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My_Ref Fremen Edition Interest/Group Buy

Hi all,

This thread starts to test interest/organize a group buy for the My_Ref Fremen Edition, 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.

294140d1343827893-my_ref-fremen-edition-rc-build-thread-dsc_0181-800.jpg


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

Schematic
Google Drive BOM
Mouser BOM

Prices will depend on number of partecipants/kits, the Group Buy is about PCBs only

Approximate prices (one kit = 2 PCBs, PayPal fees and 2€/kit donation to DIY audio included):

25-49 kits 36€
50-99 kits 28€
100-199 kits 24€
200 or more 22€

Shipping prices will be (for each kit, for 2 kits add 1€):

Italy 7€
Europe 10€
Rest of the world apart Oceania 13€
Oceania 14€

PCBs will be blue, 2mm tick, 2 Oz/70um copper, gold plated, made in Italy.

BOM cost is around 76€ per board (premium industrial BOM) which can be lowered to 52€ (On a budget BOM)

If interested please fill your nickname, country and number of kits on the Google Spreadsheet

Greetings:
Mauro Penasa for his great design and kind permission
LinuxGuru for his help on new compensation
Luka for the LM318 PS initial design
Soongsc, Marce, Sebaastian, KSTR and Metal for help on PCB design
BMCBob for all support, tests and reviews

Images of RC boards:

292132d1342607319-my_ref-fremen-edition-beta-build-fine-tuning-dsc_0067-1024.jpg


292133d1342607319-my_ref-fremen-edition-beta-build-fine-tuning-dsc_0068-1024.jpg
 
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The My_Ref is certainly one of the best circuits i've ever built. I get impressive results with it. Can't wait to see what this new implementation gives.

I think you'll be amazed... ;)

I put the country as Brazil on the spreadsheet. i will, however, be moving to Italy next April. Does that make a difference for now?

The GB will close in some weeks, around the end of February and boards should be ready for shipping by the end of March.

It depends on you.

If you want to wait April I can ship it to Italy when you move so you can avoid import duties.
 
I think you'll be amazed... ;)

Good to hear! :D

The GB will close in some weeks, around the end of February and boards should be ready for shipping by the end of March.

I thought it would take longer than that. In that case, i will put Italy in the spreadsheet. My girlfriend is already living in Rome so i'll provide her address for the shipping then. Thanks.
 
I'm a little curious and would like some feedback about this amp. So anyone can answer this question or please redirect me to the right thread.

Since this is a LM3886 design, how does it differ in sound from the standard layout that everyone else does (specsheet, etc...) and that we have been seeing everywhere for the last many years.

Does it still has the monolithic 3886 signature or the design really makes it in a different league? Can the LM318 be changed to a higher performing opamp or it is not needed to go overboard?

Thanks
Do
 
Since this is a LM3886 design, how does it differ in sound from the standard layout that everyone else does (specsheet, etc...) and that we have been seeing everywhere for the last many years.

For a short answer I recommend you take a look here: http://www.diyaudio.com/forums/chip-amps/212626-mauro-penasa-myref-vs-simple-lm3886-circuit.html and also at the associated link on the second (#2 post) on that thread. The link will lead you to the original discussion which is the presentation of the original circuit by Penasa.

I do recommend you take a thorough read of the original thread. It contains a lot of information and feedback, which i know may be a bit annoying to read fully but, it does answer most of the questions relating to the amp.

This link was also very useful for me when i was considering building the my ref: http://www.diyaudio.com/forums/chip-amps/167458-myrefc-build-guide-3.html#post2200278

Remembering this is all information relating to the My_Ref rev C. This is not feedback on this specific version (the one the groupbuy is for). Just making clear.
 
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Hi D9,

Since this is a LM3886 design, how does it differ in sound from the standard layout that everyone else does (specsheet, etc...) and that we have been seeing everywhere for the last many years.

All My_Refs are way better than a plainGainclone.

You can read my opinion here.

Does it still has the monolithic 3886 signature or the design really makes it in a different league?

No, My_Ref's sound signature is dominated by the LM138's one.

The LM3886 is used as an Howland current pump.

It's somewhat similar to Quad 405 approach, the goal is the same: approaching class A performance on crossover distortion.

The My_Ref it's, basically, a chip implementation of De Paravicini's Musical Fidelity A-370.

LM318's sound signature and the topololgy gives a really remarkable sound, not distant to best valve or class A discrete implementations.

The My_Ref performance, though, like the MF A-370 one, can be vastly improved by the LM318 PS (In fact the better sounding A-370 II included a discrete regulator for LM318 PS).

The Fremen Edition improve that area and include other significant improvements.

Can the LM318 be changed to a higher performing opamp or it is not needed to go overboard?

The LM318 is integral part of the A-370/My_Ref topology and can't be easily swapped withoud redesigning completely the compensation.