Soul Sonic - Hunny Bunny, sweet overdrive

soulsonic · Post by **soulsonic** » 09 Jan 2009, 08:33

Here is the overdrive I mentioned in another thread. I call it the Hunny Bunny because it sounds sweet.
Soul Sonic Hunny Bunny

It's a cool little hybrid combo of an opamp driving a MOSFET. I came up with the skeleton of the circuit this past summer, and today I built it up on the breadboard to flesh out some details. It has a great range of drive, from light and crunchy to thick and heavy. At it's highest settings, some people might consider it a distortion, I guess it just depends on how hot your pickups are.

You can see some fun tricks used in this circuit; subtle things that give it the special charm it has. I'll post up a layout soon if there's enough interest.
This thing sounds good enough, I'll probably start selling them. There's alot of good mojo in this one.

nagshay1818 · Post by **nagshay1818** » 09 Jan 2009, 08:39

Very interesting. I'm gonna whip one up tomorrow.

Skinpimp · Post by **Skinpimp** » 09 Jan 2009, 08:46

Looks Great .. I need some LM 301's You will have to excuse me i havent messed with single ops much , but is R9 R10 and C7 C8 network setting the Frequency of the input as well as providing Bias for pin 3 through R2?

soulsonic · Post by **soulsonic** » 09 Jan 2009, 08:55

Thanks for checking it out, guys!

Yes, R9, R10, and C7 are the bias network... and yes, the input impedance is lower than what you see on many pedals, but the size of C7 is big enough that R9 and R10 don't have any affect on the AC impedance.

Input Z is purposefully kept low, and the 301 is over-compensated.

Skinpimp · Post by **Skinpimp** » 09 Jan 2009, 09:01

I am an idiot!! LOL I just havent seen a bias network drawn in that way (used to the standard Format) .. at first glance

it looked like a tonestack RC network rather ... sorry

Ok carry on

WhiteKeyHole · Post by **WhiteKeyHole** » 09 Jan 2009, 09:05

Looks cool, definitely. Could you post a clip?

I'll order some LM301s just to try this out.

soulsonic · Post by **soulsonic** » 09 Jan 2009, 09:10

WhiteKeyHole wrote:Looks cool, definitely. Could you post a clip?

I'll order some LM301s just to try this out.

Sorry, my recording gear is in storage at the moment....

Yes, please try it; 301s are so cheap, they're practically free!

The topology of this circuit was the result of my first experiments with getting a nice overdrive/distortion without resorting to diode clipping... something intended to be a non-TS as possible.

RnFR · Post by **RnFR** » 09 Jan 2009, 09:12

i'll be giving this one a shot. i'm up for any overdrive not involving diode clippers.

WhiteKeyHole · Post by **WhiteKeyHole** » 09 Jan 2009, 09:52

Hey, I don't know if you're open to other ideas at this stage, but I've been working on something in a similar vein. Anyways, my suggestion is to try a discrete stage similar to those found in the Blues Driver in place of the LM301. You can limit the slew rate by increasing (referring to the BD schematic) C21 and R32. Also, for extra mojo, use a germanium transistor (~ 60 hFE) in the Q9 position.

The Blues Driver uses 2SK184 (2SK117) for the FETs and I know you like those, so there's some incentive to try it.

plexilover · Post by **plexilover** » 09 Jan 2009, 13:05

hey guys,
looks interesting, honest...
but what do you mean with "sweet", sweet harmonics like a overdriven jtm45 oder how would you describe it, when i hear "sweet" i first think of the jtm45, i'd like to know, if you have a layout please post

thanks
keep it up

greets

soulsonic · Post by **soulsonic** » 09 Jan 2009, 23:14

WhiteKeyHole wrote:Hey, I don't know if you're open to other ideas at this stage, but I've been working on something in a similar vein. Anyways, my suggestion is to try a discrete stage similar to those found in the Blues Driver in place of the LM301. You can limit the slew rate by increasing (referring to the BD schematic) C21 and R32. Also, for extra mojo, use a germanium transistor (~ 60 hFE) in the Q9 position.

The Blues Driver uses 2SK184 (2SK117) for the FETs and I know you like those, so there's some incentive to try it.

