Clip Indicator (LED) for Any Power Amp

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Introduction: Clip Indicator (LED) for Any Power Amp

About: Music: my profession for over 40 years... Electronics: my beloved hobby always.

A power amplifier cannot deliver an output wave wider than its power supply voltage. When you reach the limit, increasing gain may sound louder but sound will be distorted and can even damage speakers .This simple clipping indicator circuit will announce with an LED that you have reached that limit.

Step 1: Circuit Diagram & Main Components

Q1 BC547NPN transistor

Q2 BC557PNP transistor

D1-D3 1N4148diode

note: If your amp V+ voltage is higher than 45v use BC546/BC556(up to 65v) or other higher voltage ones.

also increase R4 for a led current of 30mA. ( R=v/a )

Step 2: Q1: Emitter Follower

Step 3: Q2: Led Driver

Step 4: C1: Peak Hold

For longer "peak hold" time increase R3 up to 100K

Step 5: D1-D3 Voltage Drop

Step 6: For More Datails, Watch Video. Thank You!

6 People Made This Project!

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47 Discussions

0
bassblaster505
bassblaster505

4 months ago

I made it, I used the KSA992/KSC1845 as thats what i had on hand. seems to work. altho it doesnt react instantly, and is "hit and miss" as i scoped my amps output and it doesnt light on most of the flat tops. and it only lights if the clip is extended or is into a hard clip point, at which point the indicator is useless as you can clearly hear it clipping.

20200506_133739[1].jpg
0
MatīssB4
MatīssB4

Reply 2 months ago

Hello, take my schematics. Works so excelent as never!!!

parslodze pastiprinatajam.pngparslodze pastiprinatajam2.png
0
someloser
someloser

3 years ago

Could I replace the x3 diodes with a single LED? As the circuit continuously drains several milliamps but putting a power indicator LED in there would put that current drain to good use especially when powered by a battery.

0
simpletronic
simpletronic

Reply 3 years ago

Hi! yes you can, but make sure the forward voltage (Vf) drop of the led is close to 2v. Lower Vf, and indicator wont light. Higher Vf, and the indicator will light prematurely.

in this chart you will find the typical Vf´s of different color leds.

Greetings & thanks!

0
Filippo1980
Filippo1980

Reply 11 months ago

Ciao a tutti! Ho intenzione di costruire questo indicatore a clip ... Mi chiedevo se potevo sostituire i 3 diodi sull'emettitore q2 con uno zener in modo da poter accendere il LED 4-5 Volt prima dell'alimentazione V + Grazie a tutti!


0
someloser
someloser

Reply 3 years ago

Oh that's handy then, a green LED will drop around 2.1v which is very close to the 2.2v I measured being dropped by the diodes.

0
livoto80
livoto80

1 year ago

hi guys. i can use this indicator for preamplifiers? thank you.

0
Alexander4269
Alexander4269

Question 1 year ago

Hello, I really liked your circuit but I need some help, I put it together and the led stays constantly on no matter what I do I'm connecting +12 to +of battery and +0 to -of battery and the middle (from output of amp) to +of amp output my amp is a Chinese board amp any help will be very appreciated as this project is my first electronics project and I really want it to work :) thanks

0
Alexander4269
Alexander4269

Answer 1 year ago

The ic is a tpa3116d2 and here's a photo of it

1561099858052..jpg
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BobzB1
BobzB1

1 year ago

Beautiful simplicity! I've integrated 2 of these on each channel of a 16 channel preamp I've made. (One for signal present and one for clip). I wanted low component count, self adjusting, no ic's and easily modded. This ticked all the boxes. Your a very clever man. This scheme is now in my catalog of go to schematics. Thank you so much for your contribution. Thanks to you my preamp is working hard in my band keeping all our mic signals clean and loud!

0
codebeat
codebeat

3 years ago

Nice tut. Just wondering, in the 80's some speaker cabinets (see photo on the right side) got a overload indicator, any idea's how these work?

831730010_5_Big.jpg
0
codebeat
codebeat

Reply 3 years ago

Another one that got this feature, it is a passive speaker (like the other example), not an active one.

technics sb-r3.PNG
0
BobzB1
BobzB1

Reply 1 year ago

Zener and led in parralell with the input?

0
JustasK1
JustasK1

2 years ago

How to make amplifier limiter on relay, that turns off speaker then amplifier is overloading?

0
BobzB1
BobzB1

Reply 1 year ago

You could replace the led with an optocoupler and use that to drive a relay that switches a resistor in series with the input? Disconnecting the sub or power mid operation is very risky and could cause a lot of damage. I certainly wouldn't recommend it.

0
AndrewM491
AndrewM491

3 years ago

Hi, nice work on your circuit design... few questions...

It would appear the LED is only lit while the output is clipping, if that is for fractions of a second then the led may not be visible... would i be correct to say adding a capacitor between the LED anode and the 0v rail will allow the led to stay lit while the capacitor discharges through the LED?

0
BobzB1
BobzB1

Reply 1 year ago

It seems to be the purpose of the electrolytic on the emitter of the npn transistor. The led is switched off by shorting it. So a cap added there would be drained instantly by the PNP transistor. My testing indicates a sufficient viewing time with the original values in the original design, but if you wanted the led to stay on longer, reduce the 100k resistor to maybe 47k.

0
LodeO
LodeO

Question 1 year ago

I got a (probably) very stupid question. I'm want to build the high voltage version (amp rail +85V) for a hypex module (https://www.diyclassd.com/product/ucd2k/8) . This is a bridged classD. Will your circuit work? and next stupid question. For the BC557 i find 2 models; BC557ATA (all data negative/negative voltage) and BC557B (all data positive/positive voltage) . Which one is correct? Thank you for your time and effort !

0
Maltep1
Maltep1

2 years ago

hi! i have read the comments but im sorry to say that i still dont know how to connect this to a subwoofer amplifer. so the v+ goes to 12v+ in the input of the amp, the v- go to ground or battery negative pole? and the "from power amp output" is one off the speaker outputs? but which of them? + or -. i have not built one but if it works and is preatty simple, i migth do, but im not very good at circuitry. but i maybe send to someone more professional to build to me. but i really want this to work on my car amplifier!

0
PicaPicaPhys
PicaPicaPhys

Reply 1 year ago

firstly what amplifier have you got? if its Mono 1ch then its easy, if its 2ch bridgable, then its a little bit more complex,( this circuit will monitor 1 rail of 1ch, theres 2 rails per channel) so for a 2ch amp you may want 4x this, where for a mono amp you may want 2x this