum used a link, in a reply, to a Stereophile review. I found it fascinating reading.

http://www.stereophile.com/showarchives.cgi?54:1

I need to build a few buffering circuits and was wondering if the BUF-03, mentioned in the article, is still a great buffer? I see the article was written in 1991. Is there a better buffer now? Is there somewhere I can find plans to build a circuit using the better buffer?
Thank you,
steve

 

[Nisbeth]

The BUF-03 has been discontinued. The replacement is called BUF-04. If you plan to build this particular circuit (Aunt Coreys Buffered passive preamp) then, stick with the BUF-04. Otherwise, there are other options. The BUF-634 will output more current than the BUF-04 and lots of people speak highly of the Elantec buffers although I have no personal experience with those. Try searching the forums here or at www.headwize.com for more information (lots of posts of HW regarding the BUF-634). Or you can just use Google to find the datasheets for anything you might be interested in.

HTH
/Uffe

 

[ppl]

Boy this must be the time for Preamps with no gain. the BUF-634 will not work hear because you need an FET input buffer otherwise the DC offset will change dramictily (enough to be not useable) so check my reply to this thred http://headwize.powerpill.org/ubb/sh...20020408083526 this should get you started

 

[mlloyd1]

I agree with PPL about the BUF634 buffer input current. I've had good success sticking a pair of JFETs in front, configured as JFET source follower w/JFET current sink. Toshiba 2SK170 is a low noise, relatively cheap single (2SK389 is dual, much more expensive, save it for your RIAA preamp

I also do this with another buffer I like, the National LM6321 and I suppose it works with another buffer where you're concerned about bias currents, including discretes.
If you really want to go all out, you could always cascode the source follower as well as the current sink. I think PPL has talked about that lately, too.
I wish he'd bottle some of that free time he has and sell me a jug or two!

Michael

 

[ppl]

Most of the circuits i have talked about came over years of Playing with Different Parts in a virity of Application both Professionaly and on my own. latly I have been recovering from a Debillitating Operation and spent some of That time Exploring The Virtues of a Casscode circuits low miller capacitence to an advantage as a current source, With Pleasing results over what i was using, a mear 1N5298 CRD in series with a 1K resistor to Buffer the CRD's Nonlinear Capacitence when Rev. Biased by the Signal. Putting a One way diode also helps but has serious disadvantages over the better Casscode and takes up the same board space. Selection of a low capacitence Dual supper-matched Pair like the LS-840. When i get fealing better i will investigate using ultra Low capacitence UHF FET's Ill bet that might be evean better but will have to wait.

The BUF-634 i have used in both Pro any my DIY stuff every conceivable configuation including Casscoding the BUF-634 to Bipolar power Transistors for a output switn of greator than 50 Volts RMS to be an output Buffer for a 12AX7 based Line gain stage, with out overloading the Solid state output stage at the Clipping voltage of the Tubes.

In another Circuit i used a EL-2009 Buffered by a Casscode source Follower and a Casscode Current source. Great High Current Active Preamp without any Gain or Neg. Feedback. So hope this helps ya.

 

[Steven Everett]

Thanks guys for the help. I'm afraid PPL a lot of what you said sailed right over me. I understand that the BUF-634 will not work in my situation because it needs to follow a FET. I also understand that the BUF-04 would work but it is not as good as the EL-2004, EL-2005, or the LH-0033. Casscode circuits, low miller capacitance, and bipolar power transistors, are words that kind of bounce off of me because I have no understanding of them.
I have a high end microphone tube preamp that I want to drive a Vu meter and a Szekeres headphone amp without effecting the output of the preamp. I what the buffer to pass the audio signal as cleanly as possible so that I can position the microphones by using the headphones. I was warned by the designer of the preamp not to hang too much off of the output. It would drag down the signal. Can any of you point me to a schematic using the EL-2004, EL-2005, or the LH-0033. I've read "Designing an Opamp Headphone Amplifier" and everything else I can find but I'm not at a level to make the choice of circuit on my own.
Thanks,
steve

 

[ppl]

Sorry Hope this Helps >
If the input to the Buffer is a high Impedance like above 4K then a FET type like the BUF-03 and LH-0033, EL-2004 and EL-2005. The later mentioned parts being Better. You connect the Pins in the LH-xxxx just like you would on the BUF-04 in the Stereophile Artical. Output pin to correct corrosponding output Board location.

If the Impedance is less than 5K ohms as would happen if you used a 5k Resistor from the Buffers input to Ground or evean a 5K Volume Control. In these cases Buffers like the BUF-634 and EL-2001 cad be used insted of the BUF-03 and the LH-0033 and similar Maxium MAX-460.

 

[wallijonn]

yes, but what about the sound?