Introduction: Clip Indicator (LED) for Any Power Amp

Picture of Clip Indicator (LED) for Any Power Amp

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

Picture of 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

Picture of Q1: Emitter Follower

Step 3: Q2: Led Driver

Picture of Q2: Led Driver

Step 4: C1: Peak Hold

Picture of C1: Peak Hold

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

Step 5: D1-D3 Voltage Drop

Picture of D1-D3 Voltage Drop

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


JustasK1 (author)2018-01-14

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

supersilve (author)2018-01-09

Hi I designed a PCB according to the improved version of this clipping indicator. I have a peak rail voltage of 82v-0-82v and when the amp loads to full just before clipping the supply sags to around 70v. I also built an opposing circuit to go with the negative rail so that I can monitor both channels. I changed the transistors to 2N551 and 2N5401. These can handle 160v. My problem is that the clip indicator is very sensitive on the input and even if I touch it with my finger the led lights up. One other problem is that as I go beyond 30v on the rail voltage the led starts to light up prematurely and the difference between the rail voltage and speaker input voltage starts growing and goes beyond 15v or more. Have you some advice how can I correct this. Thankyou

Maltep1 (author)2017-12-22

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!

ctopher1 (author)Maltep12017-12-23

Speakers use AC like your house, not DC like a battery. So with AC there is no + or - unless you're concerned with Phase, either side of the speaker will work.

andre19972010 (author)2016-06-25

hello, this clipping indicator also works if I connect it to a 1000 watt rms amplifier? I await response thanks!

simpletronic made it! (author)andre199720102016-06-25

Hi! This circuit is optimized for higher power amps:

AdrianD95 (author)simpletronic2017-06-21

i know im kinda late to this, but i have a question about the VRail, is that a simple wire that can take 100 volts dc?? something like 16 gauge speaker wire?

and how would i connect this to my car amplfier?

orgive me , but - V RAIL ( N.C. ) What is it? is the amplifier's negative pole ??? one last thing I wanted to feed the circuit with a power supply that I have at home and delivers 18 volts dc okay how supply ?? Thank you very much excuse me yet !

Hi! sorry, maybe my schematic is not tidy enough. High power amps (and many lower power) have a power (+)supply and a (-)supply voltage (often referred to as "rails") and a 0 volt rail (ground). The -v rail N.C means: NOCONNECTION to the -v rail. The only connections to use are: Supply +v , Supply 0v, and amp output. As for your 18v supply, you should not use it at all. The clip indicator circuit operates from the amp´s own supply voltages. A word of caution: high power amps use high voltage supplies. You may have over 200volts between v+ and v- . A shock could be extremely dangerous. Greetings!!

hello, look you are very very kind you one last question, I opened today my amplifier, the power transformer delivers about 24 volts AC, and to follow there the rectifier diode bridge which then becomes continuous voltage of 30 volts; question: clipping indicator circuit I have to feed a DC voltage or AC? ; Last question: the condenstore 10 uf must be electrolytic or ceramic? thank you very much.

simpletronic made it! (author)andre199720102016-06-26

Hi!! I interpret your supply is +30v / -30v split supply. Or is it +15v/-15v ? . I optimized the circuit for a +30v/-30v split supply. Change the values to the ones in green color. If supply is other, let me know.

Connect circuit to amp as I show in this diagram. Condenser is 10uFx50v electrolytic.

Sorry for the transformer drawing , I did it with the mouse!

thank you very much indeed ! however, the power and my amplifier is +30 , 0 , -30 ; however, now I understand it all, thank you so much I was much help ! thank you so much !

AndrewM491 (author)2017-05-14

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?

KataramanK (author)2016-11-09

if i want to connect this clip indicator with a car audio amplifier i have to find the internal power supply output or it has another way like a portable oscilloscopebut instead of monitor we can user led just to tell us if the output is not clean???

KataramanK (author)KataramanK2017-02-03

any help please???

