BJFE Bone Bender 1 - Verified

[anders]

A local DIY Pedal supplier, Moody Sounds have in cooperation  with Björn Juhl released a DIY project based on his Bone Bender which is based on Tonebender Mk.1.

HERE is a schematic and a writeup by Björn himself.



I must say it sounds pretty darn good once you have some leaky NPN germs. I tried several transistors, AC187, AC127, AC176 and 2SB72 sounded pretty good but these big russian GT404B's sounded fantastic in there.
Low leakage MP38A's worked too but it sounded more like a muddy overdrive than a fuzz.

This is the first project released by BJFE/Moody Sounds and it's supposed to release a few more in a few months.

*Edit*
Here is a couple more layouts with some of the suggested mods made by Björn.
One takes one of the trimers out board and has a switch for an additional Miller cap for treble cut. Björn's notes suggest a 330pF cap here but feel free to experiment. I ended up with a 560pF cap.


And an unverified layout of an all germanium version.

[SpaceCommandant]

Now that I'm revisiting some old fuzzes I've made over the past few years I've been far more curious as to how they actually work, from a circuit design perspective. The explanation by Björn is super interesting and insightful.

[Absolutelyfibulous]

nice layout!  love the symmetry!

built this one yesterday with a 2n5457 because i have a bunch and 2 tungsgram ac176's and it sounds pretty damn good.  i have a "faithful reproduction" clone of it and comparing the two they sound very very similar.  this one has more top end but it still has a very sweet sound to it.

i'd say skip the "use the stock resistors and test hundreds of transistors until it works" mindset and make this if you want an mk 1 type fuzz.  

a note...i did need to add a 10n cap from the circuit's input to ground to tame the oscillation (like every other time i've tried to clone an mk 1) which did not affect the fuzz at all.  also shielded circuit in and out wires to make this thing dead silent.

[HamishR]

I just built one of these with your fab layout Anders - what a cool pedal!  I used a pair of AC127s with the J113 and it works a treat.  I have trouble with Tonebenders in general and previously my only real success was with a Marshall SupaFuzz which is a cracker.  But this one sounds excellent.

Any idea what the voltages should be set to with the trimmers?  I just fiddled to get rid of some gating and get a big full tone and I have no idea of where the trimmers are set but it sounds great.

Thanks Anders - good stuff!

Oh, and I got rid of the slight oscillation issue I had with gain on full by tweaking the trimmers.  It actually helped get me a fatter tone too.  But I don't think I will ever use it with gain on full - I seem to like it with gain on minimum.

[HamishR]

Aha - I just read the article by Bjorn so used his suggestions as a starting point for bias.  I just built a second one of these and it's equally good.  I would recommend this to anyone who wants a great Tonebender as it is a cool circuit and easier to get a great result from than a regular TB circuit.

[anders]

Agreed, this one sounds great dimed but even better with the Attack pot rolled back. I plan to build another one as well, but with an external bias pot from Q3 and a treble roll of switch.

[iggy]

Hey anders thanks for doing the layout. Got it pretty much built a d waiting on a part
. When you guys say leaky , how leaky are we talking. Ive been testing my npns and damn tbose things are leaky. Got some gaIn ,but the leakages are crazy. And i would.assume standard gains for q2 &3 is a good starting point.
Hope this works. Been wanting a mk1 bender but i just dont have the patience to do the standard build.

Them germs can make you crazy.

[iggy]

Finished it up. Fired right up. Wow that's a nice sounding circuit. Highly recommend this for anyone wanting a tone bender. It seems to be very stable. So I recommend this for some one that has struggled with germanium builds. Thanks again for the layout.

[tracer03]

iggy wrote

Finished it up. Fired right up. Wow that's a nice sounding circuit. Highly recommend this for anyone wanting a tone bender. It seems to be very stable. So I recommend this for some one that has struggled with germanium builds. Thanks again for the layout.

Curious - what gains did you end up going with?

[iggy]

I've only tried one set so far, and will try some others. I went with 2 AC127's i think the gains were 75 & 90.  fairly leaky as well.

I'll update this when I pull them out & recheck them.

[iggy]

I played around with some different transistors. While the different model trannys sounded different. Brighter, darker. etc.   The gains didn't make as much of a difference as I would have expected. I think the biggest issue is the leakage. I tried some TI 2n1306's with little to no leakage and it was crap. No fuzz. So I'd say pretty much anything in the 70- 120 range should work just fine. Leaky is important. High gainers are more likely to it to squeal thou.

[tracer03]

How leaky were the transistors? most of the NPN germs I have aren't terribly leaky - worst ones I have are 71hfe/.276 mA lkg and 67 hFe/.36mA lkg. Everything else I have is under .15mA leakage (darn consistent Ru germs...)  

[iggy]

pretty much everything i put in worked. except the ones that basically had no leakage.  Here are the specs for a few that i tried, all worked

ac127 73    .38ma
ac127   89    .75ma
GT404 136    .45ma
GT404    84     .34ma
  GT404    89    .23 ma

The last two I really liked so they'll likely stay.

But i also tried a couple ac176 i think they were. gains were fairly low. Lower than these listed above and they worked also. So those ones you have will likely work. Its a easy build and small parts count. I would certainly recommend giving it a try.

[iggy]

this is a nice little circuit for building a tonebender. and seems to be very stable. Is there a FET that could be substituted in for the J113 so this circuit could be modded to work with PNP's. Obviously the power and electros would need to be swapped. But how would I deal with that FET?  Sorry don't know much about those bits.

Got a ton of PNP's I'd like to try out in this format.

[Frank_NH]

Based on the Idss and Vp from the J113 datasheet, I think you can substitute a 2N5457 JFET.

EDIT:  As for modding this for PNP, I'm not sure what JFET is required.

[Tesla]

Try a J177 it should get ya clone enough. If you like I can test that first as I have a few P channel jfets on hand. I’ll post some results when I find one that works equally well.  

I’ll also pick up other varieties next time I’m at my supplier

[Mulekicker]

If I wanna take that 25k trim on q3 externally how would you hook that up?

[BetterOffShred]

Put wires for the bottom 2 blue dots and then attach them to lugs 1 and 2 of your pot..   if it's backwards swap 1 to 3.  

[Mulekicker]

Right on. That's what I thought but I have a head cold and can't form thoughts. Ha! Thank you!

[Mulekicker]

Finished. You were right. External bias 1 and 2 from bottom two spots from the trimmer respectively. I'll echo what's already been said, this is a great, easy take on the mkI. Sounds killer with the gain rolled off too. I used russian 404b's, leaky as they are, at 90 and 115 hfe.