Here is the stripboard (veroboard) layout for the jfet buffer that is shown a few posts below. The board is 10×10 with no strip cuts necessary and only one jumper. If you plan to leave this on all the time, no footswitch is needed and you can put the project in a very tiny box. Link to the complete article is below:
[11] Jfet Buffer on Stripboard
Date: May 23rd, 2007 | Comments : [6] | Categories: DIY, pedals.6 Responses to “Jfet Buffer on Stripboard”
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Jack Orman has been involved in FX design and construction since the mid-1970s.
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[…] at the start of this article and it can be built on stripboard using the same layout as for the jfet buffer that I published previously. The transistor pin configuration is different for the germaniums so you will have to match the […]
Hi, where did you get the stripboard editor program thing from?
Download it from here:
http://www.storm-software.co.yu/diy/index.php?project=software
regards, Jack
[…] improved wah buffer is identical to the jfet buffer on stripboard that was shown previously in this blog. The 10M (R1) resistor is not needed since the circuit is […]
I was comparing the layout here with the schematic of the “Basic buffers” article and I have a couple of questions.
1. What is the purpose of the 100k resistor (R5)? Is it there to prevent popping sounds when switched on / off? Could it be omitted?
2. What would be the output impedance if I use an MPF102 transistor and the 1 uF output cap and omit the R5 resistor?
Thanks in advance for any answers
R5 is a pulldown for the output and not absolutely necessary if you are building the project into a box to be “on” all the time.
The output impedance is approximately 1/gm so you have to look at the spec sheet for the transistor that you are using to find the value of gm.
If gm is 4000 uS (0.004 S) then the output impedance is 1/0.004 = 250 ohms
Low gm transistors will have higher output impedance; if gm is 2000 uS then the output impedance is 500 ohms