freestompboxes.org

The MC3340P voltage-controlled attenuator is still available from many far eastern sources at reasonable prices. This is a circuit from the late 70s that worked really well. If anyone's interested, I can provide Vero and PCB layouts for this one too.

interested

Nicht Bernd wrote:interested

OK. I'll post them later today.

Here we go: It really is worth looking on line for MC3340P ICs!

Looks interesting!

Maybe someone could make a re-design for a modern and easily available IC?

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If someone in germany or nearby has a MC3340P, please send me a PM.
(I know where I can buy them new, but 3€+5€ for shipping is a bit too much...)

Hi,

I found this other compressor schematic online using the mc3340 also seems interesting so here it is for all you compressor loving electronic attenuator people.

The cap lists with the vero and pcb layouts don't match the schematic parts. Is the schematic the correct parts to use?
Thanks

johno9 wrote:The cap lists with the vero and pcb layouts don't match the schematic parts. Is the schematic the correct parts to use?
Thanks

They are a bit different...

- One real error: In the pcb layout, pin 1 of the mc3340 is not connected (missing cap)
- the parts for the buffered bypass are left out.
- pulldown resistor at the input is added (but not at the output ?!?)
- the 10k level pot at the output is left out
- a few values are a bit different (330nF instead of 470nF)

pedalgrinder wrote:Hi,

I found this other compressor schematic online using the mc3340 also seems interesting so here it is for all you compressor loving electronic attenuator people.

mc3340 compressor schematic.docx

Not everybody uses word. It's always better to post schematics e.g. as a .pdf file.

pedalgrinder wrote:Hi,

I found this other compressor schematic online using the mc3340 also seems interesting so here it is for all you compressor loving electronic attenuator people.

mc3340 compressor schematic.docx

Not bad, but R10 won't work "as advertised" - I'll draw a corrected version later.

roseblood11 wrote: They are a bit different...

- One real error: In the pcb layout, pin 1 of the mc3340 is not connected (missing cap)
- the parts for the buffered bypass are left out.
- pulldown resistor at the input is added (but not at the output ?!?)
- the 10k level pot at the output is left out
- a few values are a bit different (330nF instead of 470nF)

To make this project even more professional i would add at least a cap across the supply rails...

Has someone used the vero layout in the meantime? Is it verified? Looks ok to me but I want to be sure...

roseblood11 wrote:Has someone used the vero layout in the meantime? Is it verified? Looks ok to me but I want to be sure...

Yes. I built one using that layout yesterday (I needed a quick compressor).

I've also done another, slightly smaller Vero layout which I'll put up shortly.

Look what I found here in the archive from May 2007:

http://circuit-electronic.blogspot.com/ ... chive.html
Sadly the MC3340P has already been discontinued in 1998.

there still available on evilbay for about $7 or so and if you look on octopart they come up with a few places with the mc3340 also. seems a lot to pay though when you can get a nice vca for around the same money or even use a cd4007 for the same purpose or there abouts.

And look what I found here. Back in 1980 a Mr. Barille from Italy - credits to those who deserve them - was so kind to draw a pcb layout and even write an article for the italian magazine "Sperimentare" for this circuit.

Buon divertimento!

pedalgrinder wrote:there still available on evilbay for about $7 or so and if you look on octopart they come up with a few places with the mc3340 also. seems a lot to pay though when you can get a nice vca for around the same money or even use a cd4007 for the same purpose or there abouts.

I've got a strip of seven of them left from "the old days". I used two more earlier today in a pair of compressors - one for keyboard, and one for guitar. The guitar one has noise reduction - the usual pre- and de-emphasis - and is probably the best simple compressor for guitar I've heard. It has a really fast attack, and sustains for ages. Experience shows that it's usually best to put the compressor as the first pedal in the chain, but it's good to have an uncompressed (but buffered) feed of the guitar signal for the control of envelope-sensitive effects (like auto-wah, auto-flange, auto-phase and so on). I find myself making lots of use of BS170 buffer and gain stages for clean, uncoloured impedance conversion. The only minor downside to these is the requirement to bias them really accurately.

After recent things built with these ICs, I'm going shopping for more!

Are you buying them and sending them to me cause iam your favourite forum member mictester????? hahahahah your the best man hahahaha