Fremen Edition My_Ref Amplifier – Completed Projects and Photos

A few of us who have been involved in the Fremen Edition for a while realized the other day that been nearly a decade since the project was started and even longer for the My_Ref design that the Fremen Edition is based on. It would be easy for someone on the outside to think no one is building this amp so many years later or that it is an old design that has likely been surpassed by newer designs. Or maybe someone would be put off by the more than 450 pages in the “Build Thread”.

However, this design is most definitely alive and has continued to be improved over the years. It started out as a great sounding amp and is even better today. The basics of the circuit have remained, but improvements in layout by Dario and continuous refinement in the BOM and optional alternate builds have made it an exceptional amp. So, on the suggestion of Stream, we are going to ask builders that have completed a build to post a few photos, talk a little about how it sounds, and compare it to other amps where available.

By the way, Dario has a Group Buy for Fremen pcbs going on right now, the 14th Group Buy for the Fremen Edition. This one is a little bit special because he is trying to incorporate a TO-247 resistor in addition to the current TO-220. This resistor is important to the circuit and the TO-247 size will open up several interesting options for power resistors.

If you are interested, we are trying to recruit at least 4 more stereo kits into the GB to keep the price down and quality up with a European board fabricator.

https://www.diyaudio.com/forums/group-buys/351643-my_ref-fremen-edition-gb-14th-gb.html

So what is a My_Ref amplifier? It is a current pump design using ICs. It is conceptually based on ideas from the Music Fidelity A370 but designed using an opamp as a voltage stage and the LM3886 chip amp as a transconductance or current stage. Mauro Penasa explains his design ideas in the pdf below.

If you are curious about measurements, schematics, etc., see the Group Buy at the link above.

I'll start off the pictures and such with the Fremen Edition in my main system. There is a lot more inside the box than the basic Fremen amp, in fact, its a little bit of a rats nest, but it gets the job done. The blue boards at the bottom of the picture are the Fremen boards and those plus a couple of transformers is all that you need. In my case, I am converting the input from balanced to single ended, plus summing the left and right signal for a sub woofer output. That is the stuff between the blue boards. The boards with the LEDs are a regulated power supply for the balanced line converters.

These Fremen boards have some premium parts and person component choices, for example, Cree Schottky diodes in the power supply and an optional opamp choice with its own compensation. But that kind of thing is for each builder to decide. Building it with the basic BOM still results in a great amp.

As a comparison, I built an amp with an Impasse voltage stage and a Pass F4 current stage. In my system, the Fremen amp is clearly better for both clarity and sound stage. And that's with some pretty expensive tubes in the Impasse.

So jump in if you are interested. The Fremen Edition is a great amp and still improving.
 

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Hi Jac -

Thanks for posting ! As someone who's dabbled in DIYAudio for several years but not steeped in it, getting a general introduction to an amp project (with pictures) is fantastic.

I hope you can persuade others to join in and post as well !

I've just started to *consider* building an amp. So the most basic descriptions, applications, stats -- along with pictures -- is of great help. Thanks.
 
Welcome truepaul. Whatever project you choose, its a great hobby. As you can tell by the 450 pages of the build thread, the Fremen Edition has a great community and can be very helpful. You will find other projects with equally enthusiastic build support. Personally, I find that kind of help invaluable no where near the expertise of some of the people on DIYAudio.

Several of the other guys have promise to post, so look back from time to time.

Have fun.

Jac
 
Member
Joined 2019
Paid Member
My journey with My_Ref FE began after a frustrating battle with other LM3886 or LM3875 builds that did not leave me a satisfying musical reproduction experience. I had been using a Yamaha M80 as my primary amp for many years (preamp’s tone controls were always muted). I acquired it from a colleague ay work after he shorted out one channel. I had it repaired and it served me well until the dreaded “conductive glue shorts” took place on the main PCB one day. Repairing it became questionable as shipping that beast half-way across the country was expensive. I brought out my old Carver receiver (25+ yrs old) but the sound was just not the same. There were neither a wide soundstage nor presence after all these years (maybe there never was). I happened to come upon several articles marveling at the beautiful sound possible from “chipamps” based on either LM3886 or LM3875. These stories were already a decade old (if not more) so I had the benefit of weeding out projects based on people’s reviews of how their builds went or sounded.

