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Post by Tinkerer on Sept 28, 2021 15:02:00 GMT -5
Can anyone recommend some DIY OP Amp based buffer and also phase inverter circuits? I have Craig Anderton's book "Electronic Projects ...." , and he has a buffer circuit and a phase inverter circuit in there, but they both call for a 9 volt bi-polar power supply, and I want circuits that will run on a single 9 volt battery. I want to play through two amps simultaneously - one amp with the clean guitar signal and my effect pedals through the other, so I need the buffer to split my guitar signal and am anticipating I might need a phase inverter.
Thanks!
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Post by reverendrob on Sept 28, 2021 21:35:06 GMT -5
Why not just use a stereo pedal that you turn off?
Buy a dirt cheap Boss chorus or something, never turn it on, profit.
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Post by Pinetree on Sept 29, 2021 2:43:46 GMT -5
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Sept 29, 2021 4:47:25 GMT -5
A buffer can be made with a single transistor circuit, many / most pedals do that rather than an op amp. Same for polarity inversion. So with 2 transistors the battery will last a decade. Studio gear might use opamps due to their near perfect linearity at very high signal levels into 600ohm loads. But that capability seems like a sledgehammer to crack a nut for guitar stuff. Have a looky at eg a TS9 schematic el34world.com/charts/Schematics/files/Effects/Ibanez_ts9_tubescreamer.pdf Q1 being a buffer, the 2 x 10k resistors deriving 4.5V for biasing it. If you’re still stuck I’ll draw a schematic if I can find a convenient envelope:) |
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Post by Tinkerer on Sept 29, 2021 9:12:07 GMT -5
Thanks everyone! I was hoping to make something rather than buying. Thanks for the circuit suggestion pdf64!
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Post by Pinetree on Sept 29, 2021 13:25:52 GMT -5
I hear ya.
But as much as I enjoy making things, an ABY switch is mighty handy.
Be sure to show us a pic if you end up making one.
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Sept 29, 2021 14:50:51 GMT -5
It’s worth noting that the Radial splitter is passive, no buffer. So in the Y mode, cable capacitive loading on the guitar will increase. ie the transformer will reflect the secondary side capacitance back to ghe primary. And if a pedal or amp input has a ‘non high’ input impedance, the guitar signal and hence other branch of the signal path may be affected.
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Post by Pinetree on Sept 29, 2021 20:04:14 GMT -5
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Post by Peegoo 🏁 on Sept 30, 2021 2:44:07 GMT -5
It’s worth noting that the Radial splitter is passive, no buffer. So in the Y mode, cable capacitive loading on the guitar will increase. ie the transformer will reflect the secondary side capacitance back to ghe primary. And if a pedal or amp input has a ‘non high’ input impedance, the guitar signal and hence other branch of the signal path may be affected. You could cheat your way around this by adding buffered pedals downstream on the Y branches, as follows:  |
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Post by Tinkerer on Sept 30, 2021 17:57:58 GMT -5
I have been rummaging through my parts bins and I found a General Guitar Gadgets IC single buffer (link) buffer PCB that I made up a number of years ago. I used it in something and then took it out and saved it. It is ready to go. It is a TL071 chip. Can I split the output from that for what I want to do? Thanks again! |
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Oct 1, 2021 3:28:58 GMT -5
Yes, use a resistor, anything in the range 100ohms to 10k, to feed each output.
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Post by Tinkerer on Oct 1, 2021 9:29:28 GMT -5
Thanks pdf64! When you say use a resistor to feed each output, do you mean that each output requires a resistor and I should wire them so that one end of each resistor goes to the output leg of the 10uF capacitor and the other end of the each resistor connects to each output jack positive tab, or do the resistors go between the outputs and ground?
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Oct 1, 2021 12:37:46 GMT -5
The former, in series with the output signal, one lead to the cap, other to the jack tip terminal.
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Post by Tinkerer on Oct 1, 2021 12:45:53 GMT -5
Thank you! May I also ask please - 100ohms to 10kohms for the resistor is a huge range - what does the resistor do and why does the value within that range not matter? Is there a "best" value within that range? Thanks again!!
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pdf64
Wholenote
Posts: 557
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Post by pdf64 on Oct 1, 2021 16:20:34 GMT -5
On a log scale, 1k is in the middle, and is a good default value. But it’s not critical, anything is better than nothing, but too high and it will become a source of hiss.
It’s necessary to the maintain stability of the opamp. Without it, cable capacitance can interact with the opamp and result in oscillation, possibly ultrasonic.
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Post by Tinkerer on Oct 1, 2021 18:47:02 GMT -5
Thank you!!
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