Measurements > Output power

Flex3 power

The Line6 specs have been confusing as to how much output the Flex3 can deliver. In some places 60 Watts per channel is or was mentioned and the most current spec claims it is 75 Watts per channel for a 150 Watts total. Time for some measurements to find out what's what.

So, what I did is make dummy loads for both channels and measure the output with an oscilloscope. The amp was powered up while the channel A button is pressed, which seems to bypass modeling and feed the input straight to the end stage. The input used is a 1 kHz sinus wave generated by a Spirit Folio mixer.

Here are the results:

This shows the output of one channel while a continuous signal is fed to the input. It is the highest you can go without clipping. The amplitude then is 32 Volts, which means 64 Watts into 8 Ohms (1 channel).
This shows the output of one channel with the same input but the master volume turned up further. The end stage is now overdriven and peaks of 36 Volts may occur (although they are hard to capture on camera). This corresponds to 81 Watts into 8 Ohms (1 channel).
So, taking into account measurement accuracies etc, and a marketing preference for round numbers, the verdict is: the actual continuous power output of a Flex 3 is roughly 60 Watts per channel. Peaks of 80 Watts may occur.

The proper spec therefore is: The Flextone 3 XL delivers 2x60 Watts into 8 Ohm speakers.

A Flextone 3 Plus may deliver more than 60 Watts to its one speaker, because the power supply is not loaded as much. However, as soon as you add one external speaker, it becomes an XL and you're down to 2x60 Watts.

What overdriving the end stage means for modeling

When you turn up the Master volume, the end stage of the amp will start clipping. This changes the sound significantly. Your carefully tweaked patches that sound so great via a PA or headphones will now sound like crap coming from the speakers. You may like the crap that's coming from the speakers, but it will certainly sound different from what comes out of the PA. And that may be consideration if on stage you only hear your amp.

To put it short: if you turn it up too loud, the overdriven end stage will screw up your sound.

Now, how do you know for sure the end stage will not start clipping? Here is a good rule of thumb: The output will start clipping with the MASTER volume set to 5 or higher, so keep it down.

This rule of thumb ensures that clipping will not oiccur too often or not at all, but the price to pay is less output power because the patches you use may not even come close to the worst case that the rule is based on. The rule builds in headroom that you may not need. See the Levels section for more detail on signal levels.

If you want to get really loud, you may need everything the amp has. See Clipping detector for a different way to avoid clipping and make the most use of the amp.

The power IC

TDA7293V is the part number of the power IC that is used in the Flex3 amp. I.e. one user reported it blew out in his amp and he replaced it.