MORLEY PVO

[Shakey 1047]

I have just acquired this pedal and of course out of curiosity I took the back off to have a look inside, now I am even more curious. The circuit board (Dated 1992) is made for mono or stereo and has the basic circuitry ldr's led's 3 resistors etc.
The board also incorporates a stereo (or two mono) circuit which utilises 2 x MC3340P chips. I can't find this circuit among the Morley Schematics so can anyone tell me what this circuit does.
Cheers Dave.

[Jazz P Bass]

The datasheet of the MC3340P suggests using it as a compressor or an expander.
The call the ic an electronic attenuator.

[Shakey 1047]

Thanks JP, As I am using it for Pedal Steel I'm wondering whether it would be worth adding the components to see what it does.
Dave.

[Mark Hammer]

First let's establish that it is a 3340 and not a 3403 with a typo. Morely was fond of that quad op-amp for a while.

At the same time, that would be 8 op-amps over the two chips, andI can't see even a stereo volume pedal as requiring that much.

The Motorola 3340 is an electronic attenuator chip. I've got a couple in my parts bin. What's nice about them is that turning them into an attenuator that can be controlled by a simple 50k variable resistance to ground is a breeze. That feature also means that wiring up a pan control that uses a single linear pot with the wiper at ground is also a breeze.

They CAN be controlled in dynamic fashion as you would a VCA, but apparently their specs are not that good for such applications. I seem to recall building a 3340-based compressor from an lectronics Today project and was not all that impressed.

Whatever you do, don't confuse them with the CEM3340, which is a kickass, and ultra-rare, VCO chip.