Tag Archives: clapton

Building a Z.Vex Box of Rock on vero-board

0405_Marshall_Amp_630x420Why?

As most guitarists will admit, we’re always looking for a better sound. Some look for new and perhaps innovative sounds. Others, such as myself, want to sound like the players we admire. One classic tone I had never really toyed with is the sound one gets when you crank a JTM45 Marshall. In my opinion it is in my Top 5 sounds. The likes of Clapton, Hendrix, Young (Angus), and many others, started their careers with it. There’s no need for me to recount the origins of the circuit as that’s well documented.

So, you might ask “why not just buy a JTM45?”. Well, one in good condition from the 60’s might set you back 5-10 thousand <local currency units>. A new one, such as those available at Ceriatone go for about $1000….a ‘real’ Marshall? more like $1800.

How

One solution is to approximate the tone in a pedal. And yes, I’ve built way too many overdrive/distortion pedals already, but not one like this. The approach here is to cascade two or more gain stages to ape the design of the JTM45. This has been done may times in plenty of pedals, but a popular one is the Z.Vex Box of Rock. I first heard of this device when it was mentioned by Davy Knowles, who is an excellent blues guitarist. Searching briefly online and I found that the design of the pedal built upon the Super Hard On booster; one of which I built last year. This struck me as a great way to go as I understood that circuit.

Schematic

ZVex Box of Rock schematic

ZVex Box of Rock schematic

Even if you can’t read schematics, you can probably see a pattern repeating itself. There are 4 BS170 transistors arranged as gain stages. They’re chained together and setup in such a way to simulate the characteristics of a tube amplifier. There’s a 4th one (at the bottom right of the schematic) which is the boost section. That will have its own footswitch, so it can be turned on when you “need a bit more”.

I went for a slightly different EQ section. As it stands the BoR just has a simple Muff-style filter. As in, a low-pass filter and a high-pass filter ‘mixed’ together by the tone knob. There’s a great variant that adds a ‘mid scoop’ control, as specified beautifully here by AMZ. It was simple enough that I decided to add it myself.

Layout

I got the veroboard layout from my usual place: Guitar FX Layouts. This guy always does a great job, and is always around to help or explain things. Fantastic!

ZVex Box of Rock - Complete

ZVex Box of Rock – Complete

Build

The build in-progressThe build started off ok, but proved tricky. I quickly realised that I’d done something very wrong as it just sounded very odd. I remembered experiences from previous builds and went back with a fresh printout of the layout, and ticked off each cut, link and solder spot, and made sure the component values were correct. It turned out I had got some cuts in the wrong place. Literally as simple as that. I was careful to use sockets for the BS170s; this meant I was able to leave them out until the last minute so as to not expose them to static shock risk.

Enclosure

Spray and bake

Spray and bake – the black paint hardening under the lights

I went for some custom graphics again. As is typical I couldn’t really think of anything particularly innovative, and ended up calling it “Bed Rock”. This stands to mean two things: 1) This tone is the bed-rock of modern music 2) You can get that tone at low volumes so you can ‘rock’ in your ‘bedroom’. I know, cheesy.

Most of all I wanted to created something with a splash of colour. So many pedals look so very boring. I did the usual flow of finishing the enclosure with enamel based spray paint. This time it was a cheap can of black from Ace Hardware. I was actually going to try something new and bake the enclosure in a toaster oven, but I realised that I was already doing a kind of slow bake with my work-lights. And as I wasn’t in a hurry, I stuck to my usual routine.

For the decal itself, I used a combo of Photoshop and Illustrator to create an image. It was printed on my trusty HP Office ink-jet printer, onto white-backed decal paper; purchased from Small Bear Electronics.

One pleasant discovery was that you can get high-quality fonts for free at sites like FontSpace. Here’s the one I used for the main wording, All Ages.

Almost there!

Almost there!

The finished 'Bed Rock'

The finished ‘Bed Rock’

Demo

I think it came out well. With a Les Paul, it’s ridiculously easy to get that classic AC/DC rhythm tone with everything at 12 o’clock, and with the boost section kicked in you’ve got just that little bit more sustain available for a solo. Even a Strat sounds good. On mild gain settings it really makes single-coils come alive. I ought to do a recording of that too, I suppose. Here’s a demo file of the device.

My setup is the same as usual: Steinberger GM-7SA plugged into an AX84 tube amp, running clean into a 2×12 open-backed cab, with Celestion G12-75T speakers, miced by a Shure SM57 being recorded by an Apple Mac.

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The quest for tone

Further to the Tub-screamer pedal project (I’m waiting for a few final parts), I found a great article on the Geofex site all about the original Tubescreamer internals. Here’s a quote I found amusing:

The best thing to do, I believe, if you’re hunting the Tube Screamer Holy Grail is to stick in an 8 pin socket on the board, noting the orientation of the original chip carefully, and then just plug in various dual opamps until you find one that conjures up images of your own personal guitar deity.

In this world of tube amplifiers and guitars/effects there are snake-oil salesman around every corner trying to get us to spend hundreds (if not thousands) of dollars on all kinds of gadgets that’ll bring us closer to “that tone”. They recognise that at the heart of it we (guitarists in general) are star-struck wannabes that have a very simple desire to be “as good as that guy”. And “that guy” may be Clapton or Vaughan or whomever. In quiet moments when we’re listening to our favourite music we think “if only I could sound like that”. I don’t care who you are, you do it. I bet even Clapton does when he’s listening to Buddy Guy, or Freddie King.

For me it’s Eric’s tone on the studio version of “Spoonful”. It’s clearly some kind of Gibson, probably a Les Paul. It’s also certain to be a 100 watt Marshall cranked pretty high so it’s “alive” and on the brink of feedback. In my view that’s the sweet spot for any rig. In the mix there’s an ocean of reverb on the track which adds to the haunting sound she creates. You can hear him playing with a variety of pick strength…sometimes he’e gentle, other times he’s really digging in. Never does his guitar sound harsh; it’s always creamy smooth and very, very musical. Now for me to get that tone I simply use my 50w 2204 Marshall and either my mid-70’s Les Paul or my Tokai copy. That’s all I need to fulfill that particular dream; especially as I realise I’d never truly be able to recreate that sound as I’m not Eric.

However, if I were more susceptible to the snake-oil salesman I could do the following:

So the question is, how much closer to that tone will I get by spending > $200k? Maybe 1% closer. I can get 95% of it with my so-called cheap rig. The other 5% is all about Eric.

Back to Tubescreamers. The aura surrounding them is due to people like Stevie Ray Vaughan. He used a TS-808 in his rig, so naturally everyone wants one. Conversely, nobody wants the TS-9 or any kind of reissue as folklore would have it that they “aren’t the same”. The fact is, the pretty much are the same. The Geofex article linked above proves that beyond doubt. So why is it that people will pay $350 for a handwired TS-808 from Ibanez? Why is it that sellers on eBay think they can get $600 for an old one? It’s all snake-oil.

I’m going to build my $37 clone from the circuitboard I got at DIY Effects, and the parts in got from Small Bear Electronics/Pedal Parts Plus, and be 95% there. 🙂

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