Discussion in 'General Electronics Discussion' started by Yoa01, Jan 26, 2013.

1. Yoa01

214
0
Jun 18, 2012
Hi all,

So I had this neat idea for an analogue sequencer that involves a voltage input that will sum with the voltage already being played by the sequencer, thus causing the sequence (or just an individual step) to be transposed. Fairly simple idea, and would probably work.

However, my question to you is preceisly how would I go about doing such a thing? It seems that running a voltage directly into another voltage would cause an explosion, and I think LTSpice agrees because it says:

'Voltage Source 1 and Voltage Source 2 are paralleled making an over-defined circuit matrix. You will need to correct the circuit or add some series resistance.'

As a note, V1 is 2V, V2 is 1V. It seems that either a diode or resistor between the two voltage sources would be necessary. However, in simulation, the voltage before the component (using a 1k resistor or a 1N4148 diode) is V1's 2V, but after, the voltage is V2's 1V. Am I missing something?

2. DuctDuck

52
0
Jan 26, 2013
Linear mixing is what your circuit is going to accomplish. A potentiometer is the simplest linear device. You can take the resultant off the centre wipe (e.g- 2.5 Kohm).

Vr = V1sin(w1t) + V2sin(w2t)
...this means a signal rides on another signal yet all frequencies remain intact!

3. Yoa01

214
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Jun 18, 2012
If I wanted to mix signals, that would be perfect! Sadly, I need a raw voltage summer here.

Given the 1V/Oct standard that most synths nowadays like to use, if the sequencer was outputting 2V (my V1), which is a C2 note, and I wanted to transpose it 1 octave, I could theoretically add 1V to the signal and get 3V, thus giving me the C3 note.

A voltage input with a pot would give me an arbitrary voltage, and the tuning would be off. I need generally precise voltages here, which is why I want to merely add raw voltages, not mix them.

However, I appreciate your knowing how to mix signals!

4. BobK

7,682
1,688
Jan 5, 2010
Look up op-amp summing circuit.

Bob

5. Yoa01

214
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Jun 18, 2012
HOLY CRAP THAT WORKS AMAZINGLY I mean uh... Thank you, Bob. Always helpful.