Sabbath Drive

This is a post that has been a very long time in the mak­ing. I start­ed this project back in Octo­ber of 2018. Gui­tarPCB had a sale and it looked like their Sab­o­tage Dri­ve would be an inter­est­ing chal­lenge. There were six (!) tran­sis­tors in this cir­cuit. But I want­ed to make this a real­ly fun project so I designed some cus­tom art­work as well, all themed around Black Sab­bath — the inspi­ra­tion of this cir­cuit’s sound. This cir­cuit fur­ther seems to be inspired by Catal­in­bread­’s Sab­bra Cadabra ped­al, anoth­er pre-amp in a box effects that tries to cap­ture Tony Iom­mi’s sound of a Dal­las Range­mas­ter tre­ble boost push­ing a Laney Super­group head1. Or, put it anoth­er way, the sound of doom metal!

I did some lay­out in an SVG file for the graph­ics, which you can see above. This is also large­ly where I did the drill hole pat­terns for the enclo­sure, as those go hand-in-hand. My graph­ics incor­po­rat­ed some of the Sab­bath album cov­ers. I was fair­ly proud of the design, if not the actu­al imple­men­ta­tion. I then got to sol­der­ing the cir­cuit com­po­nents. Bar­ry Stein­del of Gui­tarPCB did a great job design­ing this for a rel­a­tive­ly com­plex build, it is a very clean layout. 

I think I’ve men­tioned this before, but I am in the habit of tap­ing out all the com­po­nents to a parts sheet with labels that cor­re­spond to the PCB silk screen labels. This would­n’t scale up to a large pro­duc­tion, but for one-at-a-time builds, it real­ly takes the stress out of try­ing to find the right com­po­nent for each step.

Once the com­po­nents were in place, it was time to final­ize the enclo­sure lay­out. The rel­a­tive place­ment of the pots/knobs are fixed since they are sol­dered direct­ly to the PCB. But the place­ment of every­thing else is depen­dent on get­ting it all to fit. I would have loved top-mount­ed jacks as you can see in the orig­i­nal sketch below, but that was­n’t going to hap­pen with this PCB lay­out (in the size of enclo­sure I chose, any­way). I need­ed to for­go that in order to squeeze every­thing in place. Regard­less, no 9v bat­tery in here! I don’t use ’em anyway.

When it comes to drilling the enclo­sure, I use a step bit in my drill press. Anoth­er thing I’ve prob­a­bly men­tioned: I have a small med­i­cine syringe with machine cut­ting flu­id. That way I can use my cen­ter punch to mark the point on my tem­plate and the put 1–2 drops of cut­ting flu­id right at that spot.

As you can see below, I actu­al­ly test­ed the cir­cuit before I even com­plet­ed drilling all the lay­out holes. I drilled the holes for the pots to get those mount­ed to the PCB in the cor­rect ori­en­ta­tion. I think wired up some leads for sig­nal in/out, the 9v pow­er, and ground to hook up to my test­ing rig.

Then it was time to fin­ish drilling the holes and wiring up the off board switch, jacks, and LED.

It was a bit of a tight fit into the enclo­sure, but part of that was my desire to place the LED near the top of the ped­al I real­ly don’t like LEDs right by the footswitch, where the get cov­ered up by your foot! Sure, they’re a lot eas­i­er to put there, but they don’t make it easy to tell you’ve prop­er­ly engaged the effect.

I tried using our vinyl cut­ting machine to cre­ate paint­ing a paint­ing tem­plate from my SVG file. My first mis­take was using some cheap vinyl which did­n’t stick to the pow­der-coat­ed sur­face well. 

Then I used acrylic paint which bled under that tem­plate. Also, the tiny let­ter­ing details were just about beyond the scale was which the Cri­cut could suc­cess­ful­ly cut this vinyl. The end result looked about like I’d just hand-paint­ed the whole thing. I was­n’t at all hap­py with the paint job, but know­ing I was­n’t like­ly to improve on it, I went ahead and sealed it with some spray clear coat.

So I fin­ished all this Decem­ber of 2018. I nev­er post­ed about it all last year though because I real­ly was­n’t able to get a good sound record­ing of this. My iPhone demos so far have been pret­ty lack­lus­ter. And this effect did­n’t sound as great as I’d liked any­way because it’s real­ly meant to run into a cranked amp. Though I used my pre-amp, pas­sive vol­ume con­trol I could­n’t real­ly push the pow­er amp sec­tion of my tube head. Well, in the past cou­ple of months I got a pow­er atten­u­a­tor and a pret­ty good mic to record some audio with. My ampli­fi­er has a “cab emu­la­tion” out­put, as does the pow­er atten­u­a­tor but both frankly sound pret­ty ter­ri­ble. None of the record­ings with those ever had any of the low end that the amp actu­al­ly pro­duces. But using the atten­u­a­tor with the head vol­ume cranked and the mic into my record­ing inter­face, I’m final­ly hap­py with the sound I can get recorded.

So here is the full sig­nal chain: 

• My Fend­er Tele­cast­er with a Lace Sen­sor Death­buck­er pick­up in the bridge posi­tion2
• This runs through a TC Elec­tron­ic P0lytune 3 (I men­tion this because it has a buffer — all oth­er effects are true bypass) and then into the Sab­bath Dri­ve pedal. 
• The Black­star HT5 Met­al head on the clean chan­nel (cranked to 10) and a TC Elec­tron­ic Hall of Fame 2 reverb ped­al in the effects loop. 
• The head runs through the Bugera PS1 pow­er atten­u­a­tor into the Black­star 1x12” cab­i­net with a Celestion G‑12T speaker.
• The cab­i­net is mic’d with a MXR R144 rib­bon mic into the Behringer UMC22 audio interface. 

I use some of the EQ set­ting in garage band for the gui­tar and the over­all mix. This par­tic­u­lar record­ing was used with one of the “auto” drum­mers in Garage Band. This video is the live record­ing you’re hear­ing; just poor­ly sync’d to the audio. The gui­tar is a sin­gle track.

On the whole, I’m real­ly pleased with the sound of this ped­al. The Range and Pres­ence con­trols give a real­ly wide tonal range. I’ve cranked the dis­tor­tion here (hon­est­ly, not even sure why that knob exists! Just fix it at 10!). The vol­ume is about at noon. I shud­der to think just how loud this ped­al would be with that cranked. 

1. For the record, even though the old­er Sab­bath records were record­ed using those, it does­n’t appear Tony Iom­mi uses those any more. He has a sig­na­ture Laney head that appears to have the tre­ble boost “built in”. Laney also has a sim­i­lar, sig­na­ture ped­al which claims to box all this up, but appar­ent­ly Iom­mi does­n’t use it at all accord­ing to his site. [↩]
2. Yes, I need to write an entire post on my gui­tar and the mod­i­fi­ca­tions I’ve made to it. [↩]