volume/frequency activated gates/triggers

[darren adcock]

Hi all, I've been asked to make a device which allows a rapper to produce gates/triggers to interface with midi equipment. After an initial discussion we decided that we could use certain or a series of volume and frequency windows which would activate the gates/triggers. This would all be derived from vocal's via a microphone. It is preferred that the circuit runs off batteries.

Usually in a project I head straight in and then have to back paddle when i get stuck. So thought I'd try and start with a post of how I think i need to achieve this, see what folk here think (It's new ground for me) and try and get the circuit drawn before i start plugging things in.

How I've imagined things so far;
For frequency detection
- SM58 - Pre amp/buffer - frequency to voltage converter (LM331) - window comparator - gate buffer with a comparator input leading to 40106's for both trigger and gate out ( this circuit is from MFOS here http://musicfromouterspace.com/analogsynth_new/HOT_TIPS/PDF/gatebuffer20090923_assembly.pdf )

For dB detection
Is the same as above but the frequency to voltage converter is changed to a single op amp amplifier to amplify the mic signal into a larger voltage range

 

[kellys_eye]

Amplitude is 'easy' - any circuit used to indicate signal level (LM3915/LED bar) can be 'tapped' to take off a switching signal.

Frequency is less easy - you have to consider the frequency and the bandwidth but it's still (fairly) easy to achieve and, 'back in the day', the NE567 was commonly used.

 

[Alec_t]

LM3915 is obsolete, but may be still available somewhere.

 

[darren adcock]

Amplitude is 'easy' - any circuit used to indicate signal level (LM3915/LED bar) can be 'tapped' to take off a switching signal.

Frequency is less easy - you have to consider the frequency and the bandwidth but it's still (fairly) easy to achieve and, 'back in the day', the NE567 was commonly used.

Ok thanks. I can find the NE567 quite easy and will look at related schematics today and try to understand the consideration needed of the relationship with frequency and bandwith (I understand the terms) in this application.

In terms of amplitude, I'll follow your advice as makes my making much simpler!

 

[darren adcock]

LM3915 is obsolete, but may be still available somewhere.

Hey Alec, I can find it quite easy on ebay for cheap.