#7403
LectronFan
Moderator

Hi all,

It seems like the circuit proposed on above link doesn’t perform well.

So it’s time to grab our electronic parts and build it ourselves !

For this, I’ve created a new Lectron block: the proto block !

A small breadboard fits perfectly inside a 4×4 cube. I cut a rectangle hole in the white surface so the breadboard protrudes a little bit. Then I used acrylic stand offs to keep the breadboard steady. The self adhesive tape underneath keeps the breadboard at it’s place.

I soldered some breadboard wires to the contact plates and used black for ground.

This will make it easy to experiment with parts for making a permanent Lectron block.

Here’s a closeup :

Proto cube

Now, for the tone control, I come up with this easy yet great working circuit, which fits perfectly on the Protobit.

Here’s the schematic:

Baxandall schematic

A1 is a half of the popular LM1458 chip. It’s used here as a buffer/preamp. For my Lectron radio module it was not necessary to amplify the input signal. You may increase R2 if you want to.

The tone control is slimmed version of the Baxandall I made with the Lectron cubes proposed above.

I tuned the circuit with better values to achieve a sweet sound control.

The bass potentiometer controls towards 350Hz, which greatly helps our tiny speaker.

The treble potentiometer influences the signals above 5000 Hz.

I used a sweep generator and a oscilloscope to visualize.

Of course, you may experiment with these values, but please use good quality capacitors.

C5 serves for suppressing HF oscillations.

Just remember, the measurements are made with the improved speaker box as mentioned in this topic.

When it was already sounding good, the Baxandall circuit helps to make it even better ! I enjoy some classical and jazz music playing while I write this topic 🙂

The output of the Protobit (+/- 3V pp) is strong enough to drive a typical class A amplifier for the speaker via a volume potentiometer.

Here’s a picture with the protobit of the circuit:

FM Protobit Baxandall

Many greetings

 

 

  • This reply was modified 2 years, 8 months ago by Michael.
  • This reply was modified 2 years, 8 months ago by Michael.
  • This reply was modified 2 years, 8 months ago by Michael.
  • This reply was modified 2 years, 8 months ago by Michael.