SIMPLE Limiter circuit reccomendations

[PeterPan]

For an instant and simple limiter for that very problem, do a forum search for guitar power amp concept and my name about a year ago. I never finished that design but still intend to. ..a few resistors, two transistors and a pot for setting the level...You get the idea. ..

I'd like to see that if you have a link. I note that in the LDR circuit I had found online, the author noted that a capacitor was later added to help eliminate distortion in the bass register, and apparently bass distortion is an issue requiring special attention in most compression/limiter circuits I've seen.

[merlinb]

So it sounds like you want a limiter followed by a clipper (just to be on the safe side), followed by the class-D amp.

In that case, choose your poison. The Dynacomp is an old favourite. This is also an ideal opportunity to pimp the Engineer's Thumb compressor/limiter!

[bool]

+1 "choose your poison"

You need to know what exactly you want to accomplish.

If you want a "hard" overload protection, IMHO the idea I suggested in my previous post is really tough to beat. Such principles were used in commercial broadcast processors after all.

I'm not so sure about LDR "limiting" - there is always some leeway with these, but to their credit, they will "sound" much more musical. You will have to "trim" these so they will not "allow" for the full amp's power when engaged (with a steady sine or square wave), because you will have to provide some safety headroom for their (too) slow attack time.

Imho the "power amps" that used LDRs as "power limiters" were designed as "soft-clipping" from the get-go (that's technically possible, some use baker clamping and some use different methods) and/or use current limiting on the output transistors (which is the norm).

So the LDR was there to act as an "fast" AGC to prevent gross distortion that would "happen" if a not-too-careful user cranked these too hard (which would happen fast with smaller amps) - or if the user was too "DUI" to begin with.

[Hatredman]

+1 for the Dynacomp. I have a multi-purpose PA amplifier wirh integrated mixer + graph eq + compressor that uses an enganced version of the Dynacomp. Simple and effective.

[PeterPan]

+1 "choose your poison"

You need to know what exactly you want to accomplish.

If you want a "hard" overload protection, IMHO the idea I suggested in my previous post is really tough to beat. Such principles were used in commercial broadcast processors after all.

I'm not so sure about LDR "limiting" - there is always some leeway with these, but to their credit, they will "sound" much more musical. You will have to "trim" these so they will not "allow" for the full amp's power when engaged (with a steady sine or square wave), because you will have to provide some safety headroom for their (too) slow attack time.

Imho the "power amps" that used LDRs as "power limiters" were designed as "soft-clipping" from the get-go (that's technically possible, some use baker clamping and some use different methods) and/or use current limiting on the output transistors (which is the norm).

So the LDR was there to act as an "fast" AGC to prevent gross distortion that would "happen" if a not-too-careful user cranked these too hard (which would happen fast with smaller amps) - or if the user was too "DUI" to begin with.

I think you understand exactly what I need... Soft limiting followed by diode clipping, followed by the class D amp. Parts count and cost is always a concern, because this is to be part of a bigger project, so I'm anxious to try the LDR and the clip combination. Its a small practice amplifier after all, and the desired effect is just to (a) prevent class D overload, and (b) allow for a greater overall "apparent" volume during normal playing.

But the "pick your poison" is appropriate! Having a good mental picture now of what I BELIEVE needs to be done, i now need to do some bench playing to see how it actually SOUNDS. Its one of those cases where you truly can never know until you build it, and see what problems you solved, and what new ones have been created!