The JLH amp – prelude

The JLH-amp, or more correctly John Linsley-Hood’s class A amplifier, is probably one of the most well-known designs in DIY audio. The original version was published in 1969, but that’s a little before my time. I first started reading about the design when Linsley-Hood published an updated version of it in the magazine Electronics & Wireless World in 1996. For me, the JLH is one of those designs that tick all the boxes (cheap, simple, good sound quality etc.) and I have been fascinated by it since I first read about it, but I never managed to actually build one.

Since the 1996 article, both the updated and the original versions have been helped back to popularity (or at least dragged out of obscurity) in the DIY audio community  primarily by two things I think:

The first factor is Geoff Moss’s excellent “The Class A Amplifier Site” (TCAAS) resource, now hosted by Rod Elliot of ESP, that started around 10 years ago (ugh, how time flies!). The site collects a lot of information about Linsley-Hood designs as well as other well-known Class A designs from the likes of Jean Hiraga and Musical Fidelity.

The second factor is the proliferation of extremely cheap ebay kits using the original JLH design as basis. Obviously, if you can get a whole kit for less than it would cost most people to manufacture the blank PCB, there’s really no excuse for not trying 🙂 I have bought one of these kits, substituted some key components (namely the caps and the output transistors) for some more “dependable” types (read: of less questionable origin) and mocked it up to see if it works. Below is the state of affairs at the moment, obviously not living-room friendly just yet, but it plays music! I’ve only hooked them up to my test speaker, but it is going to be fun listening to these once I get an enclosure ready for them.

JLH board on heatsink for testing.


Now the real point of this post is actually that I am working on a PCB based on Geoff Moss’s updated version here:

It’s still not quite ready yet, but the PCB design files have been shipped off to manufacturing and should be back within a couple of weeks. More to follow when I have one assembled.



One Response to The JLH amp – prelude

  1. Pingback: JLH build(s) update | theslowdiyer

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