- This topic has 4 replies, 5 voices, and was last updated 1 year, 7 months ago by
.
-
Posts
-
I bought six BC108c for the DSOTM Triple Combo. Four are around 440 hFE and two are around 720 hFE. This is a large difference. Is there a best hFE range or am I overthinking this.
The hFE range varies due to tolerance.
You can see in the datasheet that the expected ranges for BC108C are between 420 and 800 hFE.
I am not sure you would hear a difference between 400 and 720 but if you socket you can experiment.
Dunlop Fuzz Face pedals range from several hundred hFE to over 1000 hFE in the same round, red pedal.
As for the DSOTM I really do not believe the difference between 440 and 720 matters but you can socket, experiment, and decide.
I just built one and didn’t check the Hfe on the 109Cs. It works fine and sounds very cool. But agreed, if you’re concerned, try socketing them as Barry says.
My assumption when I built my second version of that fuzz was to use the basic 3 transistor mojo/rumor guidance – put the lowest hFE in Q1, next highest in Q2 and highest in Q3. Liked it a lot but can’t say that it actually made any difference. Made me feel smaert though.
Chuck
With silicon NPN transistors I personally have found that in general the leakage is nearly non-existant so that is kinda a non-issue to give concern to. Also it seems from my experience that when you are dealing with the gain ranges given for the BC10*(A,B,C) type transistors the actual hFE is also somewhat irrelevant.
Nearly all of the those transistors are above ~200hFE and from what I have tried in different fuzzes, once you get above the ~200 hFE in NPN silicon to my ears it all starts to sounds quite similar.
As an example, I currently have a silicon fuzz face w/ a trimmer inside to bias the transistors. In both Q1 and Q2 I have some really spicy BC109C transistors. Q1 is ~440 and Q2 is well over 700. To my ears it sounds extremely similar to another FF (Silicon SunFace) which has some BC108Bs in it that are in the ~200-300hFE range (it too has a bias trimmer). My point here is that playing with the bias on each of these pedals varies the tone much more that the transistors I started with!
Fortunately, Barry has done a really really good job on parts selection for the Nostalgia Tone boards and as long as you follow his guides lines about which parts to use, the actual stats (as long as they are not defective) doesn’t matter as much.
All of this of course is my personal experience, so this post should be taken with a grain of salt. My best advice mirrors what others have said: with transistors of a vintage nature, always socket them and play with it a bit!
- You must be logged in to reply to this topic.