F5m kit

Here you go


  • PXL_20240509_042254988.MP.jpg
    256.8 KB · Views: 142
  • Like
  • Thank You
Reactions: 1 users
Good to hear. Essentials kit came in the post today, Digikey per NP's BOM due Tuesday. Oversized surplus heat sinks from another member here on the swap page, ~ 3x by volume vs. the 3U option in the R.1 article. Ordered some raw material cut to size chassis parts from Metals Depot, first try with them, will report results. AS-4218 ordered, plan for two bridge rectifiers for least noise. Switch, fuse holder, binding posts are available spares. Therefore, deem it

Fugly 5ive maximinimalist

It will be a good summertime option
  • Like
Reactions: 1 users

I am assuming you are using an IEC inlet fuse holder like the Schurter types supplied with the diyaudio deluxe chassis.

If both the hot and neutral wires are fused, for safety, the neutral fuse should be higher current capacity so that in the event of a fault, the hot fuse will blow. If the neutral blows instead, the hot line is still live and there is still electricity in the chassis which is dangerous. Therefore the neutral fuse should be a high value like 10A slow blow in your example and the line fuse (hot) should be VA of transformer divided by 120V. For example 300VA transformer/120V = about 2-3A.


Identifying the primary and secondary windings is important and you should use your DMM to assist.

For 120V line input as you probably have in the US, connect wires 2 and 4 together (Red colors), this connects to your “hot” or ”line”. Connect wires 1 and 3 (Black colors) together and these become your “neutral”. This should be easy.

For secondary wire identification, pull out your multimeter or DMM and check to make sure you identify the secondaries that have continuity (0 ohms on the resistance setting). Wire 5 and 6 should have continuity, similarly, wire 7 and 8 should have continuity. You can double check this and also make sure that wires 5 and 8 do not have continuity and read infinite. Similarly wires 6 and 7 should not have continuity.

Wires 6 and 7 are your ‘CENTER TAP’ and should be connected together as you have shown in your schematic diagram which is also connected to power supply ground and to the thermistor that is acting as a ground lift to chassis ground.

Although all the colors of the wires should match with the above pic, do note that you need to use your DMM to properly identify the secondaries here since you cannot distinguish wires 6 and 7 by color identification alone or by the location of the wires on the transformer itself.

Hope this helps,

  • Like
  • Thank You
Reactions: 7 users
Quite some of you have built the F5M already and some of you have also available the original F5 (may be without output limiter and Th1 and Th2) or a version of F5 Turbo. Can you please describe the sonic differences between the various F5's? Is it worth building an F5M (due to less parts) ?
Well I have a "mark 1" F5 that is about 15 years old now, in the end I found it a bit too strident and unforgiving with some material. The F5M changes that and is superbly balanced and detailed without ever going ott. It simply has a magic sparkle to the sound!! I prefer the bias at 1.1 so no need for massive heatsinks if that's a consideration for you. Go for it!!