Dung Beetle hfe gain

debrad

debrad

Active member
Hi everyone!


I just dropped four 2N5088s into my completed Dung Beetle PCB to make sure it worked before boxing everything up...and it did (YAY!)...but I thought that I would ask if there was a consensus on hfe values for the Dung Beetle.

Looks like the four I chose measure around 235 hfe but I have some closer to 220 hfe and some more in the 400 hfe range. Does anyone recommend high gain versus low gain or is the circuit a little more forgiving than other fuzzes? Any specific transistor that might prefer a certain range of hfe?
 
Thanks everyone!

I hadn't found any discussion of Dung Beetle or Scarab Deluxe hfe so I figured the circuit must sound pretty good with a wide range of gain.

Thankfully there are folks like @Big Monk who understand the circuit in ways that I hope to some day and I will definitely take his advice to test drive a few different gains in the Q2/Q4 and Q1/Q3 positions. I will also do a little more reading online to see if there are additional tips on sites like diystompboxes, madbeans, tagboardeffects, etc., etc.

The good news is that this build is already sounding great!
 
Still test driving different transistors to see if I can find THE combination. Right now it has a group of 2N5088s that increase in hfe from Q1 (~220) to Q2 (~235) to Q3 (~380) to Q4 (~405) but, if I can be perfectly honest, I haven't heard much difference as I swap them in and out. I also had pretty high expectations based on all of the reviews I've read but, with the exception of the Dung Beetle's awesome bias control, I feel like I'm still happier overall with my recent Marigold build.

Here are a couple of photos...
 

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This circuit should be pretty insensitive to hFE, provided the hFE isn't so low (<20?) that the circuit won't function.
Q1's hFE doesn't matter. R4 & R5 set the gain for Q1; R2 dominates the input impedance.
Q2's hFE influences the bias, however the BIAS pot can dial out any bias difference cause by Q2's hFE.
Q3 is fed by a fairly low-impedance source (R7), so its hFE is immaterial.
Q4 is an emitter follower, so its hFE doesn't matter.

YMMV
 
Thanks @Chuck D. Bones! This is not only a huge help for me in this specific instance but, as I hinted at with @Big Monk above, it's also TOTALLY inspirational in terms of where I hope to get with my comprehension for pedal circuits!
 
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