Blackfire stage Question

[petemoore]

where does the first blackfire stage end..at the 1meg or just after the 470k/470pf...?
 This is assuming the first stage is the one to use as a gain stage for a post FF position...
 I've built a PNP BF first stage, up to the 1 meg [I'm also assuming the .1uf from Q2 collector to 1meg DC couples or do I need the .1 after the 1 meg also?

[petemoore]

I'm using 5087's...I looked up at NTE cross and it didn't say anything about high gain/low Noise...
 Anyone know of a Good PNP Si High gain/low Noise transistor for a PNP Blackfire Stage?
 I tried it anyway, seems like I should at least be getting a sputter with the 5087's?...
 Ii socketted the 10uf cap and it's been in there with the Pos to ground the whole time...Positive of the battery is also connected to ground.
  Any immediate messups you see from my descript?... everythings straight foreward perf build...everythings been lookin just fine too for a while/the whole time as far as connections...

[brett]

Regarding transistors for a Blackfire, I've had success with BC549Cs.  They are sufficiently high gain and low noise for the job.

Regarding where to end the stage.  Either before the 1Meg pot (but then you don't have a drive control) or after it.  Doesn't really matter, as long as you have that 0.1uF (or similar) cap after Q2 to block DC voltage.

Good luck.

[WGTP]

I built an NPN one and 2N5087's were the highest gain trans. I could find.  I bought some and tested for hFE and found several over 500.  You could also use BS250's for Joes' Mosfet's version since it is NPN.  Sounds like you got a bad connection somewhere.

I would say the stage ends at the .1uf cap.

[Joe Davisson]

I checked it out and the problem appears to be in the biasing. Try this:

Use a 4.3M resistor instead of 4.7M (3.3M + 1M in series).
-or-
Use a 15k resistor on Q2's collector instead of 10k.

Basically, the 4.7M is your bias adjustment tool for this circuit. It should be raised or lowered slightly until the collector of Q2 is close to 4.5v (anywhere between 4 and 5 volts is okay.) It's touchy, and different batches of transistors can be slightly off. Maybe your transistors were biased out of range. Good luck!

P.S. This thing works with 2N3904's, and even Germaniums with some biasing alterations. Anything goes. I've made it work with JFET's, MOSFET's, etc. You can use one type going into another. But the 2N5089's win for sound quality, no improvements were had from the other transistor types. (IMO) With low gain trannies you may need 3 stages (eliminating the output inverter.) Any maybe put the 470k/470pf before the gain control, with a 470k resistor afterward when using 3 stages (or for a lower-gain pedal.)

-Joe

[petemoore]

Big Boost, and nice OD clip under stress [hard attax].
 Glad I decided to do this one...it works great alone, with Peaches or Cheese...lol...Booster, Fuzz, really helps get the 'inbetween' gain stages hapnin' ['places between Boost OD and Fuzz] and easy to find...what it does to the FF is marvelous...it waswooly...Very Nice and thanks again and again for all the help...dohh Q1's 10k off emitter...lol
 The Electro cap...4.7uf got elected here...for now...I'll probly do more messin' with values..WOW !!

[WGTP]

Thanks for the insight Joe.  Sounds like a 2meg trim pot is in order.

[petemoore]

With a 1 meg pot on the output of the BF stage for volume...there's like 2.3 tons of it.
 I had to turn to about 2.3 on the vol dias to get unity.
 I'm thinking something more along the lines of a 100k will damp the output more and still have a big vol kick  [100k - 500k...]