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Building a “Tremulus Lune” on vero-board

One of my favourite pieces of music, let alone guitar playing, is by Ry Cooder. A track called “Feelin’ Bad Blues”. This video is an excerpt from the film Crossroads where the tune was used to great effect. For me it is the epitome of blues guitar. Sad, slow and gritty. And that thick tremolo (probably from an old Fender amp, not a Pignose) is the icing on the cake.

So that’s what this post is all about; making a pedal to give me that tremolo effect. It didn’t take long to find the defacto standard tremolo pedal; the Tremulus Lune.

Layout

Layout

Layout

Research showed that I could buy a kit, or even a pre-made one, but where’s the fun in that? I went for the layout from Guitar FX Layouts (seen here).

The novelty with this circuit for me was it used a component called a Light Dependent Resistor (LRD). Essentially one part of the circuit is a Low Frequency Oscillator (LFO), controllable with various potentiometers. The ‘low frequency’ part refers to the fact that it is creating a sine-wave in the range of 3-10hz (I haven’t actually measured it). This wave is used to drive a normal op-amp, thus varying amplitude over time, which is in fact the definition of “tremolo”. One difficulty was getting hold of the correct LDRs. ¬†They needed to have the range 5k/500k. It was easy to get hold of all kinds of LDRs, even from Radio Shack, but I had to trawl through Ebay to find the right ones. I have a bag of 20 now.

The build

The finished board

The finished board

This isn’t my first veroboard build, so the build/assembly went quite quickly, in a pleasant way, and I had it operational on my prototype rig within a couple of hours. It sounded amazing! It truly is a versatile tremolo; you really don’t need anything more complex than this.

The device has three LEDs. One for the usual on/off indicator; another one to couple the LFO with the op-amp (by pointing the LED at the LDR, kind of like a vibe pedal does) and a third one to show the speed of the LFO externally. I decided to use the nice fresnel lens LED holders I bought a while ago. I just think they look really cool. The picture below shows them in their full glory, although the red LEDs look somewhat pink. To fit them I needed to get a 17/64ths drill bit. I have hundreds of drill bits, but not that one. So, a trip to Ace Hardware for that.

Fresnel lenses

Fresnel lenses

The enclosure

This one’s got 5 knobs, so I had to use a 1590BB and I chose to go for a vertical orientation. As for a design I went for the whole Crossroads theme. I combined the lyrics to the famous song, and depicted the actual crossroads by using highway signs. As far as the decal goes, I wanted it to wrap over the sides as I thought it would look cool. I printed it on transparent ink jet decal paper this time as the enclosure is bright white.

Drilling the enclosure

Drilling the enclosure

The decal

The decal

Demo Recording

So I finished the assembly and got it all plugged into my usual rig, and recorded a swift demo. As I mentioned earlier, the reason I wanted to build this was for that archetypical blues tone. So here’s my own sloppy rendition of that kind of sound:

Click here for MP3

The setup was: Tokai Les Paul, neck pickup (a humbucker from a 1961 ES-335); my AX84 P1 Extreme into a 2×12″ speaker cab, with Celestions; my Box of Rock clone for some grit, and the Tremulus Lune of course. The reverb came from Logic, and was a ‘small church’ kind of setting.

The finished pedal

The finished pedal

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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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An introduction

I am starting this blog to help document my experiences as I learn about how tube amplifiers work.

Back in the mid eighties I was bought my first electric guitar, which was a Les Paul SG copy made by Hondo. I also was given a Fender Champ. All I knew at the time was that it was really small, and had no reverb. To me that was somewhat boring, so within months I traded it in for a transistor based amp branded with John Hornby Skewes. It was brown and heavy, but it had reverb!

A few years later I saw the light and bought an old Marshall 50W (the 2204 model) for about 80 GBP ($150 in today’s money I suppose). I had to have spells cast on it to get it to work, but for what amounted to $200 I had a gem of an amp. I purchased an Orange 4×12 from out of the paper, and was soon up and running. Henceforth I discovered “that tone”…you know the one…Eric Clapton..Peter Green…Angus Young. Not much in the way of distortion by today’s standards,but soooooo much sustain and¬†sensitivity.

Since that day, tube amps have always been a mystery to me. I know how a tube works…not hard. But how it all fits together is somewhat confusing to one raised on digital technology. I’m old enough to have owned and played vinyl, but I’m also young enough to know that all that analogue crap is just a horrible compromise.

So, this is my effort to come to grips with basic electronics, with these goals in mind:

  • Repair my old Marshall. (It is now noisy and resonates)
  • Build a tube amp, from existing designs.
  • Modify said tube amp.
  • Design new a magical tube amp.
  • Profit!!!
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