I first built a LM3886 chipamp which sounded just beautiful but the bottom frequency responses were not fulfilling. I unsatisfyingly chased that missing “bottom response” through several other 3886 or 3875 builds. My belief was that my Yamaha provided a deep satisfying sound so there was nothing wrong with the rest of my system. When I Googled “missing bass on chipamps” it appeared to be a common complaint with simpler 3886 builds. Then a more complicated LM3886 build appeared during one of my internet searches being praised as one of the most fulfilling in terms of audiophile sound reproduction but more costly than any of the other “less parts is better builds”. So began my journey with My_Ref FE. I joined much later than the rest of you (circa 2018?) so I had all that reading to do in the forum. Those many, many pages later and key players named from their contributions along the way I knew the support was there so I should take the chance. But I needed to get the building & assembling experience from those prior projects.

I have three builds of the FE Evo A variety. Dario populated the first set of V1.72 boards’ SMDs but the next two builds were my handiwork. Here are the builds and anything special about them. Pictures will be presented below the text. As a reference, I don’t sit directly in front of my speakers and tweeters are slightly below my ear level due to room constraints. I do not listen at very loud levels.

Build #1 – Ver 1.72 boards (China ) Evo A build , recommended “audiophile” components added, single ANTEK 300VA 22+22 (AS-3222) transformer, Mundorf Supreme Siler Oil at C13. Experimented with polystyrene at C30, Jac’s quad resistor or Ohmite Thin film resistor (TNP10SHR330JE) at R3 (suggested by Jonathan, aka jwjarch).

Notes: Even though I still love this first build (and I always will) I was always bothered by the slight “veil” over the music (but the soundstage was beautiful and the music presented in front of the speakers was extremely pleasing). The first variation was Jac’s quad resistor at R3 (and I thank Jac immensely for his thoughts and sending blank boards for me to build & use). They were like breath of fresh air to the music. Everything sounded amazingly cleaner, but the bottom frequency warmth (on my speakers & DAC) wasn’t pleasing to me anymore. It did indicate to me there is always some room to make FE builds even better by “rolling” components. I switched to the Ohmites at R3 and they were/are wonderful. Airy, good definition of instruments in an orchestra setting, and the bottom warmth became prominent again (although the overall sound was not as clean sounding as with the quad resistor at R3). Polystyrene was placed at C30 to see if a greater lightness could be achieved but it was a bit harsher than I desired so the Amtrans went back in. Currently the Ohmite remains in R3.

Build #2 – Ver 1.72 boards (China), Evo A build. This was the op-amp experimentation build inspired by George’s, Jac’s and Luca72’s work in the forum. Recommended “audiophile” components were added and Z-foil SMD resistors used underneath instead of Susumu. Single ANTEK 400VA 28+28 (AS4428), Mundorf Supreme Siler Oil at C13 & HEXFRED diodes at D101-104 & 201-204 (suggested by Luca72c I believe). Op-amps tried were OPA627, OPA827, ADA4627 (C32 adjusted appropriately & C34 left open). C9 was shorted. . Eventually experimented with polystyrenes at C30 & C32 , Jac’s quad resistor at R3 or Ohmite Thin film resistor at R3.

Notes: There’s a lot here. The op-amp rolling found 627 to have a fine sound but left the sound stage a little compressed on my system. The much heralded 827 did enliven the musical presentation but didn’t convince me, that on my system, it was superior to the original Evo A build with LM318 enough to leave it in place. The ADA4627 turned out to be the most pleasing to my ear; not tremendously better than LM318 but more lively, articulated and airy. The 4627 stayed in this build. Substituting Jac’s quads for the Caddocks at R3 did as they did before…just a wonderfully clean musical presentation but as before the bottom “warmth” left my system. Putting in the Ohmites at R3 really gave the music a more opened & full bodied sound. I then tried polystyrenes at C30 & C32 with the ADA4627 & Ohmites (I wanted to try George’s suggested Russian glass caps but couldn’t find them anywhere). It’s less warm than Build #1 but the precision and separation of musical instruments, in orchestral music, is superb (IMHO). It’s not better or worse than Dario’s original BOM design, just different. Some folk may find this build a bit brighter than they’d like.

