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My_Ref Fremen Edition GB (11th run)

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Preface

This is the first GB from Mauro Penasa (the original My_Ref Designer) death.

Mauro, thanks again for your priceless contribution to the DIY community, rest in peace.

To keep prices lower in case of a small number of participants, up to 20 kits, PCBs will be produced in China.

From 20 kits and up PCBs will be produced in Italy as in previous GBs.

There will be, for whom is afraid of SMD soldering, the option for boards with SMD parts already hand-soldered with ROHS silver solder, thoroughly cleaned and visually inspected for 50€ more per kit, including SMD parts (a 20€ value).

If interested please PM me your PayPal associated email address and fill your nickname, country (2 letter code) and number of kits on the Google Spreadsheet (please leave blank the 'PP account sent' column, I'll fill it so you have a feedback that I've received your data)

November, 19 price will be fixed and I'll start sending PayPal Invoices, all payments are due by November, 26.

Until PCB order from manifaturer is done it will be possible to partecipate to the GB

Boards will be ordered by November, 26 and should be in my hands in 15-20 days, then packaged and shipped in a week or so.
Remember to sign-up on the Google Spreadsheet to partecipate!

Now the usual (updated) opener
:

The My_Ref Fremen Edition is a variation of Mauro Penasa's My_Ref with this goals:

  • a more stable and performing amp using SMD parts
  • raise LM318's PS voltage thanks to a voltage limiter
  • better PS for LM318
I've designed a brand new PCB with these features:

  • bigger caps (16mm diameter with both 7 and 5 mm pads) for C1, C2, C9
  • large use of SMD components
  • quite all small caps and some critical resistors are still through-hole
  • very small paths thanks to SMD
  • ground planes design
  • zener limiter based on schematic 5b from this link (which seems pretty similar to My_Evo one)
  • CCS shunt PS for the LM318
  • An alternate C9/R10 arrangement
  • Different grounding
  • Different compensation
  • a double diode bridge like in most gainclones
Both PCB and schematic have been tested organizing beta and release candidate mini group buys

I've been authorized by Mauro Penasa to proceed with this My_Ref derivate amp.



You can find references on development, beta and release candidate here:

My_Ref Fremen Edition - need help on PCB evaluation - diyAudio
My_Ref Fremen Edition - Beta build/Fine tuning - diyAudio
My_Ref Fremen Edition RC - Build thread - diyAudio
My_Ref Fremen Edition - Build Thread

KSTR's measurements on beta boards (final boards measured a tiny bit better but almost the same performance):



7th run boards measures even better (Measure by JosephK):



Distortion goes down ten times Vs. Beta (and previous) Boards

On my Google Drive you'll find:

Schematic
Schematic (PS)
BOM
Build Tutorial

And a YouTube video on SMD soldering of FE modules.

Mouser shared projects (order 2, each project is for a SINGLE board):
Industrial BOM
Industrial BOM without SMD parts
Industrial BOM + Evo A Mod
Industrial BOM + Evo A Mod without SMD parts

Actual price will depend on number of partecipants/kits, the Group Buy is about PCBs only, with an option for SMD populated ones.

Approximate price is 25-27€/Kit (one kit = 2 PCBs, PayPal fees and 1€/kit donation to DIY audio included):

Actual price will be calculated and fixed before ordering boards and it will lower as kits numbers goes up.

Shipping prices will be (up to 2 kits, more than 2 will be calculated):

Italy 9€
Europe 13,5€
Rest of the world apart Oceania 17,5€
Oceania 18,5€

PCBs (circa 12 x 10.5 cm) will be blue, 2mm tick, 2 Oz/70um copper, gold plated, made in Italy (from 25 kits) or in China (up to 24 kits).

One transformer 160VA-300VA will be needed for each board (monoblock design)

BOM cost is around 67€ per board (premium industrial BOM) which can be lowered to 53€ (On a budget BOM).

Build a complete amp (premium industrial BOM with case, connectors, cabling, transformers etc.) will cost around 400€ and up.

Greetings:
Mauro Penasa (R.I.P.) for his great design and kind permission
LinuxGuru for his help on new compensation
Luka for the LM318 PS initial design
KSTR for the new C9, R10 arrangement.
Soongsc, Marce, Sebaastian, KSTR and Metal for help on PCB design
BMCBob for all support, tests and reviews
JosephK for his measurements and advice on further reducing distortion.

