[sdiy] Tuneable CV Quantizer

[Theo]

The most common "VU" meter ICs are the LM3914, 15, 16.
These can be cascaded, so more than 10 steps are possible.
The LM3914 is not UV but linear and might be the best choice for use as a
quantizer.

However all these IC have a drawback.
At first sight DOT mode suggest that only one output at the time is active,
however this is not true.
The "levels" overlap for a few mV, so when changing from one level to the
next two outputs are active.
This limits the usability as a quantizer, because when your input voltage
hits one of the "in-between" voltages the output is the sum of the two
levels.
Especially with slow changing inputs, this may cause unwanted effects.

I tried to overcome this by using a feed back method, so when the next
output gets active it pulls the input voltage up.
This works, but I still got short peaks in the output.

An alternate option is to use a simple 3 or 4 bit AD build from 4
comparators (opams, logic gates, whatever) and a multiplexer.

Theo


From: Curtin, Steven D (Steven) <sdcurtin at agere.com>

> Another thing that would work is the VU meter chip (don't remember the
> number) with the LED outputs- you then run each output through a pot and
sum
> them together.  This has been mentioned in this forum many times as a good
> tunable quantizer/sequencer.  You're limited to 10 steps, however.
>