Building a Z.Vex SHO clone from scratch

In my previous post I had some great success building a very simple boost circuit, the Electroharmonix LPB-1. While learning all about that particular circuit I kept coming across discussion surrounding the Z.Vex SHO; mostly questions of tonal comparison. So I decided to build one of those too, and was greatly excited to find this thread, which spelled it all out for me in simple terms. Here’s the circuit in a simple schematic form (I made it in ExpressSCH (on a Linux box)), then a diagram with some options. And finally one with external components that you’d find on a typical pedal schematic:

My own SHO schematic, with bill-of-materials

My own SHO schematic, with bill-of-materials

ZVex SHO circuit

ZVex SHO “diagram”

Z.Vex SHO schematic

Z.Vex SHO schematic

As you can see, it’s very simple. So much so that a fair few forum members decried it as “too simple” and in fact “retarded”. But I admit to wanting to know how Z.Vex can sell one of these circuits in a pedal for more than $150.

ZVex SHO Updated - from Zach schematic-762360Layout

As with the LPB-1 I wanted to attempt a layout myself, and do it on veroboard. This genuinely was quick easy as this really is a simple circuit. My approach as to keep the relative positions of the components on the schematic. It practically wrote itself. It turns out my own layout was wrong, and non-obvious, so I’ve replaced it (on the left) with a decent layout from Mark at Guitar FX Layouts.

Soldering was simple, and went without drama. I was able to test the circuit within the hour. It worked! When I built it I didn’t have all the hardware, so as you can see from the picture, I used a trim-pot rather than a full-size potentiometer.

SHO clone on veroboard

SHO clone on veroboard

Enclosure

Then the fun part, the enclosure! I’d been wanting to do a decent custom enclosure for quite some time, but never got around to it. This time I decided to make the effort and do something special. First step was to take some good measurements of the enclosure. I had ordered the enclosure from Small Bear, and started by spraying it a lovely fire-engine-red, using Rustoleum paint. That stuff goes on really well and I had no issues with drips or runs.

Decal

Then it came to the decal. I’m not a great designer, or at least not one dripping with amazing ideas for these things, so I looked around at other pedal manufacturers for inspiration. In the end I went for a cheesy tribute to Nigel Tufnel in the spirit of his ‘one louder’ philosophy. With my measurements in hand I used Inkscape to create a set of guides so I would know where all the hardware was going to go on the face of the enclosure. Then I made a simple panel-oriented design that would hopefully go well with the red enclosure. I had deliberately chosen the decal paper that had a white backing to it, so I knew that the upper panel would appear white. I also knew that the gap between them would contain the on/off LED, so that was intentional.

Decal shown in Inkscape

Decal shown in Inkscape

Application

Then it was a case of printing out the design on the water-slide inkjet paper (also purchased from Small Bear). Prior to printing it on the (expensive at $2 per sheet) paper, I did some trial runs on plain paper, just to check for size. You can see in the picture below how the ink looks nice and bold on the real paper compared to the plain paper.

Once printed, I then sprayed a reasonable coat of Rustoleum clear onto the inkjet waterside paper, to seal the ink without letting it run. I was surprised that even after drying for 12 hours the paper was still flexible. Next, I cut out each panel with small, sharp scissors, and made sure it all fit nicely. Finally I soaked each panel in water for about 30 seconds so that the decal was ready to slide off the backing paper. It was simple to apply the decal to the enclosure and get it lined up with the edge. It was most pleasing that my measurements were good, and also that the printer was accurate enough to obey my measurements. After smoothing out the decal with a bit of tissue I left it to dry overnight.

Decal ready to be applied

Decal ready to be applied

Finish

The next day I got things setup to shoot some clearcoats onto the enclosure. I planned on applying 5-6 coats, or until I got bored. This proved easy as long as I kept within the one hour time limit. If I waited longer than that I’d have to wait a further 23 hours to apply another coat.

Assembly

Well, it’s all assembled, and it is fully functional, but I’m not magically happy with the finish. It looks great, but it’s really really soft. It dents easily, even with cloth and finger prints. Maybe this means it will hold up really well to abuse because it won’t chip? Time will tell.

I am however pleased with the LED lenses, which I got from Mouser. Fulltone use a fresnel-type lens on their pedals, which I liked immediately. And to be honest I’m tired of the standard ‘chrome plated cone’ type that I’ve been using up until now. These ones are made by VCC and available from Mouser…try part 593-3210C (tall, like on this booster) or 593-2800C (flatter)

The finished article

The finished article

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Building an Electro-harmonix LPB-1 from scratch

Thus far my effects building experience has all been limited to assembling pre-made boards and soldering the components. Along the way I’ve tried to study the schematics of the original effect, such as the Tubescreamer, but none of it was really sinking in. To remedy this I have decided to go back to basics and learn more about the principles of audio electronics from the bottom up. I have defined ‘the bottom’ as a guitar tone control.

