Complete kits are now available on my website
What is it?
This kit is for you if:
Complete kits are in the works which will be available on my website, reduxkits.com, and with any luck, at Burning Amp Festival 2024. If you'd like to be notified when the kit goes live, there's an email list sign up on the website, or you can just follow this thread.
I’ve built a few prototypes, sent out a pre-production kit, and am currently working on sourcing the last few items to be able to make kits reliably. The BOM will be posted once sourcing is complete.
Pricing is not yet finalized, but $480 is my best estimate at this time. That’s around $100 less than building an F5m in the 4U chassis with a linear supply.
Thank you to Nelson Pass, Mark Johnson, and all others at diyAudio who share their excellent designs and ideas. I built an F5 many years ago when I was in high school and it's proven to be an excellent and reliable amp, maybe the best I own. So I knew I had to build an F5m when it was presented at Burning Amp last year. I am extremely pleased to be working on my own version and hope I can help bring the joy to even more builders.
A video build guide is now available!
What is it?
- The F5m by Nelson Pass in a different form factor
- Monoblock design, each measures 140mm wide, 160mm deep, and 125mm tall (5.5” x 6.5” x 5”)
- This design borrows objectives, ideas, and some parts from my ACA Redux development. In short, ease of assembly and cost reduction are the primary focus. You can read more about that here.
- Dual switching supplies for each monoblock creates +/- 24VDC
- No mains voltage present. +/- 24V is just under the 50V threshold for what is considered touch safe.
- Two of Mark Johnson’s AmyAlice power supply filters are integrated on board to clean up switching noise
- AmyAlice uses surface mount components, but the pads are large, parts are well spaced, and it’s designed to be soldered by hand with a regular iron. Tweezers are a must, but even something from the dollar store will work.
- An inaudible, slow moving fan keeps the heatsink cool and the design compact
- Thermal switch for safety in case of fan failure. Fans are rated 80,000 hours (over 9 years of continuous operation)
- Reduced thermal mass means the amp gets to a stable temperature more quickly.
- All connectors are on the PCB. The only wiring is shortening the fan leads if you choose to do so.
- Upgraded RCA jack and power switch compared to the ACA Redux.
This kit is for you if:
- You’ve been eyeing the F5m kits that recently hit the store but are unsure about building the power supply (mains voltage ⚠️).
- You want to build a Pass diy design for less time and money invested.
- You need something a bit smaller for desktop use.
- You need something that looks less like an amplifier for the family living room.
- You’d like a gentle introduction to surface mount soldering.
- You don’t enjoy wiring.
- The original F5m parts kit / chassis / transformer is out of stock.
Complete kits are in the works which will be available on my website, reduxkits.com, and with any luck, at Burning Amp Festival 2024. If you'd like to be notified when the kit goes live, there's an email list sign up on the website, or you can just follow this thread.
I’ve built a few prototypes, sent out a pre-production kit, and am currently working on sourcing the last few items to be able to make kits reliably. The BOM will be posted once sourcing is complete.
Pricing is not yet finalized, but $480 is my best estimate at this time. That’s around $100 less than building an F5m in the 4U chassis with a linear supply.
Thank you to Nelson Pass, Mark Johnson, and all others at diyAudio who share their excellent designs and ideas. I built an F5 many years ago when I was in high school and it's proven to be an excellent and reliable amp, maybe the best I own. So I knew I had to build an F5m when it was presented at Burning Amp last year. I am extremely pleased to be working on my own version and hope I can help bring the joy to even more builders.
A video build guide is now available!
Attachments
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I was given the amazing opportunity to be an F5m Redux build guinea pig. I would describe my level of build experience as just above novice having built an Alpha Jzm, F5m, and F4 over the past 9 months. Prior to this I built a number of store provide fully complete kits such as the Korg B1, ACA Mini, ACP+, ACA, and ACA MinMax. This was my first time building an amp with surface mount device (SMD) components, which is something both very new to me, and just a little bit intimidating. I stepped out of my comfort zone and gave it a go and I’m so glad I did.
The board layout and schematic are straightforward. I was careful to check off each part against the schematic when stuffing the boards, and the silkscreen with parts values and notes is incredibly helpful.
After stuffing the boards, the initial testing and bias setting process is just like many First Watt clone builds. I set the bias at 1A2 by adjusting the multiturn pots to achieve 0V55 across the 0R47 source resistor and achieved within millivolts of 0V DC offset across the speaker outputs. The heat sinks are still cool to the touch at this bias, which may leave some room to try higher bias as long as one is conscious of the heat output of the 0R47 resistors.
After initial testing with my inexpensive test speakers to be sure music played I paired the F5m amps with my current listening setup which includes:
Even with what some may consider lower sensitivity speakers, the F5m Redux makes them sing and bump effortlessly. I’d like to think that the “m” in F5m may not only stand for “minimal” from a component level, it also stands for “mighty”, “magnificent”, and “magical”. Paired with good components in the chain, it is wholeheartedly all of those descriptions. The highs sparkle and the bass is full and firm. I attribute the excellent sound to not only the great F5m design, but to the inclusion of Mark Johnson’s AmyAlice filter. How these 4 little SMPS wall warts can provide so much powerful sound is just astonishing to me. The fact that the amps are less than 6 inches in diameter and put out so much full range sound is mind boggling. Dark side of the Moon shook the windows in my living room and Zeppelin’s Whole Lotta Love had me bouncing my knees with my hands in the air. These little guys need to get out into the hands of lots of interested folks. I know they will seriously impress. I will venture to say that they sound better and have a little more “oomph” than the F5m I built with a linear power supply in Modushop 4U/300 chassis. It seems counterintuitive to me, and yet, they just do a little better than my F5m. It is astonishing!
