Guitar effects pedals are an exciting and fun addition to any guitarist’s rig. So much so that it can be keyboardists/synth players jealous (even with all their own knobs and controls. If you’re a synth fan looking to get in on some guitar pedal action or a guitarist with pedal looking to get in on some synth action, this article is for you!
Do guitar pedals work with keyboards and synthesizers? Yes, we can plug our synths and keyboards into guitar pedals and take advantage of the wide variety of effects pedals. However, to get the most out of our pedals, we should attenuate the output signal of the synth/keyboard (from line level to instrument level) before it reaches the pedal.
In this article, we’ll discuss connecting synths and keyboard to guitar pedals; the differences between guitar and synth/keyboard outputs, and other concerns when sending synth and keyboard signals through guitar effects pedals.
Connecting A Keyboard Or Synthesizer To A Guitar Pedal
Fortunately guitars, guitar pedals, keyboards and synthesizers all have 1/4″ jacks. Therefore, a simple patch cable can be used to physically connect a keyboard or synthesizer to a guitar pedal.
That was easy! However, getting the best results when combining a synth or keyboard to a guitar pedal (or a board full of pedal) takes a bit more effort than simply connecting them via patch cables.
Let’s get into it.
*To make things a bit easier to read, I’ll refer to “keyboards and synthesizers” simply as “synths” throughout the rest of this article except when they must be differentiated. Please know that, in most cases, synths and keyboards will act similarly to one another in terms of output and interaction with effects pedals.
Keyboard/Synth Output Vs. Electric Guitar Output
We’ve already mentioned that synths, keyboards and guitars all have 1/4″ output jacks and that this fact allows us to easily connect synth and keyboards to guitar pedals (which also use 1/4″ jacks) with patch cables.
That’s just scratching the surface of the actual connection, though. There’s more to an audio connection than form factor!
Electrical factors that affect the connection between a synth and guitar are:
Impedance is a rather complex topic that I could go on for ages about.
Impedance is essentially electrical resistance (which is the opposition to the flow of direct current) applied to AC signals. Since analog audio is AC, impedance is a factor we should be aware of.
When connecting audio equipment together, we’re concerned with signal transfer (voltage transfer). This means we should have a load impedance (the input impedance of the device being plugged into) that is much higher (optimally 10x or more) than the source impedance (the output impedance of the device that is plugging into the load).
This general rule can be visualized with a simple voltage divider circuit:
- VS is the source voltage or the voltage (signal strength) outputted by the synth
- ZS is the source impedance or the output impedance of the synth
- ZL is the load impedance or the input impedance of the pedal
- VL is the load voltage or the resulting voltage (signal strength) that will drive the pedal
We want as much signal transfer (voltage transfer) as possible from the amplifier to the speaker. The following formula applies:
VL = VS • ZL / (ZL + ZS)
So, then, the larger ZL is in comparison to ZS, the more voltage/signal transfer there will be from the source to the load!
Related My New Microphone article pertaining to impedance:
• The Complete Guide To Speaker Impedance (2Ω, 4Ω, 8Ω & More)
• What Is Amplifier Impedance? (Actual Vs. Rated Impedance)
• The Complete Guide To Understanding Headphone Impedance
• Microphone Impedance: What Is It And Why Is It Important?
Guitar pickups may or may not tell us their output impedance but they are generally in the range of 7 kΩ (and even less in the case of some lipstick tube pickups) to 15 kΩ (or even more in the case of modern high-output pickups).
Synth and keyboard specifications sheets rarely tell us the output impedance of the instrument. That being said, the output of most keyboards and synths is in the 10 -12 kΩ range and are really quite similar to guitar pickups in terms of impedance.
This is great news. It means that, generally speaking, a synth can plug into a guitar pedal without having to worry too much about impedance bridging (having the load impedance about ten times greater or more than the source impedance).
This is because most modern pedals are designed in such a way that their input and output impedances “play nice” with other pedals, guitars, amplifiers and, yes, synths!
Let’s have a look at a few impedance values of popular pedals to further our understanding:
|Guitar Pedal||Effect Type||Input Impedance||Output Impedance|
|TC Electronic Bonafide||Buffer||1 MΩ||100 Ω|
|Audio Source C4||Synth Pedal||1 MΩ||600 Ω|
|Dunlop GCB95F Cry Baby Classic||Wah||1 MΩ||1 kΩ|
|DigiTech Whammy 5||Pitch-Shifter||1 MΩ||1 kΩ|
|Ibanez TS9 Tube Screamer||Overdrive||500 kΩ||10 kΩ|
|DOD Carcosa||Fuzz||500 kΩ||1 kΩ|
|Electro-Harmonix Small Clone||Chorus||220 kΩ||1.1 kΩ|
|Palmer PEFLA||Flanger||1 MΩ||100 kΩ|
|Boss DD-8||Delay||1 MΩ||1 kΩ|
|Eventide Space Reverb||Reverb||500 kΩ||470 Ω|
|MXR Clone||Looper||1 MΩ||100 Ω|
*Yes, there are synth pedals for guitar! You can skip ahead to the section about these pedals by clicking here.
