Tír Na HiFi

wheres the like button!

Thats speedy work Nigel, shout if you need a hand with anything.

Fran wrote:wheres the like button!

Thats speedy work Nigel, shout if you need a hand with anything.

More than one way to skin a rabbit
Like button added ;)

Prob will be after everyone comes back from hols before we all get stuck into it
Ive some design revisions i need to test out in mean time

Fran wrote:wheres the like button!

Pushed the button ;)

A pity I am too far away to join the party...

toroid dispatch notification polish style....

Great to see it all coming together Nige, any suggestions/ideas for the case yet?

I suspect your postman must be really scratching his head by now :-)

i was struggling with the pcb design a bit
its taking me longer than i hoped to learn how to do it
however ive managed to get help from a very obliging friend Enrico whom also shares a compulsive soldering habit and a keen interest in audio
hes been able to convert some bad doodling into pcb

here below is basically a single channel of the amp

this incorporates the jfet buffer
based on audiosector lm3875 pcb and simplfied pass b1 buffer
this simplified system will likely not sound great without an exceptional power supply


i have a prototype of the new power management system on test, testing suitability of parts
if that looks good tomorrow Enrico and i will start design of power management pcb

Nige - suggest getting a critique on the layout from one or two others - or even posting it on diyaudio and seeking suggestions. That trace from R6 to the LM3875 looks pretty close to the pads? Maybe its fine, just need to watch it.

Peters layout on his boards is pretty good, so if you're working off that then you ain't gonna be too far wrong

Maybe consider going double sided for an even smaller footprint?

Nige, Fran is right
- clearance of track from R6 to LM375 is too tight (pcb manufacturer will reject it)
Some stuff wrong around R7 - it has a track running under it & running under the pads of R7, R6, R5 & R4
I suspect you are using double-sided in which case R7 track is fine but you still have to sort out R6 track by re-routing it around the outside or between the two rows of LM375 pins & connecting to the correct pin.

Why not post the schematic & people can check if there are any routing errors?

Nige

Two cents from me:

* make +/-33V power tracks wider - much wider
* what is the value of R11,R12? What power do then need to dissipate?
* swap Q2 and R3
* make the output track wider
* ground plane - try to keep the hi current ground (+/-33V) separate from signal ground. That applies to decoupling caps (C2/C3)
* try to add multiple pads for decoupling caps - to try various options. As far as I can see you play to use tantalum caps. Try to add pads for electrolytics on top.
* jfet buffer power pins: try to arrange them in following order: +18, GND, GND, -18, also input GND should be close to power GND.