A few short videos I put together to show how to use the Blue Nebula and it’s Librarian software.
I finally got around to optimizing my FET-based eTap2HW, the one with automation. (I also have a manual eTap2hw that I already optimized a while ago now).
What’s this optimizing I hear you ask? It’s a well known fact that FETs are notorious for having widely varying electrical characteristics even when they come from the same batch and this makes it difficult to design a circuit that will work well with any FET you plug into it. Aside from buying a big batch of FETs and testing them to find the most suitable ones, it’s usually necessary to resort to trying different biasing resistors and measuring the source and drain voltages, and keep repeating this until the FET is operating in the desirable part of it’s characteristics. By doing this we are arranging that the FET will behave very much like a triode valve and thus give us the sweetness of tone that every guitarist seeks 🙂
This could all get very tedious but thankfully Steve Mitchell came up with a fairly straightforward ‘flow chart’ approach that will get your FETs biased nicely with the minimum of trial and error. Steve has kindly produced a set of ‘Bulletins’ that explain what’s required. You can download these over on Piet Verbruggen’s Echotapper blog. The ones required for optimizing your FETs are Bulletins 1 and 2 and Bulletin 5 is worth following as well as it improves the gain of the FETs and reduces the white noise or hiss that some people find problematic, especially for recording.
While I had the unit opened up I decided to make a few modifications I’d been thinking about doing for a while.
1. First up, I decided to cut a small opening in the end panel directly opposite the USB connector on the Arduino so I could easily connect the unit to my PC whenever I wanted to update the firmware and when I’m using the Librarian software to backup my patches and arranging them into a set list. Before this I had to unscrew the end panel to get access to the USB connector which was inconvenient.
2. My second modification replaced the ‘Wet’ output mono 1/4″ jack socket with a stereo jack socket that will accept the patch change foot pedal I described in an earlier post. I never found a use for a ‘Wet only’ output signal so this jack socket was never used and it was easy to replace it with a stereo TRS 1/4″ socket. The sleeve (S) connects to Ground, the tip (T) goes to the ‘Up’ switch and the ring (R) goes to the ‘Down’ switch.
3. My original tactile push buttons were beginning to play up. Frankly I wasn’t surprised as I had always thought this type of little ‘clickety-click’ switch wouldn’t be very durable and so it proved. I decided to remove the strip-board sub-assembly that held all five switches and replace the Edit and Mem switches with panel mounted miniature momentary push buttons.
I was able to retain the ribbon cable and connector and make up a suitable matching connector for the new switches and patch change wiring.
As I was going to be adding a rotary encoder I no longer needed the Up, Down and Select buttons so the holes for the up and down were plugged with a couple of little rubber grommets that I happened to have lying around and the rotary encoder went in the hole where the Select button used to be, after enlarging it with a reamer.
4. I’ve described how to add a rotary encoder to the eTap in a previous post and I followed that when adding the new encoder to this project. The Sparkfun breakout board makes it easier to wire the encoder. I used an RGB encoder even though I don’t use the built-in LEDs as this type has a mounting bush to fit it to the front panel; other cheaper variants can’t be easily panel-mounted. I really recommend the rotary encoder as an alternative to punching the up and down buttons like a mad thing when choosing patches or editing the patch name!
And here’s the EchoTapper Vintage Echo Unit with all it’s mods and optimizations completed.
A two-button foot-switch is a handy way to change patches on the Echotapper and I finally got around to wiring one up for myself. You’ll need to add a 1/4″ (6.3 mm) stereo jack socket to your Echotapper and wire this to the Up and Down buttons (or the Up and Down pads on the LCD shield pcb if you don’t have Up and Down buttons – see following photo).
At the Jack socket, connect the UP wire to to the tip terminal, the DOWN wire to the ring and the GND wire to the sleeve terminal.
The foot switch consists of a small die-cast box (approx 110 x 60 x 30 mm) with two momentary foot switches and a stereo 1/4″ jack socket (you could omit this and wire a suitable length of three core cable directly to the switches).
The Adafruit LCD Shield kit which is used in my automation project is supplied with pcb mounting tactile switches but they are too short to protrude through the front panel with the lcd mounted in the enclosure. Switches with extra-long actuators can be purchased to replace them but I have concerns about the long-term reliability of these little tactile switches so I opted to replace them with off-board panel mounted switches when I built my Valve EchoTapper.
A couple of builders have asked for the details of how to wire them to the LCD Shield so I’ve prepared a document to show how I’ve done it.
Click here to download the instructions as a pdf file.
I’ve personally found that adding a simple rotary encoder to the EchoTapper makes selecting and editing patches a whole lot faster and more user friendly. The Automation firmware has supported the use of such an encoder for some time but I have been remiss in not documenting how it is connected.
Before I delve into the details let me explain what the rotary control does in the EchoTapper with Automation. It basically replaces the up, down and select buttons so you can simplify your control panel to just a knob for the rotary encoder (which acts as Up, Down and, by pressing the knob, Select) and two buttons, Mem and Edit.
I recommend labelling the encoder knob Patch/Adjust and Select (Push) as in this photo.You’ll notice that I have retained the Up and Down buttons (and these still work but you can omit them) and turning the Patch/Adjust knob clockwise and anticlockwise will act as ‘up’ and ‘down’ respectively. Pushing the knob acts as the ‘Select’ button.
Patch/Adjust Knob Functions
- Turn to flick through presets and User patches.
- In Basic Editor mode, turn to adjust the ‘Prog’, ‘Wet/Dry’ and ‘Feedback’ values of the patch.
- In Manual mode, turn to change the echo model.
- In Advanced Editor mode, turn to change the echo model then Press to select it for the patch you are editing.
- When editing the patch name (Advanced Editor) turn to change the current letter and press to advance to the next character position.
Wiring it to your Arduino
So how do you wire it up then? I’ve covered this in detail in a document which you can download here.
The recommended parts are:
In order to upload the EchoTapper Automation code (contained in a HEX file) to the Arduino UNO microcontroller in your EchoTapper unit, it is necessary to connect the UNO to your computer via a USB cable and run a suitable uploader tool.
As users (including myself) have recently found, the original uploader tool that I recommended no longer works. This may be failing due to an incompatibility with the version of .NET installed on the users pc.
I am now recommending users to download and use XLoader and use that to upload the code to your EchoTapper. XLoader can be downloaded here.
These are the default settings for the Uno and they seemed to work fine.
When you run it choose the Uno option from the Device list, select the COM Port that your Uno is connected to, leave the Baud rate at the default (115200) and click the … button to browse to the hex file you wish to upload, then click the Upload button and a few seconds later your software will have been updated and the EchoTapper will restart – check the version number displayed to make sure everything went ok.