Hey all,
I'm working on a series of big muffs. I'm going to muck about with transistor/diode combinations aswell as Silicon/Germanium combinations. Anyway, I've a quick question about the transistor selection. I've breadboarded a muff before, and when i did, i tried out a bunch of different silicon NPN's. I did my best to get them all to have IDENTICAL hfe's, and it worked great. I tried a few different diodes, and similarly, i tried to match them according to my DMM.
So anyway, i'm waiting on a bunch of GE's in the post, with the intention to try them too. How crucial is it to have the hfe's consistant in a big muff? Like, would i be ok if i limited to a pretty narrow range of hfe's even.
Lets say i was looking for 4 transistors, and after testing all 20 of my GE's, the range of hfe was 100-300 (i'm not sure what it is till i test them lol!!!) While testing them, i came across 4 pretty similar one, with hfe's of 120, 125, 127 and 130. Would that suffice? I'm basing all this on when i was doing the silicon ones, and the difference in hfe was about 5 between 4 of them.
The next step will be seeing what hfe's the normal big muff transistors give and trying to get something similar! :P
Cheers all,
tm
You shouldn't have to match the trannys for a big muff. I've never tried it, so I can't testify as to whether or not it would sound better, but I can't imagine after going through the 2 clipping stages anything about the gain characteristics in terms of matching would matter. The signal has been mashed and clipped to hell at that point.
The only reason I can think of to match BMP transistors is to impress people who don't know how the circuit works.
I wouldn't call it matching but in general higher hfes sound good. 400+ish
But then there are good sounding version with 2N3904s in there...so .... :icon_neutral:
john
Dont worry about matching but put the highest gain ones from whatever part number you use in rather than lower gain ones. I generally go from low gain to high gain from Q1 to Q4.
I generally go from low gain to high gain from Q1 to Q4.
What's your rational there?
I would think that the first transistor (which is amplifying the guitar's signal
whould want to be a high gain for better signal to noise ratio and to drive the
clipping stages harder. Curious to know otherwise.
Quote from: Nitefly182 on March 23, 2010, 01:45:44 PM
Dont worry about matching but put the highest gain ones from whatever part number you use in rather than lower gain ones. I generally go from low gain to high gain from Q1 to Q4.
i did the same in mine, actually q1 was 2n2222 q2-3 3904 and q4 was mpsa18
that was just what sounded best in the test
sorry im only getting back to this now. i´m abroad with a distinct lack of the internet. :(
when i breadboarded it before, i tried out 2N3904s, and they produced a pretty standard muff sound. nothing special like. My parts arrived, but im not home till saturday, so i´ll be breadboarding it on saturday night and measuring hfes. Im somewhat curious as to what it might be like to have one of the transistors for the clipping stage as germanium.... or something similar with the diodes... still, we shall see when i have it breadboarded :D .
I got both NPN and PNP germaniums, so i might do it with those, and have the polarity the other way around like, just so i can try out the PNPs. only thing is, all my other pedals are positive polarity and having a negative one in there wreaks havoc on the daisy chain. Unless there´s an easy way to go +9V DC input, and then reverse the polarity...
ugh... starting to think i might be overcomplicating what should be a fairly easy project...