The Week on the Breadboard: The Wizard

[Chuck D. Bones]

The Wizard is Castledine's take on the Tony Iommi sound. It's a modified Germanium RangeMaster driving a JFET-based amp sim. I breadboarded it stock and had a listen. I felt it was too harsh so I made a few minor mods. The most significant change I made was add a RANGE switch. In the center position, we get a stock RangeMaster freq response. In the up position, we get the stock Wizard response that mimics Tony Iommi's modified RangeMaster. In the down position, we get a nice fat tone. I originally installed a 2N1308 for Q1, but it was way too harsh. Too much gain and to many harmonics. I subbed in an MP38A and it smoothed out nicely. We don't want high HFE here. I tried a couple other Ge trannies, but the MP38A sounded the best. I increased C4 to smooth out the high treble. I felt the bottom was still a little too heavy with the RANGE switch up, so I reduced C6. This is a matter of personal tast and you may prefer the stock 22nF cap. I decreased R10 to extend the bottom of the GAIN knob's range. C7, C8 & R12 don't do much of anything, so I took them out. I increased C9 to smooth out the distortion on the low notes. I changed Q6 to 2N5457 because none of my J201's had a high enough Idss. Q6's drain current idles around 500μA and peaks out close to 1mA. Most J201's run out of steam well below 1mA. I consider changing Q6 to be mandatory. Q2 - Q5 run around 100μA, so there is no need to cherry-pick or match them. I found most of the TREBLE knob's range to be way to hot, so I increased R17 and changed TREBLE to B-taper. I also added C13 to shave a bit off the very top end. Depending on your amp, C13 may not be necessary. That's about it. If you want to goose the gain another 12dB or so, stick a 1uF cap in parallel with R13. The Wizard is a decent distortion pedal, but if you already have a JFET-based amp sim and a treble booster, it may be redundant.

One more thought: the RangeMaster has a reactive input impedance and will interact with the pickups and guitar knobs. I found that the tone was very nasal when the guitar's volume was dimed. Backing the volume down to 8 or lower cleared it up.

Next up: Catalinbread's Sabbra Cadabra.



Blue knob: VOLUME. red knob: TREBLE, rreen knob: GAIN. Range switch between TREBLE & Gain.

 

[steviejr92]

My interest is piqued. I love treble boosters and the connection to Tony Iommi makes this a biased build (pun intended). Building this asap!

 

[Chuck D. Bones]

It's a simple enough build. Looking forward to your feedback

 

[steviejr92]

First thing in the afternoon! I have some free time and I’ve been meaning to breadboard a new circuit. This is right up my alley. Will be giving some feedback for this bad boy!

 

[Laundryroom David]

Very cool. I’m going to breadboard this tomorrow.

I am really interested to see what you do with the Sabbra Cadabra. I had one briefly.

 

[Chuck D. Bones]

I am really interested to see what you do with the Sabbra Cadabra.

Yeah, me too. That thing is a gain monster. 100dB at the output of the 3rd stage.

 

[music6000]

Yeah, me too. That thing is a gain monster. 100dB at the output of the 3rd stage.

I built it for one of my mates who is a big fan of Tony Iommi:

Sabbath Distortion

My mate loves Black Sabbath & Tony Iommi so this was a No Brainer when he asked if I would build a him a Pedal (October 2018). Brushed Aluminium Top. Mods : Battery Clip & Stereo Input Jack.

forum.pedalpcb.com

 

[music6000]

Here's another Tony Iommi that's available:

Dark Esbat Boost - PedalPCB.com

Compare to Black Country Customs TI-Boost

www.pedalpcb.com

 

[Chuck D. Bones]

Indeed.
We were discussing that one over there.

 

[temol]

C11 - I guess it should be 3.9n, not 3.9k.

 

[Chuck D. Bones]

Good to know someone is reading my schematics.

Corrected.

 

[temol]

It works. Thank you, good night.
Just kidding.
Don't know what to expect from the circuit. I prefer middle position of the range swith, with tone set past 15 o'clock. As for the gain range - huge.
Q1 collector voltage 6.2V. MMBFJ201 with Vp around -0.72V, MMBF5457 -1.4V.
Some drawings from oscilloscope. Yellow trace - output, cyan trace Q1 drain.

Input 50mV, gain min.


Input 50mV, gain max.


Input 200mV, gain min.


Input 200mV, gain max.


Input 400mV, gain max.


FFT - Q1 drain collector.
Input 50mV, 200mV, 400mV



And some playing.

wizzard.wav

Shared with Dropbox

www.dropbox.com

Guitar -> breadboard -> audio interface. Speaker cab IR - 4x12 V40 Mesa. Gain from zero to max.
First part - C1C only, second part C1C + C1B.

 

[Chuck D. Bones]

Q1 collector you mean, right?

Maybe my Tone stack mod made it too dark? You could try removing C13.

Which guitar / pickups are you using?

 

[temol]

Q1 collector you mean, right?

Of course... collector, not drain. Corrected.

Maybe my Tone stack mod made it too dark? You could try removing C13.

Will try.
C2 - anything from 1u to 47u sounds good.

 

[Chuck D. Bones]

Yeah, I noticed in simulation that 47uF is more than enough and going down to 4.7uF made very little difference. Lowering C2 also affects the input impedance in the lower midrange and bass frequencies.

What did you use for Q1?

 

[steviejr92]

Ok just finished it and it fired right up!

I agree that too high of an hfe will kind of harshen the sound. I have a MP38A in there with a gain of 88. I would certainly say you could bring it down to the 70s and it would do more good than harm. Q6 Drain Current is reading 1.06ma. All of my J201s have a Drain Current of 240 - 334ua. I know this is a treble booster but i'm finding it fun playing on the bridge, cutting back on the TREBLE and messing with the different tones the switch provides. There's a warmness my amp nor the guitar has ever come close to making....Will be playing with it more. BTW im using single coils. Ill be honest here i cant tell if i like it with C13 installed or not.

 

[Chuck D. Bones]

Good report! One of the reasons I experimented with the RANGE switch was to make this thing work with single coil pickups. If you think C13 is too dark, try 220pF or 100pF. Another option is to make R17 smaller, maybe 22K.
C13 & R17 tune the range of the TREBLE control. Bigger = darker; smaller = brighter.

I just finished the Sabbra Cadabra breadboard, but that's a topic for another thread.

 

[steviejr92]

Good report! One of the reasons I experimented with the RANGE switch was to make this thing work with single coil pickups. If you think C13 is too dark, try 220pF or 100pF. Another option is to make R17 smaller, maybe 22K.
C13 & R17 tune the range of the TREBLE control. Bigger = darker; smaller = brighter.

I just finished the Sabbra Cadabra breadboard, but that's a topic for another thread.

Whats funny is i actually put in a 100pf and loved the sound! Im keeping it in there for sure.

Let me try fiddling with R17 and get back to you! Ill be very honest with you though im loving the range of the TREBLE control. It has the proper response and doesnt get too brittle.

As for the Sabbra Cadabra, Im hoping to see that soon!

 

[steviejr92]

Ok little update im keeping R17 47K. I think changing R17 is going to come down to preference, and i like it where it was.

 

[temol]

What did you use for Q1?

MP38A (did not measure hfe).