Slew Limiter and Passive Attenuator

Next in line is a simple slew limiter associated to a passive attenuator.

Nothing fancy.  No CV control.  No choice of slope.

Finished module

When I removed my DIY-101 module, I lost the portamento on the oscillator.  Mind you, I seldom used it, because the VCO was not good enough. 
Nevertheless, it is an effect I fancy on an analog oscillator.

Bob drills the panel.

The slew limiter circuit is inspired by Yves Usson own Dual Gated Slew and the simple schematics from Synovatron.  Components value were constrained by what I had on my drawers at the time.

The attenuator is a simple passive one.

Layout and schematics

I changed the way I wired the panel.  In fact, I don't wire it anymore : pots and jacks are soldered on their own PCB, with the main board attached via spacers.  I'm not sure it spares connection wire but it is cleaner on the panel side : no more screw.  On the other hand, I have to be very accurate with my designs and my drilling.  I did three paper prototypes before finding the correct positioning of things.

Thonk proved a good resource to find the appropriate parts.

Assembled

Finally, here is a small sonic example.  The effect of the slew limiter on the pitch CV of the oscillators can be heard after 16 seconds.

Jay F. · Slew Limiter on a Bass Pattern

Passive attenuator and reference voltage

This module combines in 4HP some utilities I first planned for a 2U utility panel.

Finished module chilling on bench

From top to bottom : a passive attenuator, two reference voltages and a manual gate.

The attenuator and the gate are normalled to the 10V reference voltage.

The reference voltage electronic schematic is scavenged from the same function in Mutable Instrument Shades.   Hence the reference to Olivier Gillet, whose work is a great source of inspiration for me.

Ongoing panel assembly

Some of the components are soldered on the panel.
I hesitated to include the 51 ohms protection resistors at the op-amps outputs.  Maybe I should have put them inside the feedback loop of the op-amps ...  Nevertheless, the  circuit was built when I thought I might add them and I did not want to  ruined my earlier work, so they ended up on the panel.











The op-amp went into smoke as soon as I began the first test : I had inverted the -12 V and + 12 V pins.  :-(
I resorted to solve it with some trace removal and a couple of wires.

Problems solved.

So no layout this time : i'm too ashamed.  :-/
Still, here is the final electrical schematic.

Passive Attenuator and Reference Voltage