Images of boards from the 7th GB:


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I am interested in building a GC of some sort. I would like to drive mine with a Class A preamp. In this scenario, what sonic advantages might the My_Ref Fremen hold over the much simpler original GC circuits? If possible, some comparisons would be useful...I am more interested in subjective listening impressions than THD figures. Surely this has been documented previously but there are so many GC threads at this point my head is spinning. Thanks for humoring a newcomer.
 
I am interested in building a GC of some sort. I would like to drive mine with a Class A preamp. In this scenario, what sonic advantages might the My_Ref Fremen hold over the much simpler original GC circuits?

Mmh, how I can explain the difference... Simply Night and Day, literally! ;)

Jokes apart the My_Ref is a nested feedback curent pumping amp, way better than any plain Gainclone.

It has a tight grip on speakers, plenty of detail without harshness, wide and deep soundstage and a pretty transparent timbre.

If possible, some comparisons would be useful...I am more interested in subjective listening impressions than THD figures.

THD figures simply are tools to prove that the homework is done, they don't tell you how it will sound.

The My_Ref FE simply sound fantastic! ;)

I will try to post some links of builders reviews.
 
Some impressions on old boards/BOM

I heard these AR10pi speakers driven by a couple of my fathers Marantz amps (the 80s models, don't remember which) and lately by a LM1875 chipamp (not bad). Compared to those My_Ref FE is distinctly better. Music appears well balanced and articulated. That is, instruments are not obscured one by the other. Merely by refocusing attention one can distinguish the particular line. The challenging string instruments are very authentic. I look forward to examine the sound of egyptian horns in the Aida with this amplifier. Never heard them properly reproduced.
I must say it is impressive to say the least! The sound is so natural, the instruments sound absolutely real. Ofcourse after some time the brain will burn in and I'll see possibilities for improvement (at the moment it is just industrial BOM), but now I am absolutely dazzled by the result! And it was so simple to get there. But that is because someone has produced this simplicity for us with his natural talent and hours and hours of work ;)

this amp is PURE MAGIC
Dario, could you please add this to the amp's description:
It is the moment then music stops being just a record and becomes an experience !

So what have I learned from these adventures? I can honestly say I feel there is no such thing as "The Best Power Amplifier". There are just too many components, personal preferences and varying budgets for such a thing to exist - IMHO. I have come to respect and appreciate what the Class A designs offer and will most likely keep one of the builds. I can also say that Dario's FE remains my favorite and most enjoyable. I think Ivan summed it up the best...."this amp is PURE MAGIC". It appears some new developments like Roender's FC-100 prototype are seeking similar response/performance, but I've seen nothing close to the simplicity of the single board, low temp, flexible installation/configuration high quality solution provided by the FEs.

OMG!!!

This amp is totally fantastic!! Kind of remind me of a transistor Class A amplifier but with the spaciality of a Single Ended Tube amplifier. Really impressive!!!

I find that in transparency, my Goldmund wins but there's really nothing to hate of that My_Ref FE. It is in my list of preferred amps. Imaging is where I find it extremely pleasing, the soundstage is really deep. In Miles Davis - Kind of Blue on So What track, you can really feel the distances of the instrument, the double-bass is in the back of the scene and you can really feel the room. I find this is the harder part to reproduce. Many amplifiers will have a wide soundstage but the depth is not always well defined this is where this amplifier shines. There's also a lot of air between the instrument and separation is very good. Heavy passages don't come all compressed. Also the reproduction of timbres is right on!

As you can tell, I'm really excited about this amplifier. :D

I’ve not heard any of the My Ref before so it was interesting to hear the sound open up from switch on and boy did it do that.
To My ears the most obvious sonic quality is the Midrange which is just so open and makes for a really deep and wide soundstage. Lots of detail and really smooth in a way that I’ve only heard SE DHT triodes manage previously. Vocals are particularly impressive sounding clean, clear and natural. Top and bottom do a great job of underpinning the music with bass deep and tight but not overblown.
Treble is also sweet and clear.
Overall the sound has punch and dynamics a plenty.
It’s been a few days now since I completed my build in which time I’ve managed to clock up about 24hours of burn in.
(...)