As we can see, connecting a synth with a 15 kΩ (a relatively high output impedance) into any of the above-listed pedals would give more than enough load impedance for optimal signal transfer.
We also see that the higher listed output impedance of the randomly selected pedals above (1.1 kΩ) would also be less than one tenth of the lowest input impedance (220 kΩ).
All of this is to say that, in terms of impedance, we’re safe to connect a synth into any modern pedal without fear of severe signal degradation.
Unless we plan on using vintage type fuzz pedals (fuzz faces, tone benders, etc.), we should be fine! If we are planning on using these pedals, perhaps a buffer pedal should be put in-line immediately after.
For more information on buffer pedals, check out my article Are Buffer Pedals Necessary & Where Do They Go In A Chain?
There is a pretty significant signal level disparity between synths/keyboards and guitar pickups.
I tested my Stratocaster with its active EMG pickups (I cannot remember the pickup model as it’s been nearly a decade since the pickups have been swapped). The most signal I could get was peaking around 500 mV AC with an average voltage around 80 – 120 mV when playing normally.
Those values, which are pretty typical of electric guitars, equal out to be about -20 dBu to -16 dBu. This, combined with the output impedance (varying, loosely, from < 7 kΩ to > 15 kΩ) defines the ballpark for guitar output “instrument level”.
dBu refers to decibels relative to 0.775 volts, where 0 dBu = 0.775 V.
For everything you need to know about decibels, check out my article What Are Decibels? The Ultimate dB Guide For Audio & Sound.
Synthesizers and keyboard output different levels, defined as “line level”. Confusingly enough, there are two different nominal values for line level:
- Professional line level: +4 dBu or ~1.228 V
- Consumer line level: -10 dBV or ~0.316 V
Again, this is confusing, so please refer to my article on decibels for clarification if need be!
Unfortunately, not many synths or keyboards actually specify (on their datasheets or on the instrument itself) whether the output is “pro” or “consumer” line level.
The synth output may be labelled “balanced” or “unbalanced”. Balanced line outputs are generally professional +4 dBu while unbalanced line outputs are generally consumer -10 dBV.
Either way, we can see that synths output much higher amplitude signals that typical guitar pickups (3x to 10x the voltage).
Guitar pedals are designed to process guitar signals and some pedals may get overloaded from synth signals.
So how do we deal with this discrepancy in signal level?
The immediate solution would be to simply turn down the output of the synth. However, this can negatively affect the signal-to-noise ratio of the synth’s output. A proper SNR is critical to have in general and especially important if we plan to run the signal through any significant length of cable and any number of pedals, which will naturally degrade the signal (at least partially).
A better strategy is to use an attenuator or a “re-amp” to adjust the signal while maintaining a decent signal-to-noise ratio.
The JBL Nano Patch + (link to check the price on Amazon) is a great example of an attenuator box. It even has a stereo input and output (left and right channels) to fit in-line between stereo synths are stereo pedals, if you so desire!
Reamp devices, like the Radial Engineering JCR Passive Reamp (link to check the price on Amazon), convert a balanced line-level signal to a high impedance instrument-level output. This allows us to run our synth through various guitar pedals with more clarity and less noise.
Note that, if you’re running the synthesizer through a guitar amp (or bass amp), the last pedal should be able to drive the amp without issue.
However, if you’re looking to drive a typical line input (into a mixer, recorder, or a dedicated synth amp), then a DI (direct inject) will help tremendously in-line between the last guitar pedal and the line input.
The DI will convert the impedance so that the signal can properly drive a line input. The impedance of a line input is typically around 10 kΩ, which is potentially too low for optimal signal transfer, even from modern guitar pedals.
Once again, Radial Engineering deserves a shout out. This time for their Pro DI (link to check the price on Amazon) passive DI box.
Of course, this is all for optimization. Plugging a synth into a pedal and then running the signal to a line input will produce results. It may even produce superb results. However, if you’re looking to improve the overall signal integrity, consider the information (and products) listed above.
The final big difference between synth and guitar outputs worth mentioning here is frequency response.
Guitar pickups tend to drop off significantly in the upper mid range (often between 5 – 10 kHz). Guitar amps/cabinets generally only produce up to about 6 -7 kHz.
On top of that, long runs of patch cable (the unbalanced 1/4″ tip-sleeve cable used to carry guitar signals) have significant capacitance that effectively filters out high-end.
The result of all this is that guitars tend to have very little information in the high-end frequencies.
Synthesizers, on the other hand, are typically designed to produce frequencies across the audible spectrum (20 Hz – 20 kHz) and even beyond this range.
Guitar pedals, fortunately enough, are often designed to process wider frequency ranges than guitars typically output. However, many manufacturers leave this information out as unimportant so it can be difficult to know the exact frequency responses of certain pedals.
