Anyone familiar with the Addrock Ol' Yeller overdrive?

[mort]

Recently acquired a very early one that looks like a project/prototype and it's easily the smoothest sounding overdrive pedal I've ever heard. I don't have tons of experience with pedals but I do have plenty of experience hearing things and this thing is extremely pleasing to the ears.

It sounds so good I'm inspired to build a couple dozen of them as a project. Haven't drawn out the schematic yet but here's the parts list, straight from the pedal.

It sounds tube screamery but better... smoother.. any idea if this might be a straight copy of something that came before it? recognize the recipe?

Thanks for any info, thoughts or comments... they are all welcomed.

47uF 50v (2)
.22uF 50v (1)
.1uF 100v (1)
1uF 50v (1)
.051uF ?v (2)

1M (2)
10k (2)
100r (1)
47k (1)
4.7k (1)
470k (1)
220r (2)
1k (1)

4580D op amp

1N914 (3)

25kL pot
100kL pot
500kL pot

open jack (1)
stereo jack (1) (what's the point of a stereo jack when using mono cables??)
9 pole switch
LED
Power jack
Battery clip

[g1]

stereo jack (1) (what's the point of a stereo jack when using mono cables??)

Usually to disconnect the battery when the cable is removed, so battery is not being drained when pedal is not in use. The battery (-) wire connects to the ring terminal. When you plug a mono cable in, ring gets connected to sleeve (ground).

[Jazz P Bass]

Interesting that they used a 4580 op amp.
(or was that slapped in a a later time)
They can be a tad power hungry.

[35L6]

I'm just guessing but its probably op amp diode clipping and the "smooth " is in the tone shaping components . Can you trace it out ?

[vintagekiki]

About Addrock ol' yeller

https://www.thegearpage.net/board/index.php?threads/addrock-ol-yeller.648033/

https://reverb.com/item/6214890-addrock-ol-yeller-overdrive-pedal-808-tube-screamer

[mort]

Can you trace it out ?

You mean make a drawing of the circuit? I plan to and will update the thread when it's complete.

[EricScott]

Oh man what an old thing you have, I hope you figure out how to work with it)))

[Helmholtz]

From photos I've found here's the schematic

That looks like a phaser, not an overdrice. Also the 4580 only has 2 opamp sections.
I guess it's more like a Tubescreamer without the switching Fets.

[mort]

Ok I think I got everything into the drawing except the power connections for the op amp, LED, output connection and power jack but the main circuit I think is complete.

Does it look like it has errors in it?

[The Dude]

Not that it isn't easy enough to figure out and generally assumed, but ground symbols on the jacks are missing and the ground switching circuit on the input jack isn't shown (+ wrong ring/tip for input). None are major issues, IMO. Just pointing it out.

[mort]

Yup I gotcha and always appreciated.

The main point of the exercise is to prepare for having some boards made up.

I'm going to go through it again a couple more times but thought I'd throw the drawing up now that it's on paper.

[The Dude]

Also, where's the output? I think you've got something drawn wrong on that second op amp.

[mort]

Ah good catch. The output is on the wiper of the 100k pot. I've added it to my drawing and will update the thread later after more refinement.

[mort]

And what was that schematic drawing software that can be used for having pcb's made up? I had it on an old computer and only ever used it for drawings.

[dmeek]

I see 2 problems The 470K resistor from pin 5 needs to go directly to point A. The 220 ohm feedback resistor on the second op-amp should be 2.2K or 22K?
I've re-drawn it in a more conventional layout.