freestompboxes.org

Hi everyone, as I'm sure many of you know, Björn Juhl sent me a Honey Bee pedal to play with. The idea was to listen to the sound and see if it can inspire a nice DIY project. Well, after spending some time with it, I've come up with something that sounds good and will certainly remind people familiar with the sound of the Honey Bee.
My goal was to keep the design as simple as possible, but still try to fit in some tricks. This uses both positive and negative feedback to get its sound. R8 is something I learned from the big old red RCA book - it's positive feedback to boost the gain of the first stage; it was suggested as an alternative to using cathode bypass capacitor in a tube stage, well, it works just as well with a transistor. The combination of R9+C4 is negative feedback to reduce the high frequency gain and give the signature smooth sound. It also promotes stability in the circuit. I settled on the clipping diode combination after trying several different kinds, and the 1N4001+1N4148 combo had the best sound for this thing and reminded me most of the HB.

The Timbre control adjusts both the low-frequencies and the amount of drive. At the 12 o'clock position is the minimum drive amount. At one extreme it's max gain with lows emphasized, and the other is max gain with the lows cut. It's sort of like having the HB's Gain and Nature controls on one knob.

Here is the schematic: http://www.soulsonicfx.com/FolkDIY/Folk ... Driver.GIF
I have a PCB design done up with ExpressPCB so people could order some if they want, and the board is a single-sided design so it is easy to make yourself. I will post the file up after I verify it (probably tomorrow...).

Enjoy!

Looks good, thanks for sharing! There's a couple circuits you've designed that I've been itching to breadboard up when I get some free time, and this is another.

I really appreciate the explanation of some parts of the circuit too. I usually have a passable guess about what's going on but I'm pretty new to electronics and its always helpful to have it confirmed, corrected, or explained.

That 'timbre' control looks great, a really nice piece of design!

R5 is quite a high value (at first glance), how would lowering that affect things?

rackham wrote:That 'timbre' control looks great, a really nice piece of design!

R5 is quite a high value (at first glance), how would lowering that affect things?

If you lower R5, it would lower the gain, and you'd probably want to use a lower value for the Timbre control as well because the gain of the second transistor is affected much by the interaction of those two values.

I like it. Makes me think of a mutant fuzz-child between Tim Escobedo and Joe Davisson.

Just curious in case you've already tried this, how does it sound with different transistors? Either of the same batch or different types... just trying to get a feel for how "hFE dependent" it is.

I'm curious to try this Positive feedback on some ideas of mine! How much does it boost the gain? If you lower R8 you'll get more gain?

looks cool! i find it interesting that you chose to use a transistor with very high gain in a circuit that is supposed to be on the overall less gainy. care to elaborate a little on that?

Emanuele wrote:I'm curious to try this Positive feedback on some ideas of mine! How much does it boost the gain? If you lower R8 you'll get more gain?

Oh yes, but if you go too low, it becomes an oscillator. I will look up the formula for determining the gain of this feedback. I know it has to do with the ratio of R8 to R4 - it forms a voltage dividing network which determines how much of the signal gets fed back into Q1.

RnFR wrote:looks cool! i find it interesting that you chose to use a transistor with very high gain in a circuit that is supposed to be on the overall less gainy. care to elaborate a little on that?

It's all about the feedback networks. My logic is that if I start with very high possible gain, it gives you more available to control with feedback - it's the same basic idea with an opamp, where the theory is to start with essentially infinite gain. But if you look at the first stage the gain is pretty low, so that's why the positive feedback is there to boost it up.
Overall, the circuit has about the same amount of possible drive as the original Honey Bee... which is not much, it only gets a very mild overdrive at its extremes.

The board is coming along well... Should have the first one complete soon-ish.

ibodog2 wrote:Corrected C5. Can anyone else check this for me? I'll see if I can build it this weekend.

You might want to watch the spacing on some of the caps - the standard "box" type caps need 5mm spacing, and anything less or more than that can be a chore getting it to fit.
I also wouldn't have the input and output busses right next too each other, because they are on the same phase and may cause oscillation.
Overall, it looks like it would work, but I would arrange it differently if I were doing it.

I think that vero layout should work fine.


I got the first one built now. Here's guts: This is one is going to Sweden!

I'd say the circuit board layout I did is verified now.
Here is the image suitable for PNP: And the layout for it:

cellophane finish! once again, looks great.

It's acrylic paint. Took me some effort to get that color mixed up. I'm really getting into this style of painting... makes me feel like an artist.

I've breadboarded this yesterday. And from the few clips that I heard of the HB I must say that it sounds pretty darn close. (especially with the highs cut). I do feel that it lacks a bit overall brightness and I found it sounded a bit more defined with a 2N5088 in the first position.
Although the timbre conrtol is really nice, I doesn't give good gain control but at the extremes of the pot rotation. Overall impression, very nice and very close to the HB sound.

soulsonic wrote:The board is coming along well...

FDBoard1.jpg

Should have the first one complete soon-ish.

Hi
Just curious about the 470P cap!
What kind of cap is it, Ive never seen one that looks like that.

Thanks
Glen

~arph wrote:(especially with the highs cut)

I hate to quote myself, but since I can't edit that post anymore.. I meant 'with the lows cut'

ibodog2 wrote:If your board doesn't have the mounting holes you can probably fit C6 a little easier.

Or you could move it along the strips ... for example around column 11.

Looks like a polystyrene film cap - mouser part# 23PS147 to me..

biggy boy wrote:

soulsonic wrote:The board is coming along well...

FDBoard1.jpg

Should have the first one complete soon-ish.

Hi
Just curious about the 470P cap!
What kind of cap is it, Ive never seen one that looks like that.

Thanks
Glen

Yes, it's the Xicon polystyrene cap that Mouser sells. I really like them.
For the price, they're hard to beat.

22uf wrote:Looks like a polystyrene film cap - mouser part# 23PS147 to me..

biggy boy wrote:

soulsonic wrote:The board is coming along well...

FDBoard1.jpg

Should have the first one complete soon-ish.

Hi
Just curious about the 470P cap!
What kind of cap is it, Ive never seen one that looks like that.

Thanks
Glen

That's a sexy looking finished product, Soulsonic. I've been debating building a light overdrive and was going to breadboard a Trotsky, but if I have the caps kicking around I'll check this out first.