DIY PONG PEDAL: Building Polyphonic Octaver and Noise Grabber Using BWE-PONG Module and BGPM-1 PCB
BWE-PONG is an octaver and noise grabber effect module designed for guitar effect pedal application. More than just producing polyphonic octave and sub octave sound, it can also capture the noise spectrum and then using it to remove the noise from the original input signal. As the result, your guitar signal will fade out to the silence without any gating transient. Here a re some highlights:
- Noise grabber function
- Independent controls for dry, sub, and up levels
- Glitch-free tracking
- Low latency
- Dry output: 10 ms
- Up octave output: 65 ms
- Sub octave output: 55 ms
- Zero latency analog-pass-through bypass
Because the physical size and the electrical interface specification of BWE-PONG module follows the BLACKSTOMP-CORE (BSCORE) module open standard (https://www.deeptronic.com/blackstomp/i-blackstomp-hardware/), it is possible to build a PONG pedal using the module with the BGPM-1 PCB (BSCORE generic production model-1), which is one of the generic PCB versions designed for BSCORE module. As the BGPM-1 PCB is licensed for everyone to use in any type of products (including commercial one), it could be the cheapest option to build the BWE-PONG pedal since we don’t need to design a specific PCB for this.
II. Schematic Diagram of PONG Pedaland BGPM-1 Circuits
Figure 1 shows the schematic diagram of typical BWE-PONG pedal circuit. Compared to the BGPM-1 circuit shown in the Figure 2, the pedal circuit has less components since it uses only the left channel, and doesn’t need the MIDI interface or selector switches.
III. BGPM-1 PCB and The Bill of Materials (BOM)
The BGPM-1 PCB is shown in Figure 3, and the BOM in the Table 1. It is clear that in order to use BGPM-1 PCB for building BWE-PONG effect pedal, we just need to populate the PONG circuit’s components only, and leave the unused component pads in the PCB blank. The PCB design is free to use (even for commercial products) and the gerber file is available here: https://github.com/hamuro80/blackstomp/blob/master/hardware/Gerber_PCB_BGPM_1_V2.zip
V. Drill Template
BGPM-1 is designed for 125B enclosure size, and the printable drill template is shown in the Figure 4. Make sure the printed template’s actual size fits into the actual pedal enclosure. Note that the input and output socket hole is marked with 9-12 mm diameter. This is because the socket should be of isolated type, or a standard type with insulation washer (shoulder washer), so you need to make sure you know the real diameter to drill from the actual socket.125B-PONG-DRILL2
Figure 4. Drill Template
VI. Enclosure Label
A printable label for 125B enclosure is shown in the Figure 5. It can be printed as a sticker or directly printed to the enclosure using UV printer.125B-PONG-LABEL3
Figure 5. Enclosure Label
VII. Building Special Notes
- All the bottom-side-mounted components height (when mounted) have to be lower than the PCB mounted potentiometers (P1, P3, P5), so MKM type capacitors is recommended for the 47nF and 100nF, and short body elctrolytic capacitors is recommended for the 47uF/16V capacitors.
- To enable smooth insertion/plugging of the module, the leads of potentiometer P1 and P3 should be cut before soldering to the PCB from the top side, so a perfect flat surface after soldering could be made.
- In some cases, connecting the enclosure to the analog ground through two points or more causes audible near-ultrasonic buzzing noise. To avoid such problem, a single point connection should be used for enclosure grounding, here are some options:
- An isolated mono sockets for the input and a non-isolated mono socket for the output can be used.
- You can also use isolated type for both input and output with separate analog ground-enclosure connection via scun/ring terminal at the isolated DC socket or foot switch.
- If you can’t find any isolated socket types, then you can use rubber/teflon shoulder washers to isolate the non isolated socket, or you can just use some insulation tape hacks.
- See Figure 6 for off-board parts easy wiring reference.
- BYPASS switch is used to activate/deactivate the effect by un-bypass and bypass. In tap menu operation, this switch is used to do a single-tap or multi-tap command (see sections X)
- NOISE GRAB switch (see section IX)
- SUB knob controls the sub octave level of the effect output
- UP knob controls octave level of the effect output
- DRY knob controls the dry level of the effect output
IX. Noise Grabbing Function
PONG has noise grab feature that you can capture the spectrum of any noise that comes with the input, and then use that captured information to remove the noise to produce a very clean output. There are 2 control operation that can be done by the GRAB switch:
- Grab. Do the following steps to grab a new noise profile and apply to the noise remover:
- Although not mandatory, it is recommended to bypass the pedal first, so you can hear the noise clearly
- Mute all of the guitar strings by touching them with your hand
- Keep the noise exposure at maximum, usually by keeping the strings and all ground-connected metal parts untouched, and adjust the guitar position at certain direction
- Tap the GRAB switch. Immediately after tapping, the CHECK indicator will blink to indicate that the new noise spectrum is being acquired and analyzed.
- Wait until the CHECK indication stop blinking. After it stop blinking then no matter the previous effect state is bypassed or engaged, the effect will switch to engaged state to apply the noise remover.
- Grab and Add. If we just grab a new noise profile at a new guitar position but then the noise comes back when the guitar is moved back to the previous position, it means that the noise profile at the new position need to be added to the previous noise profile (from the previous guitar position).
- To grab a new noise profile, add to the previous noise profile, and update the noise remover, just do the step 1-3 of the grab operation, then press and hold the GRAB switch until the CHECK indicator blink.
- Release the GRAB switch. The CHECK indicator will continue to blink to indicate that the grab-and-add operation is in progress, so wait until it stops blinking.
X. Knob’s Center-Position Calibration
At the first time the module or the pedal is powered-on, or when the potentiometer knob is replaced or readjusted for maintenance, the center position of the knob reading (by the firmware) need to be calibrated. Use the following steps to do the calibration:
- From a normal operation (either bypassed or un-bypassed), do a multitap of 10-taps. Make sure the period between successive taps is not more than 0.5 seconds to be a “single multitap operation”. A repetitive 5-blink will be shown by the CHECK indicator to show that the pedal is in the knob calibration operation. Retry the multitap if the CHECK indicator doesn’t show it.
- Turn all the way down the first knob, then turn to the center position. Do the same for all the knobs one by one.
- Exit the knob calibration operation by one of the following three ways:
- Do a triple-tap to accept the adjustment and save the setting
- Do a double-tap to cancel the adjustment and apply the default (factory) setting
- Do a single-tap to cancel the adjustment and revert back the previous setting
After exit from this menu operation, the CHECK indicator should stop blinking and turned continuously-ON to indicate the normal operation.