Research

My starting point then is some kind of boost circuit. Many great tones from the 60’s were achieved by driving the front end of a tube amp quite hard using something like the Rangemaster. Certainly Clapton was rumoured to have used one to brighten up his Les Paul in the Beano sessions.

So I looked for boost circuit schematics. One of the first ones I found was a really good single page explanation on how a boost works:

Beavis Audio – How It Workz

This was perfect as it explained it in dumb-musicians terms. For more detail (and for later consumption) I am reading this:

The Transistor Amplifier

Things of note:

  • Notice how similar a basic common-emitter transistor amp is to a common-cathode tube amplifier?
  • All boost circuits are basically the same. They might bias the transistor differently, or they might have extra components (for protection or good behaviour) but fundamentally a clean boost is a common-emitter amp.
  • I can probably build one of these quite quickly.

Which one to build first?

The LPB-1 schematic I started with

The LPB-1 schematic I started with

My choices were between the ZVEX Super hard-on (the SHO) or the Electro-harmonix LPB-1 as they have plenty of reputation in the industry and they’re incredibly simple devices. I decided on the LPB-1 for no apparent reason other than it featured in an article on Beavis Audio’s site which helped me greatly in knowing how to approach this. Here’s that article, go and read it if you’re interested in doing this.

Layout

As encouraged by the beavis article I downloaded DIY Layout Creator, and literally created my own veroboard layout using the LPB- 1 schematic. This was loads of fun and surprisingly simple. It forced me to know the schematic in great detail. I tried to keep in mind the how-it-workz article so I had a feel for why each component was there. Here’s the resulting layout:

Simon Allaway's First LPB-1 veroboard layout

Simon Allaway's First LPB-1 veroboard layout

As you can see, it is pretty simple and even though I haven’t done this in years I was able to assemble all the on-board components in about half an hour. I bet I can do it in half that time now as I kept screwing up.

I made a part substitution as I failed to order some 2N5088 transistors. I was under the impression I already had some, but didn’t. Instead I used a 2N4401.

Testing

So, once I’d wired up power, switching and signal jacks I plugged it into my amp to try it out, but all I got was hiss and distortion. So I unplugged and checked all the solder joints, reflowed a few and tried again. No different. I began to suspect the transistor as that was the only deviation from the schematic. I tried a 2N3904 this time, with much better results. I do get a boost (not as much as expected) and also lots more bass, which isn’t necessarily a good thing. At this point I was discouraged.

Time to re-evaluate. After some thought, I recalled the Beavis document, and some other discussions surrounding the SHO boost; check your transistor pin-outs. I had stupidly placed the transistors pins into the overboard without honestly checking that the collector, emitter, base pins were actually in the right place. I couldn’t tell what brand I was using, so I used a technique I found online here to derive the pins using the diode test function of my multimeter. And sure enough, I had it wired incorrectly.  Literally 180 degrees wrong.

Alright, so put the transistor in the right way around and it now works. There’s definitely lots of gain in this device, and lots of bottom end boost too. And its more than happy driving the hell out of a tube-amp.

The following pictures is before I trimmed the board down to its final size. You can also see I went for an on-board trimmer (as I didn’t have a 100k pot to hand). I may well leave it like this for when it gets integrated into my OD2.

My LPB-1 clone

My LPB-1 clone

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Fitting a 1961 Gibson PAF Humbucker in my Tokai Les Paul

The Tokai LP with its original chrome covered pickups

The victim

The Tokai Les Paul that my wife bought me back on 2005 is a glorious instrument. I have a nice set of guitars; even a “vintage” 1970’s Goldtop, but I always return to my Tokai. It just feels right. The neck is quite fat, and the frets low, but not too low. And the flame maple top underneath a beautifully sprayed cherry-sunburst is simply beautiful.

With all that in mind you’d wonder why I’d ever want to change anything, right? Well, I’m a tinkerer that just cannot leave things alone. Also, I have old bits of guitar hardware laying around and it’s always fun to try new things.  So I decided to take out the stock Tokai humbuckers and fit two pickups that I’ve had laying around for  a very long time. A Seymour Duncan JB (SH-4) and an honest-to-goodness PAF from a 1961 ES-335.

Work begins

I knew in advance the problem was going to be the old PAF. It seems to be quite fragile, and what’s left of the braided wire is very short. Luckily I had some RG-174 left over from building my amplifier, so I grafted some of that onto the old cable.

