Aldrin Fuzz - stock and two variants

[MattG]

I bought three Fuzz Aldrin PCBs, and built one stock (Lunar Module), and the two variants, Screw Driver and Hybrid Fuzz Drive. A huge thanks to @Chuck D. Bones for all the legwork in sorting out and posting the modifications!

I like all three, though I like the Screw Driver and Hybrid Fuzz Drive better. I'm trying to decide which of those two I like best. Right now I'm leaning a bit towards the Screw Driver, but haven't given them both enough side-by-side time to say for sure. I like the versatility, and the "vintage" voicing; I like dialing in a sound that's medium(ish) overdrive with a hint of the fuzz peppered in. To me, the settings I like best are kind of an amalgamation of a lot of classic rock tones, while at the same time being unique. I've only used them at home so far. I'm hoping they work equally well in a live band situation!

I used Tayda's pre-drilled enclosures. Note that the board calls for the "125B 5-Knob (Type 2)" enclosure, but Tayda only has "Type 1" pre-drilled. I went ahead and ordered the Type 1, but had to enlarge both middle holes: the top one to accommodate a pot (originally intended for an LED), and the lower one to accommodate the chrome LED holder. Doing this also makes the LED not line up correctly, so I soldered some longer wires onto my LED. Case drilling is my least favorite part of the pedal building process, so even with the extra bit of hacking I had to do, I'm still happy with the result.

Finally, a question: for anyone who's built the Screw Driver and/or Hybrid Fuzz Drive variants (or the Madbean Cosmopolitan, which by default is the Screw Driver): has anyone found a suitable silicon transistor that works well as a replacement for the AC127?

I am going to do another build (with the Madbean PCB) and socket the AC127, and see if I can find such a part. But if anyone has done any experimenting, I'd like to hear it. That's my only nit thus far, the reliance on the not-current-production germanium transistor.

Here are gut shots of my builds. I didn't take pics of the front (no fancy graphics, just solid color enclosure with labels from the label maker).

First, the stock Fuzz Aldrin (Lunar Module):




The Screw Driver:




Hybrid Fuzz Drive:

 

[MattG]

@jeffwhitfield - it sounds like you're talking about the Narcissus, not the Fuzz Aldrin or its variants... If so, I think you replied to the wrong thread, here is my Narcissus build thread. I created both threads back-to-back.

 

[mdc]

I built a lunar module on vero last year and really love it - looking forward to hearing how the different versions compare.

 

[jeffwhitfield]

@jeffwhitfield - it sounds like you're talking about the Narcissus, not the Fuzz Aldrin or its variants... If so, I think you replied to the wrong thread, here is my Narcissus build thread. I created both threads back-to-back.

Oops! Wrong thread. But, while we’re at …..

Built a Buzz Aldrin recently. So, what’s the major differences in these three? Got me curious.

 

[jeffwhitfield]

Nm. Reading the notes of the builds. Sounds like the Aldrin is better for me. My main guitar has two rather feisty humbuckers.

However, I’ll probably play with the Hybrid build at some point.

 

[Chuck D. Bones]

Nice builds! Those caps get a bit crowded down by the stomp switch, hmmm? I ran into the same issue with mine.

Marc Ahlfs intended the HFD to be more humbucker-friendly by backing off on the gain and low freq response. I think he also picked up on the fact that BJTs are quieter than MOSFETs, which is why he went back to a low-noise Si tranny for Q1 on the HFD.

If you want to try Si for Q3 in the SD or HFD, it should plug right in. Adjust R12 as req'd to get Q3's bias to the desired point. It will not sound the same as Ge.

 

[MattG]

If you want to try Si for Q3 in the SD or HFD, it should plug right in. Adjust R12 as req'd to get Q3's bias to the desired point. It will not sound the same as Ge.

Perhaps the question I should be asking: in practice, how temperamental and reliable are germanium semiconductors in an application such as this? This might actually be the first pedal I've made with GE. I've tried to steer away from it because of everything I've read about temperature sensitivity, and how the environment can affect performance. "It will not sound the same as Ge" - but will the Ge sound the same if I play a 100F outdoor gig? Is the difference between Si and Ge at 65F greater than the difference between Ge at 65F and Ge at 100F?

 

[Chuck D. Bones]

Q3 is the only Ge transistor in the circuit. Its bias point is regulated by Q2, which is Si and thermally stable. This is a good circuit for your first Ge build because it will not be temperature sensitive.

 

[MattG]

Q3 is the only Ge transistor in the circuit. Its bias point is regulated by Q2, which is Si and thermally stable. This is a good circuit for your first Ge build because it will not be temperature sensitive.

Thank you for the clarification! Though, I must admit, I'm now less motivated to try different transistors for Q3.

Marc Ahlfs intended the HFD to be more humbucker-friendly by backing off on the gain and low freq response. I think he also picked up on the fact that BJTs are quieter than MOSFETs, which is why he went back to a low-noise Si tranny for Q1 on the HFD.

I haven't noticed any noise with the SD, but now that you mention it, I probably will.

Just out of curiosity, how would you expect using BC109C (or BC549C) for Q1 in the SD affect tonality (and/or other characteristics)?

 

[Chuck D. Bones]

I only notice the MOSFET noise at high FUZZ & RANGE settings.

Let's assume that you configure the first stage the same as the Aldrin. The input impedance will be lower, which affects the pickups' response and the response to the guitar's controls. How much lower depending on the RANGE control setting. The max gain available in the first stage will be quite a bit higher that with the MOSFET. We could play with the values of R2-R6 to adjust Q1's gain range.

It would be worthwhile to try it and see if you like it.