freestompboxes.org

Hey Guys,

I'm planning to build a Fuzz Central Axis Face rev. 3 in the near future.
I'm having problems finding the BD139 Transistor, though. Musikding only sells the BD135/16 which I think is not the perfect choice because it is to gainy. What is the other difference between 135 and 139? I can't really tell from the datasheet.
Banzai and Mouser have them, Banzai has expensive shipping which isn't worth it for a couple of transistors, and Mouser would be international shipping, same thing.

Do any of you guys have a good source for those in Europe, and should I get the BD139/10 or BD139/16? should be in the normal gain range of 110-130.

cheers

Seiche wrote: What is the other difference between 135 and 139? I can't really tell from the datasheet.

I believe the main difference between the 135 and 139 is the voltage handling capability. I think the
139 can be used in circuits up to 80V, while the 135 is about half that.

Seiche wrote:..... should I get the BD139/10 or BD139/16? should be in the normal gain range of 110-130.

You may want to get a few of each. I say this for two reasons:

1) Both have gains that overlap into the 'good' zone, increasing your chances of getting the gain you want.

2) Batches of transistors tend to produce transistors with similar gains. If you go with the 10s, you could
end up getting all with gains of 65, or all 175 with the 16s. There is no guarantee you will get the gain
you want even by buying both. It just increases your chances. Although transistors are advertised with
a wide gain range, that's not the case, usually, within a batch.....especially silicon transistors.

+1

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@Seiche: Schreib das mal in den "Was soll noch ins Sortiment"-Thread bei Musikding! Es fehlt generell ein ANgebot für nach hfe selektierten SI-Transen, BD139 wären da eine gute Wahl, aber auch die anderen beim Axis Face genannten Typen, auch bc108/109 etc

PokeyPete wrote:I think the 139 can be used in circuits up to 80V, while the 135 is about half that.

Ah okay, so they are interchangeable for stompboxes. I figured they can't be much different. That's good news.

PokeyPete wrote:You may want to get a few of each. I say this for two reasons:

1) Both have gains that overlap into the 'good' zone, increasing your chances of getting the gain you want.

2) Batches of transistors tend to produce transistors with similar gains. If you go with the 10s, you could
end up getting all with gains of 65, or all 175 with the 16s. There is no guarantee you will get the gain
you want even by buying both. It just increases your chances. Although transistors are advertised with
a wide gain range, that's not the case, usually, within a batch.....especially silicon transistors.

this sucks, and most places don't stock silicon transistors presorted for gain.

roseblood11 wrote:Schreib das mal in den "Was soll noch ins Sortiment"-Thread bei Musikding! Es fehlt generell ein ANgebot für nach hfe selektierten SI-Transen, BD139 wären da eine gute Wahl, aber auch die anderen beim Axis Face genannten Typen, auch bc108/109 etc

ok hab es reingeschrieben, die Frage ist halt ob es sich für Klaus lohnt, diese zu sortieren, da das ja auch nochmal extra Arbeit macht die durchzumessen, etc. Ich habe vorgeschlagen, die sortierten Transistoren in einer kleinen Anzahl und zu einem höheren Preis anzubieten, so wie es ja auch mit den Germaniums gemacht wird. Oder man fragt einfach Klaus beim Check-Out ob er einem den BD135 mit einem bestimmten Gain-Wert raussucht. Er ist ja oft offen für Extrawünsche.

In actual fact, you don't really have to stick with the 70/120 gain combination when building a Fuzz Face type circuit, I've used transistors as low as 60 and as high as 680 to build Fuzz faces, and you can get them to work, you just need to tweak resistor values....

I reckoned i'd just order the BD135/16 and see if i get lucky. If not, i'll have to investigate further, either getting more of the 135/16s and look for the right one, or going to the local store here in Berlin, which I'm usually too lazy to. I don't want to order at banzai and spend 5 Euros shipping for a couple of transistors.

Alternatively I might just try changing resistor values (I'm including a trim pot for Q2 anyway).

ok well the 135/16 both have a Hfe of 160. The PN2369A are ~60. I think I will just try if they sound good (I will include trim pots), if not i have to keep on looking

It may be that I have laying BD139 and DB140 home. Will check it tonight.

ampman