Old Tokai hum buckers. Look at that curly maple!

But before I could fit the ‘new’ pickups I had to remove the old ones. That proved to be very easy as there’s only two conductors from each pickup, so it took longer to remove the strings and screws than it took to de-solder them.

More luck; I didn’t think I had the right screws to support the PAF in the surround. Gibson pickups from the 60’s use “imperial” threads; Tokai pickups from 2005 use metric. So far so good, but the other pickup…the JB…also uses metric, despite being made in the US. Over the years I have accumulated lots of pieces and parts so it took only 5 minutes of searching in my old parts cabinet and I was rewarded with the appropriate screws. I bet I bought them years ago for the PAF and promptly forgot. The soldering part was trivial. I even replaced the dodgy looking caps with some Mallory 0.022uF ones. Why not? I was already in the guts of the thing.

I am now the proud owner of a Tokai Les Paul with an odd pair of pickups. Now its looks have changed….much more like the one Clapton played in the 60’s.

Here’s an MP3: CLICK HERE

Look at how gorgeous she is:

Job complete...looking cool

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TS Overdrive – new enclosure & sound samples

Old enclosure ready for tear-down

Old enclosure ready for tear-down, next to the new one.

Why?

When I built my first Tubescreamer clone (built with a great circuit board from DIY Effects) I was very pleased but left with a few issues that at the time I could not be bothered to fix.

Firstly, the paint finish I used on the enclosure did not turn out very well. I used Rustoleum, and sprayed it on way too thick (because I was impatient…lesson learned). It looked cool, but it didn’t wear well.

Secondly, the DC power connector I originally bought for it turned out to be the wrong size. I only discovered this when I got hold of a power supply, and it didn’t fit. In fact, it was at this point that I tried to use what I thought was an adapter for a smaller power connector. Little did I know that although the adapter fit, it was actually a polarity inverter too; so I blew up 3 JC4558 chips in the process.

So I decided to try an enclosure from Mammoth Electronics, who can provide a painted an drilled enclosure for around $10. Ridiculously cheap.

Wires for the LED "off-board"

Wires for the LED "off-board"

Getting on with it

The rehousing process was very easy; mostly a case of taking the old one apart and carefully assembling it all back into the new enclosure. I did have to redo the LED as the DIY Effects PCB allows you to solder it directly to the board, and let it just stick through the enclosure. I couldn’t do that with the new enclosure and still have it line up with the hole, so I attached wires to the LED and then soldered those to the board. Nice and easy.

The shiny copper on the MOSFET clippers

The shiny copper on the MOSFET clippers

Clipping with MOSFETs

Months ago, after I built my OD2 which uses plain diodes for clipping, I decided to change this OD to use MOSFET clipping. SLW had mentioned it in the excellent PDF file that lays out instructions for building the pedal, and he rated it highly. I was able to purchase the parts easily, and after doing the necessary physical modification (i.e. cutting off most of the mounting lug) the mod was trivial. But what a result in terms of sound! You’ll hopefully hear in the MP3 file below that it has a wonderfully soft clip. It’s as if it has rounded edges. Like an overdriven Marshall, but without the harshness. It does definitely get harsh if you turn the tone all the way up, and responds very well to tone adjustments on the guitar itself. In the clip you’ll hear a variety of pickups and guitar tone control settings (and sadly a lot of repetitive playing).

The setup was:

  • My own build of an AX84 P1 Extreme, with a 6V6 for the output section.
  • Tokai Les Paul with a 1961 Gibson PAF in the neck, and a modern Seymour Duncan JB in the bridge.
  • 2×12 cab with Celestion G12T-75
  • SM57 microphone
  • Recorded in Logic on a Mac. And a touch of reverb in the master output channel.

Click here for the MP3

Almost done

Almost done

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Rehousing a Danelectro Coolcat Vibe

Why bother doing this at all?

Bad knob positioning on the Coolcat Vibe

Bad knob positioning on the Coolcat Vibe. Who thought of that?

Take a look at the picture on the right; that’s the back end of the stock unit. While this device sounds great once you get it dialed in, it’s almost impossible to interact with it while you are playing. While I’ve never thought about it before, it seems that I like to see where my controls are when I’m playing. Perhaps it is akin to driving a car in that even though you might be just cruising along, you still want to be able to glance down and see what speed you are doing. So when you’re tinkering with the vibe’s controls you just can’t see anything because it’s all hidden.

Secondly, the big switch isn’t quite perfect. I’ve become accustomed to the basic switch that every custom builder knows and loves. This one doesn’t seem to switch effectively unless the force you apply is perfectly in line with the axis of travel of the switch.

Thirdly, it’s a really ugly box.

