FF not matched Transistors (Finetuning)

[Oliver]

Hello Guys,

i build several FuzzFaces and for my ears they all sounds good.

Lately i build one and put in two old BC107 Transistors (Q1 = 84hfe and
Q2=120hfe) i grabbed them out of a Box of old Parts and was happy to
see those hfe values.
The Fuzz sounds a little bit noisy compared to the same circuit with two 2N3904 Trannys (the 2N3904 are very quiet - only slighly noise), but
the Sound with the two BC107 is so great!!

I thought about finetuning a Fuzz with randomly picked Trannys.
I have a bunch of BC549C, but using those and setting the Q2 Collector Voltage to 4,5V the Sound overall is OK but too much Gain for my Taste.

Is there a Way to build a FF Circuit and tune it to every Transistor Setup?
For Example Q1 BC549C with hfe=450 and Q2 BC549C hfe=600
Or Q1 2N3904 hfe=200 and Q2 BC549C hfe=500
I think there must be a way to build the circuit to perfect sound without
to pick the Transistors at one of thousand...

any idea??

Thanx

Oliver

[petemoore]

I build a FF board for FF tunings on perf.
 Socket or trimpot all the caps and resistors...and the battery clip connections...that way you can reverse all polarized  caps, and Go from NPN to PNP in a snap.
 If you get something you like, take notes so you can reproduce that with soldered in parts.
 If you pull the transistors, most of the pots resistances can be measured in CCT., however if there's another route for current to flow around the pot through the CCT, you'll lift one lug connection of that pot to get an accurate reading of the value you'd carefully adjusted it to. Read the actual value of the pots with the DMM, and use a Fixed resistor for the 'road' build.
 I keep this board here in case I want to do a different FF type build...Oh and very recently this became probably most important of all...Piggyback the transistors.
 Use an 8 pin IC socket to piggyback FF Q's. Turn it so you have left and right columns of pins. the left column is for the active Q. top pin C, 2nd pin down B, bottom TWO pins to Emitter.
 Right column is for the 'dummy' Q. top pin is not connected, the 2nd pin down goes right across to the actives base, the emitter gets the 2 bottom  pins. This way you can swap transistors, and the EmitterS resistor [between active Q and non active Q] goes across from left column to right, using the bottom pins. Piggybacking like this or not piggybacking is as easy as pulling the non active Q. You can adjust the gain of FF Q's using the piggyback method. It is very good and new, definitely worth installing on a FF Mod board as described above.

[petemoore]

That or breadboard...
 I just keep that perf FF test board there, as the 'bench FF', so when I want to tweak something else, or get it to work right with a FF...there it is.
 I just never know when I'm gonna want to play FF mod again.

[RedHouse]

I too built a board very much the way Pete describes his, I call it a "jig" saves me MUCH hastle when dialing-in the bias on a transistor set.

Today by chance I had some extra time and tried to dial-in some 2N3906 and 2N5087's. I tried everything, piggy-backing, gain matching, everything but just couldn't get the silicon to cooperate.

Best I could get was a Si/Ge (Q1/Q2) which sounded great, and of course the Ge/Ge combo always sounds great when they are biased right.
(I shoot for 4.75v)

[Oliver]

HI Guys,

thank You all for Your fast and informatife replies!!

i think i'll go to build an all socketed FF to play with it...

bye
Oliver

[RedHouse]

My goof, when I tried the piggyback thing, I didn't notice the resistor between the two emmitters, after adding that, the piggyback system worked very well.
(really REALLY well)

[petemoore]

Guys are talking Buffered FF again.
 Looks like I'll be trying that again too.
 Probly put a switch on the buffer, that way I can get the solid Fuzz high gain Buffer tone, as well as the guitar Rolloff tones of an unbuffered FF.

[Gus]

Its not just Hfe, its Hfe vs Ic.  Build a real tester that tests the transistor at working Ic.  DMMs use very low current to test.  Better yet do a two or more point match.  read about how transistors are speced.  it sometimes like how CPUs are.    



                            Its in the curves!!!!!!!



Gus