AndrewM491 (author)KataramanK2017-05-14

yes measure rail voltages...or find a schematic

VitalyN2 (author)2017-05-11

Can you describe components parameters ?
Voltage of capacitor and led, and power of input resistor ?
Input voltage in my case is 25V. Output amp power 150W

pedroenrique04577 made it! (author)2017-03-28

Hi i have made its
circuit but it does not work, i connected it to the + dc output of the
rectifier diodes before the capacitors, my voltage is positive rail +47
dc -47 dc and positive measurement + dc and rail ground + 23 v dc only
turns on Clipping led when I turn off the amplifier say
that my amplifier clip in a channel to 12 volts ac 40 watts and in
bridge to 17 volts ac 80 watts measured with oscilloscope computer, my
amplifier is car with 4 ohm charge, I hope I can help With a schematic, sorry for my English but I use the translator since I am Spanish, thanks, regards

someloser (author)2017-03-11

So I just checked on a scope and noticed that the clip LED comes on slightly prematurely, is there any way of fine tuning when it comes on? maybe increasing the value of R4 will reduce the diode current so that it doesn't drop as much forward voltage?

someloser (author)someloser2017-03-12

OK I scoped the saturation voltage of the LM386 and the top transistor is the worst with 1.9v across it when it clips, should this be what I aim for when selecting the top LED/diode series string?

someloser (author)2017-03-09

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.

simpletronic (author)someloser2017-03-09

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!

someloser (author)simpletronic2017-03-10

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.

BigBoyKLD. made it! (author)2016-11-18

Hello There Sir So I Already Finished This Schematic of this Clip Light But How do i install it An Amplifier Like This One

simpletronic (author)BigBoyKLD.2017-03-09

You can find some useful examples in this same comment section.

someloser (author)2017-03-08

I just signed up to say that I made this and it works great with my crappy little LM386 amp. Its easily one of the most underrated audio instructables around.

JudelT (author)2017-01-17

i already build this but i have a problem whenever i connect it to my amp. the led lights turn on steadyly how do i properly connect it from the power supply (30 o 30) vac toriod transformer thanks in advance!

simpletronic (author)JudelT2017-01-17

HI! in this same comment section you can find a reply (7 months ago) to your question. That circuit diagram is suitable for your amp (higher voltage supply). In that case it was +30V / -30V. Extreme caution when opening your amp as you will have around 85v between + and - rails. Capacitors may hold the charge for a long time even after disconnecting the amp from the mains..

illumation_ (author)2016-11-22

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?

illumation_ (author)illumation_2016-11-27

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

dilbags2 (author)2016-10-16

How it is set in bridge configuration power amps

914Subaru (author)2016-09-21

Won't the LED start to light about 3v before V+?

SaadS32 (author)2016-05-03

Hey i made an audio amplifier using LM386, can i somehow use this circuit in it? If so can u guide.

Many thanks

simpletronic (author)SaadS322016-05-07

Hi! Connect pin 5(output) to indicator input (10k resistor) and your power supply to +v and 0v.

LM386 can operate with low voltage supply (4/5v) At this low voltage, indicator reading may not be accurate. --|>|-- greetings!

skymak12 (author)2016-03-29

Nice design.

However, would you re-building up this circuit for compare the signal and amp -ve rail?

simpletronic made it! (author)skymak122016-05-05

here you go!

DarkDeepRed (author)2015-11-25

Would this circuit work on a small 2 or 3 watt amp running on 12VDC?

simpletronic (author)DarkDeepRed2015-11-28

Sure, it will work perfectly! In my demonstration circuit I´m using an op-amp powered from a 12v battery. Greetings.

ogrossman (author)2015-06-22

I'm just curious why you chose not to build the circuit around a comparator.

simpletronic (author)ogrossman2015-06-23

It is a very good question, and has more than one answer: This circuit is inherently simpler than an IC comparator. It uses only 2 transistors while a comparator contains dozens and still requires many additional passive components. If you add it to a preexistent amplifier, you can build it on a simple terminal strip, while a comparator will require a PC board. Additionally, most high power amplifiers use supply voltages much higher than a typical IC comparator can withstand. You would have to add a supply circuit and also scale the monitored voltages to a safe value.(more and more components). Greetings!

nqtronix (author)2015-06-15

I didn't know it would be so simple do do this! I'll definitly add it, if I'm building some sort of audio amp. Thanks :)

simpletronic (author)nqtronix2015-06-18

In this digital world, analog is still strong !

DIY Hacks and How Tos (author)2015-06-14

That is a cool sensor. Very simple and effective.

Thank you !!

About This Instructable




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