Build #3 – Ver 1.05 boards, Evo A build. Bought these unused, Italian produced boards from a member of the forum. LM318 with accompanying Susumu SMDs. Built with less expensive components just to see how it turned out. WIMA caps, 1uF CDE cap at C13 (the big old white thing), Vishay Dales RN55 used in a couple of places (R11 & R13) , vishays in R10, Nichicon MUSE used at C9, and I used Mill-Max PCB mounts and solder pins so I could quickly switch out at R3 instead doing the de-soldering/soldering work all the time. A single ANTEK 300VA 22+22 (AS-3222) transformer. Nichicon KS 12000uF 50V caps in the Power Supply section (I think they have cleaner sound than the KG “goldtone” series caps). Rolled through Caddocks, then the quads and finally the Ohmites at R3. No experimentation at C30 or C32. This is not the cheapest build one can do but it’s not overly costly compared to the “audiophile” build.

Notes: This build sounds absolutely wonderful! I didn’t think I’d keep it running as long as I did. I have to give credit where credit is due. Mauro P for the theoretical design of the My_ref, Dario, Luca , George, Jac and many others who got this FE edition up and morphed to where it is now. Yes, there is still SMD work to do unless you let Dario do it for you (but it’s really not that difficult once you get the hang of it and these are BIG smd parts compared to some others). You should learn SMD soldering on these components instead of the WM8741s that I first frustratingly cut my teeth on. The R3 story is the same as before, Caddocks gave a warm bottomy sound (actually quite enjoyable), the quads gave a beautifully clean presentation but lightened up the bottom response, and the Ohmites won again.

All three builds are dead silent. Never got any hum with just one transformer. Next on the list? Either Dario’s new TO247 at R3 boards or George’s OPA828 suggestion on a pair of beautiful, new Italian ver 1.72 boards I bought off Giacomo several weeks back. This all becomes addictive although I will be exploring making and modifying DACs to complete the sound package exploration.

Many thanks to Jac for starting this thread. Sorry I was so verbose.

Pete
 

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Pete,

Thanks for posting. Quite a journey. I think it shows your enthusiasm very well.

And you also may have led me to try different SMD resistors on the Quads. I don't see the Quads as necessarily the best solution, but it does offer some interesting possibilities, so I play with it further. Now where did I put those MELF resistor?

Jac
 
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A few years ago I started looking for a new amplifier ... ecological!
Yes, you read that correctly. I was tired of my AM Audio amplifier, class A mosfet, 3.000 euros, high electricity consumption and exaggerated heat (I live in Rome and in the summer months I couldn't turn it on). I started trying some small class D or T substitute for the summer months. I tried Hypex, very good, but musically I was missing something. I tried an AB class like the Denon PMA1600, 1.500 euros, very complete, but without magic.
Then I started reading about Gainclones. I was intrigued by an article by Diego Nardi, a very competent tube amp designer, who said that among the very few solid state amplifiers he tolerated there were few Japanese models from the 70s and some based on ICs like LM3886. Looking for this chip I came across Mauro Penasa and Dario Inserra. Their 3886 implementation impressed and convinced me compared to normal gainclones.
I built the My_Ref FE using Evo A compensation, following the BOM with Amtrans capacitors and without C13 (I have a transformer passive pre and this protects me from the circulation of DC). In the images you can see this simple and cheap realization, contained in a Galaxy 34x29 cm. Even in a box like this, excellent heat dissipation is achieved. Just use 2 cm spacers to correctly align the LM3886, so that it is not on the grooves of the side profile and no precious contact surface is lost. Even in the Roman summer, the amplifier remains little more than lukewarm.
To simplify the construction I used a power socket with integrated fuse and switch and to avoid holes on the front I put aluminum tape in order to see the red LED light reflected through the upper grid. One of the shortcomings of the inexpensive Galaxy box is the lightness and flexibility of the top and bottom. I solved it by putting more feet under the transformers.
What can I say, since then I enjoy music. With a small amplifier, which heats up little and consumes little, by the excellent musicality and by the best speaker control I've ever listened to. Better than my previous amps.
A friend, as soon as he heard the amp at my house, wanted me to build another like it. He immediately sold North Star Design monoblocks amplifier and pre (he had bought them used for more than 2,000 euros).
In recent months I am also listening to a version with fet-opamp chip made by JosephK. A little different, even more incredible.
I took my My_Ref to comparisons with some top amps at friends' houses. A couple must be told.
McIntosh MA7200: tonally and musically we are in the same league. Yes, the feeling of total control, of refined and soft reproduction are on the same level. Only the power is higher in McIntosh. But also weight, consumption and costs (10,000 euros). Awesome.
Spectral and VTL: compared to McIntosh, these amps make you feel that a basic My_Ref like mine has a perceptible little veil. But working on the best components or better on the fet-opamp version, which allows you to eliminate C9, even this small difference, the veil, disappears. Again, awesome.
The experience, the passionate experimentation and the courtesy of forumers like Jac, who opened this thread, as well as Dario as a designer, and many others are a great added value.
I just ordered another pair of boards...