Preparations

I knew I would have to replace a few parts here and there. Here’s what I bought:

  • Potentiometers. I saw from this post that I needed 2 x B50k pots and 1 x C 50k pot. I found 16mm Alphas at Mammoth Electronics, who I had been wanting to try since a recommendation from Shawn over at DIY Effects.
  • DC power connector. The existing one is square and I don’t have an square drill bits.
  • 1/4″ jacks. The existing ones are probably crappy PCB mounted ones.
  • An enclosure. You can get a painted and drilled enclosure from Mammoth for $10. At that price why would I ever do this myself? When I tried it for my first ever pedal build it was messy, time-consuming and ultimately I was not pleased with the results.

Coolcat Vibe - in pieces ready for rehousing

Coolcat Vibe - in pieces ready for rehousing

Disassembly

This part was easy as I could use normal tools, so it only took five minutes. It’s a shame really; this enclosure is really well made, and would probably stand up to a considerable amount of abuse. If only they had located the knobs in a useful place (and it didn’t look like a clam).

The coolest part was finding a ‘real’ 3PDT switch underneath all that cast zinc. It fit the pre-drilled hole in the new enclosure and it seemed I would not have to bother removing the small PCB that it was soldered onto.

Still functioning, sans enclosure.

Still functioning, sans enclosure.

At all stages in disassembly/assemblyI wanted to make sure I didn’t break anything, so I made the effort to plugin and power up the device.

Mounting inside new enclosure

Mounting inside new enclosure

Assembly

The first task was to isolate the power supply jack, and the input/output jacks. You can see that the jacks are PCB mounted, and there are thin shield wires going between this PCB and the switch PCB. I chose to use those wires, and simply solder them to the appropriate replacement parts. At this point I was able to mount the switch and the new signal jacks into the new enclosure, and test once more. So far, so good; I haven’t broken it yet.

One by one the pots get replaced 'off board'

One by one the pots get replaced 'off board'

The next stage was to replace the pots. I had a feeling this was going to be painful, and I was not wrong. Over recent months I’ve replaced many a component in my amplifiers, and other pedals, but I’ve never dealt with PCB mounted potentiometers. What a terrible, terrible nightmare. I fully understand that they are designed this way so that untrained monkeys can assemble the boards, and then they slap some molten solder underneath and its done. After all, I did buy this device for $40 online,so you can imagine that its out-of-factory price is probably closer to $5. But it makes repairs very hard indeed. I managed to cook one leg of the first pot, which meant the PCB trace lifted from the board. Nothing that super-glue couldn’t fix though. My technique of removal was using a solder-sucker. It wasn’t very efficient as the suckers nozzle is quite larger compared to these component legs, and it was hard to keep the sucker ‘focussed’ on the leg AND hold the soldering iron in place. I was more careful with the other 2, so they went more smoothly. And when I say ‘more careful’, I mean I desoldered as much as I could with the sucker and some wick, and then mechanically pulled the pots off the board while trying to keep their solder molten. I know, I know.

The tabs that hold the LDR/Bulb enclosure in place.

The tabs that hold the LDR/Bulb enclosure in place.

Potentially the most treacherous part was rewiring the LED. To get to the soldered legs I had to take off the little metal box that enclosed up the light bulb and LDRs (light dependent resistors). Here’s a great article all about the inner workings of a classic Univibe.

The bulb and LDRs in action!

The bulb and LDRs in action!

You can see in the picture to the left, that there are three metal tabs surrounding the blue LED. All I had to do was gently bend those perpendicular to the board, and the box came right off revealing the bulb. Of course I couldn’t resist powering it up again, just to see the bulb working. In the picture you can see that there are two solder points above the bulb; these are for the LED indicator. Once again I had to carefully de-solder these, so as not to de-laminate the traces. I then attached wires, and connected a bright blue LED in its place.

Enclosure finished

Once I’d mounted the LED in it’s little bezel, I was basically done. I had to make sure I put the metal bulb enclosure back in place, of course, but all that was left was to tighten up any mounting nuts, and close up the box. Here’s a shot of the newly rehoused Coolcat Vibe next to my also-recently-rehoused DIY Effects OD (fantastic Tubescreamer clone).

The finished item...so far

The finished item...so far

An idea

I suddenly had an idea to make this rehouse a little more interesting. In other words, I looked at my vibe and the DIY Effects OD, which I had also rehoused (the green one, duh), and thought they looked somewhat plain. I’m basically proficient with publishing/layout-tools, so I thought I would try and create a decal for the top of the units. I took some basic measurements, and setup grids and guidelines, and just kind of went for it. Sadly I cannot find my decal paper (must buy some more), but I did do a basic printout onto photo paper. This is a work in progress, so updates to follow when I do finally buy some decal paper. The real one would not have the yellow background obviously. I can turn that layer off when I print so that it’ll be transparent, but you get the idea.

