My_Ref Fremen Edition - Beta build/Fine tuning

[ClaveFremen]

In this thread we will discuss about the beta build of the My_Ref Fremen Edition and fine tuning of it.

I've attached the actual beta PCBs picture and schematic.

[ClaveFremen]

Some pictures of the build process.

I think the SMD soldering was quite easy and with good results.

The secret is to use thin solder and thacky flux

[ClaveFremen]

I've finished the build and it works!

So, apart the poor manifacturing, the PCB design don't have any major problem.

It's a bit early to judge how it sounds but it seems promising

It seems to sound as good as the modded TP boards, in fact better, there is more detail and depth.

All components are brand new so I expect things to improve further with a minumum of burn-in.

Just one (incredible) note:

In pictures you can see the 390R Takman REX orientation.

In this config it sound strangely thin, I've reversed that single resistor (matching the orientation I've on TP boards, red band on ground) and the full sound I'm accustomed to got back...

[dalbach]

[PreSapian]

Clave, your dedication is frightening.

I think this is how italians made ferrari

[ClaveFremen]

Thanks

The amp now sound gorgeous, just a problem with one channel.

It has a strange electric noise when volume is very high, like there is arching between tracks.

In fact the corresponding PCB is the worst among the batch, pads and copper are not well aligned.

I've checked visually all the others and they seems better.

[ClaveFremen]

It seems that I've resolved the left channel issue.

I was wrong, bad BD140 and LM337.

[ClaveFremen]

Beta PCBs are ready for shipping, tomorrow mornig, that it means in 10 hours, packages will be shipped.

I can't wait beta testers opinions and suggestions!

In the meanwhile I was puzzled by some strange artifacts I was hearing...they disappeared when finally I've connected PGND of each module to the star ground (which is connected to safety earth).

[ClaveFremen]

Packages shipped.

You'll find, apart PCBs, Elnas, zeners and partial kits (for whom asked them) also some thin solder (Sn/Pb/Ag) for SMD soldering.

I've highlighted with white paint the manifacturer 'fixes' on PCBs, take maximum care on that sections, consider them as without the solder mask and after soldering check with a multimeter for shorts.

The ground plane connections are more difficult to solder, thermals width too large (it will be fixed in the final boards). Use a higher soldering temperature on those.

Don't forget to short LM3886's ground to PGND or 0V using a solder bubble on the solder jumper (see attachment).

Please let me know when packages arrive.

[KSTR]

Originally Posted by ClaveFremen

In the meanwhile I was puzzled by some strange artifacts I was hearing...they disappeared when finally I've connected PGND of each module to the star ground (which is connected to safety earth).

So, before that, the "GND" potential was floating, with respect to Protective Earth? If so, any noise current between your multiple, seperate (?) transformers was forced to mainly flow through through the 1R's, then through the signal cable shields to the point when these combine at your source device (CD?) for then to possibly interact with the source's own GND system.

EDIT: I see something even more suspicios, you used full bridge on each rail. So any leakage current gets chopped, it only flows when the diodes are conducting.