Ciao a tutti
Giacinto
 

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I like solid core cable. But I don't like to spend (I can't ...). So I used a piece of Cat6 Belden. With a pair of orange-white conductors I made a braid like Kimber for the signal and with 3 other pairs of twisted conductors I made the speaker connection.
And what you call genius is just laziness! Although to ennoble it I tell myself that it is not laziness, but the philosophy of otium, the practice of meditative rest, of small creative activities, of the contemplative enjoyment of the world around us, typical of the ancient Romans ...
This is closely related to the "carpe diem". All of us who love music and work hard to reproduce it at best should read Epicuro's short "Letter on happiness (to Meneceo)".
Ciao e grazie di tutto
G
 
I like solid core cable. But I don't like to spend (I can't ...). So I used a piece of Cat6 Belden. With a pair of orange-white conductors I made a braid like Kimber for the signal and with 3 other pairs of twisted conductors I made the speaker connection.


The internal signal cable I use, simply stunning and cheap too:

MOGAMI W2944 Modulation cable OFC Copper 2x0.15mm2 O2.5mm - Audiophonics


This should be very good for power output and cheap too:

CANARE 2S11F Copper Speaker Cable 2x3.62mm2 O11mm - Audiophonics


Alternate:
CANARE 4S11 Star Quad Speaker cable Copper 4x2.08mm2 O10.7mm - Audiophonics
 
I agree, Dario. Among the stranded core cables I find very valid brands such as Mogami, Canare and others with pro-audio skills. Less witchcraft, more science. And as you underline, unbeatable Q / P ...
Ciao!
Giacinto


W2944 is not simply a good sounding cheap cable... it's a stunning performer beating Audioquest Mackenzie (single core) and Neotech NEI-3004 (stranded).
 
For those in the US and Canada, Redco is a pro audio supplier that has good prices on bulk cable. Dario's Mogami:

Mogami W2944 | Redco Audio

I like solid wire too and have used both CAT5 and MIL spec. Again in the US, Johnswireshop.com has quality wire for a good price. Usually more solid stuff available than now.

Great deals from John's Silver Plated PTFE Wire Shop in 24-AWG- | eBay Stores

Great deals from John's Silver Plated PTFE Wire Shop in Shielded-Wire-2-or-more-cond- | eBay Stores

Jac
 
I am just a gray haired old guy without fantasy, so I simply went for Neotech Silver-Gold Up-OCC 26awg internal cabling, though I ripped out the onboard connectors and soldered directly everything.

Output is UP-OCC Neotech copper, maybe 14awg?
In the past I liked very much some (belden?) silver plated stranded OFC cable, 14awg. The Neotech is less spectacular, but more balanced in tone..
Or, maybe, is the usual covering-up story, and maybe should try again the? Belden cable..

Ciao, George

(I had NEI-3004, but found the NEI-3001-III more refined, neutral, extended. Nice. I use also a stranded silver cable, which gives more resolution, opens up more. But has a less beautiful tone than the NEI.. Would be nice to find something bringing both advantages.. Maybe some Zenwave cables?..)

Ciao, George
 
For those in the US and Canada, Redco is a pro audio supplier that has good prices on bulk cable. Dario's Mogami:

Mogami W2944 | Redco Audio


Wow, much cheaper... it makes it a bargain.


