Is the frequency response of the Orange Pedal Baby flat?

The frequency response

Many online sources claim that the frequency response of the Orange Pedal Baby is flat when the bass and treble controls are set to the middle position, and they compare the device to power amplifiers and active speakers with flat frequency responses. Well, the response is definitely not flat with those settings. In addition to the EQ, the credit for filtering the low frequencies goes to a single capacitor.

The image below shows the frequency response of the preamp section with the controls in the middle position.

In our simulation model, the cap marked as C4 is primarily responsible for cutting the low end. And yes, the treble boost in the middle position can already be seen directly by looking at the values of resistors R4 and R7. Resistors R5 and R6 represent the treble potentiometer, with the wiper at the junction between them. Similarly, R9 and R10 form the bass potentiometer.

Both listening tests and actual measurement data—which are not available for publication at the moment—confirm this.

With the bass control set to around 8 and the treble to about 2, the resulting response, as shown below, pairs nicely with our cabs and a Neural DSP Quad Cortex.

The clipping

The preamp section significantly clips one half of the waveform in a soft, tube amp-like manner with a 0 dBu¹ input signal. With a -20 dBu input signal, the signal remains symmetrical and clean. The volume control is positioned after the preamp, between the preamp and the power amp. This means it does not affect the described clipping behavior, and the output level from the device feeding the Pedal Baby should be adjusted to taste.

Clipping at 0 dBu input, measured² at the top end of the volume pot:

The phasing

At the measurement point, the phase has been inverted three times, making it inverted relative to the input. The power amp section, utilizing two TDA7294 DMOS audio amplifier ICs in bridge mode, does not invert the phase.

Note: The simplest way to invert the phase is to reverse the speaker wires between the amplifier output and the speaker(s).

A detail unrelated to this: In our units, the operating voltage of the power amplifier section is ±27 V, measured without a signal and without a load.

The frequency response of our preferred QC cab sim model

As a side note, here’s the Quad Cortex’s Orange (or Range) PPC412 V30 03 model frequency response measured from an actual unit with Room EQ Wizard (REW):

We prefer this model because our real-world physical speaker cabinets are from the same manufacturer and house identical speaker elements.

1. 0 dBu = 775 mV RMS = 1.096 Vpk = 2.192 Vpp ↩︎
2. Bass and treble both in the middle position ↩︎

---

A reader reached out with a question concerning this article:

Q: I have a question and was hoping you could help me. Recently, I got a Hotone Ampero II Stage, which I run through my Pedal Baby into a 4×12 Celestion V30 cabinet. Based on what I’ve read, the ideal settings for the Pedal Baby seem to be bass at 8 and treble at 2 (picture below …).

However, I didn’t quite understand the part about phase. Should I switch the + and – connections on my cable from the Pedal Baby to the cabinet, or was this specific to your setup? Could you explain why this adjustment might be necessary?

A: In mono use, you can ignore the part about signal phase.
Phase only matters if you’re using two separate Pedal Babys, or a Pedal Baby alongside another power amp in a stereo or wet/dry setup. In those cases, it’s important that both speakers (or speaker groups) are in phase with each other. In a mono configuration, phase—or more accurately, signal polarity—doesn’t make a difference.

If polarity reversal is needed in a specific case and can’t be done through the devices themselves, the easiest way is to swap the + and – wires on the desired speaker—either inside the speaker cabinet or at one end of the speaker cable.

Back