What circuit is this based?

[JohnDRhoads33]

So some time ago, I bought an Enigmatone Transparent overdrive. At the time, it wasn't exactly what I was looking for, so I gave it to a friend. I kind of realized after that I actually wished I still had it, and a few years of constant shows did it in for my friend. Now, they don't seem to appear on Reverb or for sale anywhere, so I want to try my hand at building my own. That said, does anyone know what circuit this might even be based on? I did some image searches of the guts inside, and I can't narrow down what it might be because the circuit itself looks a lot more simplistic than basically any other OD I'm seeing. My other plan is to see if my friend still has the non-working one, and I can try and figure it out from that, and possibly even fix his while making another.

 

[Betty Wont]

A bufferless Tube Screamer perhaps?

 

[JohnDRhoads33]

A bufferless Tube Screamer perhaps?

Well I'll be... that looks exact. Thank you!

 

[benny_profane]

From the reverb listing:

So I set out to design a pedal from ground up that is fully transparent, has fairly low gain, and behaves like a tube amp when pushed. It uses very very little filtering, and is fairly natural and organic in response. It doesn't cut any bass, and filters out just the very harshest treble harmonics. Each guitar sounds like itself through this pedal. The mids are boosted only slightly as you turn up the gain knob. When the gain is all the way down the volume knob can get about 25db of clean boost. The tone knob behaves like a presence or brightness control, cutting or boosting only the higher treble frequencies. This was done to preserve the transparency and to eliminate any honk or muffled sound.

That doesn't sound exactly like a tube screamer to me. The tube screamer has an active filter in the gain stage that limits clipping to frequencies over 720Hz. This sounds like a soft-clipping overdrive with low-pass filter cap in the gain stage op amp with a second active mid-high frequency boost/cut. It's probably built on a TS architecture, but some key elements have been stripped out.

 

[JohnDRhoads33]

From the reverb listing:


That doesn't sound exactly like a tube screamer to me. The tube screamer has an active filter in the gain stage that limits clipping to frequencies over 720Hz. This sounds like a soft-clipping overdrive with low-pass filter cap in the gain stage op amp with a second active mid-high frequency boost/cut. It's probably built on a TS architecture, but some key elements have been stripped out.

Do you know of anything like that? A bufferless TS seems to have almost the same exact components, something like a Lovepedal Eternity Boost. I'm hoping my friend still has his broken one I can go through and actually identify each component in it to get a better grasp. It looks like from the screenshot I found, if I'm lucky I might be able to get an okay trace of the signal path too.

 

[benny_profane]

Take your pick at overdrive circuits. Any non-inverting op amp gain stage will have some high-pass filtering. You can set it so that it doesn't affect guitar frequencies, though. Based on the four clipping diodes, I'm thinking that this is based on a Timmy with a fixed BASS control.