Earthquaker Devices Erupter - Verified

[anders]

 Found a schem at FSB HERE.
Lookes like a input buffer >pickup simulator > silicon fuzz face witch bias pot.

Edit 2. Now verified by Sphere80. Thanks!



Edit 1.
Found a photo from EQD workshop with a part list and how to set up the pedal. There seems to be an extra trimmer there, though.

[Zanius]

Lol, I imagine some forum member dressed as a janitor walking around the Earthquaker building and snapping photos!
That's straight up spying.

Good job otherwise :)

[Travis]

The funniest part of imagining a spy going in there is that after all that effort it’s a modified Fuzz Face and the sheet is just telling us to bias it to 4.5V

[Mulekicker]

I've been in there twice, but it wasn't me.

[iefes]

The workshop photo is great! Thanks for this.

The trace over at the FSB forum was made be me. I found that there are different versions of the Erupter. Some have an additional Volume-Trimmer to set the output volume and also some seem to have 2 bias trimmers additional to the Bias pot. So you can include an additional volume control if you like. It should be a 100k.

Edit: I'm not sure what the notes about the transistor hfe really means. Does it mean, they should both have about the same hfe in the range of 60-120 with Q3 being the higher? Or does it mean Q2 should have around 60 and Q3 should have around 160 hfe?

[Sphere80]

Built with the larger 42TM019 instead of 42TL019.

https://i.imgur.com/DYerXt5.jpg

It has sockets as I'm still experimenting with transistors. That Q2 needs to be very low gain.

[Teddeeh]

Does the transformer have to be specifc or similar?

[Sphere80]

I don't know.   This is the original article that most likely inspired this design:
http://www.muzique.com/lab/pickups.htm

[Sensei Tim]

i got the transformers yesterday and i've got some 2N496 transistors on their way.

Will be able to report on this soon.

meanwhile, here's the layout i made before i found this thread:

[GrooveChampion]

Any news on the layouts?

[Sphere80]

I built  Anders'  and subbed 2 low output transistors, close (but not exact) to  the values on workshop photo.  I used a 2N2369 for Q2.

Sensei Tim has the original model transistors on the way, so I look forward to hearing his report.

To me, my build sounds and operates just like the demos.

[GrooveChampion]

What was the other tranny?

[Sphere80]

"Thompson CSF 40400" from Smallbear, that had "07H04" printed on it.

I was able to also get close with an MPSA06 and pn2222a.

[GrooveChampion]

2 2n2369 didmt cut it?

[Sphere80]

I only have one .  I was shooting for a 60hfe/160hfe combo, as the photo shows.   Or those could be the overall acceptable ranges for both, I don't know.

[GrooveChampion]

Is there any other equivalent(not necessarily modern) to the 2n4970?

[anders]

Built this yesterday and it's quite picky abaout transistors. A 2N2369 (hfe 62) for Q2 and a 2N1711 (hfe 141)  for Q3 worked best for me. Did an equivalent search at alltransistors on 2N497 and ended up with a lot of odd part numbers. LINK

I guess the motto "socket and see" should be used here.

[GrooveChampion]

So its like every Fuzz Face ever

[Sensei Tim]

got the trannies today.  I'll see if i can measure the leakage and hfe tonight and see what i get.  I ordered 10 of them. hopefully there will be a decent spread.

[Sensei Tim]

so it seems like the hfe on this batch of 10 is mostly in the high 20s with a few in the 30 and 31 range.

not sure if these will sound good or not - definitely not good for Q3. too low for Q2?