True peak limiting PCBs?

tegendemuur

tegendemuur

Well-known member
There's plenty of neat compressors, but I don't seem to find anything that clearly states to be a fast attacking / high ratio limiter; something I would feel comfortable putting behind some gear (Filterbank, T-Resonator, AeganMatrix, etc) that comes with warnings that they should be used with peak limiters right behind them because of extreme bursts of feedback when experimenting.

Keeley for instance answered someone's question about his compressors being used as a limiter: "You would want the blend past halfway and the sustain almost off. That pedal really is not made to act as a limiter as much as say the gc2 or compressor pro but that should allow you level out and reign in some of those peaks."

Not sure if that's what I need. My guts say no. There's plenty of simple boards like the SoloDallas Storm (which calls itself a limiter), or the Flatline Compressor, that would do a similar job as the Keeley with a lot less work. Shit, I'd probably build a Guyatone PS-020 before any of those because it has some other uses than just compressing, if the compressor range is all I got to choose from.
 
Virtually all the compressors pass through the signal and then have a side process that feeds back an attenuation. This means the large Vpp is already past the attenuation stage and out the door.

The issue is with feed forward attenuation, ie where the signal is attenuated after it's sensed then you have to add phase delay in so the attenuation is done on the wave as it progresses. If you don't then what happens is you get a distorted waveform as the attenuation is attempted part way through the waveform.

The alternative to pass through is to sample, sense then recreate the signal at the attenuated level. Digital attenuators for example. Issue is that there can be lag introduced due to the ADC, the processing and then DAC compared to analogue forms.

A hard limiter if you're concerned - a front end buffer opamp with a limiting diode clamp can offer unit gain and enforce a limit. The opamp power supplies have a current limiter, for example: https://www.ti.com/lit/an/sbva011/sbva011.pdf
The opamp then can't actually create the output high enough to damage your equipment but would create a distortion.
 
rossbalch said:
I would recommend Douglas Self's small signal audio. It has a chapter on gain control. Of interest to you might be this circuit. The voltgages and values could be tweaked for your signal level.

View attachment 102268
Click to expand...
That should work - the diodes recovery time is way faster than audio and phase shift across the opamps won't be a problem either.

I blame PTSD (power traumatic signal disorder) over phase delay for power shunts, using current rather than voltage comparison from clock noise..
 
LIMITING, but not limited to...


AMZ's Q&D compressor/limiter/gate — get the PCB at Orman's site and the SSM2166 IC from SmallCubeSynthBear (SMD, but may already be sold with adapter — I forget)


Bajaman LA2A Optical Limiter
agc amp using half LM358 AUTOMATIC GAIN CONTROL

Build Your Own Clone Parametric Multi-Band Compressor (PMBC) — really, it's a limiter; you'll need to find one used or use the schematic and make your own layout on vero/perf/PCB.


Danelectro Orange Squeezer derivatives — Maybe the Wampler version... PPCB Median


Demeter Compulator
Works well in the roll of limiter

EQD Warden

MBP's Kompromat (Keeley-Barber mashup)
Madbean also has the Holey Roller (IIRC, based on Bajaman's LA2A Optical Limiter)


THAT
http://diy-tubes.com/index.php?route=product/product&path=59&product_id=683
THAT4301 Compressor/Limiter PCB (ver. 1.7) - PCB for high quality Compressor/Limiter project utilizing THAT4301.
The scheme is based on THAT Corporation documents, datasheets (simailar design used in Pico Compressor, Rane, Seventh Circle B16, L-1 Compresor and some other designs).
also check THAT 4136 LIMITER


w2aew PCB on oshpark, there are a few variants so choose the best-for-you option
https://oshpark.com/profiles/LRY/page/2 and page 3
- W2AEW audioleveler w amp : newest version
- Audioleveler by W2AEW (C4, new value) : improved or just different cap value?
- Audio limiter/leveler by W2AEW : Original




Last Resort:
The DyanaRoss circuit is actually a limiter, or so I keep reading, tweak it to taste.


Ovnilab's list of limiters:
Origin Cali76, Broughton Apex, Rane DC24, Valley People Dynamite, Aphex 661/651, Keeley Bassist, MXR M87, Maxon CP9 Pro+, Pigtronix Philosopher series, Alesis MicroLimiter, Guyatone BL2, Boss LMB-3, various Joemeek models, Markbass, FEA Comp-Limiter and DE-CL, Ashly DPX/CLX/CL series, Aguilar TLC, dbx 160A and its clones, and Symetrix 501 all do a pretty good job of cleanly limiting big signal peaks.

The limiter function in a DBX166 is purportedly a great distortion, but lousy clean-limiter.



Additional miscellaneous dribs & drabs:

alesis micro limiter which isn’t micro at all

audio_compressor_limiter_03 NL3ASD Amsterdam Radio blah blah

baja LA2A limiter schematic Have Layouts perf vero (MBP’s SKINFLINT IIRC)
MADBEAN HOLY ROLLER

CRAIG ANDERTON Compressor-Limiter vero layout by MAO

DOD FX30 GATE LOOP?

epfm08 Compressor Limiter Lazy Finger Layout

FAST AUDIO PEAK LIMITER sacked dot co

wholenote BLM-270 limiter (Boss LMB-3 Clone) [Guts Shots

http://freestompboxes.org/viewtopic.php?f=1&t=18385




PHIL ALLISON LIMITER
attack time with the values shown in schematic is 5ms, with a release time of around 1 second. Maximum Attenuation 40dB Noise Level (unweighted) -80dB (ref....



More for an amp:
MARK HAMMER: smaller Crate bass amps tend to use a vactrol-based limiter circuit, using feedback fro the power-amp chip output to a network ahead of the power stage.
Look for schematics for amps like the BX15A, BFX15A, BX25, BFX25A, BX50, or BFX50A.
http://www.eeweb.com/electronics-quiz/design-this-clipper-circuit
 
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