The boost in Fulltone Fulldrive 2

[gutsofgold]

The boost switch on the Fulldrive 2... does that add an independent boost in series with the screamer circuit in there? Or does it just increase the gain of the screamer circuit? I like what that boost switch does so I'm trying to add something similar to one of my pedals.

[kurtlives]

All passive...

Just increases the value of the gain pot. There is also a bypass cap too to increase gain and such.

[gutsofgold]

thanks!

[alex frias]

It's a simple and smart way of doing the thing. But in my experiments I found much more interesting the use of a FET, MOSFET or even a RangeMaster kind of boost in front of the overdrive. Using a moderate gain at the overdrive and the boost, a more complex and richer sound is achieved. Just my 2 cents...

[gutsofgold]

It makes sense, not relying on that single opamp and two diodes for all that gain then.

[Ben N]

To put a fine point on it, the Fulltone approach actually lowers the value of the pot when "unboosted", then restores the gain that it took away with the boost.

I have long wondered about reconfiguring the output buffer for gain as a "boost"--especially if, like Fuller, you use a germanium tranny there. That would have to sound good, I figure.

[gutsofgold]

Do the new FD2's really have Ge transistors in there? The older one I played definitely had silicon from what I could tell. They're only used for in/out buffers, no?

[kurtlives]

To put a fine point on it, the Fulltone approach actually lowers the value of the pot when "unboosted", then restores the gain that it took away with the boost.

I have long wondered about reconfiguring the output buffer for gain as a "boost"--especially if, like Fuller, you use a germanium tranny there. That would have to sound good, I figure.

Ya its kinda funny actually. They use a 22K resistor or so to lower the value of the pot then when you engage the "boost" the resistor is taken away.

[Ben N]

Do the new FD2's really have Ge transistors in there? The older one I played definitely had silicon from what I could tell. They're only used for in/out buffers, no?

I have never seen it, but have read that at various times they used Ge. Take the quality of this information FWIW, absent corroboration, but I'm pretty sure I got this from John Greene, IIRC.

[alex frias]

I opened two Fulldrives: no Ge Trannies, No boosters. The info about "just increase the OpAmp gain" is OK. Anyway it sounds very good. The built quality is excelent.

[Ben N]

Just to be clear: At this point, there are an awful lot of FD2s out there, including quite a few variants. I know Fuller only used Ge in some FD2s, and I am not aware of him ever having used them to boost. I was just suggesting that as an avenue to explore for boost.

[alex frias]

I agree with you, a Ge booster (I used a RangeMaster variant) is a very good path. But try something like a Fetzer and listen to them!