Monthly Archives: May 2016

Mailing List for Blue Nebula Info


The sign-up form for the Blue Nebula mailing list is now on the Stanley-FX website.

If you’re interested in receiving the latest information on the Blue Nebula, including availability and prices, just click on the ‘Mailing list’ link, fill in the form and click ‘Subscribe’.

(If you’ve already filled in the contact form on the ‘The Last Stage …’ page here on my blog there’s no need to subscribe  again as I’ve already added you to the list).

I promise you won’t be bombarded by emails about anything else or from anyone else, just relevant information about the Blue Nebula pedal that you’ve already expressed an interest in.

Joining the list doesn’t commit you to purchasing anything and you can unsubscribe at any time.


New ‘Firmware Update’ Feature in Librarian

In part prompted by the lack of a Mac OS version of an app to upload firmware revisions to the EchoTapper and Blue Nebula effects units, I decided to add this feature to the Blue Nebula Librarian and also to update the older EchoTapper (eTap2HW) Librarian.

This now means that users of both Windows and Apple Mac OSX computers can update their firmware in both effects units without needing to use a third-party app such as XLoader, which in any case was only available for Windows :-).

Blue Nebula Librarian beginning with Version 4.00 and EchoTapper Librarian from Version 3.00 include this very useful feature and you can download them now from the ‘Latest Updates Here’ link in the menu bar above.

Note to Mac Users: you will need to download and install the Arduino IDE in Applications. Don’t worry, you don’t have to understand it our even need to run it but it contains an application that is required by the Librarian. Windows users do not require the Arduino IDE.

Both Windows and Mac require the Java Runtime Environment (JRE) Version 8 or above to be installed. If you don’t already have it – if Librarian is working you DO have the JRE 🙂 – click here and choose the version of the JRE for your operating system.

Blue Nebula Librarian 4.00

Blue Nebula Librarian 4.00


EchoTapper Librarian 3.00

EchoTapper Librarian 3.00

When a firmware update is released the first step is to download and unzip it (if necessary) to your computer from this website and make a note of where you saved it (by default it is usually saved in the Downloads folder). Now connect your Blue Nebula or EchoTapper  to the computer via the USB cable and choose the Serial Port that it is connected to in the usual way. Click the red Firmware Update button at the bottom of the Librarian window and a file browser will open to allow you to locate the file you downloaded previously.

Select the correct file (it will have a .hex extension) and click Open. Depending on the speed of your computer the update takes about 15-30 seconds after which the Blue Nebula/EchoTapper will restart. As your effects unit displays its Welcome screen, you can check that it now shows the version number of the updated firmware to confirm the update has been successful.

Please note that the firmware update ‘disconnects’ the effect unit from the computer’s serial port so if you wish to continue using the Librarian after an update you need to click the Re-scan button and reselect the Serial Port to re-establish contact with the Blue Nebula/EchoTapper.

The Last Stage …

“A box without hinges, key, or lid,
Yet golden treasure inside is hid.”
J.R.R. Tolkien, The Hobbit   

The Final Part?

At the end of the last Chapter I told you that I had decided to design an effects pedal-sized version of the vintage echo box that had started out as a rough prototype over three years ago.

Initially I made a few measurements to see if there was any chance that Piet’s original eTap2hw motherboard and my Arduino automation could be squeezed into a typical guitar effect enclosure, such as the Hammond 1590XX. It quickly became apparent that this wasn’t going to be possible so I started a re-design of the whole thing from scratch. At first I simply tried to stick with Piet’s motherboard design and designed a new PCB layout for it. One of the most popular PCB design applications is undoubtedly Eagle but I never really liked it or found it user-friendly and once team member Mick Taylor had pointed me in the direction of DipTrace, I immediately found it intuitive and easy to use.

Following various false starts I was beginning to settle on a two-board design with the audio circuitry on one PCB (basically this was Piet’s original motherboard design) and the ‘brain’ which consisted of the Arduino and the circuitry from Piet’s Universal I/O board on another PCB.

Two Boards

An early design with the Audio (L) and Digital ‘brain’ (R) on separate PCBs

This early design retained Piet’s original preamp including the Fetzer valve input stage but Steve and Mick had been quietly working on a new improved design that used four FETs which would end up as the Stanley-FX Baby Blue pedal, a replacement for the already successful eTap2hw pedal from the same company. (The Baby Blue, effectively a Blue Nebula with the original eight eTap2HW echo effects and without the ‘bells and whistles’ of automation etc., is already available to buy from the Stanley-FX website at £129.99.)

BabyBlue echo

The Stanley-FX Baby Blue

I had also discovered the Arduino Nano which is a much more compact little Arduino which still retained all the memory and processing capability of the Arduino Uno I had used in the original designs.

The team consisting of myself, Steve, Mick and Piet (by the way none of us has, as yet, ever met in the flesh) exchanged ideas and designs via email and Dropbox eventually ending up with a ‘final’ schematic that incorporated the 4-FET preamp, the Arduino Nano ‘brain’, the FV-1 DSP chip, two EEPROM memory chips for the DSP programs and another EEPROM that would store the User patches, allowing up to 128 patches to be stored.

