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My_Ref Fremen Edition GB (13th GB)

Hello Dario,
I have already paid on 6.02.2019 and wanted to ask if my PCB's are already on the way to me?
greeting
Ulli


Hi Ulli,


your boards have been shipped yesterday.


I've missed last shipment for your boards since I've had some problems with OneDrive sync, your details were on my work PC and not on my home one, sorry.
 

chindman

Member
2015-06-10 8:31 am
LA
Boards arrived yesterday, today I've shipped all bare boards.


Boards with SMD option will be shipped 16/2/2019 (or if time permits even 9/2)
Thank you Dario,

SMD option received in LA CA
(left coast US) 1300 PST 2/26/2019 so any US recipient should by now have their boards!

couple of questions:

1. what is right BOM for building this SMD pre-populated board? I am confused about "EVO A" etc. My board says Rev. 2.17
.
2. There is a "budget" BOM on the list, has anyone provided any measurements as to the difference this makes. I don't much care about 10-15 euros difference per board but I do as an engineer have a lot of reservations about the claimed sonic differences of components that noone has found a way to build in a way that measures electrically better. I do not want to start a ******* contest here I'm just looking for objective info.

3. Just for my curiosity, Mauros design is rather old and far better amplifiers than the 318 are now available in terms of CMRR, PSRR, noise density, and simplicity of stabilization in this particular circuit context. Has anyone done any serious work on these issues to your knowledge?

TIA
Carl H.
 
1. what is right BOM for building this SMD pre-populated board? I am confused about "EVO A" etc. My board says Rev. 2.17
Hi Carl,


On boards you will find the following text: "Revision 1.72 - January 2017"


So your boards should be revision 1.72.


The correct BOMs are:

Just order the first for original FE compensation or the second for the Evo A compensation (desolder R39 from both boards).


The technically better compensation is the EVO A and obviously sounds better too.


See the build guide for some more info.



2. There is a "budget" BOM on the list, has anyone provided any measurements as to the difference this makes. I don't much care about 10-15 euros difference per board but I do as an engineer have a lot of reservations about the claimed sonic differences of components that noone has found a way to build in a way that measures electrically better. I do not want to start a ******* contest here I'm just looking for objective info.


All evaluations and measurements were made using the standard industrial BOM.


The budget BOM simply omits all hardware and replaces some parts with lesser ones and made sense with the first BOM revisions were a lot of costly Caddocks were in.


After v1.5 revision the standard BOM costs a LOT less and the budget BOM is no more useful.



If you look at the Google Docs BOM (which is the ONLY official one) the only 'economy' parts still in BOM are C34 (C0Gs instead of Micas) and R3 (Cement/ceramic generic resistor instead of a Caddock)



The 'economy' C34 is still a very good choice while the cement resistor is much worse than the Caddock.



3. Just for my curiosity, Mauros design is rather old and far better amplifiers than the 318 are now available in terms of CMRR, PSRR, noise density, and simplicity of stabilization in this particular circuit context. Has anyone done any serious work on these issues to your knowledge?


JosephK modified the compensation (starting from Evo A one) to accept some other opamps, I've yet to try that mod but who did is pretty happy about it.
 
Dario,
I am glad keep up this thread from time to time. Vaguely remember removing R39. Will double check next time I open FE.
I assume it is mounted to the bottom like many of the surface mount components.
No desire to play with the opamps. The LM318 works fine.
My last opamp evaluation project involved quad surface mount. Spent many sweaty hours removing and installing various types. Ended right back with MC33189. Another old, cheap, low spec part that worked as well as any tested.