Clipping detector
A little DIY project.If you want to push the Master volume beyond 5, it is hard to avoid clipping unless you can actually monitor the signal at the speakers. See Output power for a discussion on the topic of clipping and its consequences.
Enter the clipping detector. A simple piece of electronics that lights up a LED whenever the output signal gets too close to the max.
With the aid of the clipping detector you can make the most use of the headroom: simply turn up the master volume as far as it will go without any of your patches causing the LED to glow or light up.
It also allows you to run the Master up as far as you want. Some people seem to like that. With this detector you can still control clipping then.
Build and use at your own risk. If you don't understand what you see here, leave it alone.
Principles of operation
- In case of an XL, measuring either speaker is OK. There is no need to measure both speakers.
- The max output voltage that can be measured at the speakers is about 32V. So, we're looking to detect peaks just below that voltage.
- The combination of a 27V Zener, the diode, and the b-e junction of the transistor, gives us a detection level of about 28V, which is close enough. It also allows for variations in the power supply voltage as a possible result of variations in 110V (230V) line power, wherever you may be.
- When the output rises above the detection level of 28V, the LED is switched on.
- Any LED that can handle 20mA will do here.
- This circuit does not add any significant load to the output stage of the amp.
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