Skip to content

Category: Preamplifier

BC109 Direct Coupled Preamp

It’s a very nice, warm, full-tone preamplifier. The soul of the circuit is two BC109 transistors. These are old, well-proven types. Interestingly, the base of transistor T2 is connected to collector T1. This is called direct coupling, and the signal is transmitted between stages without attenuation. This means that there is no capacitor, resistor or transformer between the two transistors. This makes it less repressive to the guitar signal. This circuit does not distort, that is, only when the guitar volume is at its maximum.

This is the first version:

Direct Coupled Preamplifier with BC109 Transistor
Direct Coupled Preamp Schematic

In this video it works on 9v voltage, see:

Leave a Comment

Bassline – Bass Guitar Tube Preamplifier

So far, we do not really dealt with bass guitar  effects, amplifiers. Here, in this time of change!
One of my favorite band The Beatles, inspired a new tube bass preamp creation.
The plates can hear great tunes and sounds of the XXI century it is significant. This’ 60s-edge
tone you want to give a little back. This simple, little preamplifier may be able to create a good bass sound.

The idea

Okay, what do we need? First, a simple tube preamp and a tone sections. And yet… put a little extra! Whether it is a switch which can give more prominence to the bass sound. And finally result in the power amp section. The tube 12AX7 or ECC83 should be. And we are ready to go.

Build the bass guitar preamp

As shown in a schematic diagram, not complicated circuit. The circuits are designed triodes ordinary way. Located between the two triode the tone control section. Here we must mention the little extras are what we promise you. It was built in the SW1 signal switch and capacitor C7. This will give even more powerful bass sound.

Even a small change in the circuit (well, not so little, the C8 is quite large capacitor). The C8 was originally 100nF, it was replaced with 1uF. Thus, it improved bass response with what is perceptible difference. Suggested type for a high-quality MKP capacitor. We conducted a little experiment, was left inside the 100nf and 1uf capacitor, one switch to choose between the two, and thus is connected to the output. so you can compare the two capacitor deep voice transmission. Feel free to experiment with different manufacturers and types of capacitors.

Bassline - bass guitar tube preamplifier
Bassline – tube bass guitar preamp – click to open full size