A mock-up of the decal

A mock-up of the decal

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AX84 – P1 Extreme – grid stoppers?

The problem

While playing my P1 Extreme over the last weekend I noticed an odd sound when letting a note sustain. Even when run clean, the amp would produce a fuzzy/distorted version of the note and then within a second or so the whole amp would cut out.

Investigation

It didn’t seem to matter which guitar I used, or which note I played. This has meant the problem has been hard to reproduce. Still trying though.

I asked members of the Hoffman forum and they thought it was caused by oscillation, and suggested the following:

  • “Chop-stick” the wires inside the amp. i.e. use a non-conducting device to reposition wires in relation to each other. The proximity of low level signal wires (guitar input) to high voltage wires (power supply) can lead to problems.
  • Make sure the grid-stoppers are located as close to the tube socket pins as possible.

Upon reading the forum’s suggestions I realised that I knew nothing of what grid-stoppers were meant for. Also, looking at the amp’s schematic I saw that the input stage tube, V1, doesn’t even have a grid-stopper. Here’s an excellent discussion on why this might be, in the case of an AX84 amp. Secondly, the power tube’s grid stopper is located on the main board, with a wire linking it to the tube socket. This would appear to be an opportunity for improvement.

Here’s what I’m going to do:

  1. Digest this article about grid-stoppers on the Aiken Amps site.
  2. Get myself a chopstick and carefully poke around the amp while trying to reproduce the problem. “Lead-dress” might be the issue, and is relatively simple to fix.
  3. Move the existing power tube grid-stopper to be soldered directly to the tube socket.
  4. Add a grid-stopper (10k – 65k value resistor) to the V1 grid.

Work (not) done

I read the article about grid-stoppers and also some more specific AX84 project stuff. These articles were discussing why the P1eX doesn’t have grid stoppers on the pre-amp stages, and why the grid stopper for the output stage is on the main board, and not soldered directly to the pin on the tube socket. One poster reasoned that the pre-amp stage grid stopper was “missing” due to the fact that the original designer didn’t have RF problems in his house. THere is a note about this on the schematic. Who knows?

As for the output stage? I didn’t move the resistor. I didn’t make any modification to the output stage at all as I could not reproduce the problem. What I think I saw/heard was oscillation caused by resonance from the speaker cab. It was literally vibrating itself into oscillation.

However I did replace some of the cheap/crap/oversized Monster shielded cable that I had originally used. Now it has some decent shielded cable bought from Hoffman Amps. It’s listed here asMini shielded cable RG174″ I got about 5 feet, so that’ll last me a while. This also meant I was able to rewire the input jack properly and take advantage of the Cliff Jack’s switching feature. When a guitar cable is unplugged, the tip is now shorted to ground. It makes for a silent amp when nothing is plugged in.

I also added a shield for the pre-amp tube.

Outcome

So my P1eX sounds great again. My son and I had time for a jam yesterday, so I was able to use it for a couple of hours without any issues at all. These days I use a a 6L6 for the output tube, that I bought from Hoffman at the same time as the wire/shields. It doesn’t sound all that much different to the EL34, but I haven’t trully cranked it which is where I may hear differences.

Also I noticed the power transformer (PT) was warmer than I had noticed with a 6V6 output tube. After some brief reading I decided to not worry about it at all as it’s not so hot that I cannot keep my hand firmly on it with no problems.

Update!

I recently made a few little changes:

  • Switched back to a 6V6, and changed the output tube cathode resistor to a single 680 Ohm.
  • Replaced the last of the crappy Monster cable.
  • Moved the grid-resistor to the tube pin.

This led to the amp not producing any sound at all, which was worrying. I decided to check all the voltages, record them and ask a question in the Hoffman forum. You’ll find the thread, here: Odd voltages in P1 eXtreme.

The outcome was that I found a dry solder joint right where the cathode resistor/bypass-cap attach to ground. Once I removed old solder, and re-did these turrets all the voltages returned to within spec.

Dry joint in cathode ground

Dry joint in cathode ground. I removed and re-did thes joints inside the orange box.

Here’s a shot of the grid resistor in its new location right on the grid pin of the output tube:

 

Grid resistor wiring

Grid resistor wiring and heatshrink

Eye-candy

I noticed some blue glow in the output tube. I’ve read enough to know not to worry about this either as it’s apparently normal. But I used it as an excuse to take a long exposure shot of it in relative darkness. This was a 20 second exposure…

An Electro Harmonix 6L6 in an AX84 P1 eX

An Electro Harmonix 6L6 in an AX84 P1 eX....ain't she purdy?

