Here is a stripboard layout for a simple opamp buffer.
There has been lot so interest on the forums about buffers, so I made this quick layout for a simple opamp buffer. It uses one amplifier from a common dual opamp chip as a unity gain buffer amplifier. The input impedance is over 1M and the output impedance is low, so that it can drive long cables.
Note that there are 3 cuts that have to be made under the opamp, and they are marked by the red squares with dots in the middle. The R3 resistor is optional and is shown standing on its end in the layout.
Install the opamp first, then the jumper wires and finally the two resistors and capacitors.
The Opamp Multi-Purpose pcb can be used for this circuit if you like pc boards instead of working with stripboard.
Very cool! So…say I wanted to use the other opamp for another buffer (like in an input/output buffer configuration) and incorporate them together–should I anticipate any unfavorable consequences of running the in/out through the same chip?
There should be no problem using both opamps as buffers. Pin 5 is the input to the second buffer and you will need to cut the trace underneath the opamp that is tying it to pin 4.
Why in most guitar pedals voltage Vb = 4.5 V?
>>>Why in most guitar pedals voltage Vb = 4.5 V?
The Vb is typically a bias voltage that establishes the proper operating point for the circuit. It is put in the middle of the available voltage supply so that the signal can swing equally above and below the bias operating point.
can this be added at the input or output of a pedal circuit? or is this separate as a “line driver” type circuit?
It may be built into a pedal, such as a wah, or used as a standalone buffer.
-Jack
I am interested in a buffer to place inside my guitar before an on board effects loop designed by Jerry Garcia. He used a buffer in his guitars to drive his long lines and loops, each pedal in its own true bypass loop. When I switch my OBEL off, I am only driving the line from the guitar to the amp totally bypassing the effects loop. Very natural sounding. When I turn on the OBEL, the buffers in the pedals, even in bypass, change the tone like night and day. a remedy would be to buffer the non OBEL. My question, how similar is this buffer to John Cutler’s CB1? And will this buffer add to the already buffered signal from the Boss’s?
Hi
What type of capacitors should I buy, I notice one has a plus sign and the other not. Does that mean 1 has to be polarised and the other none polarised? Sorry if this is a numpty question but I can follow a diagram and solder but don’t know much at all about resistors capacitors etc.
Cheers
The one with the plus sign is an electrolytic capacitor and the other would be a film capacitor or even a ceramic.
I see. Anyway, I tried to build the AMZ super buffer and had mixed results, I am sure it has to do with beginner luck,not design. At times it was popping and interference. I used 2 TL072 and radio shack board. The circuit was working had sound high Z output, but the pot acted funny, and circuit would not work when grounded to guitar. I would lke to take another stab at making the above buffer, which looks the same but one stage, where can I find the etching to complete the project?
Hi thanks for the advice about the caps.
It’s weird I have built it, but it actually seems to work the opposite ,it makes the guitar quieter and dulls the tone. I cut the 3 segments as directed behind the tl072. I have double and triple checked I got all the wires in the right place and components, any ideas??
Thanks
Ian
Jack, what is the purpuse of R3? I’ve built this buffer before w/o R3. Is it an improvement?
R3 is a pulldown resistor for the output. It is not necessary unless you want to switch the buffer off/on.
Great little board I suspect!
Using the two sides of the opamp on the same output, stacking them (with 2 100Ohm resistors) just as in the super buffer…Would that work (well)?
very nice! so would this be suitable a an output buffer for using a wah in front of a fuzz pedal?
[…] split. I searched around and came across a great buffer that uses an op-amp over at Jack Orman's Site. The input impedance is over 1M and the output impedance is low, so that it can drive two amps. It […]
Hi, could this be used to boost the level of an fx loop from an amplifier so that it can travel down longer cables to floor effects? Or would the Dual Buffer PC Board be better?
I see that this design doesn’t have a input filter cap on the 9V supply line. If this pedal is used as an addition to another circuit, I can always source it from the supply line of that board, but if this circuit is used as a standalone board, adding a cap would probably be smart(?).
André, I would definitely use a capacitor on the 9v power to cut out hum and noise from poor quality power supplies. Since this type of buffer is often used with just a battery, it would not be necessary with a 9v battery only.