Probably not surprising to anyone here, but I concur! I just finished building a pair of these boards, and installed them in my dual-mono PSU chassis last night. What I had intended to be a brief sound check turned into a 2-hour listening session. This amp really hits a sweet spot with my system, especially at moderate to very low listening levels. It's driving a pair of Spatial Audio X4s, 4-ohm open baffles. Upstream is a Benchmark HPA-4; an OktoResearch dac8 Stereo for digital; and a Pearl 3 for vinyl. Hopefully I'll get to crank things up during today sometime, see how it behaves when pushed a bit harder.
Biasing seemed easier to me with this circuit than the F5m or Aleph J. After only half an hour or so of warmup, adjustments to the bias pots settled within 5 minutes, so it only took me about an hour to dial in to 200mV on both channels. Offset tuning was more tricky. Immediately after adjusment, the offset voltages would swing around by as much as 30mv before settling back down. It took me a few cycles to get the hang of adjusting them.
Total power draw after biasing is about 140 watts (measured with the long-discontinued Watts Up? inline meter). The 3U/400mm MiniDiss chassis should be able to safely dissipate 90 watts per side, so there's some room for higher biasing. But I doubt I'll need it for this setup.
Well its taken a while to get around to putting my F4 together but now happily at the point where I can power it up and set the bias. Really enjoyed the build, especially as I've finally learned to restrict the amount of metalworking I try to do - I have to remember I don't have a fully set up metal shop! (nor the skills).
Can I just check on the position for the P1 & P2 pots before I start? I'd like to not fry anything too ealry in the game 🙂
Should they both be fully clockwise to begin with? (I've gone with pots as per the BOM).
Thanks in advance & thanks to all for the excellent content & guidance.
G
Can I just check on the position for the P1 & P2 pots before I start? I'd like to not fry anything too ealry in the game 🙂
Should they both be fully clockwise to begin with? (I've gone with pots as per the BOM).
Thanks in advance & thanks to all for the excellent content & guidance.
G
I would start with P2 at midpoint.
Ideally P1 should be set at 5K (max value) for minimum current. I don't know which direction would accomplish that for you though.
Are you using 22.1k for R8?
Ideally P1 should be set at 5K (max value) for minimum current. I don't know which direction would accomplish that for you though.
Are you using 22.1k for R8?
She lives! Well actually I finished the build a few weeks ago but have been too busy listening to follow up with a post.
Certainly different in a good way from my F5t and plays very nicely with the BA3 front end. My better half even approves - its quite sophisticated she said (she used to work in film & audio post production so I take her judgement seriously even if she doesnt like hifi) . Mellifluos was my first though but then I steered off using big words so early in the year.
Boards went together really nicely and the enclosure from Modushop was very straightforward.
Biasing was pretty clean too except it would only go to about 100mV at first so had to piggyback another resistor in the R9 position for both sides. Set bias at 190 for a few hours before moving on to 200mV. (as you can see in the pic the F4 is perfect for a tabletop system!)😉. You'll also notice the power section is in a separate enclosure, supporting the multimeters. For my F5 i deliberately built a power supply i could use on other amps with only minor mods.
I've gone off trying to do professional looking metalwork so was really pleased when the Modushop DIY Audio Pass Labs special came up last summer. So i treated myself and think its very appropriate for the F4. It deserves it.
My BA3 pre with the F4 is a great combo but struggles to produce decent volumes with my ATC SCM 11 bookshelf speakers (my BA3 was built with lower gain than standard so its my fault). But I'd half expected that as they are not so efficient, around 83dB i think. With my recently built Elekit TU-8550 its a different story so we have some pretty good & loud (when desired) sounds now and thats with only 10-15 hrs on both as yet.
The Impasse Pre is in the wings and will be an adventure that I'm looking forward to. But i need to take my time with the pre build selections and the build itself.
Back to the F4 - thoroughly recommend it and thanks to Nelson, Jim and others for all the great content thats helped put this together. Really appreciated.
Thanks
Giles
Certainly different in a good way from my F5t and plays very nicely with the BA3 front end. My better half even approves - its quite sophisticated she said (she used to work in film & audio post production so I take her judgement seriously even if she doesnt like hifi) . Mellifluos was my first though but then I steered off using big words so early in the year.
Boards went together really nicely and the enclosure from Modushop was very straightforward.
Biasing was pretty clean too except it would only go to about 100mV at first so had to piggyback another resistor in the R9 position for both sides. Set bias at 190 for a few hours before moving on to 200mV. (as you can see in the pic the F4 is perfect for a tabletop system!)😉. You'll also notice the power section is in a separate enclosure, supporting the multimeters. For my F5 i deliberately built a power supply i could use on other amps with only minor mods.
I've gone off trying to do professional looking metalwork so was really pleased when the Modushop DIY Audio Pass Labs special came up last summer. So i treated myself and think its very appropriate for the F4. It deserves it.
My BA3 pre with the F4 is a great combo but struggles to produce decent volumes with my ATC SCM 11 bookshelf speakers (my BA3 was built with lower gain than standard so its my fault). But I'd half expected that as they are not so efficient, around 83dB i think. With my recently built Elekit TU-8550 its a different story so we have some pretty good & loud (when desired) sounds now and thats with only 10-15 hrs on both as yet.
The Impasse Pre is in the wings and will be an adventure that I'm looking forward to. But i need to take my time with the pre build selections and the build itself.
Back to the F4 - thoroughly recommend it and thanks to Nelson, Jim and others for all the great content thats helped put this together. Really appreciated.
Thanks
Giles
I'm wondering, has there ever been a Gerber for the board design that has been published with the Owner's Manual (page 15)?
^ Not that I've ever seen, but if someone wanted to copy a copyrighted board... even one that would likely be fairly simple to copy... they'd likely not be so blatant as to publish it in an area where Nelson Pass and a lot of his supporters hang out.
Perhaps a different question may be something similar to: "Has General Amplifier, the copyright holder, released any intellectual property for public or private use surrounding the design of the production First Watt F4 boards => Did they release files that I could send to a manufacturer to make exact copies?".
That may help differentiate between finding "copies/fakes" that may not be authorized and what I'm sure is your intent, which is to possibly find authorized versions.
Truly trying to help vs. start yet another discussion on intellectual property.
Perhaps a different question may be something similar to: "Has General Amplifier, the copyright holder, released any intellectual property for public or private use surrounding the design of the production First Watt F4 boards => Did they release files that I could send to a manufacturer to make exact copies?".
That may help differentiate between finding "copies/fakes" that may not be authorized and what I'm sure is your intent, which is to possibly find authorized versions.
Truly trying to help vs. start yet another discussion on intellectual property.
True, especially since the pcb artwork falls under copyright protection as an original work of authorship.
Best not to pursue this any further.
Best not to pursue this any further.
Hi,
Can someone who have, off late bought Current Transistors kit from Store confirm-Kit is coming with Harris P or Vishay?
Can someone who have, off late bought Current Transistors kit from Store confirm-Kit is coming with Harris P or Vishay?