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OD2 – final assembly

The Clay Jones circuit, plus layout

The Clay Jones circuit, plus layout. Click to see the big version.

In my previous post I was discussing a new project. Another distortion pedal based on a clone of a Landgraff Dynamic Overdrive. The circuit was drawn out (possibly from looking at the Landgraff device) a few years ago by someone called Clay Jones. See the picture on the right here. This circuit was made available to me, as a beautiful pre-built PCB, by the guys over at DIY Effects. They have a great OD circuit (currently at revision 2, I believe) that I had used previously, but this one is using their “revision one” board.

The clipping switch

The clipping switch. 3 diodes on the left, 2 LEDs on the right.

Clipping

The major difference between the revisions has to do with the clipping section of the circuit. Rev 2 has ample space for all kinds of options whereas Rev 1 is limited in terms of on board space. In this context that didn’t matter. I knew I wanted to mess around with clipping options and that meant it was easier to do that with a switch off the main board. I chose to try 3 diodes in one position and 2 LEDs in the other. The middle ‘off’ position is just the raw clipping of the circuit alone.

OD1 and OD2

OD1 refuses to make eye contact with the conspicuously naked OD2

Initial tests

I was able to wire up the board with power, pots and jacks very quickly, due to the great instructions, and had it plugged into my amp in no time at all. The goal here was to compare the clipping options and just make sure I wasn’t going down the wrong path. And I was not disappointed at all. The 3 diodes position has tons of gain, but in the lower positions sounds much like a cranked Marshall, but with a slightly softer attack. It doesn’t have the harsh bite of the typical Angus Young tone, which isn’t a bad thing. Then I switched it to the middle ‘off’ position, and it immediately got much louder, presumably because there aren’t any diodes clipping anything. Also for the same ‘drive’ position, the middle position had way less drive. Position 3, the 2 LED’s wasn’t a huge change from the middle position, but it softened the attack a little. Either way, I completely love this pedal!. So now to get it into a usable enclosure.

The enclosure

Measuring and drilling the enclosure holes

Measuring and drilling the enclosure holes

Based on a recommendation from DIY Effects I bought a box from Pedal Enclosures, specifically the YY type, in red hammer finish. All that remained was to drill some holes and start the assembly. This meant I had to think about how I wanted to lay things out inside the box as well as outside. But the basic dimensions of the box decided a lot of this for me. Here’s the basics:

  • The circuit requires Drive, Tone and Level pots.
  • I wanted to eventually add a switchable boost, so I need 2 foot switches. This will be like the “more” switch on Joe Satriani’s Vox distortion pedal.
  • I need a hole for my clipping switch.
  • LEDs for both the switches so I know where I am.
  • The usual 1/4′ jacks and power.
Making sure the parts fit as I go

Making sure the parts fit as I go

I covered the box with masking tape and found my old vernier calipers and a pen. With the box of components at hand, for dimensions, I was able to mark out the locations for the holes and punch them quite quickly. Then it was time for the drill press. After starting with an 1/8th ” bit for pilot holes, I layed into it with my El Cheapo “unibit” that I got from Harbor Freight Tools.

Assembly

Belly up, with new parts

Belly up, with new parts

Now for the fun part! As I had done most of the assembly work with parts I had laying around, I did have to replace the pots with smaller ones (16mm rather than 24mm), and also I had to wire up the full bypass switch (and the LED). But all of that was just busy work. This time, I purchased extra components from Small Bear Electronics.

I was lucky enough to have wired it correctly first time (as with the original OD pedal) so within the hour I had it plugged into my amp and was jamming away.

I am very, very satisfied with this pedal. I can get a wide variety of usable tones from it very quickly. I do need to replace the drive pot with something else as the range of “no drive” to “loads of drive” all happens in the first few degrees. Not sure if this is simply the difference between linear and logarithmic taper. Anyway, here’s another photo.

(Almost) finished in it's shiny red box

(Almost) finished in it's shiny red box. The toggle switch is for the clipping options. Forward is the 3 diodes, backwards is the 2 LEDs.

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New distortion pedal project, based on Landgraff Dynamic Overdrive

A few months ago I built a clone of a TS-808 Tubescreamer (based on a PCB and build instructions from DIY Effects) and that proved to be successful.

I recorded a sample of what it sounds like: Steinberger into P1 Extreme, with OD pedal

Now that pedal was built with the standard clipping circuit i.e. two diodes. Some would say this is dull, and indeed the DIY Effects build instructions contain other recommendations. These range from using three diodes instead of two, for a kind of asymmetric clipping, to using MOSFET devices.

