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100n

f

390Ω

100KΩ

1MΩ

10KΩ

100n

f

sw

sw

C1

100 nFInput

R11MΩ

9v DC+

Q1

2N5088

E

C

B VR1

A100K

(Volume)R4100KΩ

R21MΩ

R310KΩ

R5390Ω

C2

100 nF

output

LPB-1Booster

The Electro-Harmonix LPB-1 booster is an old design dating back many

years. It’s simplicity belies the fact that you can get great sounds out of

just a few parts. The single transistor does all of the work. R2 and R4 set

the bias level, C1 is the input cap, and C2 is the output cap.

beavis board project

A100K

Volume

in

out

Mods!The C1 capacitor filters the input signal. The 100nf part is large enough that bass

content of the input signal is preserved. But what if you want to remove bass

content? In other words, make a treble booster instead? Simple: lower the value

of C1. Try values from 50pf to 22nf.

You can increase the amount of headroom (how loud you can go before the

signal starts to clip/overdrive) by increasing the input voltage. If you have a 12

volt DC adaptor, plug that in to experiment.

You can lower the gain of the circuit by using lower gain transistors. Try any of

the bipolar silicon NPN parts in the parts stash. Be sure to check the pinouts!

1MΩ

2N

5088

E

B

C

revision: 1.0 28 may 2008 © 2008 beavis audio research