F O R T R E S S O F S O L I T U D E
Wayne Barger needed a 4-output splitter so he could play through four amps at the same time . It occurred to me that everyone wants to play through four amps at once, so I made a Buffer / Splitter I call the "Fortress of Solitude".
His current splitter, a Morley Tripler, only has 3 outputs, and there was excessive hum on one of the channels, probably because the outputs are not isolated, and ground loops were present.
The Fortress of Solitude has 4 transformer isolated outputs, a direct output, individual channel output volume controls, and each channel has a phase reversal switch and a ground lift switch.
In front of the Splitter is a LM833 Buffer, with Gain control. In front of the Buffer is a linear booster with volume control - the Booster is based on the legendary Electro-Harmonix LPB-1 Power Booster. A very simple clean boost. The LPB-1 was the first guitar effect to use a silicon transistor; until then all effects used germanium. (In high school, my band used LPB-1s, which plugged into the amplifier (usually a Fender Bandmaster). We would turn the amp up to 10, and LPB-1 all the way up.)
On another note, I am almost totally deaf.
The schematic, above, is pretty straightforward; based from an R. G. Keen design, using the Mouser 42TM018 audio transformers. A 3PDT push-button activates each channel, and when "OFF", the primary side of that channel's transformer is grounded to reduce noise. The bipolar 9VDC power supply is inside the enclosure, and it and the transformers are shielded with Mu-metal to prevent stray EMI fields. The regulated power supply was a kit I bought from China.
It is difficult to find a center-tapped 15VAC transformer / adapter, but I managed to locate a Group West Class 2 transformer rated at 1.8 A. If you are thinking about building a Fortress of Solitude, you will have to scout around; you want a Center-Tapped 15VAC transformer (mine is a wall wart), of about 1 Amp.
Each channel switch lights up blue when that channel is active. Bi-color LEDs are green when the phase and the ground lift are "normal", and turn red when they are switched. There is also a green LED for the power supply "ON", and a red LED for the Boost "ON". You can never have enough LEDs on stuff.
The three guys who invented the blue LED won the Nobel Prize, by the way. It was a big deal; everybody thought it was kind of impossible. Without blue LEDs, we wouldn't have color screens for iPhones and TV and computers; we wouldn't have white LED lights that are so much more efficient than Thomas Edison's incandescent bulb.
The Fortress of Solitude's input impedance is high, and the output impedance is low, so cables can be pretty long on the output to the amplifiers without losing signal. Likewise, the guitar input signal won't lose anything.
The power supply is not on the schematic, but there are lots of ± 9VDC regulated supplies out there, either as a kit or ready-made on a PCB, like this. I don't have a layout of the enclosure yet (the enclosure has to be pretty big), or a parts list, but I will post them as soon as I, um, make them.
The (prototype) Fortress of Solitude was hand-wired, with lots of tiny soldering, and looks well, busy. It works, though, and it is quiet. Note that the transformers are mounted at right angles to each other.
Send me an e-mail if you want me to send you a
Paint document of the latest version of the schematic.