"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets

opc

Member
Joined 2004
Paid Member
Hi Guys,

I finally finished writing up the instructions for the amp assembly, so you can take the time to read them now while we all wait for mosfets to arrive :)

Any comments, suggestions or corrections are welcome. I tried to cover all the major points, but I am assuming a certain level of skill when it comes to this project.

Also attached is the functional schematic showing the resistor values for an SE circuit. Every part is carefully covered in the assembly document, so please read it thoroughly. If a question is asked here, that is already answered in the instructions, you'll simply get a "Read the instructions" post.

I will be posting all these documents, along with the worksheet and anything else in a build Wiki that should be up in the next few days.

Cheers,
Owen
 

Attachments

  • LME Amp Assembly Instructions.pdf
    163.3 KB · Views: 3,170
  • LME AMP SCHEMATIC.pdf
    32.7 KB · Views: 4,486
nice!! well put together mate, funny you mentioned thin film RF caps, i was thinking of trying the shielded SMD CDE teflon RF caps here, but i would have to put 2 in parallel to reach the value, as the same cap is mica after 10pf or maybe before and that wouldnt be such a good idea for resonance in this position i would think. ive been meaning to look into other brands to see if anyone goes higher in a similar component
 
@ Mark, call me jaded, lets just say the threads so far have been an eye opening experience.

lolo: hmm maybe, but the good thing about this amp in that respect is its thick copper, chunky ground planes and the PCBs are tiny, so there isnt too much opportunity for significant voltage drop across them. you'll have your work cut out for you, but probably not as badly as with many other amps
 
Oh do I hear you loud and clear.

I stopped buying the flavor of the month audio rags in the late 80's and have not been to a commercial audio show since 1990.

And I work in and around audio every day.

I took to this design because it is based on sound engineering principles. I understand the driver ship and that it can be used to create a really good sounding amp. The driver transistors are chosen for their abilities as well. This is a great design that will stand the test of time. Can't wait for everything to be in place!
 
well i got them done, but wow thats a pita! I stress guys, use a fairly large but sharp chisel tip screwdriver for levering the bar up so you can push it over the LME, anything too small simply wont give you enough leverage.

what is almost as bad, is soldering the LME decoupling caps. opc, i like the instructions, i think youve done a good job and i followed them to the letter, the problem is, i'm not sure if you meant it to read like it does. would it not be better to solder all of the low SMD parts top and bottom before installing the LME and sink? they wouldnt get in the way, but i tell you what the LME plus sink gets in the way of soldering them!!! you cant sit the board flat on anything upside down after its installed, so you have to prop it against something or hold it in your hands and it took all my will power to not smash it, even with a good pair of tweezers and a chisel tip. Soldering C71 and C81 while doable finally was very very frustrating and needlessly so imo; getting the soldering iron tip in behind them against the heatsink and holding it still is HARD, i only got it done with a bent tip and more solder than needed then mopping the excess off with braid

you could use a blank board to get the lme mounted to the sink properly at the correct height and then set it aside till youve soldered all the low smd and in particular the parts surrounding the lme. thats what i'll be doing with the second pair of boards, or am i missing something? i got it done without smashing anything...just, but i'm not all that happy with the resulting less than perfect alignment on some of the parts. Precious? maybe, but I take pride in my work
 
Last edited:
apologies for the frustration that came through in the above post; it should not be misinterpreted as anger. those doing smd for the first time should not be put off, its not a hard board to solder, but i really think at least the topside small smd parts that surround the lme should be soldered first. it makes sense to mark out and attach the driver to the sink in the correct place first with the blank board, so you can get the level right easily, but then at least to me it makes more sense to solder the smds both sides before installing the driver + sink. intuitively that is how i would have done it, but i took there to be a reason not to, but now after doing 2 boards i cant think of one and i'm thinking this was just an error in writing the instructions and not what you would have done even yourself Owen? am i right?
 
qusp: The way I read it is exactly the way you suggested doing it. Using the unpopulated board to align the lme then setting the assembly aside to solder later.

The fact that you were able to do it the way you did is extremely impressive though!!! I wouldn't have thought it possible to be honest :D