Roender's FC-100 Rev.1 Group-Buy

[Rudi_Ratlos]

Gentlemen,

last December METAL and I made up our mind and did our own layout for Mihai's (Roender's) FC-100 AMP.

This is Mihai's original thread:

RMI-FC100, a single stage audio power amplifier

The reasons for our decision have been:

- the frontend of Mihai's FC-100 belongs to the best (!) designs I have ever seen in the AMP's world
- we had a couple of NJL - ThermalTrak - transistors at hand and wanted to use them on the backend

We offered our layout in a Group-Buy thread, but after some discussion have been asked to prototype
our PCB first before offering it to the community.

I ordered a couple of professionally etched prototype PCBs and ZSAUDIO and I built the prototypes.



http://www.abload.de/img/fc-100nduq1.jpg

The result:

An absolutely "rock-stable" amplifier playing at its best.

Two comments about its sound-quality:

by ZDR (who did his own layout):
"Well, I am done now. I just have one little problem - how do I stop those little hairs on the back of my neck from standing
up while this baby is playing?"

by ZSAUDIO:
"All of you guys who plan to build this amp just do it. The PCB what Rudi and Metal offer is an art."

I had a problem related to my own build though.
The typcial forward voltage drop of the integrated TT - diodes of my charge of NJL-transistors was higher than of Mihai's transistors,
and I was not able to activate 5 diodes in the TEMPCO - string.

Thanks to a sudden inspiration of FranzM. I bypassed one TT - diode by an external SCHOTTKY diode and fixed my own problem.
Since then I have been able to listen to the beautiful sound of the FC-100.

My "Prototype - Experiences" are documented in this thread:

Roender's FC-100 prototype and builder's thread


I have incorporated ZSAUDIO's and my own experiences and your requests into the Revision 1 of the FC-100 PCB
and will offer you in this group-buy:

- the FC-100 Rev.1 PCB:



http://www.abload.de/img/fc_100_gerbv91ybk.png

The PCB includes the Frontend, the Backend and a complete, high-quality Backend - PSU.
Its size is 245 x 74 mm.
For those of you who plan to use your own PSU, reservoirs CAPs, etc..., I have inserted a pre-determined breaking line on the PCB.

The quality of this PCB is the best that you can imagine:
- 2 mm thick FR4 PCB, double-sided, 70µm copper traces covered with Gold immersion, soldermask, silkscreen, ...
Its price will be 15€.

- Mihai's FrontEnd Shunt-PSU:



http://www.abload.de/img/fc-shuntagytp.png

Its size is 76 x 74 mm; its price will be 8€.

- whatever you like to have to "make this group-buy complete", for example:
Futaba 0R1 / 5W emitter resistors, MKP 1839 / 1µF capacitor, input capacitor, Speaker Protect PCB, Soft-Power-On PCB, ...

One of the pre-requisites to make this AMP a real success is to match certain transistors: the input differential pair,
the output- and pre-output drivers, LEDs, ...
I am currently thinking about designing a "Transistor-Matching-PCB" (if you would like to have).

I will leave this group-buy open, until all of your questions have been answered (but will terminate it on April, 15th at least).

I feel a little bit sad, right now.
Mihai's FC-100 is beating my current favourite DIY - AMP, the TO3-SYMASYM.
This is the best-sounding DIY amplifier I have come across so far.

Will there be any AMP - PCB that I will be going to offer you in the future?

Find the current order list below.
Feel free (you would be a fool if not) and join this group-buy.

Best regards - Rudi_Ratlos

[meanman1964]

Rudi,
Is there a difference between amp boards of the previous batch and this one?Did you make the solder-pads bigger?
For me 2 FrontEnd Shunt PSU boards and a set of resistors.
Those matching boards are a good idea

[Rudi_Ratlos]

Patrick,

the main differences are:

- 4 reservoir CAPs (instead of 2)
- filter and space for bigger heatsinks in the backend PSU - section
- bigger solder PADs for the emitter-resistors
- each TT - diode can be jumpered individually

I did not change anything regarding the frontend- or backend - section of the AMP.

Best regards - Rudi

[meanman1964]

There is no need for me to take the other amp boards from upcoming groupsbuy?

[franzm]

I'm in with 2 complete sets.

[zsaudio]

Hello Rudi and Metal,

i'm with you guys and will order my next boards.
zsaudio

[rellum]

Hi Rudi and Metal,

Nice work, I like the pcb.
Count me in for :
- 4 amp boards
- 2 shunt psu boards
- 2 set of 0.1R resistors

Any chance for the TT transistors to be included in your offer ?

Cheers,
Francis

[Rudi_Ratlos]

Patrick, the Rev.0 - PCBs that you have, work very well!
You do not necessarily need the Rev. 1 - PCBs.

A small update of the order-list.

Best regards - Rudi_Ratlos

[meanman1964]

For me 2 FrontEnd Shunt PSU boards and a set of resistors
Do you've also four 0,22 emiter resistors left?

[Rudi_Ratlos]

Francis,

if you want to: I will order NJL0302DG / NJL0281DG from MOUSER or FARNELL or ...

In the original thread Mihai recommends to closely match the output-transistors (hFE and VBe).
I had a dozen of each of the transistors and the Hfe varied from 91 to 117 (for the NJL0281DG, f.e.).
But I found 2 closely matched triples of each.

I will contact ZSAUDIO and ask him for his experience.
Then I know what I can offer you.

Patrick: I have 4 0R22 resistors left.


Best regards - Rudi_Ratlos