Active Buffered Splitter (ABS) for use with either bass, guitar, keyboard or other electric instruments as either a buffer or a splitter. Name may change in the future if i can think of something more creative. * This is only a signal splitter! It does not work in reverse to combine two separate audio inputs into a single output signal! ** Not recommended to use for splitting signal between two amps! You will need a transformer ground isolated converter to use this to splitter between two amplifiers to prevent ground loop hum! Yes, researching a version with a transformer ground isolated output. Not into shelling out $65 for a Jensen xformer; it would cost less to purchase a commercial splitter with isolator. Trying to find a decent xformer under $10 is challenging. Compare price to: JHS Buffered Splitter $80 Saturn Works Buffered Splitter $50 ABS guestimated price $25 (PCB Fabrication + Parts from Tayda + S&H) Fits in a 1590A enclosure to take up less space on your pedal board cause we all want to add another pedal but don't have the space. // Status // October 12, 2020 - Aside from the following bug on the prototype PCB that i fixed by connecting incoming ground to one of the socket grounds, the splitter works very nicely! // BUGS // Gerber Y8-2251001A Bugs - Net R4_1 incorrectly connected to input Net ground pad. - May need to remove 1-2 mm off PCB width for better fit // Specifications // Zin: ~1Meg Zout: 500 Ohms (your choice of op amp will not affect much) Power Supply: +9V Vin Max w/o clipping: +13Vpp using NE5532. *Choice of other Op Amp, output swing may vary. Frequency Range:20hz - 20Khz with 3db rolloff/octave at 40Khz Loss: 500mdB (Simulated - 6Vpp @ 1khz ) // Build Notes // PJ-609BA Stereo Jack: Available from Tayda: SKU: A-1122 3mm Bi-color LED (Tayda SKU A-1076) When the longer lead is connected to positive and shorter lead to negative, the LED lights up red. When reversed,and shorter lead is connect to positive, the LED lights up green. This is the recommended installation so that when a center postive power supply is connected it lights RED indicating a reversed power supply. All resistors are 1/4W metal film to reduce circuit noise. Only really need them on R1, R2 & R3. // Troubleshooting // [ LtSpice Test Points ] Voltage on Q1.B = +8V Voltage on Q1.E = ~ 7.3V Volage on U2.1, U2.2,U2.3,U2.5,U2.6,U2.7 = Q1.E [ **Actual Test Points ] Voltage on *Q1.B = +8.39V Voltage on *Q1.E = ~ +7.23V Voltage on U2.8 = +16.78V Volage on U2.1, U2.2,U2.3,U2.5,U2.6,U2.7 = Q1.E ** I accidentally used my only 2N5089 for something else and used a 2N5551 because it was all i had on hand but no where near the Hfe of a 2N5089, so the actual voltage test points for a 2N5089 will differ. // Design Notes // R1,R2,R6: Anything 2.7M or higher will have a Zin of 900k and higher The BS uses the "switched tip" concept of grounding the input and output of the circuit until jack(s) are plugged un to reduce "pop noise" in combination with anti-pop resistors. Bi-color LED: serves as a power on/reverse polarity indicator. The LED will be green when a negative center power supply is connected and red when reversed. Resistors R7 & R10 limit the maximum curent thru the LED to roughly 1mA regardless of polarity. So if you want dimmer or brighter LED's you must calculate the value of both resistors. I_led = 1 mA V' = Vcc - LED_Fv = 9 - 2.2 = 6.8V R' = Vcc/I_led = 6.8/.001 = 6.8k R'' = R'/2 = 3.4k (3.3K nominal value) Just about any Op Amp with the standard pinout will suffice. The NE5532 has an input impedance around 300K which is far less than most op amps, so any will do but may affect max output swing. U1 I always build using the LT1054 voltage converter. R9/C3 & R4/C7 combination form the LPF with Fc = 40Khz -3dB/octave drop Legal Stuff **This work is licensed under the CopyLeft and CC-BY-NC-SA 3.0 license agreements. By forking,sharing or downloading the contents of this project(herein referred to as the KdB Merlin(c) Buffered Splitter you acknowledge,accept and agree to abide by the terms & conditions of Copyleft and CC-BY-NC-SA 3.0 license agreements.** No direct support is offered for this project beyond the provided documentation. It’s assumed that you have at least some experience building pedals and knowledge of electronics before engaging in this project. This circuit has been tested in good faith in its base configuration as documented in the schematic. This project may be used for commercial endeavors in any quantity unless specifically noted.The only usage restrictions are that (1) you cannot resell the PCB as part of a kit without prior arrangement, and (2) you cannot “goop” the circuit, scratch off the screenprint, or otherwise obfuscate the circuit to disguise its source. **References** The Spluffer, mother of all splitters from Craig Anderton (1980's) Pg 84 https://msu.edu/~dougl126/Electronic%20Projects%20for%20Musicians.pdf https://www.cuidevices.com/blog/understanding-audio-jack-switches-and-schematics