Time at JLM Shop:

LA500A Opto Compressor Kit

LA500A Opto Compressor Kit
  • Click to enlarge

5.0 average, based on 4 reviews

$548.90AUD inc GST for Australian Customers
(Approx $339.82USD outside Australia)

Product Information
Stock Level0
Out of stock

NEW LA500A Opto Compressor kit comes complete with every part down to the last nut and bolt.NEW A Version has extra Slow attack mod and link with leds on front panel and 3 PCB no wiring layout

If you order a pair of LA500A kits together on the same order we will automatically match the opto pairs free so you have a matched stereo pair of comps

  • LA500A Opto compressor kitis our MAC compin a API500 & 51X series format. It isfull ground up redesign of the LA3A/LA2A type compressor with several extra features. We have kept all the audio oddities of the side chain to keep the compression signature and extreme compression depthbut added extra ratio of 5:1 to 10:1 and side chain HPF switching FLAT, 100Hz & 200Hz so the low end can be fully compressed or removed from the side chain to let the low end breath and make it easy to balance the compressed sound.The audio path has been fully redesigned for better signal to noise and headroom while still having a clarity and warmth so that it is at home tracking anything or paired on stereo buss duty. The LA500 is made so even at extreme settings is it hard to make the comp sound anything but fantastic.
  • For an idea on what the LA500 / MAC comp can do read this Audio Technology magazine review here
  • Recall Sheet can be found here

Features for each Channel

  • NEW Pull threshold pot for slow attack with orange led on front panel
  • NEW Pull Makeup pot for stereo linking of compressors with blue led on front panel
  • 51X and 500 compatible with 51X pins cut off. LA500 fits all 500 and 51X racks and lunchboxes.
  • 3 x PCB's have all parts values directly on overlay for fast building.
  • Large 34mm white LED backlight GR/VU meter.
  • Hard relay bypass when comp power off or switched to LA OFF.
  • Meter switchable Gain Reduction / LA OFF (meter led off) /  VU by toggle switch
  • Electronic balanced input to handle extreme input levels without distortion.
  • Large 32mm chicken head input level control for easy setting of compression level.
  • Large 32mm Makeup level pot with 0 to 20dB of gain.
  • Ratio switchable 3:1, 5:1 & 10:1 by toggle switch
  • SideChain High Pass Filter switchable FLAT, 100Hz, 200Hz.
  • Huge output transformer (same size as Neve LO1166).
  • Internal jumper for output ground lift.
  • Double sided Gold plated rear edge connector.
  • 3mm black anodised laser cut, vertical linished with white lasered on text for long lasting zero wear finish.
  • Mix buss output on pin 11 for Radial Workhorse rack


Technical Specifications

  • Max Input level +28dBu @ 1kHz
  • Max Output +28dBu into 10k load @ 1kHz
  • Max Output +24dBu into 600ohm load @ 1kHz
  • Input Impedance 20kohm
  • Output Impedance 150ohm
  • 500 series +/-16vdc @ 55mA idle, 65mA at +28dBu into 600ohm load, 75mA clipping into 600ohm load
  • 51X series +/-24vdc @ 75mA idle, 85mA at +28dBu into 600ohm load, 95mA clipping into 600ohm load


Recall Sheet here

LA500A Parts List here

LA500A Step by step Build Thread MAY 2021 here

LA500A Step by step Build Thread OLDER here

Compressor samples by JLM Audio

Orders shipping to an Australian Address will have 10% GST added to the price below at checkout


Customers also bought

Customer Reviews

Average Rating: 5

Excellent and a breeze to build

I've built many different 500 series DIY kits and this is one of the easiest to build and is the one I will keep indefinitely. I use the pair I built on nearly everything and they sound fantastic. I'd pick this over 500/fet and CAPI offerings for the majority of uses. You can't go wrong, it's a no-brainer at the asking price! (Thu Nov 18 2021, 10:05 am )


I had been looking for an opto comp for my 500 rack for a while before finally ordering this kit. If given the option, I build my gear myself and was thrilled to build the 500A. I had read many only reviews and comparisons on sites like gearslutz and decided to give it a go. The instant satisfaction when slapping this comp on pretty much ANY track can't be denied. It is so thick and full - yet the controls give you plenty control to really shape the sound to your liking. I can not stress enough how good this comp sound! Plus it looks amazing. The black-and-white front panel with it's sleek VU meter and chickenhead knobs looks super pro and will shine in any rack. The kit itself is pretty straight-forward for anybody who has some experience. Even for a beginner it's probably doable without any trouble. A multimeter is required to (double)check resistor values and to setup the VU meter. All in all, 5/5 stars at least. Especially considering the price this kit can't be beat!! (Tue Sep 19 2017, 21:29 pm )

Excellent compressor

To me the LA500A is a high-end compressor. And you get it for a very budget-friendly price. Cleaver mechanics, good manual and easy build. I use it on vocals, bassguitar, brass and more. Slow attack: Never used it much really (so, I'd opt it out). Not the most flexible comp, but very good at what it does. Highly recommended. (Fri Nov 27 2015, 01:49 am )

Great stuff!

Have built two of them in one day. These are number 9 and 10 in my racks,have done 8 LA500s before. Quality is still outstanding,but now even more usefull than before due to the implemented slow attack switch.Again super-easy to adjust.The build is now ultra-clean because of less single wires and the new 3-pcb design.It is a big fun to build them. Congrats again Joe! Best regards, Udo Terlisten. Still my favourite compressors. (Wed Nov 25 2015, 13:25 pm )

Write Review

Anti-Spam Test
Please enter a valid email address.
This field is required.


© 2001-2022. All rights reserved.