AMZ IC Buffer using LM386 N

[AM]

  Any of the above methods design goal achievement ratings can be compared to using a short, HQ cable between the guitar and the amp.

Pete,  the short high quality cable you mention has been my approach all my years of playing. With my current band I need to run a longer cable to the amp though.
I think I will just build a Jfet booster and run that short HQ cable into that and from there to the amp. Thatz should give me extra boost when needed or serve me for when I want to run an extra long cable from there to the amp (set at unity gain). The next question would be: Do I need to change any resistor values since I will use that MPF102 and not the J113? Also, I don't have any 0.047 uF caps around. I do have some 0,1 uF and 1 uF ones though. Could I use those instead?

Schemo/Layoutr link:
http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album14/album143/DOD_201_JFET_PREAMP_VERO_001.gif.html

[earthtonesaudio]

I don't understand how that 1M pot is supposed to work, with the wiper connected to both the cap and pin 3.

It's a gain control.  At full resistance, in conjunction with the (chip's internal) 50k resistor to ground, it divides the signal by 20.  Amplifier gain is fixed at +20 so the overall gain is +1.  The 100p cap bypasses the 1M resistor at high frequencies, alleviating some of the high-end loss through the resistor itself, and boosting the highs slightly which can be useful for extremely long cable runs.  Also, the 1M series resistor increases the input impedance to about 1.05M.

At minimum resistance, the amplifier gain is 20, the frequency response is limited mainly by the in/out capacitors, and the input impedance is roughly 50k.  The 100p cap is shorted.

[oldrocker]

I don't know if Jacks' Simple buffer works at 60' but I did add one using a J201 Jfet in my Flying V.  I put a green LED and a toggle on the front of the guitar so I know when it's engaged.  People always ask me why there's a green light on the guitar.  It sounds good.


http://i218.photobucket.com/albums/cc93/ftrock/fvbuf3.jpg
http://i218.photobucket.com/albums/cc93/ftrock/fvbuf1.jpg

[Mark Hammer]

The first JFET buffer/preamp I ever made was very similar to the DOD one petemoore links to, and was used to feed a VERY low amplitude EEG signal from a rat's brain over what had to be at least 60' of cable running from the shielded recording room to the min-computer in another.  Granted, electrical brain activity is a very different sort of signal than a guitar pickup, in terms of source impedance, bandwidth, and amplitude.  But given how weak the initial signal is, the preamp did an admirable job of getting it to its destination intact.

[AM]

The first JFET buffer/preamp I ever made was very similar to the DOD one petemoore links to, and was used to feed a VERY low amplitude.....

Mark thanks for this answer. It was me who linked to that DOD preamp not Peter. I will build it when I get some free time over the weekend. The only thing I was thinking of changing was the output cap. I have some 0.1 uF and 1 uF around. I hope they will give more flexibility to impedance matching of whatever follows.