Output is UP-OCC Neotech copper, maybe 14awg?


I'm using too a thick solid core Neotech UP-OCC teflon insulated wire.


But I will try the Canare 4S11, just out of curiosity, some of my beliefs about cables has been shaked up recently.


I had NEI-3004, but found the NEI-3001-III more refined, neutral, extended. Nice. I use also a stranded silver cable, which gives more resolution, opens up more. But has a less beautiful tone than the NEI..


NEI-3004 sounds fantastic but lacks bass extension and articulation compared to the reference, much better the Mogami W3173 more balanced, fuller and more articulated.


I'm thinking to replace all my interconnects with W3173...


But we're out of topic here, wouldn't be better to move this to the build thread?
 
Hi all
I would like to share my experience.
Four years ago I decided to build a diy hifi system. Not only the amplifier but also the speakers.
Since I had already made a class AB amplifier (many years before ... too many!) I wanted to try something new, something that already had reviews, in order to be more confident about the result.
Looking on internet I came across Mauro Penasa's MyREF and immediately afterwards in Dario's Fremen Edition. Many comments spoke of a transistor amplifier that sounds "like a tube". So the premises were the right ones.
I decided to make it and the result is in the attached photos.

Now a few general comments:
1. The circuit is well designed. It's clear that it is the result of years of experiments and refinements. There are also several protection systems.
2. The PCB has excellent quality. Both the material and the finishes are well defined. There are also many serigraphs that allow to verify that the circuit is working fine.
3. The choice of components is excellent and the most important thing is that the selection takes place through a group process and not by a single person. So the judgment is shared and there is chance for customizations

The sound:
WOW !! the quality is the highest level. A high-end amplifier and you understand it immediately ... just turned on even without music ... there is no noise, no hum.
When you listen the music it is spectacular .. with all types of music. I listened rock, metal, blues, pop, classic and with all types (even without equalization) the sound is always clean, bright.
I re-discovered sounds (and instruments) in old songs that I had forgotten that exists.

So if you are interested, jump in and enjoy :D
 

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Disabled Account
Joined 2011
Hi all
I would like to share my experience.
Four years ago I decided to build a diy hifi system. Not only the amplifier but also the speakers.
Since I had already made a class AB amplifier (many years before ... too many!) I wanted to try something new, something that already had reviews, in order to be more confident about the result.
Looking on internet I came across Mauro Penasa's MyREF and immediately afterwards in Dario's Fremen Edition. Many comments spoke of a transistor amplifier that sounds "like a tube". So the premises were the right ones.
I decided to make it and the result is in the attached photos.

Now a few general comments:
1. The circuit is well designed. It's clear that it is the result of years of experiments and refinements. There are also several protection systems.
2. The PCB has excellent quality. Both the material and the finishes are well defined. There are also many serigraphs that allow to verify that the circuit is working fine.
3. The choice of components is excellent and the most important thing is that the selection takes place through a group process and not by a single person. So the judgment is shared and there is chance for customizations

The sound:
WOW !! the quality is the highest level. A high-end amplifier and you understand it immediately ... just turned on even without music ... there is no noise, no hum.
When you listen the music it is spectacular .. with all types of music. I listened rock, metal, blues, pop, classic and with all types (even without equalization) the sound is always clean, bright.
I re-discovered sounds (and instruments) in old songs that I had forgotten that exists.

So if you are interested, jump in and enjoy :D

Nice build!

What is the small board in the middle of the 3rd photo, it is not in the other photos?

What are the dimensions of the enclosure you used?
 
Thanks gglera. Nice clean build. I also like that you used the sides of the enclosure as a heat sink. Its nice that these amps don't need a huge heatsink, although I always seem to use a big one anyway. I remember the heatsink on Dario's development board was just a piece of aluminum sheet.

Jac
 
Nice build!

Thanks! :D

What is the small board in the middle of the 3rd photo, it is not in the other photos?

Last week I added a soft start circuit (of course did by myself). I need it because I have 2 toroid of 200VA so the startup current is bigger than 1,25A (fuse limit).

What are the dimensions of the enclosure you used?

The model is 1GX388N that is 310x280x80