EasterDrive !!

[v8v]

Yo Guys! - Just a little piccy of a 1-off that I put together over the Easter weekend just for fun. I wanted to do something with some nice little TO-106 transistors that I acquired recently. This is basically the published Unidrive schematic, plus a few rather fun mods. Breadboarding the original circuit I discovered that if you add a pot to adjust the negative feedback from the last stage to the first, you can go from the standard Unidrive 'gain' to absolute all out monster gain! The best way I can describe it is like the sound of two Buzzarounds wired in series Enclosure is just an inkjet transfer and not a screen print, but doesn't look bad for a quick way to get a result. Can't get over the monster bottom end of this circuit either! I've fitted a wire link onto the board internally, so that I can select between the standard input cap, or reduce it substantially to get a more conventional balance to the sound.
Cheers!
Pete

UniDrive Easter.jpg (145.55 KiB) Viewed 5701 times

[slomatic]

Beautiful!!

You planning on building more??

[1bottlerocket]

That sounds pretty cool and an improvement or variation on a classic circuit. Nice job!

[v8v]

Cheers guys!! Basically I just started out having a play with the Unidrive circuit, and the end results were so good that I thought it worth doing a quick enclosure design, just to see how it came out. Really pleased with the look! - not to mention the sound! If I did do any more, I'd probably just keep it as a simple transfer print. Here's a quick pick of the insides :

[1bottlerocket]

Nice indeed. Is this a 3 transistor circuit?

[v8v]

Yep, the first stage is a pair of transistors connected in a configuration reminiscent of the good old Fuzz Face, but the biasing is a bit more involved. The third transisitor is basically a buffer stage, from which a feedback signal is taken and applied back to the first transistor - this is where it gets interesting! The transistors that I used are BC209s and some really retro little bases which I just happened to find in a drawer in the workshop!
Pete

[1bottlerocket]

Thanks for the information. That certainly makes the circuit interesting in my mind and I'll bet it makes biasing a bit of a trick.

[jerms]

that looks awesome v8v!! super nice build! is that stripboard or just perfboard?... love those old button transistors .....let us know if you make some more of these!!

[v8v]

Thanks guys for the nice comments! Yep, this is a stripboard build as I like to use terminal pins (I just find it easier to work this way). I'll see if I can get a few audio samples together sometime. I noticed that the first two pics were a bit low rez, so here's another from last night which is a little bit more clear:

P1010021.JPG (661.33 KiB) Viewed 5499 times

The electrolytic caps in this build are just what I happened to have in the drawer. If I did any more then I'd use some proper branded parts and not the ones used here. Wiring routing also needs a bit of fettling, but other than that I'm pretty happy!

Cheers!
Pete

PS - Shame that you can't really see the Pink LED properly in this shot !

[1bottlerocket]

That is a nice looking pedal you whipped up there, thanks for sharing this and I learned a little something along the way.