I've recently started playing around with that Boss discrete opamp circuit too! So far, I've been very impressed with the possibilities and the basic sound of it is definitely a solid building block. I haven't tried it with this circuit yet, but I'll likely do so at some point. But the big difference between the Boss circuit and the 301 is that the 301 isn't a FET input opamp, so it will respond very differently. The original idea I had for this was with a FET opamp, but I found that the 301 was more fun because of how you can tinker with the compensation and the (relatively) low input Z makes for more, um, interaction possibilities.

plexilover wrote:hey guys,
looks interesting, honest...
but what do you mean with "sweet", sweet harmonics like a overdriven jtm45 oder how would you describe it, when i hear "sweet" i first think of the jtm45, i'd like to know, if you have a layout please post thanks
keep it up

greets

It does have sweet harmonics to my ears - very much a tube amp sort of crunch. And it would be easy to tweak the circuit to fit your taste if needed. I will build one this weekend so a layout will be available and I will record some clips of it so people can hear what it sounds like.

Silent Fly · Post by **Silent Fly** » 10 Jan 2009, 13:54

soulsonic wrote:... and I will record some clips of it so people can hear what it sounds like.

RnFR · Post by **RnFR** » 10 Jan 2009, 14:07

are you guys talkin about Q10 through Q9 on the BD2 schem?

briggs · Post by **briggs** » 10 Jan 2009, 14:31

WhiteKeyHole wrote:Hey, I don't know if you're open to other ideas at this stage, but I've been working on something in a similar vein. Anyways, my suggestion is to try a discrete stage similar to those found in the Blues Driver in place of the LM301. You can limit the slew rate by increasing (referring to the BD schematic) C21 and R32. Also, for extra mojo, use a germanium transistor (~ 60 hFE) in the Q9 position.

The Blues Driver uses 2SK184 (2SK117) for the FETs and I know you like those, so there's some incentive to try it.

Can you explain how this section is operating? Such as the gain setting elements and frequency setting components? I'd love to fiddle with the circuit but without having a little more understanding of it's operation I'll just make a mess

DWBH · Post by **DWBH** » 10 Jan 2009, 14:43

Have anyone here tried using an OPAMP to drive a JFET, instead of a MOSFET?

RnFR · Post by **RnFR** » 10 Jan 2009, 15:35

so 2sk184s are the same as 2sk117s? MCM won't have 2sk117s for another 2 months!

WhiteKeyHole · Post by **WhiteKeyHole** » 11 Jan 2009, 00:14

Yeah, Q10 through Q9.

Yeah, 2SK184 is the same as 2SK117, only in the smaller package.

Referring to the Blues Driver schematic and the standard Tube Screamer for easy explanation and understanding;

R31 and C22 are equivalent to the 4.7K/0.047uF network on the inverting input of the TS clipping amp (Q11 is the inverting input). So, you can affect gain and roll-off here.

R29 and VR1a are, obviously, your gain control. C23 is your 51pF capacitor in the feedback loop of the TS. So, yeah, there's the feedback loop of this amp.

R32 and C21, as I said, affect slew rate. For limiting, raise R32 before making C21 too large (rolls off highs).

It's a discrete op-amp, so play with that in mind.

briggs · Post by **briggs** » 11 Jan 2009, 12:16

WhiteKeyHole wrote:Yeah, Q10 through Q9.

Yeah, 2SK184 is the same as 2SK117, only in the smaller package.

Referring to the Blues Driver schematic and the standard Tube Screamer for easy explanation and understanding;

R31 and C22 are equivalent to the 4.7K/0.047uF network on the inverting input of the TS clipping amp (Q11 is the inverting input). So, you can affect gain and roll-off here.

R29 and VR1a are, obviously, your gain control. C23 is your 51pF capacitor in the feedback loop of the TS. So, yeah, there's the feedback loop of this amp.

R32 and C21, as I said, affect slew rate. For limiting, raise R32 before making C21 too large (rolls off highs).

It's a discrete op-amp, so play with that in mind.

Perfect! Thanks a lot, expect a fun little circuit soonish guys

when I've got my current plate finished!

nooneknows · Post by **nooneknows** » 11 Jan 2009, 13:33

soulsonic wrote:Yes, please try it; 301s are so cheap, they're practically free!

mmmh. I have a 741 around, do you think it could work too?
thnank you

RnFR · Post by **RnFR** » 11 Jan 2009, 14:25

ok, Martin, i gotta question.

whats the deal with the multiple emitter resistors and bypass caps? how do they affect the circuit, and how do they change the gain? are you basically just filtering the gain for more or less at different frequencies?