Pepo
New member
I built the Extreme Scream Machine pcb, I loved the tone, but the gain is too much. I have built several clones of tubescreamer including the ts808, and reviewing the schematic, I saw that the modifications to transform the ts808 to the od808x are a couple of components.
My understanding of the topology of overdrives is not much, so I need a little help to know what component I could modify to subtract a little gain from the pedal. I was reading the article "the technology of the tubescreamer" from Geofex.com and came to some conclusions (I hope my reasoning is relatively correct). I attached an image of the schematic and marked the differences for discussion.
The input buffer and clipping stage are the same, so the gain increase does not come from modifying C3 (47n) and R6 (4k7) and the frequency is still 720 Hz. Tone and volume control stage has modifications. C5 (100n) should be an RC low pass filter (originally 220n), from the tone pot, there is another RC filter where C6 is also modified (100n). I think these modifications change some of the original frequency of the ts808, having less mid hump and a lot clearer period. Next comes C7 (4n7) in parallel to R11 (1k). Here I don't know what function that capacitor has. Will it have to do with the increase in gain and volume?
The last difference is the output buffer. Here, the 3 components change order. It also changes a value. In ts808 the buffer has 100r and 10k, The TS9 470r and 100k and the OD808X 470r and 10k (a mix of ts808 and ts9) Is this modification to the output buffer responsible for the increase in gain?
Well, those are my doubts. I loved this pedal, but it has a lot of gain even at minimum.
My understanding of the topology of overdrives is not much, so I need a little help to know what component I could modify to subtract a little gain from the pedal. I was reading the article "the technology of the tubescreamer" from Geofex.com and came to some conclusions (I hope my reasoning is relatively correct). I attached an image of the schematic and marked the differences for discussion.
The input buffer and clipping stage are the same, so the gain increase does not come from modifying C3 (47n) and R6 (4k7) and the frequency is still 720 Hz. Tone and volume control stage has modifications. C5 (100n) should be an RC low pass filter (originally 220n), from the tone pot, there is another RC filter where C6 is also modified (100n). I think these modifications change some of the original frequency of the ts808, having less mid hump and a lot clearer period. Next comes C7 (4n7) in parallel to R11 (1k). Here I don't know what function that capacitor has. Will it have to do with the increase in gain and volume?
The last difference is the output buffer. Here, the 3 components change order. It also changes a value. In ts808 the buffer has 100r and 10k, The TS9 470r and 100k and the OD808X 470r and 10k (a mix of ts808 and ts9) Is this modification to the output buffer responsible for the increase in gain?
Well, those are my doubts. I loved this pedal, but it has a lot of gain even at minimum.
