• These commercial threads are for private transactions. diyAudio.com provides these forums for the convenience of our members, but makes no warranty nor assumes any responsibility. We do not vet any members, use of this facility is at your own risk. Customers can post any issues in those threads as long as it is done in a civil manner. All diyAudio rules about conduct apply and will be enforced.

FS: Nelson Pass "VFET2" Front End PCBs

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Here's the First Watt article in question:


I have a few of these PCBs left-over that I'd like to offer up to the community. The price is $7.50/channel plus shipping. I'd expect shipping to run between $5 (US) and $15 (international) - but the amount will be payed after they ship for exact charges (so, two PayPal payments).

They are 2 layer, 1.6mm thick, 1oz copper, black with white silkscreen, ENIG plated. I'm including a BOM and supporting files in this post. The relay controls both the feedback resistor and the "second input" available via the Cardas dual RCA input connector. This is optional.

These can also make great preamp or headphone amplifier, but such applications would be community supported efforts, not by me :)


  • vfet_fe_schematic.jpg
    154.1 KB · Views: 1,196
  • vfet_fe_block.jpg
    40.2 KB · Views: 1,164
  • vfet_fe_bom.jpg
    301.3 KB · Views: 1,141
  • vfet_fe_top_silk_dimensioned.jpg
    168.7 KB · Views: 1,110
  • vfet_fe_rendering_top.png
    436.7 KB · Views: 1,117
  • vfet_fe_rendering_bottom.png
    195.9 KB · Views: 414
I have four of the previous version of the board that most notably have the wrong BJT pinout and some random other silkscreen mistakes and poorly thought-out interface with the output stage. Those are available for free, just pay shipping.

I now have 10 of the (fixed) version above.
I haven't used the BA3 FE, but I would guess this would sound better, depending on how hard you wanted to push the FETs. Also, no output capacitor on this build, which for some is a positive.

i plan to build BA3amp,
if this front end much better then i might use it for ba3 front end.

but i still confuse about the feedback output connection,
at your schematics, is it connected between the "output" and "vfet2 out" ??

because at the original schematic the feedback is connected to the speaker out.



  • vfet_fe_schematic.jpg
    180.2 KB · Views: 317
In this case, OUT connects to the output stage output. This relay controls whether feedback is enabled. The VFET2_OUT is the output of the FE. You can use these connections as you see fit, if you are using another output stage or application.

I am heading out on business, I return tomorrow and will count the remaining boards.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.