Project files: Mini JLH1969

What is it?
This is the project files for my version of the JLH1969 amplifier as shown here. The files for the matching PSU will follow shortly.

How big are the boards?
The board measures 2.25″x2.3″ (app. 57x58mm).

What is the status of the boards?
The board is in version 1.0. I have built and tested a couple of prototypes (as described in the original post) and although they play music just fine, you should still consider this a “work-in-progress”. I would be especially concerned with confirming the thermal stability of the amp because of the compact dimensions, so if anyone decides to build this please share your results 🙂
EDIT 17th Jan. 2016: Added v1.1 of the files in a separate link below. Minor tweaks to the board and the download now includes a basic BoM as well.

Does it use any special/expensive/hard-to-find parts?
No. I have used MJL21196 output transistors because I had them, but versions of the MJE/TIP3055 should be OK as well as long as they are in suitable (meaning TO-247 or TO-264) packages. Do not be tempted to use faster transistors such as the MJL/NJL3281-types as the amp will most likely not be stable with these. Have a look at the TCAAS page on transistor substitutes for more info.

Anything else I need to know?

  • The only change I have done from the original schematic is to replace R5 with a 200k trimpot to make it easier to adjust the operating point. Oh, and I’ve made up designators for the parts that don’t have a number on the original schematic 😉
  • In my opinion the output cap should be 4700uF or larger, even with an 8 ohm load. Even if the supply voltage is 27V, I’d be comfortable with using a 25V cap in this position. All the other electrolytics should be 35V or higher.
  • Heat sink T3 as it might get hot. You’ll probably not be able to find a standard heat sink that fits. so my recommendation would be a small piece of bent aluminium or copper with a hole tapped in it for easy mounting.
  • Raise the R2 resistor 5-10 mm above the board for cooling (I haven’t done this in the prototype version but it gets quite hot).
  • The footprint for the input transistor is for a 2N3906 as described in the original BoM, but other types can be used as well. An easy to get choice is a BC560C which needs to be turned 180 deg. in order for the footprints to match.

Download design files here (v1.0)
Download design files here (v1.1 – added 17th Jan. 2016)

Related information:
Note: Always read the “intro post” for additional important information about my designs.

As usual, both TCAAS and this thread contains lots of worthwhile information.



One Response to Project files: Mini JLH1969

  1. Pingback: Evolution of a concept… | theslowdiyer

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