Signal Tracer/Injector pen - the story

This is the story of how this handy tool came into existence.

Once upon a time there was a pedal builder soldering effect circuit after effect circuit.

Most of the builds were running out of the box - soldering finished, guitar to in - amp to out - there was noise!

But occassionaly there were effects that refused to work - even refused to get going after a serious amount of time staring at them or fumbling with the wires, looking at solder joints etc.

And there it is - there is this box. Its usually hidden in a cabinet but from time to time you take it out, look at it - put the piece of your most recent frustration into it - and put it back.

You know this box exists. Sometimes you dream about it. But you rarely open it up and take something out.

You know you are able to fix it. You know it will cost a significant amount of time looking at it and setting up the equipment for testing if you want to dig deeper into it.

So you usually let it go and this box will get filled to the brim with frustration.

I also have this box. Honestly when you are developing new pedals - like I do - this box is not only a box it becomes a cabinet itself.

I made some thoughts what it is that is hindering me to just pick something from time to time and fix it. I quickly came to the conclusion its the testing setup you need (signal generator, oscilloscope, multimeter, power supply, wiring...).

I am well aware that there already are quite a few testing rigs out there you can use. But I wanted something different.

I wanted something that is formed like a pen and that I can point and use like a soldering iron. And it should have the most needed features on board. I did not want any separate parts and pieces cluttering my workspace, just the power supply, the effect in question and the pen.

And I made it. It was a long way to go. There were six! (6) revisions from the initial design. Its my first SMD design and I had a steep learning curve and it took more than EUR 600,- and 9 month for this:

I wanted other people to use it as well, so it had to be cheap but great in design and usability. Here are the features:

  • Tracing of existing audio in a circuit – works as amplifier and loudspeaker
  • Signal generator feeds audio into circuit and tracer checks existence in circuit
  • Signal generator only – when the circuit is already plugged into an amp (not recommended)
  • Continuity tester

Here is the trash pile of all the prototypes I did.

And here you can see all the revisions of the pen that were made through the development process:

You want to know how to use it?

Here is a video I made. Its a little trashy but you will get the point 🙂

The Modular Controller build report

Its here. Unbelievable but after 4 years in the drawer with no time to bring it forward finally it is here!

Effect Control Unit Update

The effect control unit has been reviewed and got a software upgrade (V1.4).

Whats new?

  • The mute feature now works even better than before eliminating nasty switch-popp noise.
  • A new feature has been added: Switch#6 (unused before) now can toggle a full unit mute. When the switch is pressed the unit gets totally silent until it is pressed again.

The new software is immediately shipped with newly ordered units. If you already own a unit you can order a newly programmed chip for your unit.

New Website Layout

We have been working hard rework the website to bring it to current website standards usable on mobile devices as well as on big screens. Information is more structured available now and - it looks better 🙂

If you find something not working or looking wierd please drop us a note to thc@ We appreciate your input.

Increased shipping cost 🙁

As of Jan 1st 2019 Deutsche Post - along with a lot of other carriers internationally - does not allow to ship goods in letters anymore. A new product has to be used which is a minimum of EUR 3.20 / 3.80 for shipping.

Sorry for this but there is no workaround.

13 May 2018

Finally Merlins Glassbower has been given a new PCB without VU-meter - which was making way too much noise when switching the LEDs despite the chip beeing a low noise version.

Its version 1.5 now. If you want to build a boost 27dB without OpAmps check it out here: Merlins Glassblower V1.5 PCB

The ROG Umble board has been verified to be workiing with the SMD JEFT versions. No more searching for the discontinued parts. Check it out here: ROG Umble V1.4 PCB


16 April 2017

The long time of silence at least has been interrupted.

Here we are presentiing new stuff:

03 July 2016

Read some interesting news about the Modular Looper project.

There is a new 3-band parametric eq for you to build. Its intended as a tone control to be built into an effect. There will be a standalone version as well.

04 June 2016

Read some interesting things about graphic and parametric equalizers in the new knowledgebase-article.

Also there is a new DIY report on the same topic Equalizers.

01 June 2016

New kid on the block: Merlins Small Time Delay (with tails). This is a nice delay circuit with tails - meaning that even if you switch it off the signal trails out (repeats) and newly played notes dont have the effect.

10 May 2016

Huge restock in boards. Lets call it the white flood 🙂

3PDT boards have been reduced: 1590B  1590A







Also there is an update on the modular controller: PControl Modular Part #5


01 May 2016

Read more about the Modular Controller here: PControl Modular Part#4

02 April 2016

Update on the Modular looper:  Modular Looper Part#4

28 March 2016

Added more images to Modular Looper Part#3

20 March 2016

Some great news today:

Almost everything in the shop has been restocked!

And here you can see what I've mostly done during the last 3 months:

Modular Looper Part#3

12 December 2015

New stuff: The Optotronics switch and Merlins Glassblower Boost. 27dB in the box.

Big restock came in, so Effect Control and EPIC looper are back together with a lot of other boards.

Check out our clearing discounts. Some boards have huge syvings!

23 November 2015

Effect Control V1.2 has been released. Packed with nice features to help you build your multi-effect or a standalone switcher for your pedalboard.

The 5-band EQ has been given an improved layout to have a little more space around the connection pads and some other small improvements. And its red now 🙂


02 October 2015

We will move to a new server on Thursday, Oct 2nd 2015. Service may be interrupted for a few minutes.
We will be back a lot faster than now 🙂

26 September 2015

Added sound demos to the Tube drivers with AT7 and AX7 tubes, the Headphone stereo amp sim and the All-in-one

18 September 2015

A lot of things happened in the last weeks!


First, we have musikdingestablished a cooperation with the well known german Parts and Kits supplier!

Klick the logo to see what we started with. International shipping from musikding starts as low as EUR 2.90 which is a very reasonable price!


Second, we have released a new project based on Merlin Blencove's Equinox II- Its a reverb built from delay chips.EquinoxII_PCB

Its not only a proof of concept but a realy good sounding and cheap reverb!





Third, we are currently sending out our first monthly newletter with news and new projects for you to build! Feel free to subscribe to not miss anything!

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