donderdag 30 juni 2011

Triggers circuit

This is the trigger circuit diagram.
Each note you press will trigger one of these by MIDI.

dinsdag 28 juni 2011

A few more tests

The last week I have done several test acording temperature stability of the master oscillators. It seems that there is a little frequency shift. In the design I will introduce NTC resistors to keep the frequency in track.
More of this later.

vrijdag 17 juni 2011

A little video

This little video shows the release function in action.

A picture of the oscillator circuit

This is the picture of the master oscillator followed by 2 dividers.
Next to it we find the Mosfet gate and the RC circuit ( for the Attack and Release ).

The trigger circuit

OK, how will we trigger these waves ?
I tried several circuits and came up with a very compact solution.
A MOSFET transistor serves as trigger and envelope gate.
This handy MOSFET has 2 gates ; 1 gate will amplify the sawtooth and the other gate will be used to control the envelope of the sound.
A simple RC circuit controls the ATTACK and RELEASE time.
I will add the schematics later for a better understanding

The dividers and sustain gates

The master oscillators produce square waves. These square waves are used to trigger the divider gates. The same circuit of the original E310 produce exact the same sawtooth waveform, only mirrored. The mixer in the final stage will reverse these sawtooth to the original shape.
The big difference in this new circuit is the positive power supply.
In this case PNP transistors BC557B will be used.

I have monitored these sawtooth waves and compared them with the original.
No differences here !

The sustain gates are like the original ones, only with PNP transistors.

Cheap BC557B transistors are very suitable for the dividers and sustain gates.

The master oscillator

This is 1 of the 12 master oscillators.
I will include a variable precise potmeter to adjust the pitch.
It is a very stable oscillator concerning temperature and voltage drift.

zondag 29 mei 2011

Block diagram

1. Circuit diagram

I will first start with a simple block diagram.
Later, every block will be designed.

Eminent E310 rack version : kick-off

Hello everyone !
I've just started to design a rack version of the very popular Eminent E310 unique organ, used by lots of musicians.
This rack version only produces the string section, including the sustain section.
Several controls will be available : trebble and bass controls, attack and release time of the sustains.
My goal is to achieve the same sound of the original string section.
Herefore, I will use the same sawtooth oscillator circuit.
The triggering of the notes will be done by MIDI.