BC108 and BC109 seem to be the Si's of choice. Why?

[PurpleStrat]

This may seem like a stupid question to some but humour me!

I see them recomended alot and in a lot of layouts and schems. I have not had a chance to try either yet. I have some on order but have a week till I get them.

What makes them special or better for Fuzz? Is it the hfe? Low noise?

[Dragonfly]

like just about any other part, they sound great in some things, terrible in others....

depends on the circuit

the reason that "some" people use them, i suppose, is the "JRC4558 syndrome"...a few people on the net said it's the best, so it "must" be.

the best transistor for a given circuit is the one that sounds best for that particular application, regardless of its' part number.

design with a goal or "sound" in mind, and that will help you choose the correct parts.

[Renegadrian]

Take the Bazz Fuss...
I used a BC108b I found in a forgotten bin...It works great...But the above circuit can take
2n5088-89
2n2222
2n3904
bc548 (which is supposed to be the newer version of the 108)

so how'd you choose one of those??? Try them all!!! And follow your ears more than words...

[slacker]

It's probably just metal can mojo, but in a couple of circuits I've built BC109s have a bit more of a "growl" than other transistors with a similar HFE.

[PurpleStrat]

like just about any other part, they sound great in some things, terrible in others....

depends on the circuit

the reason that "some" people use them, i suppose, is the "JRC4558 syndrome"...a few people on the net said it's the best, so it "must" be.

the best transistor for a given circuit is the one that sounds best for that particular application, regardless of its' part number.

design with a goal or "sound" in mind, and that will help you choose the correct parts.

I hear ya. See even on your Silicon Fuzz Face layout it says use BC108 and BC109. Even though it shows you can use others it seems like if you want the best sound you need these. I guess I am gonna have to hear for my self but I can say in the Bosstone clone of yours that I had trouble with, I changed the transistor from the BC108 (went microphonic as hell!) to a 2n2222 and it's just not the same.

Are the BC's  more consistant maybe?

[Dragonfly]

like just about any other part, they sound great in some things, terrible in others....

depends on the circuit

the reason that "some" people use them, i suppose, is the "JRC4558 syndrome"...a few people on the net said it's the best, so it "must" be.

the best transistor for a given circuit is the one that sounds best for that particular application, regardless of its' part number.

design with a goal or "sound" in mind, and that will help you choose the correct parts.

I hear ya. See even on your Silicon Fuzz Face layout it says use BC108 and BC109. Even though it shows you can use others it seems like if you want the best sound you need these. I guess I am gonna have to hear for my self but I can say in the Bosstone clone of yours that I had trouble with, I changed the transistor from the BC108 (went microphonic as hell!) to a 2n2222 and it's just not the same.

Are the BC's  more consistant maybe?

Not referred to because they're "the best" necessarily...

But they ARE referred to in that layout because they are what the ORIGINAL silicon FF's had (others in the originals were BC209 (hard to find). BC183, BC182 (pinout differences, etc)...so they are recommended for having a build thats close to the original pedal.

[rikkards]

Definitely true. When building my Kay FuzzTone, I tried 2n5088s and 2n3904s as some people had used them and said they sounded good. They did sound good but not....quite... close enough for my liking. So I decided to check Ebay and got some 2sc644s and 2sc945s and it was better. The distortion was more "marbly" (if that makes any sense)

like just about any other part, they sound great in some things, terrible in others....

depends on the circuit

the reason that "some" people use them, i suppose, is the "JRC4558 syndrome"...a few people on the net said it's the best, so it "must" be.

the best transistor for a given circuit is the one that sounds best for that particular application, regardless of its' part number.

design with a goal or "sound" in mind, and that will help you choose the correct parts.

[Jered]

  Also try MPSA18 which is a quieter 2N5089.
  Jered

[DougH]

Look at their datasheet. BC108 and BC109's M.Q. factor* is through the roof. That's why they're so popular.

For the most part, Si NPN bipolar junction transistors are interchangeable in fuzz circuits. You may prefer one over another in a particular case, or like a certain hfe, etc, but they will all work.














