JLH build(s) update

A couple of my projects that are seeing some progress at the moment are my JLH amplifiers. The JLH1969 clone boards have come a bit further as I managed to fabricate/order most of the enclosure for them. Still to go is mounting a fan control board in the enclosure and then finishing up the wiring of everything. The PSU is a Mean Well 27V USP-350 which should be more than adequate for the job – let’s hope it sounds good as well.

My upgraded JLH boards are also coming along nicely. These are based on Geoff Moss’ updated JLH design and meant to be as compact as possible. In some places, I think I have overdone it a bit but assuming everything works I am very satisfied 😀

I had a few problems with getting the offset right but after some help from some nice folks at diyaudio, it turned out that it was just a wrong value for a trimpot. After than was fixed, the assembled boards are now playing in a somewhat improvised test setup (see pictures). The boards are of course not thermally stable in this setup, but it is enough to confirm that it is possible to adjust the quiescent current, zero the DC offset etc. and that they actually play music :D.

Next up is to figure out a suitable enclosure and drilling heatsinks etc. I also need to sort out a PSU for these and at least for starters I’ll probably try my hand at the capacitance multiplier circuit suggested for the amp.

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6 Responses to JLH build(s) update

  1. awjlogan says:

    Nice work, nice tidy layout on the case and PCBs. Look forward to seeing the end result, enjoy!

  2. jamie says:

    You really know your stuff… Keep up the good perform!”

  3. Hormus Peston says:

    Looks nice! I noticed that you have a post anout another PSU for this amp. Does this switch mode PSU (the USP-350) function adequately? Or were you simply looking for a smaller PSU unit?

    • theslowdiyer says:

      It think it works well, but it was mainly used because I already had it 🙂 The JLH1969 actually draws very little power, so you can use a much small PSU without issues. The “standard” configuration is 27V and 1.3A quiescent current. A class A amp can swing double the quiescent current before leaving class A, which means for a two-channel amp you only really need around 150W (27*2.6*2 = 140.4), but a bit more usually doesn’t hurt 🙂

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