Ge vs Si For Tone Bender MkII

[Schappy]

I was about to build a Ge Tone Bender until I realized Small Bear was charging like $18 for a transistor set.

How does the Si version compare to the Ge version?

[Brymus]

I have a couple of clips of the Si version in this thread http://www.diystompboxes.com/smfforum/index.php?topic=81110.0
As well as links to pertinent threads on the subject.
The clips dont do it justice > breadboard one yourself and see.
IMO Its really ,really close to a GE version.

[Joe Hart]

I like my Si TB better because it's a bit gainier and a bit more agressive sounding.  But they are very close.  I used lower gain transistors (more in line with the recommended gains for Ge in a TB).
-Joe Hart

[amptramp]

Just for the sake of long life and reliability (and reduced temperature sensitivity), I would use silicon.  Germanium has high leakage current which varies substantially with temperature.  Germanium cannot be passivated because germanium oxide is conductive.  Silicon has much lower leakage because silicon dioxide a.k.a. quartz is used as the passivation and it works.  If you are using an effect in a home studio, germanium can work well.  If you are going to gigs and either hauling the effects in from a freezing van in a blizzard or from a roasting van in the desert, you may have to adjust a germanium unit more.  Leakage current approximately doubles for each 10 degree C / 18 degree F rise in temperature.  Germanium also has a lower maximum temperature at which it can be used or stored safely.  If you need repeatability, where the same pot settings produce the same effect every time, use silicon.

[jrod]

Hey Brymus,
I liked your Si TB clips you posted. Thanks for the link. I have not read the whole thread yet, but will. I'm interested in trying one myself. I like my Ge biased at 7 - 7.5V, but I thought your Si version sounded best at 4.5V. So, you say it sounds even better live?

[Brymus]

Hey thanks ! I'm glad you like it 
Yeah the clips dont do it justice at all IMO
Also I found upping the voltage made some really nice sounds,18 volts sounded really nice as well,more modern sounding.
Same with using a 10K bias/fuzz pot over 5k,some really cool splatty/mis biased tones available that way.
Bryan

[tcobretti]

I must say: I built a Si TB Mk II, and then I built a Ge version.  I used some random Ge transistors I had laying around, although I certainly plugged a few in to find a combo I liked.

I much, much, much preferred the Ge.  It is much fuzzier than the Si, which sounded more kazoo-like in my build. 

If you must build Si, I'd get low hfe transistors I could find to try to get closer to the Ge sound.  I suspect one of the problems with my build was the medium (probly 200-400) hfe transistors I used.

But it's been a few years now, and I literally don't remember what happened to the Si, but I know exactly where the Ge is.

[mac]

I prefer Ge as well.
But there are some Si that fuzz very well, Brymus's sounds clips are awesome.
I bought some 2n2369 and bc107, golden legs, silver case, that sound very close to a germ. These are the only Si I use.

If you must build Si, I'd get low hfe transistors I could find to try to get closer to the Ge sound.  I suspect one of the problems with my build was the medium (probly 200-400) hfe transistors I used.

Even with high gain Ge, FFs and TBs do not sound good. Go low gain! (60 - 100)

mac

[yeeshkul]

Just built a Tonebender with really weak Ge transistors (Hfe~40). It sounds just brilliant, you must use 100k res Q1 base-ground to set the bias up a bit higher so the weak tranny provides some initial gain.

[jrod]

Interesting, yeeshkul! Did you 40Hfe for all three? Also, did you settle on a particular collector bias voltage for Q3?

[yeeshkul]

Yes, all 3 were about 40 Hfe. By the way OC81D were apparently weak transistors (D for a "driver") so my point was to simulate that. I tuned the Q3 bias to my favourite 6.5V.

[Electric Warrior]

I believe those drivers usually weren't that weak. Scruffie over at FSB has some that measure between 90 and 100.
My OC82DM measures about 150 hfe.