Boosty McBuffer

Low Noise Onboard Buffer/ Booster/ EQ For Guitar & Bass 

Boosty McBuffer is a versatile, very low noise preamp you can mount to your guitar or bass. It can switch on the fly between unity gain buffer, treble booster, and bass or full-range boost. Additionally, when used with passive pickups, its variable input impedance can markedly reshape their sound. The highest input impedance can make humbuckers almost as bright as singles. Conversely, the lowest impedance settings will tame overly bright pickups.

BMB can work on its own or it can be combined with Distiller or OKC, giving them additional functionality.

The 3-way toggle switch selects one of 3 functions:

An 8-pole DIP switch can set the input impedance from as low as 145kΩ to as high as 10MΩ (great for piezo pickups). It also sets the amount of treble boost in multiple steps (from +6dB up to as much as a Brian May-grade +22dB). The bass boost side can be set for +6 or +12dB, and can also be switched to flat boost instead (great for guitar).

I care very much about low noise design because I use high gain effects and compressors and they tend to magnify any hiss to annoying levels. The DC resistance of pickups (5kΩ to 20kΩ) generates hiss due to Johnson (or thermal) noise. An average 10kΩ pickup's self noise is -113dBu when measured over the full audio bandwidth. BMB's output noise is significantly lower: -117dBu, so it will not add any perceptible hiss to the signal coming from the pickups. Remarkably, it achieves this without compromising on power consumption. Its current draw is a tiny 0.3mA, resulting in a batery life of over 1500 hours.

For more detail on the sources of guitar hiss and how an onboard buffer can both reduce noise and eliminate "tone suck", you might want to read this tech note. 

💡It's important to note that hiss (white noise) is definitely not the only type of noise coming out of pickups. Environmental noise they pick up from power transformers, LED lighting, phones and computers is a different story. BMB cannot help with this, as it's already part of the signal by the time it gets to it. Humbuckers and other "noiseless" pickups significantly reduce it, and properly shielding your guitar also helps.


Here are some suggested ways you can use Boosty McBuffer. 

Guitar: Try 12dB of flat boost on one side (bass boost is not usually useful on guitar). This helps pushing amps into overdrive, for leads or just extra dirt. The middle position always lets you quickly jump back to unity gain. On the other side, try a strong treble boost, maybe even all the way up to +22dB. This does the same job as dedicated treble boost pedals - but with less hiss. Use the first 3 DIP switches to set BMB's input impedance to whatever you feel sounds best with your pickups.  Higher input impedance results in a brighter tone, lower impedance warms things up. 10MΩ is high enough to use with piezo pickups, but probably too bright for magnetics. 500k is a good value to start for humbuckers, while 250k is common for single coils. Try the lowest impedance (145k) if you want to warm up some overly bright single coils.

Bass: 


For best performance, if you use a volume potentiometer right after BMB, it should be a low value suitable for active electronics. 25kΩ pots are commonly used. 10kΩ or even 5kΩ would be even better, but they may be harder to source in guitar sizes.

SPECIFICATIONS

Input impedance: user-configurable, see table below
Output impedance: 51Ω
Current draw: 0.27mA
Battery life (9V alkaline): 1500 hours
Output noise
(buffer or bass boost): -117dBu (21.6kHz BW, unweighted)
Output noise
(treble or flat boost): add boost dB to figure above
Maximum input level (buffer): +11dBu @9V, +18dBu @18V
Dynamic range: 128dB @9V (!), 135dB @18V (!!)  

MEASUREMENTS
Test equipment: Audio Precision System Two Cascade

Noise floor 

Note that the test equipment's own noise floor is -120dBu, which inflates the measured value for very small signals. Once we discount its contribution, the actual BMB noise floor is -117dBu.

Maximum output level (18V supply)