So to try these out I bought a pre-populated board from DIY Effects.; one that had been wired up in the style of a Landgraff Dynamic Overdrive. I had no idea what this pedal actually sounded like but a quick trip on YouTube told me what I needed to know.

The clipping arrangement has been deliberately left up to me to configure. I plan to use a switch to allow for the different clipping methods. I think I’l do the following:

  • Two diodes: for the traditional TS-808 style.
  • Three LEDs: asymmetric clipping.
  • Two MOSFETs: I have no idea what it sounds like, but its worth a try.

SLW from DIY Effects sent me great instructions on how to do this, and recently posted about it. He uses a DPDT, but I might need 3 positions to do this. I’ll see if Radio Shack has some in stock. A nice cheap project if I can retrofit this into my existing grey enclosure.

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What does an AX84 P1 eXtreme sound like?

From the posts in this blog you might know already that my first (and only, so far) amplifier build was a P1 eXtreme, which is a design from the AX84 ‘movement’. It has these characteristics:

  • Single-ended, i.e. Class A output stage, using a single pentode.
  • A two-stage triode-based preamp. My build is using a single JJ Electronic ECC83S (12AX7).
  • A simple tone stack sitting in between the two triode stages.
  • Capable of using multiple 8-pin tube types. My build is using a JJ Electronic 6V6 pentode.

Since I built it I’ve been playing it as much as possible, trying to get to know it’s sound and feel. The only decent amp I’ve ever owned prior to this was a Marshall 2204 50 watt head, which in itself is lovely, but it is way too loud for good tone to be had at home. This was the major reason why I built the P1 eX in the first place. But the question I am most asked is “what does it sound like?”. So this post is to present some recordings I did this weekend.

P1-eX with Tokai Les Paul copy

P1-eX with Tokai Les Paul copy, my 2×12 cab with the SM57 placed scientifically ‘in front’

Setup

I have a very crude recording setup at home. My ‘office’ is an 8’x10′ room with wood panels and a reasonably high ceiling, which is terrible for recording. But these didn’t come out too badly I suppose. Here’s the setup:

  • Apple iMac with built in audio input.
  • Nicely cheap Behringer mixer acting as mic preamp.
  • Shure SM57 placed ‘somewhere in front’ of the guitar speaker.
  • A custom build (I made it myself) 2×12 cabinet largely modeled on the THD design, with Celestion G12T-75 speakers I got off eBay years ago for $50.

The ‘made-up-as-I-went-along plan’

I decided to start with the master volume up full, and the preamp gain down low. Then I’d play a bit, crank the preamp gain a bit, play a bit…you get it. The idea being that one could hear the entire range of the amp from quite to full-on cranked. I also wanted to show the difference between the typical Les Paul type guitar and the typical Strat type guitar.

Recording One – Les Paul

About 5 years ago my wife bought me a fantastic Tokai Les Paul. It’s a pretty damned good copy of someones notion of what a ’59 sun burst would be like. I love it. It plays like butter. (Towards the end listen for my apology to my wife…apparently a cranked P1 was enough to completely freak-out the dog). Pickups-wise I started with the neck and made my way through both pickups on and then the bridge only. As is fairly typical when and amp is cranked you end up with a good tone on the bridge, but then you get mush when you switch to the neck.

Click the orange/white play button for the audio clip: 

I was standing about 4 feet away from the amp which was the sweet spot where feedback was easy to control….right up until it was dimed. You can hear at the end (if you last that long) where she just wanted to squeal whenever I stopped playing. So it must be said, this amp is great just below ‘full-on’. The recording doesn’t do justice to the feeling of being in the same room as this amp, but we’ve all been there, right?

Recording Two – Steinberger

This recording is with my Steinberger. It has the so called ‘7’ configuration of pickups, which means an 89 in the neck position, an SA in the middle and an 89 in the bridge. The 89s have the ability to turn off a coil and pretend to be SA pickups. This means I use this for strat-like tones rather than Les Paul tones. So this recording starts off with the neck pickup in single coil mode. In fact I never use humbucker mode on this recording at all.

Click the orange/white play button for the audio clip:

While I like the tone of a strat-type guitar with this amp, I am still so very biased towards Les Pauls. i.e. if Eric Clapton calls me right now and said “I need another guitarist tonight” I’d take my Les Paul.

Recording Three – Les Paul + a lame tune

This is a simple jam track that I made with my son Dylan. He was noodling around on the keyboard and created this lovely haunting chord pattern. I then ruined it by putting drums and bass on it. Anyway, the ‘solo’ guitar is the Tokai in the middle position, with the neck volume backed off a bit, and the P1 preamp gain at about 80% and the master volume at about 30%. Same recording setup otherwise, in fact the picture above was taken right after I recorded this.