So a quick progress report.
Well all sounding pretty good this end with the soundstage depth growing quite noticeably. I’ve been really impressed with the pin sharp imaging which makes it so easy to identify the location of instruments and vocals etc. the top and bottom seem to be filling out very nicely with bass noticeably fuller without losing definition and tunefulness.
PRAT is also first rate and the amp stays musical even when pushed hard. It also unsurprisingly runs cool on those big heat sinks. This amp seems to be a really good match for my PMC transmission lines and the combination makes for a clean dynamic sound.
So I’ve gone from being impressed to gobsmacked.:)

I finished the MyRef FE about 4 months ago and all I can say is that it's a REAL reference amplifier. I compared it with a few expensive hi-end power amps (both linear and class d) and to my ears it plays definitely in the same league.
I was honestly blown away. Simply stunning sound reproduction. The big Pass style amps I've built are truly impressive with a large super clean stage that give no hint of distortion or lack of ability to handle anything sent in their direction. Excellent sound.

But --- if you want to reach over and feel the vibrations on the crash cymbal, hear the air moving through Miles Davis's trumpet, point to the chair the second alto sax is sitting in and feel the couch bounce on the drum fills .......

I haven't heard the full width and most significantly - depth of stage the FEs produce from any other setup.

Anyway the FE's are brilliant amplifiers, the best I've ever heard and I fully encourage anyone to build them, the sound quality is so good that it's well worth getting them right.

I am extremely pleased at the conclusion of the overall performance of this amp that doing nothing but amaze me all the time. My reference amp has always been my homebuilt OTL in Circlotron configuration (two mono blocks, with 4 6C33C). The Fremen looks good in almost anything compared to him. The most obvious attribute is its neutrality and in my opinion this is a huge honor.
 
Impressions on current generation

I really love how this amp sounds. Had some worries about the base sounding a little bit muddy, but after maybe 25-30 hours of break in the sound signature changed a lot. Now it is very well defined and balanced. Mids are very detailed, good separation, highs are awesome - very clear and natural sounding without being bright.
Altogether really an amazing sounding amp. Can't stop singing along with my favourite songs now *lol*

The first big difference i noticed was the soundstage. It really made it sound like the music was not coming from the speakers anymore. Very good separation and placement. Also, it definitely has this "tube-touch" not as extreme as with a normal tube amp, but to get an idea what it sounds like a very good picture. The voices now sound a lot more realistic to me. Now i sometimes hear a noise and only afterwarsd realize it was from the recorded music/movie *ggg* In my eyes a really worthwhile build with incredible bang for buck

1st impression is that it sounds fast and tight, with clear separation of instruments. Excellent harmonic structure with brass etc.

Guys... I love this amp.
(...)
How does one put it in words? Just so musical.. Silky.. Tonally correct... Separation of each instrument. When playing loud it still holds everything together.. I can't wait to listen to music
(...)
Does everything right in my book.. Worth every cent. Too afraid to put it in my main system... I'm afraid it will beat my valve amp.

I thought I had a very good amp. And I did, it was way better than the one before that (rotel RA07)

But this one. Another league. Better control of the bass and more detail.

My wife and I were listening to Arcason the other night(from Candido - the Master). Control of the bass and detail in the bass is better than my tube amp. Somebody said he liked the 'thereness' of the musicians, I completely agree! Razor sharp imaging, not too big, just right. As if they are in the room. Not warm, surely not analytical. You feel the enthousiasm of the musicians, at a certain point someone on the left is really enjoying the moment, and starts laughing/humming. You just 'see' him playing, laughing, enjoying. We both smiled. Listened to that song a few times, that never happened...

And that's most important, at least for me. Not the lowest THD+N or some other statistic/measurement. So a big thanks to Dario for this great sounding amp! I love that I can have a sound quality at home I can't​ afford if I should have to buy it from the store! You and all the FremenEdition pioneers made that possible.
 
Wow! I can see that the extra effort put into this topology has really paid off. It must sound special indeed.

Looking back at some of the earlier threads I am impressed by all of the critical listening used to choose every single component on the board. I have personally heard huge differences with my own cap rolling experiments, so I appreciate this uncommon attention to detail.
 
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