Clip Indicator (LED) for Any Power Amp

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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!

5 People Made This Project!

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44 Discussions

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livoto80

2 days ago

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

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Alexander4269

Question 4 weeks 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

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BobzB1

5 months 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!

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codebeat

2 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
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codebeatcodebeat

Reply 2 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
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BobzB1codebeat

Reply 5 months ago

Zener and led in parralell with the input?

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JustasK1

1 year ago

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

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BobzB1JustasK1

Reply 5 months 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.

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AndrewM491

2 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?

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BobzB1AndrewM491

Reply 5 months 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.

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LodeO

Question 9 months 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 !

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Maltep1

1 year 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!

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PicaPicaPhysMaltep1

Reply 9 months 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

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ctopher1Maltep1

Reply 1 year ago

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.

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supersilve

1 year ago

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

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PicaPicaPhyssupersilve

Reply 9 months ago

Hi i had the same issue, just remove the capacitors from the circuit, then it will work fine, the leds will light only when you clip your subs, but i have a question aswell,( i drew a schematic and lost it, so was unsure on what transistors to use? 2n5551 BC557 for +Vrail and 2n5401 bc547 for -Vrail?) redrew another, check it .

schema.PNG
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PicaPicaPhys

Question 9 months ago

Hi simpletronic, thank you for the schematic and partlists for +100v rail, i copied your schematic, and tried to reverse it for the -V rail, as i need to detect clipping on both rails, for the 2n5551 i substituted a 2n5401, and for the bc557 i substituted a bc547 for the -V rail, is this correct?,

schema.PNG
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PicaPicaPhys

Tip 9 months ago on Introduction

Hi i used this for a mono class D 1000W rms car amplifier, the clip indicator works fine on the amp with no load, but as soon as you put a load on the amp (i.e. connect a sub) the clip indicator lights up all the time, removing/avoiding the c1 capacitors solves this issue (i dont know if a smaller one works better, i just avoided it completely), now it turns on just before clipping.

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IsaacM109

1 year ago

Hi.

First of all thank you very much for the video and the help. But I would need a circuit for my car audio amplifier class A / B (2 channels) 2x800w 1X 1500 Wrms at 2 ohm.

I have read your website since there are people who asked for an 800W amplifier and the scheme varies. but I still do not know how to draw a scheme for my amplifier (since the 800W boy sent another circuit, mine guess it will be even bigger).

I would appreciate the help.