AMI Range Booster

andrewsrea · Wed Jul 13, 2022 6:51 pm

I modded an EHX LP-1 (Linear Power Boost) a few months ago, learned a bit and created the AMI 'Range Booster.' The design isn't too far off from the Catalinbread 'Naga Viper'.

As the name implies, it is in the treble boost genre with a few extra tricks:
- Can be adjusted to full-frequency range to very trebly, via a 'Range' control knob.
- Unlike a Dallas Rangemaster, the inherent distortion is controlled by a 'Grit' knob.
- Unlike a traditional boost, I selected a specific low self-noise silicon transistor for less hiss and performance reliability in various environments.
- It also has a bit more head room, especially with the grit control down.

I personally love the day-glo lime body with yellow knobs and the small enclosure (2"x4"x1"). Took a lot of planning and packing to get everything in it.

I took it through its paces today and think it sounds fantastic!

mozz · Wed Jul 13, 2022 7:18 pm

The EH treble booster, old time, was the screaming bird, there was also a "Mole" which was for bass. I think the LPB used a 2N5133 transistor, which was the favorite at the time, used in the big muff. Not easy to find. Today's transistors are definitely lower noise.

andrewsrea · Thu Jul 14, 2022 5:39 pm

mozz wrote: ↑Wed Jul 13, 2022 7:18 pm The EH treble booster, old time, was the screaming bird, there was also a "Mole" which was for bass. I think the LPB used a 2N5133 transistor, which was the favorite at the time, used in the big muff. Not easy to find. Today's transistors are definitely lower noise.

I bought my EHX LPB for next to nothing in the 2000's, in exchange for receiving some broken tubes from EHX (Owen Matthews was my rep at the time and was awesome). Owen sent me my replacement order and gave me the pedal at less than dealer cost. It had a healthy 2N5088 which has good gain and pretty low noise. It goes a little asymmetrical with the knob at 70%.

I was originally using it as a solo boost and it was flubby, so I modded it by changing the input cap from the stock 150nF to 68nF.

For the Range Booster I have it variable from 70.2nF to 2.2nF. I like the range at about 60% (a meatier than a Dallas Rangemaster). The 'Grit' brings in an emitter bypass cap that is boosting the upper mid-range.