Biyang - AC-8 Woody Acoustic Simulator

~arph · Post by **~arph** » 25 Sep 2009, 12:33

Hi Guys,

I just recently found out about the biyang AC-8 "Woody" Acoustic simulator.
The name struck a bell as Mark Hammer from DIYStomp designed an acoustic simulator named woody too.
On first glance it seems to be the thing. Same name, same controls and heck even the same font on the pedal for the name "Woody". I does appear to be the 9V version.

I just received one from evilbay (marktplaats) and I will reverse it.
As for now here are some guts I found on the net already.

http://handicrafter.kilu.de/Gitarre/biyang_ac-8.html

Will report..

Dirk_Hendrik · Post by **Dirk_Hendrik** » 25 Sep 2009, 13:38

~arph wrote: Will report..

Am interested!

DimebuGG · Post by **DimebuGG** » 26 Sep 2009, 09:07

,

So D5, D6, D7, R12, and "TOP" control = D1-D3, R17(150K), and TR1(500K trimmer) in Mark Hammer's "The Woody" design?.

~arph · Post by **~arph** » 26 Sep 2009, 12:14

Yes I'd say so. It controls the amount of distortion in the high frequencies, giving you harmonics

~arph · Post by **~arph** » 30 Sep 2009, 10:19

The Biyang AC-8 follows Mark's original schematic.

https://img232.imageshack.us/i/woodyschematic.gif/

Since it uses a simple 9v supply, the opamps are connected to 9V and ground and all ground references (bar the volume control) are replaced with a Vref reference. Constructed by a 10k/10k and 2x 100uF voltage divider. One other difference is on the input stage.
Input pulldown res is 2.2M (orig 1m) and the input cap is 0.1uF (orig 1uf) and the gain resistors used ars are 100k/120k instead of 10k/12k thus keeping the gain the same.

I only played through the unit on my strat and found the sound disappointing and lacking bass reponse. Marks soundclip sounds much better. ( it's somewhere in a zip on hammer.ampage.org )
And I recall having breadboarded a modified version of Oliver Alex's 9v version once that sounded much better too (the signal only split once. One side was the treble/distortion and the other side was the unaffected signal with a variable active bass boost)

I will put out a schematic with modified values when I have some time to spare again.

Post by **modman** » 25 May 2015, 15:12

Did you ever complete this arph?