A huge thank you to Nelson Pass, Nelson Brock, Zen Mod, Mark Johnson, and all the other people who put their heart and soul into designing and sharing freely the best practical diyAudio equipment that can be made. Thank you all!
I feel so blessed to have stumbled upon this experience in life. Although I may not be a musician, I am a music enthusiast that lives for and loves this sort of experience. Anyone listening to this sort of system will be truly moved by its pure excellence.
For anyone who’s interested in avoiding AC mains wiring and a big chassis, you can’t go wrong with the F5m Redux. These little amps hit the mark way above their price point by a significant margin. Don’t hesitate to jump in and get some astounding class A sound.
Cheers!
The board layout and schematic are straightforward. I was careful to check off each part against the schematic when stuffing the boards, and the silkscreen with parts values and notes is incredibly helpful.
After stuffing the boards, the initial testing and bias setting process is just like many First Watt clone builds. I set the bias at 1A2 by adjusting the multiturn pots to achieve 0V55 across the 0R47 source resistor and achieved within millivolts of 0V DC offset across the speaker outputs. The heat sinks are still cool to the touch at this bias, which may leave some room to try higher bias as long as one is conscious of the heat output of the 0R47 resistors.
After initial testing with my inexpensive test speakers to be sure music played I paired the F5m amps with my current listening setup which includes:
- Source - PC
- DAC - Topping D10
- Pre - Iron Pre SE SMD
- Loudspeakers - Aerial Acoustics 7B (86dB / 1W / 1m - 6 ohms nominal)
Even with what some may consider lower sensitivity speakers, the F5m Redux makes them sing and bump effortlessly. I’d like to think that the “m” in F5m may not only stand for “minimal” from a component level, it also stands for “mighty”, “magnificent”, and “magical”. Paired with good components in the chain, it is wholeheartedly all of those descriptions. The highs sparkle and the bass is full and firm. I attribute the excellent sound to not only the great F5m design, but to the inclusion of Mark Johnson’s AmyAlice filter. How these 4 little SMPS wall warts can provide so much powerful sound is just astonishing to me. The fact that the amps are less than 6 inches in diameter and put out so much full range sound is mind boggling. Dark side of the Moon shook the windows in my living room and Zeppelin’s Whole Lotta Love had me bouncing my knees with my hands in the air. These little guys need to get out into the hands of lots of interested folks. I know they will seriously impress. I will venture to say that they sound better and have a little more “oomph” than the F5m I built with a linear power supply in Modushop 4U/300 chassis. It seems counterintuitive to me, and yet, they just do a little better than my F5m. It is astonishing!
A huge thank you to Nelson Pass, Nelson Brock, Zen Mod, Mark Johnson, and all the other people who put their heart and soul into designing and sharing freely the best practical diyAudio equipment that can be made. Thank you all!
I feel so blessed to have stumbled upon this experience in life. Although I may not be a musician, I am a music enthusiast that lives for and loves this sort of experience. Anyone listening to this sort of system will be truly moved by its pure excellence.
For anyone who’s interested in avoiding AC mains wiring and a big chassis, you can’t go wrong with the F5m Redux. These little amps hit the mark way above their price point by a significant margin. Don’t hesitate to jump in and get some astounding class A sound.
Cheers!
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@birdbox excellent post btw!!!
This project is excellent. The form factor, simple design, and performance is off the charts… IMHO would be an excellent third project after a acp+ and aca mini.
Furthermore, there isn’t nearly as many small form factors amps that come to mind that can touch this with a ten foot poll. On the commercial side, I can only think of a single product, the Burson Audio timekeeper 3x Grand tour at many more times the cost of this kit….
This project is excellent. The form factor, simple design, and performance is off the charts… IMHO would be an excellent third project after a acp+ and aca mini.
Furthermore, there isn’t nearly as many small form factors amps that come to mind that can touch this with a ten foot poll. On the commercial side, I can only think of a single product, the Burson Audio timekeeper 3x Grand tour at many more times the cost of this kit….
Lovely build @birdbox ! Allow me to suggest that after "Dark Side Of The Moon" and "Whole Lotta Love", your setup will very likely give a thrilling performance of "Jump Into The Fire" and also "La Grange". Try it and let us know. 100% puro de Agave may be warranted.
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Whoa - what a cool concept for the F5m Redux!!!!! Well done!
I saw Mark's "Jump into the Fire" link and immediately thought:
I saw Mark's "Jump into the Fire" link and immediately thought:
You can climb a mountain, you can swim the sea
to that home out on the range (they gotta lotta nice girls)
So, come on ... jump in the fire.
Could be a solid mash up...
to that home out on the range (they gotta lotta nice girls)
So, come on ... jump in the fire.
Could be a solid mash up...
I have no idea how difficult/feasible it would be, but it would be outstanding to have 12v triggers.
What a fabulous project. Kudos. Across the related threads, I haven’t seen a defined model of SMPS used. It looks like it’s a Jameco product. Did I miss the model number? I know some SMPS agree with class a loads and filter caps and some don’t, so a known entity always helps in having options for a number of uses. Apologies if the model number is being held for the kits shop. I expect there are Meanwell equivalents that would also work.