When in doubt, listen to the change in tone with and without the pedal in-line after the synths and with the pedal engaged and disengaged after the synth.
Are Mono Or Stereo Pedals Better For Keyboards & Synthesizers?
Perhaps a better question would be: is giving up the stereo output of the synth or keyboard worth having the effects from guitar pedals?
Guitars output mono signals. Some guitar pedals (particularly the switchers, modulation and time-based effects) can effectively turn this mono signal into a stereo signal.
Synths and keyboards will often output stereo signals (though not always).
Mono guitar pedals can only handle mono signals, and so using your synth with a mono pedal may not be the way to go if you’re looking to maintain stereo.
Unfortunately, most “stereo” guitar pedals have mono inputs (again, because guitars output mono signals).
That being said, we can certainly process mono synth signals and, with stereo pedals, turn the signal into a stereo output (with separate left and right channels).
If you had the cash, you could always duplicate the pedal chain for each of the synth’s output channels.
It’s ultimately up to you whether the stereo output of the synth is more important than running through inherently mono pedals (or if it’s worth duplicating the pedal chain from each channel of a stereo synth output).
A Note On Modular Synthesizers
So far we’ve been more or less focusing on standalone synthesizers (and keyboards).
We’ve been ignoring the wonderful world of modular synthesis. Let’s address this now!
Why would you want guitar pedals if you’ve built up a modular synthesizer with hand-picked Eurorack effects units?
You’ll have to answer that question yourself if you’re even interested in running synths and keyboards through guitar pedals.
Sometimes the old familiar built-in effects (and perhaps even the modular components) in a synth can get a bit boring. Adding guitar pedals you a synth rig can open doors to new sonic possibilities and a new-found joy of experimentation when it comes to getting synth sounds.
Guitar pedals, themselves, are “modular” in the fact that they are standalone units; can be bypassed, and can be ordered and routed in any way we see fit.
For those modular synth fanatics, pedals can provide an excellent alternative (and addition) to other modular synth effects.
The Intellijel Pedal I/O 1U and Pedal I/O Jacks 1U (links to check the price at Intellijel) are a great example of synth modules that act as an interface between a modular synth rack and a guitar pedal(s).
If connecting pedals through a modular I/O isn’t for you, it’s always an option to plug the pedals into the signal chain after the output of the modular synth. This would effectively put us in the same situation as described in the previous sections except we’d have a modular synth rather than a standalone synth.
Pedal Effects Vs. Built-In Synthesizer Effects
You may be asking yourself “but if my synth has all these effects built-in, why would I want to use guitar pedals?”
That’s a perfectly fair question.
My first thought is that the built-in effects of a synthesizer may be a bit bland, limited or boring after some time and experimentation. Guitar pedals, like modular synth units, offer more flexibility in signal flow programming and open the door to new possibilities. This can be a breath of fresh air, so to speak, for your sonic catalog.
The next point is that the synth may not have the effect you’re looking for built into its circuit design. This is perfectly possible. There are plenty of boutique pedal manufacturers (and big name brands) that are producing absolutely wild effects pedals.
Really, the reason I would personally opt for guitar pedal effects with a synthesizer is the same reason I’d opt for modular synthesis racks over “all-in-one” synths. That reason is, put simply, is artistic freedom and the ability to stack effects the way I see fit.
Pedals On The Floor Vs. Pedals On A Stand
Guitar pedals are designed as stomp boxes so that the guitarist can engage, disengage and, in some cases, modulate effects with his or her feet while keeping both hands on the guitar.
That being said, the control knobs present on a majority of pedals are more easily dialed by hand.
As a keyboardist or synth player, the musician can opt to have the pedals at arm’s reach in front, behind, or stacked above or below the synth/keyboard. This will allow for easier control over the effects when compared to using the pedals as stompboxes.
A Note On Synth Pedals
This is beside the point of this article but I figured it’s worth mentioning.
There are synth pedals on the market that will effectively change a guitar signal are the input into a synth signal at the output.
With these pedal, we could do away with the synthesizer altogether and use our guitar as the synth.
Boss is featured in My New Microphone’s Top 11 Best Guitar/Bass Effects Pedal Brands To Know & Use.
Do guitar pedals work with any amp? Yes, all modern guitar pedals are designed with 1/4″ output jacks and output impedances that will properly drive the input of any modern guitar amplifier. When using older vintage models that perhaps do not have the level or impedance necessary to drive an amplifier, a buffer pedal can be put in-line to solve the impedance bridging issue.
What pedals should every guitarist have? Without getting into specific pedals, the most common and useful types of pedals for guitarists are as follow:
- Tuner pedal
- Volume pedal
- Wah pedal
- Boost, ocerdrive, disortion and/or fuzz pedal
- Chorus pedal
- Delay pedal
- Reverb Pedal
- Overdrive Pedal