3 Legged Dog + CMOS questions

Michael Allen · July 13, 2004, 02:42:05 AM

I put this together today using a CD4069 instead of a CD4049. I've got a bug in it though, it fades in and out. It's like the power source is getting modulated by some sort of LFO or something. I think it's a bad capacitor but I'm not sure. Any ideas anyone?

Otherwise I like this distortion a lot! I was wondering if anyone has any links to desinging with CMOS chips? Or information on using them as amplifiers?

Thanks!

Fret Wire · July 13, 2004, 03:12:02 AM

Try Texas Instuments' site. The usually have good app. notes on their IC's.
Glad to hear it sounds good, I'm planning on trying it when I have some time. I ordered 10 CD4049's on my last TI Sample order.

Edit: typo, I ordered 4049's (UBE).

Nasse · July 13, 2004, 03:20:20 AM

I believe Motorola had an application note in 70Â´s using cmos in linear mode

puretube · July 13, 2004, 04:48:33 AM

free information sucks...

Paul Marossy · July 13, 2004, 10:55:48 AM

I like mine a lot. I remember that you had to use a CD4049UBE, which is a buffered type, instead of the non-buffered type. If you have an unbuffered type, that could possibly be a contributing factor?

Mark Hammer · July 13, 2004, 11:30:35 AM

UBE indicates an unbuffered type. Unbuffered invertor are the preferred type

Prefixes, man! Can't live with 'em, can't specify without 'em. :wink:

One of the Japanese sites has an invertor based distortion that uses (I think) a 74C04. Might be wrth considering.

Paul Marossy · July 13, 2004, 01:12:05 PM

You're right Mark! Sorry about that, I got that mixed up... :oops:
One other thing, that circuit will squeal like a pig going to slaughter with a low battery! (at least it does with a CD4049UBE in it...)

Peter Snowberg · July 13, 2004, 01:20:01 PM

In the part number suffix the UB is the important part. Different makers use different codes for the package and the E in UBE is just an indicator that a couple of companies use for plastic DIP. (not to be confused with avacado dip)

The 74C04 has a similar designation for unbuffered, but in that case you want the 74HCU04 for linear mis-use.

A couple of other things to try are using a current limiting resistor in the power lead, or a JFET current source, or a 5V linear regulator. Each will give you a slightly different sound.

take care,
-Peter

Michael Allen · July 13, 2004, 03:36:42 PM

Thanks guys!

I'm using a 4049UBE, did some reading on making sure to use an unbuffered. All my unused inputs are grounded too. It's not a problem with oscillation or squealing as some of the help suggests. I was quite suprised because I put it together with a quick and dirty perf layout and some not so attractive wiring. But no squealing!

I read somewhere that somebody (Mark Hammer?) liked the sound of using CMOS to distort as long as CMOS was not used as an amplifier. Would moving the FET gain stage to the end of the circuit, or adding another stage after the CMOS stages be a worthwhile chage? Suggestions?

Thanks

Fret Wire · July 13, 2004, 03:49:29 PM

Did you use ROG's perf layout? Will Percival wipped up a nice pcb layout for that also.

Michael Allen · July 13, 2004, 04:17:08 PM

No I put together one of my own. about half the size as the R.O.G.

I drew up a pcb that i might use later too. about 1/3 the size or Will's.

Fret Wire · July 13, 2004, 05:01:56 PM

Quote from: Michael Allen
I drew up a pcb that i might use later too. about 1/3 the size or Will's.

Really, I'd like to see that layout when it's done. Will's layout is nice, but it's about 3/8" too long for a 1590b. The width is fine. A smaller layout could mount right on the bottom of the pots, and allow standard jack placement.

Michael Allen · July 14, 2004, 02:15:23 AM

My layout should definately fit in a box that size. I should be about 1 in by 1 in. Should be done in a few days....

Fret Wire · July 14, 2004, 02:44:08 AM

I'll be looking forward to that, the CD4049 is 3/4" x 1/4". I was figuring 1" x2". An inch square? Can't wait.

Michael Allen · July 14, 2004, 03:55:56 AM

This one is gonna be tight!

I didn't think about using a socket... I might need to space a little more around the IC to allow for the socket... Should be finished tomorrow

Gringo · July 14, 2004, 12:36:59 PM

I'd like to see that too!

The smallest i could squeeze it was 1.625" x 1.1". I'm getting old...

Michael Allen · July 15, 2004, 01:53:09 AM

Man, this is weird. The power is definately pulsing, and it's affecting the whole power supply that I use to power my effects. All the other effects have the same in-and-out pulse effect.

I'm not sure what to try here... I'm using a regulated power supply so it's not a low power source. Any ideas?

puretube · July 15, 2004, 02:14:25 AM

free information block:

Michael Allen · July 15, 2004, 03:49:45 PM

Quote...however also be caused by multiple grounding points
inside...

What do you mean? I used a perf layout and there is one point where all of the circuit grounds connect in one point. Then there is a jumper from that point to where the unused inverters are tied together. Could that be a cause? Otherwise my perf job is small and fairly neat. The wiring is all short and direct.

These are all homemade effects, yes. If I understand correctly you mean that I should put a 47~470R resistor between the battery/supply and the effect power supply? And then a cap across the power rails right? That's pretty standard but I don't think either are present in this circuit. I'll test that out right now! Thanks ton...

Michael Allen · July 15, 2004, 05:02:11 PM

The cap across the power rails solved the motorboating, but I've got a loud hum just like ground loop hum but it doesn't matter if the 3LD is the only effect on the Power Adapter or not....

Could this be because of the way I grounded it?

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3 Legged Dog + CMOS questions