Using Diptrace to capture the schematic from our various efforts I came up with an initial PCB design which Mick, who has vast experience in this area from his own Stanley-FX pedal designs, reworked to improve the layout, give better separation of the digital and analog circuitry and add ground planes that would ensure the Blue Nebula would enjoy excellent low-noise performance.

The design did end up on two PCBs: a Main Board (with most of the circuitry) and a Controls Board which had the pots and navigation switches. In this early design the LCD was a separate module that would be connected to the main board by a short cable. The two PCBs were interconnected with a short ribbon cable.

To ensure the design would all fit correctly in the proposed Hammond die-cast enclosure I used DipTrace to export 3D models of the boards and imported these into a 3D CAD package called DesignSpark.

3D Render Iso3D Render Iso Transparent

At this stage, with everyone happy with the progress so far, I ordered a batch of PCBs and eagerly awaited their arrival so I could start putting together the prototype. The boards arrived and I was very pleased with the quality so I got busy assembling the first working prototype.

Blue Nebula Boards

The prototype Blue Nebula PCBs, Controls Board (top) and Main Board (bottom).

By this stage I had come up with the name Blue Nebula for the new effects pedal and the other guys liked that so that name has stuck but, in honour of the original eTap2HW creator Piet, who is Dutch, I decided to built the prototype in an orange Hammond enclosure 🙂


The prototype Blue Nebula – yes it’s Orange!

This initial prototype was put through extensive testing and enabled us to decide on a number of changes and improvements that would make the pedal better from both the user’s point of view and also simplify the assembly if anyone wanted to build one for themselves. For example we decided to

  • Replace the separate LCD module with one mounted directly on the controls board
  • Replace the small navigation/editing buttons with a larger Navigation switch
  • Have the Controls Board plug directly into the Main board so avoiding the need for special tools for making up a ribbon cable
  • Relocate the MIDI circuitry onto the Controls Board (it was originally on the Main Board)
  • Move the input and output jack sockets slightly further apart for a better fit in the enclosure
  • Move the Up and Down footswitches further apart so wearers of Size 12 boots wouldn’t accidentally stomp on the bypass switch 😉
  •  Fit a Lexan faceplate to protect the LCD from scratches and ingress of dirt and liquids (fancy a beer anyone?)

Mick quickly re-designed the PCBS and after more 3D modelling we ordered a batch which myself, Mick and Steve then used to build a number of final pre-production units to ensure all our modifications had worked out and we hadn’t introduced any other issues.

Blue Nebula 3D Model

Blue Nebula 3D Model


A finished Main Board


The Controls and Main Boards powered up and working.

The hardest part of the assembly is the machining of the enclosure to ensure everything will fit together correctly and we realized that this would be quite tricky for the average builder who would possibly lack either the ability and/or the tools to produce a sufficiently accurate result.

The pre-production Blue Nebula before it received its paint job.

The pre-production Blue Nebula before it received its paint job.

Mick invested in a CNC machine and after some trial and error and making extensive improvements to the machine itself he was happy that he could produce accurately machined Blue Nebula enclosures. Mick (proprietor of Stanley-FX) can also undertake powder coating and silk screen printing and the CNC and finishing processes have resulted in a fabulous result:


The finished Blue Nebula enclosure as received from Stanley-FX

Everything fits together perfectly and the end result is really quite stunning to behold. So, at last, that effects pedal I had imagined way back at the start, is now sitting on my pedal board, looking and sounding great and with features I hadn’t even dreamt of when I set out on this ‘journey’ way back in February over three years ago!

DSC02335 (2)

The Blue Nebula will soon be available from Stanley-FX as a fully built, tested and guaranteed unit at a very reasonable price (To be confirmed). If there is sufficient interest it may also be available in kit form with the finished enclosure as shown above. Further details will be published as soon as possible.

I want to finish this story by saying a big ‘Thank You’ to Piet, Steve, Mick, Ecca, Rolf, Johan and all the others who all played some part in this journey with their generous help, designs, ideas, suggestions and encouragement that kept me going. I hope you all agree that the end result has been well worth it 🙂


If you’d like to be kept up to date on the Blue Nebula development including prices and availability, head over to the Stanley-FX website and subscribe.

The Long and Winding Road

Part the Third

“You certainly usually find something, if you look, but it is not always quite the something you were after.”
J.R.R. Tolkien, The Hobbit

In this the penultimate part of the journey the path forks and I take a look at some experiments with using a valve preamp and improvements to the original FET preamp.

Opening the Valves

Eric Thacker, better known as Ecca, had demonstrated on the Shadows Music forum that Piet’s FET and op-amp preamp design could be replaced with a valve (tube) preamp that was available from a number of eBay sellers in Hong Kong and China. (Here, for example).


The valve preamp and Eccamatic pcb mounted in an enclosure.

The circuit was originally designed to be used as a Hi-Fi stereo preamp using two 6N3 dual triode valves, one valve for each stereo channel. For the eTap2HW module we only require a mono audio pathway so the left channel of the stereo pair was used as the input preamp feeding the echo module and the right channel became the recovery amp, taking the echo module output and acting as a buffer and output level control.

