Dr. Boogey - doesn't boogie? SOLVED!

[MetalGuy]

Hi,

There seems to be some problem with my Dr. Boogey. It's very quiet and the sound sucks big time. My BSIAB2 has more gain than the "doctor".
I have J201 everywhere which for a start I biased at 4.5V. The sound sucked. The I started to paly with the trimpots until I got the most audible distortion out of the unit. The voltages read - 4.37V, 3.25V, 2.5V and 6.6V. Tried one more time - the voltage readings were not even close to that. And the sound still sucks - there's no "edge" to it - it's not even close to the sound from the soundclips I heard. Some "edge" appears when the volume pot is all the way up but it's still not enough.  The highs are kind of rolled off. Bass is too much. I removed the 1nF cap - no change. Then removed the 5nF cap - again no audible effect whatsoever. There's obviously something wrong with my build. I used the Bucksears layout.
Any help will be appreciated.

[powerplayj]

Before you start to pull caps I would try to get the voltages between 4.5 - 5.5V.  Seems to me like I could never get Q2 (or was it Q3?....somebody help me here) to bias correctly and had to increase the value of the resistor going from the JFET to ground.  A forum search might turn up this topic as well if someone else doesn't chime in.  Also, if you have the MPF102 on hand, go ahead and use it for Q1.  Honestly, with the MPF this thing is much quieter and smokes at 2/3 gain. Anything past that seems to be compression to me.

You'll know when you have it right..........

[MetalGuy]

Thanks for the advice. Unfortunately I don't have MPF102 but I do have 2N5457 and 2N5484. Which one of them is more suitable as Q1?
1nF is there to provide some high freq. rolloff but obviously those highs are not there at all otherwise I should be able to hear a difference.

[powerplayj]

You can probably just stick with the J201 then as the 2N5457 did not make a world of difference based on my experience.  Looking back at my builds it was the Thunderchief that had a finicky Q3 and not the Dr. B.  I would try your best to bias thos Jfets in order from Q1 and then if you have issues sub another JFET for the problem slot.  If you can get the bias voltages anywhere between 4.5 - 6 and still have gain / tone issues, your problem may lie elsewhere.

This build has become quite popular so, more experienced help should come soon from others......

[Paul Marossy]

An MPF102 in Q1 helps with the noise levels a little bit. I would check your bias voltages. I have the FETs in mine set at about 60% of the supply voltage.

[Connoisseur of Distortion]

run through all of your joints and values. check your wiring. INSPECT TRACES.

there's a whole topic on how to do this... i'm kinda surprised no one has mentioned it yet...

[MetalGuy]

Guess what! All 1uF caps I bought from a local retailer came out defective! They just measured open - no capacitance, no resistance. After replacing them everything now works fine.

[$uperpuma]

yikes... an entire defective batch...strange and unfortunate!  Hope to get one of these built soon...