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In deep with First Watt F4 (liberated) build

Discussion in 'd.i.y.' started by Rosewind, Jan 2, 2016.

  1. Rosewind

    Rosewind Lost in Translation

    Soon I will have all the bits for a complete First Watt F4 build, complete with enclosure, power amp modules, psu, VAS BA-2 front end, Avondale soft start module. I need to populate the BA-2 board + change a resistor value on the psu board + connect everything and test (light bulb test, set bias and all).

    Luckily, I have the help of a few friends with soldering and connecting everything. I expect to run the First Watt F4 balanced from my McIntosh C48, but I may need some help to determine the wiring scheme for that.

    I will snap some photos within the next weeks as I bodge about with the build. I will take my time so don't expect too much just now.

  2. shoom

    shoom open ears and mind

    Good luck with the build:cool:

    I'll watch with interest.
  3. orangeart

    orangeart KJF Audio Ltd.

    Yes, good luck, not many f4 builds on here.
  4. Marra

    Marra pfm Member

    Good luck with your build.

    A great amp with the right pre; although with the BA2 front end I guess not such a problem.

    I haven't heard a balanced version though. If it builds on the performance of the single ended as seem to be the case after reading peoples comments on diyaudio you will have a great amp:cool:

    Looking forward to seeing some pics as you go along.
  5. Rosewind

    Rosewind Lost in Translation


    Have all parts in the house or on order except:
    - the two "bridges" placed between the PSU and the transformer in the build guide: http://www.diyaudio.com/forums/pass-labs/234355-guide-building-pass-f4-amplifier.html
    - the terminal block (and how to wire it for 230v)

    I am waiting for the screws and wires to arrive from Germany + an IEC power inlet with power switch to arrive from the UK. The cabinet has been pre-drilled, so I am limited in the kind of IEC/Power switch i can use. Also the holes for the signal input connectors are fairly big, so I have ordered both Neutrik RCA and XLR connectors. Which set I will use, depends on whether I can find out how to wire the signal path for XLR (balanced). My pre has both single-ended and balanced outputs (McIntosh C48).

    Once everything is here, I will fit the back panel connectors and line everything up for photos. Then the fun begins.
  6. shoom

    shoom open ears and mind

    Sounding like the fun has already started:D
  7. Rosewind

    Rosewind Lost in Translation

  8. shoom

    shoom open ears and mind

    Looking good

    I've just built a BA-3 FE as a pre and I'm delighted with the SQ. Just a little gain fettling to be done.

    I'm pretty sure that you will be likewise.

    BTW has your mac pre enough gain to drive the F-4?

    looking forward to your build.
  9. Rosewind

    Rosewind Lost in Translation

    Not if I want to use all the F4 watts. For that reason I include a BA-2 gain stage in my build.

    I am itching to get going.
  10. Rosewind

    Rosewind Lost in Translation

    Oh. The predrilled holes in the heat sinks do NOT match up with the v1 F4 power AMP boards, so I will only be able to fix the two boards with two screws each at the top. The lower part of the boards will merely rest on standoffs. The legs of the 6 jfets will help hold the board fixed to the side, however. Would that be a problem?

    I am running low on space in the cabinet so the psu will be placed on 8 cm standoffs above the transformer right up front. I will place the soft start module next to the transformer and run the power wires below the amp between the two bottoms of the 4u Deluxe enclosure.

    The pre-amp VAS module will be placed centrally at the back of the cabinet.

    Tomorrow I will build the enclosure and drill a big hole in the bottom for the transformer bolt. Then I will fix it. After that I will screw the jfets onto the heat sinks and match up the amp boards to make sure they fit. Pictures forthcoming.
  11. Rosewind

    Rosewind Lost in Translation

  12. shoom

    shoom open ears and mind

    Looking good

    That's a monster PSU:D

    You could build a platform above the transformer and fix the PSU to that as I think Marra did with one of hid builds.

    Stacking the transformer and PSU sounds like a good plan.

    What's the chassis size? it looks like 4 or 5U but interested to known.

    looking forward to the build.:cool:
  13. Marra

    Marra pfm Member

    As Shaun said I built an F5 with the transformer and Avondale soft start on the base with the power supply rectifiers and cap bank on a platform raised above on alluminium pillars. It worked extremely well this way but the F5 was swapped out in favour of an Aleph J after a few years.
  14. Rosewind

    Rosewind Lost in Translation

    The size is 4U Deluxe, 10 mm front plate.

    Stacking is definitely an option.

    I have decided to buy a small Bench Drill and to tap all new holes that match up with the v1 First Watt f4 amp boards. The preamp board will be mounted on the back plate. I may also decide to mount the PSU on the inside of the front panel. Unless I go with the stacking method.

    Thanks shoom and Marra. Comments, info and suggestions are much appreciated! :)
  15. shoom

    shoom open ears and mind

    ‘’small Bench Drill’’

    Great idea.:cool:

    I bought my bench drill quite a few years ago now just incase I ever needed one.

    It’s had plenty of use since.
  16. Pete MB&D

    Pete MB&D Pete Maddex, the one and only!

    Impressive build.

    Why are you using two bridges instead of a centre taped transformer and one bridge?
    I found that my 135 clones that turned in to Hackernaps it sounded better, something to do with less diodes in the return.

  17. Rosewind

    Rosewind Lost in Translation

    Pete, are you referring to the rectifier bridges? Two of those are used in the F4 building guide on DIYAudio.

    I am a noob DIY'er, so bear with me.
  18. Pete MB&D

    Pete MB&D Pete Maddex, the one and only!

  19. shoom

    shoom open ears and mind

    Good point


    Maybe Papa has a reason for setting up the PSU that way.

    it's been at the heart of quite a few FW amps and I see no need to change much especially for a first build.
  20. Pete MB&D

    Pete MB&D Pete Maddex, the one and only!

    I know Densen use two bridges and reckon it sounds more musical, but I have found the amps I have built it sounds better with only one bridge and a centre tapped transformer.


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