Click the orange/white play button for the audio clip:

I love this tone. It’s what I always end up dialing up on any amp and the P1 gets me this tone at very low volume. That was the whole point right? 🙂

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Building a TS Overdrive – from DIY Effects

Adhoc workstation

Here's the board with the instructions on the left. All the components were in neatly labelled baggies.

After my initial trepidation about which transistor to use (and with some patient guidance from Shawn at DIY Effects) I was ready to build the TS Overdrive guitar effects pedal. I’d read the build document many times as I learned from building my AX84 P1 eXtreme that you can never go over this stuff too much.

Components

So step one was to start installing components and get soldering.  I had my less powerful 15W iron this time as it has a smaller tip and will be less likely to cook any components. I also brought out my very handy clip stand device, which helped me hold components as I assembled them. It also has a magnifying glass attached…very handy. I began with resistors, then moved onto capacitors (electrolytic first). Then it was the IC socket and transistors.

Standard TS 808 clipping diodes

Standard TS 808 clipping diodes. There are many options available here.

Clipping options and transistors

There are several options included with the board design that allow for different clipping methods. You can use the stock diodes, or MOSFETs or even LEDs. I went for the original method (which is regular diodes in position D1 and D3. D2 gets jumpered) because I wanted to hear what the original TS 808 circuit sounds like. These things are legend and I’d never had one in my arsenal before. As mentioned in the previous post, I had an issue getting hold of the prescribed MPSA18 transistors and in the end found an assortment of general purpose ones at Radio Shack. So this build used a pair of 2N3904 transistors.

Heat shrink on the pot terminals

Heat shrink on the pot terminals

The remainder of the build went very well. It really was a case of following the build notes, and carefully marking off each component (or indeed wire) as I assembled it. I knew that the board had to mount on top of the pots so I was careful to heat-shrink the wires coming off the pots themselves; I didn’t want any random wires to short out parts of the circuit.

Final assembly

This was tricky for a few reasons:

  • I used solid-core 20AWG wire. This mean that while the wires stayed where I put them, it also meant it was harder to orient the board. See next point.
  • Rats nest of wires

    Rats nest of wires, but it's physically sound and ready to go!

    The holes in the pre-drilled enclosure from Pedals Parts were such that I had to choose between having the tone pot right near the top of the pedal (which looked crap) or the tone pot near the stomp switch. I opted for the latter, but that meant the board had to be oriented the other way round, which then meant the wires I had already soldered in were about an inch too short. Coupled with them being sold core and the result was physically sound, but looked really messy.

Fire it up!

Almost done

Almost done. The view through the looking glass!

So all that remained was to solder in the LED, and put the knobs on. I’d failed to order a bezel for the LED, so right now it’s just kind of floating there. The knobs went on easily, and look good. After using a mix of Alpha and CTS pots on my amp build, I must say I like the action on these Alphas. The CTS pots I used on the amp were nylon shaft whereas these are solid aluminium which feels so much better.

Next step was to plug in a battery, screw on the back, and fire it up. And I must say it sounds excellent! I dialed my amp to be as clean as it gets…i.e. no pre-amp distortion/saturation, and dialed the TS OD to be a clean boost (no Distortion, Level just a bit louder). Harder to  dial in was the Tone. The documents are correct when they say that most of the range is at the end of the knob’s travel, so there’s a kind of sweet spot where you get some good “bite, but it’s not harsh. With the tone on maximum it can be a bit “fizzy”.

Result!

From here on I jammed for quite some time, punctuated by twiddling with the knobs on the pedal. It was hard to make it sound bad, to be honest. It’s definitely not a high gain machine, but I wasn’t expecting one (and that’s why I got the Boss DS-1). It’s a fantastic blues overdrive that works well with single-coils as well as humbuckers or P90s. If my SM57 wasn’t broken (might be the cable) I’d record some samples.

I plan to do a number of things from here:

  • Try different clipping options.
  • Try different transistors.
  • Re-finish the enclosure. This Hammerite stuff isn’t pretty. It’s been a week and it hasn’t dried properly, so I think I sprayed it on too thick. I’d probably go for green enamel as a nod to the original Ibanez TS 808 that started all this.
  • Record some samples.
  • Minor adjustments such as mount the pots lower so the knobs don’t stick up so much. Also, buy and install the bezel for the LED (which I might change to blue, just cuz).

UPDATE!

An older version of the DIY Effects board, but with a different/better design.

UPDATE AGAIN!

A new enclosure, different clipping method, and a sound sample.

Final assembly of the TS OD

Final assembly of the TS OD from DIY Effects

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