Voxer '49 - CD4049UBE-based preamp

[blackcorvo]

Hello there guys! I'm back with yet another strange idea: a CMOS-based preamp. Specifically, I'm using the CD4049UBE, and this is the circuit I ended up with after a good couple of days playing with values.

Here's the schematic:

https://24.media.tumblr.com/6c7488cbc33f0f0085410e599d359fcc/tumblr_n1gmusrwOY1r4gqjso2_1280.png

It's pretty much just a Runoffgroove "3 Legged Dog", but without the input JFET booster, and  the addition of a tone control.

I went ahead and recorded a few samples using Audacity, and just to have an idea of what it might sound through a guitar cab, I used Amplitube to simulate a 1x6 combo cab, and a 2x12 Vox-style cab. Both cabs were recorded with a Dynamic 57 right at the speaker, in the cone position. The tonality change is made via the "Mic" control on the circuit, going from brighter to darker (on the knob, in the order 0, 2.5, 5, 7.5 and 10).

First, the original dry sound: https://soundcloud.com/corvolino03/sets/voxer-49-dry
1x6 cabinet simulation: https://soundcloud.com/corvolino03/sets/voxer-49-preamp
2x12 cabinet simulation: https://soundcloud.com/corvolino03/sets/voxer-49-preamp-1

And last but not least, a PCB layout made in DIY Layout Creator:

https://31.media.tumblr.com/ef2b084f91651e705a178fea2fa87f97/tumblr_n1gmusrwOY1r4gqjso1_1280.png

[knutolai]

Cool/strange tone-stack. Have not seen that before. Whats the response as you sweep the tone pot?

[blackcorvo]

Cool/strange tone-stack. Have not seen that before. Whats the response as you sweep the tone pot?

No idea. I was just playing with the placement of the caps (10n and 22n) around that output filter, and ended up with the one I felt was more flexible.

[pappasmurfsharem]

Cool/strange tone-stack. Have not seen that before. Whats the response as you sweep the tone pot?

No idea. I was just playing with the placement of the caps (10n and 22n) around that output filter, and ended up with the one I felt was more flexible.

those 4049s sure do clip nicely.

But whats going on with pin2,4 and 6? Is that No Connection?

[Mark Hammer]

I think 2, 4, and 6 are supposed to go to V+.

[blackcorvo]

those 4049s sure do clip nicely.

But whats going on with pin2,4 and 6? Is that No Connection?

I think 2, 4, and 6 are supposed to go to V+.

Pins 2, 4 and 6 are not connected. The inputs (3, 5 and 7) go to GND to avoid oscillation.

[Mark Hammer]

My bad.  If one looks at many of the 4049-based overdrives, unused inputs (not outputs) go to V+.  So  3, 5, 7, 9, 11, or 14 - whichever of those you happen not to be using - go to V+.

[duck_arse]

the tone control looks like a modified hammer notch. should work somewhat similar.

[CLAAS]

Morning;
there´s something different in the Input-Section.
In the Schematic it´s:22N-1M to Ground-120K to Pin 9;
in the Layout :          22n-120K-1M to Ground  "    "   ".

So,what´s wrong,what´s right?

Thanks for Correction

[blackcorvo]

Morning;
there´s something different in the Input-Section.
In the Schematic it´s:22N-1M to Ground-120K to Pin 9;
in the Layout :          22n-120K-1M to Ground  "    "   ".

So,what´s wrong,what´s right?

Thanks for Correction

The layout is the correct one, since I made it before the schematic. But either way will work just fine, so it doesn't really matter which one you choose to do.

[blackcorvo]

In case anybody is interested, here's a CD4069UBE version of the layout:

https://24.media.tumblr.com/8d9e7bab13d63fd1f746ccc121f44296/tumblr_n1lytqCkXy1r4gqjso3_r1_1280.png

And here is a complete amp using this preamp and a TDA7240 for the power amp:

https://31.media.tumblr.com/0a481753a3a723fc41d1e71df5f8048f/tumblr_n1lytqCkXy1r4gqjso2_1280.png

[UPDATE]

Layout with power amp tested. Works like a charm! This preamp is a bit too loud, tho. Maybe two zener diodes as clippers before the power amp might "fix" that (and also add a more pleasant distortion at high volumes).