ALIS distributor

Broken floor or channel

If the floor of a distributor stops working completely, the RC4558 operational amplifier of its channel might need replacement.


A first hack proposed by ALIS is to replace a condenser and a resistor on each channel by a single condenser of type MKT 470nF.

See those two pictures in order to localize the condenser:

This indeed already boosts the output volume of the channel, probably because in addition to changing the condenser it also removes the quite big resistor that is originally welded together with the condenser.

Since this change occurs before the potentiometer and the split of the channel into two separate outputs, it affects both outputs of a channel.


Just after the potentiometer and the split of the channel into two, the mixer uses a RC4558 chip, an dual operational amplifier, on each one of the two outputs of a channel. See RC4558.pdf for more info.

The RC4558 is used as a balanced line converter, such as described in on page 50 and in

See the schematics of the mixer for a complete design of the circuit: distribuidor.sch.

Still it is possible to boost the gain of the first amplifier since it is somehow used as an inverting amplifier. In an inverting amplifier, the gain depends on a single resistor as shown by the following formula:

Vout = −Vin⋅Rf / Rin

The gain is given by:

Rf / Rin

So if we increase the value of Rf, we increase the gain.

Replacing the Rf of the first amplifier, Rf1, of an output by a resistor of 100 kΩ will boost again its gain. You can localize the position of each Rf1 by using this drawing:


Partial reverse engineering of the amplification system used in the distributor.


  • distributor.xcf, a version of the board for the Gimp which identifies most of the components.