*mojo quotient

[ambulancevoice]

  Also try MPSA18 which is a quieter 2N5089.
  Jered

yes, but has shitloads more gain (if the hfe is an important factor to the circuit)
the BC549C is around the same gain and its a low noise transistor

[Paul Perry (Frostwave)]

The reason you see them so often, is that they were the "best available" silicon transistor at the time the first stompboxes were being made.
Nowadays, nobody wants to make a general purpose transistor with gain that low & also design is changed so you have less noise.
I guess if the first stompboxes were being built TODAY, we would see fuzz faces etc designed right from the start to be optimised for today's high gain low noise transistors.

The other thing about those early transistors - they had lower gain than most of today's, but the gain also varied a lot. Hence you would sometimes see them divided into A,B, C subdivisions. So a circuit that just says "BC108" - it's worth checking different gain silicons in there.

[Gus]

Or one can work with the Si by making a circuit that controls the first stage open loop gain (Q1) and roll off the highs C4 R9
Takes some clues from the vox 2 transistor(collector current and resistor values and added 820ohm) and  square face 2K pot.

Background on this is years ago I traced a few FF types and looked at schematics and made  circuit with fixed resistors and series pots and did some math for the first gain stage.  From math, thinking, testing and building  I found a distortion circuit fragement I like.
http://www.diystompboxes.com/pedals/gusFuzzFace.gif

or this
http://www.diystompboxes.com/pedals/3tran.JPG
or
http://www.diystompboxes.com/pedals/rocket.JPG

[PurpleStrat]

So basicaly it's all about the gain? Nothing else to it?

Whats the closest easily available transistor to it? I see 3904's mentioned alot as replacements but I have never had one that tested close to as low as as BC108's.

[Dragonfly]

So basicaly it's all about the gain? Nothing else to it?

Nope. There are definitely "tonal differences" between many transistor types. Whether the difference is "good" or "bad" depends on the circuit, the goals, and the player/builders ears.

Whats the closest easily available transistor to it? I see 3904's mentioned alot as replacements but I have never had one that tested close to as low as as BC108's.

most new manufacture BC108's are above 200hfe...there are BC108A, BC108B, and BC108C, with "C" being the highest hfe. So in your comparisons it really depends on what you're comparing "to". NOS BC108's tend to have a bit lower hfe generally...

As far as popular silicon transistors, here are some you should probably keep around for your experiments.....at least if you plan on building a few more pedals

NPN TRANSISTORS

2N3903
2N3904
2N2222A
2N2369A
2N5088
2N5089
2N4401
MPSA18
MPSA13


PNP TRANSISTORS

2N2907
2N3906
2N5087


IF AVAILABLE

BC107
BC108
BC109
BC183
BC547
BC182L


In reality it won't cost much to get 5 or 10 of each of them... FUTURLEC probably carries most of them in stock.

[petemoore]

   fine transistor..
  And does have greater differences in sound compared to comparable Hfe transistors...among Si's...BC's kind of stand out that way.
  ..Because that's what I see when I'm looking at a FF with 1 BC transistor in it.

[PurpleStrat]

So basicaly it's all about the gain? Nothing else to it?

Nope. There are definitely "tonal differences" between many transistor types. Whether the difference is "good" or "bad" depends on the circuit, the goals, and the player/builders ears.

Whats the closest easily available transistor to it? I see 3904's mentioned alot as replacements but I have never had one that tested close to as low as as BC108's.

most new manufacture BC108's are above 200hfe...there are BC108A, BC108B, and BC108C, with "C" being the highest hfe. So in your comparisons it really depends on what you're comparing "to". NOS BC108's tend to have a bit lower hfe generally...

As far as popular silicon transistors, here are some you should probably keep around for your experiments.....at least if you plan on building a few more pedals



In reality it won't cost much to get 5 or 10 of each of them... FUTURLEC probably carries most of them in stock.

I don't plan on a few more pedals......I plan on building LOTS more! I actually have most of the commons you listed. I even have 100 5088's  and a few less common oddballs I picked up at a local shop.

Would it be fair to say that lower hfe helps with volume knob clean up? I built a Colorsound Fuzz with a 2n706 (hfe 20) as Q1 and a 3904 as Q2 and it cleaned up beautifully. Then I tried a 5088 in place of the 2n706 and it sounded awful when cleaned up.