PNP NPN Germanium Silicon You say potato...

[ildar]

I have noticed that some schems specifically call for germanium transistors. If I use a silicon transistor (assuming it's also PNP if that's what's specified), will the pedal still work? I know, I know, it won't sound as good, "because Hendrix used germanium based pedals, and he had the best tone...blah blah blah". All I really want to know is if the transistor will perform the same function even though it's silicon.

[Brett Clark]

In most (maybe all) cases, it can be made to work, but the bias points will change. When in the active region, a Germanium transistor only has about 0.2V between the base and emitter, whereas a Silicon unit has about 0.6V. SO, you need to pull the base "up" more towards the collector to bias the transistor properly.

Also, Silicon transistors have leakage currents (the current that flows when the transistor should be "off") that are thousands of times less than Germanium transistors.

You often hear that Germanium transistors are "slow" or low frequency devices. Most of them in the classic effects are. BUT, there are very fast Germanium transistors, good up to hundreds of Megahertz. And there are very slow Silicon ones.

[Ge_Whiz]

There are loads of ifs, buts, and maybes, but the truth is that when professional repairers of old germanium transistor radios restore them, they tend to just slap in a general purpose silicon PNP (such as BC559 or ZTX500) in place and the gear works.

Oh, and Hendrix used silicon FFs too...

[bwanasonic]

Oh, and Hendrix used silicon FFs too...

Yeah, I look at the Si VS. Ge thing more as two different sounds rather than "Ge good, Si BAD!" . I love "Are You Experienced" (Ge) , but I love "Band Of Gypsys" (Si) too. If you are talking specifically about the FF, there is no real reason to make a PNP silicon version. The NPN version is the more common silicon config.

Kerry M

[Ge_Whiz]

Well, it is generally accepted that the FF sounds better with low-gain transistors, around about 100 or so. Finding modern silicon NPN transistors with gains below about 400 is quite difficult, but PNP devices are commonly much lower - one reason why it MAY be better to consider using silicon PNPs. (Just a thought.)

[Ansil]

i got to playing with my second. yes people second fuzz...  a npn silicon germanium pnp. hybrid.  with a npn lpb1 type booster infront of it.

[brett]

Well, it is generally accepted that the FF sounds better with low-gain transistors, around about 100 or so. Finding modern silicon NPN transistors with gains below about 400 is quite difficult, but PNP devices are commonly much lower - one reason why it MAY be better to consider using silicon PNPs.

While SMALL SIGNAL Si devices usually have high gain, lots of POWER devices also have low gain.  I like the BD139, especially at the lower end of it's range of gain (Hfe is mostly 120 to 160).  The older-style high power NPN Si devices, such as 2N3055s also have limited bandwidth, which I believe is a significant part of the PNP Ge "magic".  (as already stated in the discussion of "slow" devices, above)

[ErikMiller]

Well, it is generally accepted that the FF sounds better with low-gain transistors, around about 100 or so.

Not in my opinion. The best sounds I have gotten are with silicon NPN's more than twice that gain.

In general, I like a lot of gain.

[Ge_Whiz]

Fair enough, Erik, but does your 'preferred' sound sound like a Fuzz Face? :wink:

[Johan]

sometimes the leak in a Ge tranny is used to bias the circuit and it wount work with a silicon unless you modify the circiut slightly. look at the last stage in a three knob tonebender to see what I mean. as for tone...its just preferences....

Johan

[nightingale]

hello~
i like both, GE/SI... but my favorite FF is jack ormans YAFF, it's on the "labnotes" on his site... i also tried it with SI 2n4401's and it had loads of fuzz, but no hiss/oscilation... pretty cool FF variation IMO... it has a cool spongy tone, and it pretty touch sensitive IMO.

[ildar]

I guess I shouldn't have even invoked Hendrix's moniker here. All I was trying to do was avoid what is purely a subjective argument about tone. I only mentioned him because I did not want a si vs. ge argument. I simply need to know if a si transistor will perform the same function as a germanium.
 Incidentally, I am building a Rangemaster clone. I want nothing to do with anything even remotely similar to a Fuzz Face.

[javacody]

Yeah mentioning Jimi, especially in the tone that you did was a big mistake. I consider it particularly blasphemous. Next your gonna tell me that Univibes are garbage.  :lol:   Just joshin ya.

But seriously, you are mistaken about Jimi because I'm fairly certain he preferred the silicon Fuzz Faces.

Is there a reason why you are particularly trying to stay away from germanium? I mean, other than the fact that they are expensive, leaky, temperature sensitive, and a pain to bias?   :lol:

[ildar]

Well, I'm not really trying to stay away from germanium, but your list of possible drawbacks may have convinced me to do so! As a father of five with a full time self-owned business and a part time playing gig, I don't have much time tracking down these esoteric components. As it is, I can only build my pedals in my spare time (after 1 am weekdays).
As far as JH goes, ALL I WAS SAYING IS: I don't give a corn-riddled crap if anyone ever sounds like him again, least of all me. No disrespect to anyone, but dude is dust. Let time move on. "Of course, I am building clones of vintage pedals" he thinks to himself.

[javacody]

Well ildar, since I still like to pretend that I'm a cool, thin, wildly talented black guy who died 30 years ago (instead of pretending to be a balding, middle aged, mediocrely talented white guy), I don't like to have my bubble bursted and to anyone who tries, I say "Duck!".  :lol:

I really wish I would have started my voyage into fuzzdom with silicon trannies. I think it would have been much more fun and way lest frustrating.

[Gus]

Years ago I built a Ge ff.  I went thur about 20 transistors to find a good sound.  I like the sound of Ge but they are a pain.

I did reading and thinking.  it seemed the the control of the fuzz via the vol control of the guitar had alot to do with both the open loop gain and closed loop gain of the first transistor in the FF circuit.

I also thought limiting the highend would help alot.

Picking devices by gain seemed a bad way to go about building something.  So I reduced the gain via the emitter and collector resistors and found the Ic that seem to sound the best with Si transistor in a FF circuit.

 I also noted that Vox did a good job with the Si tone bender adding the 820 ohm resistor.  CD with the texas square face use a 2k gain pot.

That got me thinking about adjusting the bias via the emitter circuit of the 2nd transistor.  By adjusting the bias there it would help keep the Ic were I liked it.


The results are in the GCS schematics section.

  The newest Si one is the Hot Si build that Doug H. built and tuned/voiced  He added a nice tone section and adjusted value for a nice Si tonebender sound.


If you can find an 1964 GE the company transistor book the circuit the FF is based on has all the math equations.  also reading The Art Of Electronics will help.

[C Bradley]

Some one mentioned that lower gain transistors were better for the Fuzz Face. I've been using 2N3906's and 2N2222's and the 2N2222's are great! Sort of in-between the tone of Ge and Si, at least in my circuit.

Chris B

[drew]

It depends on what you want to do... personally, I record guitar (and a dozen other instruments) in my home studio, and often find myself using pedals to shape the sound in ways that fit well in a particular track. So it's nice to have a wide range of things to choose from.

Germanium transistors have a quality that's not like silicon transistors. Rolling off the highs and reducing the gain of silicon transistors sounds completely different to me from germaniums- and in fact worse, if what I'm trying to get is that globby, melted-down-candle sound.

I put everything from guitar to rhodes to synths to drums thru my germanium-based fuzz pedals, and the results are good enough to convince me to keep making more


drew
www.toothpastefordinner.com