2n4401 issues!!!

[breather-resistor]

hey all,

Ive been building a run of pedals using 2n4401's and I am having the wierdest dilemma...  I have a good stock of 4401s but some of them sound subtstantially different. I got the transistors from two sources (mixed them together of course) and now every time its time to install the transistor (which I do last) I have to breadboard a socket and go through the transistors to make sure I am getting the right ones...  If I use the "wrong" ones there is lower gain and strange high end tracking sound...

what types of differences am I experiencing here and what should I be looking for in order to make sure the 4401s I order in the future are the ones I want....

breather

ps. of course the circuit used is identical every time to the extent that i am using Dale 1% resistors.

[foxfire]

have you tested/matched them for gain?

[Paul Perry (Frostwave)]

They are made by many different manufacturers. I checked the Vishay & the Fairchild data sheets & they look quite different.
The data sheets cover mostly different characteristics, but for one thing, at a collector current  of 1mA, the Fairchild appears to have 5 times the gain of the Vishay, on average. Plus the Vishay has a 3 to 1 range of gain variation. (Fairchild probably does too.)
And the Fairchild gain seems much more current sensitive compared to the Vishay.

As a general note, I guess this is one more reason (apart from personal taste) why there is so much argument about what box sounds good...

[R.G.]

every time its time to install the transistor (which I do last) I have to breadboard a socket and go through the transistors to make sure I am getting the right ones.

I am reminded of the aphorism about frogs.
If you have to swallow a frog, don't look at it too long. If you have to swallow a number of frogs, pick the biggest one first.

You are biting off the toes of your frogs, one at a time.

If it were me I would do one of:
(a) figure out what about my circuit *allows* them to sound different, then modify it so that anything vaguely like a 4401 would work; this is the premium approach; I had classes on how to design bipolar circuits so that the exact value of the device parameters did not matter much, and I preach that gospel here a lot
-or-
(b) figure out if it's the high gain or low gain ones that sound good, then switch to another type with that kind of gain (like maybe 2N5088)
-or-
(c) at least build a test jig and test them ALL at the same time (i.e. swallow the big frog at one sitting)

[breather-resistor]

These are good thoughts...

R.G. -

Obviously the parameters of the circuit that "allow" the 4401s (or any other transistor for that matter) to sound different depends entirely on the structure of the circuit itself (or so I would assume).

That said, are there particular pieces that are most common or more likely to be the culprit?  Where would you suggest focusing?  As a clue, when I first stumbled upon the "wrong" 4401s I tried adjusting the bias resistor incrementally on a breadboard... This alleviated the issue only very mildly decreasing the level of the high end kind of squawking but did not influence its mere presence or the overall gated effect that usually signals a bias problem to me...

breather...

[Paul Perry (Frostwave)]

As RG says, there are some circuits where the variation(s) will matter a lot, and some where it won't.
I doubt it is possible to say more, without actually seeing the schematic in question.