Eric had produced a PCB for his ‘Eccamatic’ design which allowed the echo module to be plugged in, provided a step-up power supply to generate the HT voltage and the LT heater supply for the valves and had connections for the three pots that adjust the echo settings.


The bits for Eric Thacker’s Eccamatic pcb.

Having already designed the automation circuitry it was easy to adapt the design so that the Arduino Uno would feed the pot inputs on the Eccamatic board, reading the required settings from pots mounted on the front panel.

The front panel also had input and output pots, controlling the signal levels.

I have described this valve EchoTapper build in a series of earlier posts and if you’d like more details just click on the Valve entry in the Categories list on the right of this page.

When the new unit had been completed, the sound was quite pleasing with less hiss and noise than the FET preamp but rather ‘sterile’ as might have been expected from it’s origins as a Hi-Fi design. As I am sure you will know, guitar amplifiers and the early Meazzi echo units have circuits that are far from Hi-Fi for a very good reason (at least in the case of the typical valve-based guitar amp) – the almost perfectly flat frequency response of a Hi-Fi design and it’s deliberate lack of harmonic distortion (achieved largely through the use of negative feedback) is really not what guitarists want or indeed need to get the sound they desire. The original Meazzi preamp is hardly a classic of valve design but somehow has that magic sound that we have come to love.

Piet’s FET preamp design had made use of the ‘Fetzer Valve’ circuit which uses an FET to emulate the sound of a triode valve so it does create harmonically rich sound when the input level control is set correctly to match the guitar pickup level to ‘push’ the Fetzer ‘valve’ into generating the pleasant sounding harmonics we all like.

Steve Mitchell soon had his thinking cap on and he came up with a number of modifications to the valve circuitry that, according to his simulations of the circuit which he had made using the TINA SPICE modeller, should tailor the frequency response better to the typical guitar pickup signal and also generate those desirable harmonics to give that rich sound we all love.

Steve and I came up with a three stage process that culminated in a final design that sounded great.

Stage 1: Remove the built-in stereo volume control pot and increase the input impedance

Stage 1 was essential to allow the input and output level controls to be separated and to provide a better match to the typical guitar pickup’s high impedance.

Stage 2: Remove the negative feedback from the preamp and add Meazzi-like tone shaping

Stage 2 was regarded as highly recommended to obtain a better tone and more gain which would encourage the desirable valve harmonics and tailor the frequency response which was very flat and resulted in a ‘lifeless’ sound, thus improving the sound for guitar purposes.

Stage 3: Add a separate Gain pot and three-way tone switching

The Stage 1 and Stage 2 modifications had resulted in a really good sounding preamp but Steve came up with Stage 3 which would take the whole thing to another level. Whilst not regarded as essential, these mods did make the unit even more flexible. There would now be three ‘level’ controls, the new Gain pot controlling the drive to the second valve stage in the left channel of the amp. The Volume pot controls the signal to the echo module and the Master pot controls the level from the output socket.

Modified Vavle Preamp Flowchart

Flowchart by Steve Mitchell (SCM)

Modified Valve Preamp Freq Responset

Predicted frequency response of the modified circuit


Front Panel of the final Valve-based Echotapper

The 3-way tone switch provided ‘normal’, ‘vintage’ and ‘warm’ options by tailoring the bass roll-off. On the unit in the picture (built for Mario Voltolini in Italy) I also added, at his request, a Cutting Edge Filter (CEF) which could be switched in and out if required.

Biting the Bulletins

In parallel with the improvements to the valve preamp, Steve was also working on a series of modifications to Piet’s FET preamp design.

One of the problems with any FET is that individual devices, even from the same batch, can have parameters that vary over quite a wide range and this makes it difficult to design a circuit that will allow the FET to operate in the optimum part of its characteristics.

Steve and Rolf Holmberg collaborated and came up with a spreadsheet that would calculate the best resistor values to bias the FET into the optimum operating point. This would be a bit complex for the average user to get to grips with so Steve and I came up with a simpler ‘flowchart’ approach. This would allow the best operating point for the FET to be found using a simple voltage measurement and a little trial an error with a few preferred resistor values.

Steve put together a series of ‘bulletins’ that were published on Piet’s EchoTapper blog which also included simple modifications to improve positive signal headroom, improving the FET gain and reducing white noise (hiss). These mostly involved removing or changing some resistor values and adding some extra capacitors.

Piet has since modified his original preamp PCB design to accommodate these improvements and this is documented on his blog.

What Next?

Now I had two excellent sounding echo units but I had an urge to see if it would be possible to squeeze all this technology into a smaller package, one that would fit on a pedal board or sit neatly on the floor at my feet like a typical guitar effects pedal.

Thus began the germ of an idea that would result in the Blue Nebula. It had to be compact, so that ruled out the use of valves and it needed to be much easier to build, with minimal off-board wiring so that, hopefully, anyone with sufficient experience would be able to put one together from a kit or buy a completed built-to-order unit at reasonable cost.

We had to go from this …


My first automated eTap2hw


to this …


The final Blue Nebula Design


To be continued.