The Korg TNB-1 Tone Booster is a booster pedal from Korg that, unlike a transparent clean boost, colors the tone passing through it. Builders who have reproduced and verified its circuit describe it as sitting between a booster and a drive: with the gain set low it is pretty much a clean boost, rolled back a little it is a useable dirty booster with decent EQ control, and at maximum gain it verges on distortion. That is why the circuit is often tagged as an overdrive as well as a booster1.
What it does to your sound
The TNB-1's character comes from its tone controls. The bass and treble dials give a flat EQ with both fully counter clockwise, and they boost their frequencies as they are increased rather than cutting when turned back. So the fully counter clockwise position is the flat setting, and every step from there adds bass or treble1.
With the treble maxed, builders report a Rangemaster flavor to the sound, a reference to the classic treble-booster circuit. But the treble control can also be used the opposite way, to warm things up instead of brightening them1.
"It's got a nice sparkly tone, even with the bass up, better than I was expecting."
The overall verdict from the builders who verified the layout: definitely worth a look if you are after a booster that will color your sound1.
Controls
| Control | What it does |
|---|---|
| Gain | Sets the amount of boost; clean at low settings, verging on distortion at maximum1 |
| Bass | Boosts low frequencies from a flat EQ at fully counter clockwise1 |
| Treble | Boosts high frequencies from a flat EQ; maxed, it gives a Rangemaster flavor1 |
Notes from builders
The TNB-1 is old enough that published information about it comes mainly from the DIY community, where the circuit has been laid out for tagboard construction and verified by builders. A few of their findings matter to anyone reproducing or servicing one1:
- The gain control calls for a reverse log pot. One builder who used a linear pot instead found it jumps from clean to distortion with the smallest turn1.
- On the original layout, both the bass pot and the gain pot worked backwards and needed reversing1.
- One builder used 250k pots for the treble and bass controls1.
- With gain maxed, turning up the bass pot caused heavy clipping to the point of cutting out on one builder's unit. The same builder found it fine as a clean boost with the gain set lower1.
With the gain maxed, turning up the bass can push the circuit into heavy clipping, even cutting out, on at least one verified build. Keeping the gain lower avoids the problem1.
Videos
Pepe Music
Clifton Wright
Psych Up Melodies
Questions
Is the Korg TNB-1 a clean boost or an overdrive?
It depends on where the gain is set. Builders who have verified the circuit describe it as pretty much a clean boost with the gain set low, a useable dirty booster rolled back a little, and at maximum gain it verges on distortion. That is why it can be tagged as an overdrive as well as a booster.
What does the treble knob do on the TNB-1?
The treble control boosts high frequencies as it is turned up. With the treble maxed, builders report a Rangemaster flavour to the sound, but the control can also be used the opposite way to warm things up. The bass control works the same way for low frequencies.
Does the TNB-1 sound like a Rangemaster?
Only at one setting. With the treble control maxed, builders of the verified layout say there is definitely a Rangemaster flavour to it. Turn the treble down and the pedal moves in the opposite direction, warming the tone up instead of brightening it.
Do the bass and treble controls cut as well as boost?
No. The bass and treble dials give a flat EQ with both fully counter clockwise, and they boost their frequencies as they are increased rather than cutting when turned back. So the flat position is the minimum, not the middle.
What kind of gain pot does the TNB-1 layout call for?
A reverse log pot. One builder who used a linear pot instead reported that it jumps from clean to distortion with the smallest turn, so the reverse log taper matters for getting a usable sweep across the gain control.
Sources (1)
- Guitar FX Layouts: Korg TNB-1 Tone Booster, Guitar FX Layouts (tagboardeffects.blogspot.com), 2013-04-01
