Flipster and fets, build report etc...

[Branimir]

I've been perfboarding stuff like a madman for the last couple of days and finally I got Flipster on the table.

I am not a bass player so don't have a "proper" instrument to test it, I used my guitar instead.

Anyways, here are some facts, right of the bat:

Unfortunately I cannot buy 2N5457, MPF102 or J201 in a local store so I used BF245's for this circuit.

Beware, there are three variants of BF245, the A, B, and C.

BF245C has a too high Vgs off and didn't work properly in the circuit, couldn't get it to bias properly, or to get any audible output, actually I got very very low output...

BF245B worked, but with my guitar (goldtop P90) it was all clean, and the output still seemed a bit low.

BF245A's work a bit better, I even managed to get one 2N5457 from some millenium bypass circuit I have dismantled (I periodically order stuff from various webstores so this was one was the last from the batch).

So, at last I have BF245A's in Q1, Q2 and Q3 positions, and that last 2N5457 in the Q4.

First two stages bias nicely, the third one is a bit of a pain to dial and fourth gain stage has only one sweet spot becuse voltage from 0.25V jumps to 8.6V in milimeter turn, so some reasonable bias is in that, uhm, millimeter turn. No use of setting 4.5V, I just dialed the trims by ear.

Results:
I get some distortion/breakup from this circuit when the gain pot (schematic says Volume for that one) is maxed out, tone controls work as the should and output can get above unity with turning up the Master pot.

On sunday we'll have a band practice so the bass player can test it on his amp for overdrive sounds, but I think I'm not getting the wanted results because of those darn BF245A's. Are J201 basically a must in this type of circuit or 2N5457? I have tried placing that one 2N5457 in the position of Q3 and at the end of experimenting I put it at Q4 and seems to me like it biases better in Q4 position then BF245A, and also I think that it has a higher hfe because the output is greater than with BF245A.

Basically, I'm limited to transistor choice right now so I'll have to manage with these for some while, should I try putting that 2N5457 in Q1 or Q2 to get more distortion out of the circuit? I mean, after all it should mimic the breakup of an Ampeg amp, so it should have some more fuzz to it?

I know, I'm trying it with a P90 loaded guitar, is a typical passive jazz bass pickup higher in output then my guitar's?

I appriciate any input you guys have on this matter!

ps: if I get the computer in the garage working by sunday, I'll maybe record some clips of the bass guitar. The bass player uses Albert Kreuzer's preamp, so we take preamp out (seperate DI output post gain, post eq) to the mixing board.

Cheers,

Branimir

[Branimir]

edit: I've deleted the post since I opened a new topic, not involving this pedal design