Orange Terror Stamp Review, Terror Down, and Modification

The Orange Terror Stamp was announced and winter NAMM in January of 2020.

Excited, I pre-ordered one and received it today.

My first impression was amazement on how small it was. Orange Amplification managed to pack a micro terror into a medium pedal sized enclosure. They did not skimp on features either, it contains a tube preamp, effects loop, a 20 watt class AB power amp, and a cab sim / headphone output. The controls are simple, you get a gain to control distortion, two post distortion volume controls that are switched via the footswitch and a tone control that increases treble and also sweeps the mids at the same time.


I received unit 00985 probably manufactured in December 2019.

First as a standalone amp played though a 12" speaker cab the amp sounds pretty good. It has a bit too much high frequencies for my taste, but I was able to find a good tone with the shape knob at around 8-11 o'clock. It sounds good at this setting.

I am more interested in using it as a distortion pedal so I can switch up my sound using various pedals. I also want to use the power amp section for when I do not want to lug around my Orange Rocker 30 Combo. (I like the sound of EL34s)

As a distortion box, using only Input and Send/Line Out, it has an even harsher high end that can be tuned out by a very specific tone setting. It sounds really good at this setting for both high gain and crunch, but I felt locked into only one usable sound. The pedal would probably sound fine going into any amp's effect return, bypassing its preamp, but I really wanted to use it like a distortion box so about two hours after receiving it and 4 screws later, I opened it up and look for a convenient mod point.



The design seems very clean. My only complaint is that the foot switch wires (brown) are very close to the tube, also using the chassis as a heat sink for the power amp would have been nice but there is a lot of ventilation. There is one tube (JJ ECC83 / 12AX7), an internal "tube gain" adjustment, a power amp chip attached to a large aluminium heat sink, and two main PCBs. The top PCB is used for IO, while the bottom is used for the main circuit.

I did not want to fully disassemble my new pedal, so I wanted to modify it from what I could see. I knew that I wanted to remove the high frequencies, the easiest method is a first order lowpass filter. This will reduce the high frequency at a rate of 6dB (half volume) per octave beyond a specific frequency Fc. The circuit for 1st order LP is a single resistor in series and a capacitor to ground.

From the top there are 2 volumes that are switched via a foot switch, so I thought it would be useful to only modify the tone of one channel, and retain the original sound on the other channel. ** see note below ** The 'Volume 1' potentiometer is connected to the middle right of the PCB right under the 'TERROR STAMP' label on the silk screen.


My modification is to add a single 0603 capacitor between the pins for the potentiometer.

I needed to add a cap from a signal point to ground. The potentiometer for 'Volume 1' is a convenient place to add a capacitor as one leg is signal and another is ground. The only issue is that I would need to know how much resistance is downstream to predict the cutoff frequency Fc. Fueled by lazyness and undeterred by my ignorance, I decided to just try a couple of values. First I grabbed a 1uF 0603 that was handily right in front of me at the time. This value made 'Volume 1' very quiet, at full volume it was quieter than the direct clean signal, but it sounded much better and I could now adjust the tone. I guess the Fc is very low using a 1uF probably lower than 100Hz. If I reduce the cap by 10x to .1uF it should increase Fc by 10x.

Next I tried a .047uF cap, Much louder but still too quiet as full volume.

When I tested using a .01uF capacitor, I really liked the results as a distortion box. The volume is quite a bit quieter than the original 'Volume 2' sound, but usable. 9 O'Clock on Volume 2 is about the same level as 3 O'Clock on the modified 'Volume 1'. This results in a much warmer tone and is probably the largest value I would recommend for this type of modification. As a standalone amp, the sound is a bit dull using Volume 1, but you can use Volume 2 to get the original tone. Note: You need to reduce 'Volume 1' to its minimum in order to fully remove the cap from the circuit. When 'Volume 1' is high it will effect the tone of 'Volume 2'

I should really reduce the value a bit further (.0033uF?) to brighten it up a bit or add a switch to select several values, but I am happy with the sound and need to use it a bit more before I make my next adjustment.

10nF (.01uF) - High Volume Reduction
- Muted Highs, distortion pedal only, not good in amp mode.

4.7nF (.0047uF) - Moderate Volume Reduction
- Good Balance siding on warm, Recommended value for distortion box.

3.3nF (.0033uF) - Moderate Volume Reduction
- Good Balance siding on bright, Recommended value for distortion box.

1nF (.0001uF) - Slight Volume Reduction
- Too bright for distortion pedal, Recommended to knock the edge off of amp sound.