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Can too-high voltage from a pedal damage Axe Fx input?


Hi guys, I have a boost pedal (TC Electronic Integrated Preamp) that can provide up to 25Vpp when used with a 32 volt power supply. Can 25 volts peak to peak damage the axe fx input?

I just want to know if turning the level up to 10 will cause an issue.

I've been using it with a 19 volt power supply, and it works fine like that with most guitars, but with guitars with very high output pickups, it does still clip slightly when I pick hard. I recently bought a 30 volt power supply to see if I can make it 100% clean but I haven't tried it yet.

It is a fixed-gain op amp with a passive volume control so just turning volume of the unit down does not affect the clipping within it.

I know the front input of the axe fx max input level is +16dBu and rear input is +20dBu but I don't know how this translates to voltage. Also I think the front input has some kind of soft clipping with loud signals (I remember reading it here) so I don't know how that affects things.

Thanks guys!


The 25 volts used to power your pedal will only be used to do just that: power your pedal. There is no where near that kind of voltage going in to the input of the axe, unless there is an issue with the pedal. I would just be careful not to clip the input of the axe with the audio signal coming from the pedal. You can prevent this easily by watching the front panel "Input" leds. All you want to do is turn your signal going into the input up enough to "tickle" the red. Hope this helps!


The adapter I'll be using is actually 30 volts (it can take up to 32 volts but I couldn't find a 32 volt one).

I've attached the manual which has the tech specs, hopefully that works, otherwise I'll try uploading some other way. I've read through it again and this is mentioned:

With 32 VDC at the EX.POWER socket the max. input level becomes +2dBu (2.6 Volts peak to peak) and the max. output level becomes +22dBu (26 Volts peak to peak.

So I would guess that the 26 volts peak to peak output level would be dependent on a 2.6 volts peak to peak input signal, which I wouldn't think my guitar could provide? It sounds high for a passive pickup.

The specs I originally was referring to are these:

MAX. OUTPUT LEVEL - with 9 volt battery: +11dBm (7Vpp), with 32 volts adapter: +22dBu (25Vpp)

side note, there are a lot of typos in this manual.

Also I generally turn the bass quite low to tighten up the sound a lot, so I guess that would go a ways to reducing the overall voltage out of the pedal.

Its not really that I intend to run this full-on into the axe fx, I just want to know if I will break any hard-to-replace SMD components if I accidentally bump the level up to 10.


  • TC PRE owners manual.pdf
    55.8 KB · Views: 7


Ok I got the 30 volt power supply all fixed up with the correct polarity and decided to just test the maximum output voltage with my multimeter. It's a digital one so hopefully it tracks fast enough. I guess the AC coming out of a guitar or pedal is not going to be a perfect sine wave, and as my multimeter displays RMS voltage, it might be a bit off...

My guitar by itself measured about 400mv to 500mv when strumming the strings open fairly hard. (peak to peak would then be around 1.4 volts). The pickup is a Lundgren M7 and it is close to the strings, so it is pretty high output (not EMG-loud but louder than any other SD's I've tried).

With the boost at 3/4 volume, and the bass down at like 8:00, with treble at noon, I measure about 1.5 volts (approx 4.2 volts peak to peak). With the volume on maximum it's around 2.2 volts (approx 6.2 volts peak to peak).

Since the Vrms reading is probably wrong due to it not being a perfect sine wave, I tested a modded tubescreamer, and with the volume at 3/4, it measured about 1.2 volts (3.4 volts peak to peak) which is close enough to where I like the sound of the TC preamp, so I guess its all fine. After all, I know plenty of other people run pedals into the front of the axe fx and I haven't heard of anyone else breaking one in this manner.

There you go I guess! The guitar combined with the settings doesn't provide enough volume to get a 25 volt swing, luckily.
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