a DIY valve overdrive pedal : goldie
In an amongst the guitar building I decided to break out the soldering iron to build an overdrive pedal – as light relief. I had stumbled across the “Valvecaster” schematic and layout at Beavis Audio.
This is a very simple circuit that uses a 12AU7 valve, running at a low voltage. Because it is running at such low voltage it is very easy to overdrive.
The schematic specifies an operating voltage of 9v but I decided to bump it up to 12v to give a fraction more headroom. I chose one from the tangle of old wall-warts I have tucked away in a drawer. It could use a battery but I suspect that the current draw for heating the valve would suck a PP9 dry in a matter of minutes.
If you search for “valvecaster” at Youtube, you’ll find plenty of examples of the pedal in action. One of the common comments is that this is a naturally “dark” sounding pedal. This was not exactly what I was after and so I was going to experiment with different types of tone stacks. As laid out in the schematic it includes a simple treble cut tone control. Even turned up full this would only make the pedal darker, allowing treble frequencies to escape to earth. I decided, initially, to build it with no EQ, and then add it later. One of the results of this was that it is not a dark pedal at all. It is wonderfully balanced and punchy just as it is, and it’ll not be getting any additional EQ added. To remove the tone control I just eliminated the 10nF capacitor (C2) and the A100k potentiometer (VR2).
I reused an old enclosure I had laying around, which I shot with a coat of black nitro-cellulose and a very light top coat of gold (both left over from my Shaftesbury restoration). The gold coat is thin enough to allow just a hint of the black to show through.
The chemistry geeks amongst you may, by now, have worked out where the inspiration for the name and colour came from.
I have yet to print up and apply the decals for the pedal but there’s the standard 1/4″ input and output jacks round the back. The top has the valve, a true-bypass footswitch and the power toggle switch. On the front, left to right, are the gain, a dummy pot (filling up a surplus hole in the old enclosure) and the output volume.
When I was buying the parts for this I also got hold of a 12AT7 valve. This works well too. It is more subtle and has less gain, but in some ways is all the better for it; smoother, warmer and just a bit less wild.
You can listen to a quick demo of Goldie with the 12AU7, that I recorded for my friend Alfie Lanos, who was really helpful in helping me plan this one out.
It was recorded on my mobile phone so the sound quality is not the best, but gives you an idea of what the pedal does.
COVID-19 – DIY Projects for Arduino beginners
The aim of this video is to inspire electronic engineers, hobbyists, STEM students to spend their time at homes working on different creative …COVID-19 – DIY Projects for Arduino beginners
GRETSCH ControFuzz Circuit Layout
Gretsch ControFuzz by Gretsch Instruments
Review: Seeed Studio Miniature Soldering Iron
By Harry Baggens (lol)
Seeed Studio miniature soldering iron
The Chinese company Seeed Studio offers a lot of interesting things for electronics enthusiasts. Along with selling products from various manufacturers, Seeed develops and produces their own products, many of which are very innovative. For instance, a year ago we had a close look at the DSO Nano V3 miniature oscilloscope.
Seeed has also developed their own miniature soldering iron, which is now available in a European version. The unique thing about this soldering iron is that a display and the control circuitry are integrated into the grip. From the photos and Seeed’s description, it looked like a good idea for us to get our hands on one and try it out in the Elektor Labs.
Along with the soldering iron and the associated tip and AC power adapter, the box contains a power cable, a grounding wire with a clip’, an Allen wrench and some spare tips.
The miniature soldering iron is compact (16.8 x 1.65cm) and looks more like a fat fountain pen than a soldering iron. The grip is made from plastic with a sturdy feel. A small OLED display and two pushbuttons are located on the side of the grip (or is it the top?). The tip slides into the front of the grip and is secured by tightening a small screw with the included Allen wrench. At the rear of the grip there is a power connector and a micro-USB connector for connection to a PC. The soldering iron has a rated power of 40W with the included AC power adapter. You can optionally connect a higher-capacity power supply (max. 24V). That boosts the power to 65W.
After you switch on the power, some messages initially appear on the OLED display, and after you press one of the buttons the preset temperature of 300˚C is displayed. The display is small but easy to read, but unfortunately the information on the display cannot be flipped for left-handed users. The miniature iron heats up quickly – the temperature rose from 20˚C to 300˚C in about 15 seconds. You can use the two buttons to select a different temperature (up to a maximum of 400˚C), but unfortunately the selected value is not saved for the next time you use the iron. If the iron is not used for three minutes, the control circuitry reduces the temperature to 200˚C and the iron remains in sleep mode until it is moved again (apparently it has an integrated motion sensor).The soldering iron is small, light, comfortable and easy to use. The power cable could be a bit more flexible, but that is of course difficult to change when you use a standard AC power adapter. We also did not test the power cable for heat resistance, which is a standard feature with a normal soldering iron. The included soldering iron tip has a fairly fine point and is suitable for most typical soldering tasks with leaded components. It can also be used with relatively large SMD components, but for finer work a tip with a narrower point would be desirable.The iron can also be connected to a computer through a micro-USB cable. The computer recognizes the soldering iron as a USB drive containing a file with the name CONFIG.TXT. After opening this file in Notepad, we saw a number of lines of text with various settings for operating temperature, standby temperature, wait time for standby and some other parameters. These values can be changed and then the file can be saved, after which the iron will use the new values the next time. The software is open source, so you could also modify or extend it as desired.This miniature soldering iron is very handy as a complement to your regular soldering iron. It is small and easy to take with you. The soldering performance is very good, and on top of that you can program it according to your wishes. With a price of around 100 euros, the iron is not exactly low-cost, but when an Elektor designer says he would like to buy one for home use, you know it’s worth the money.