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Old 19th November 2012, 11:12 AM   #461
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Shown on the images below is the "competitor / rival" of my FC-100.

It is a SYMASYM based upon my "TO264- SYMASYM" - PCBs.
It has a pair of matched MPSA18 transistors on the input, uses 2 pairs of matched NJW0281G/NJW0302G on the output,
has a CAP-Multiplier on-board to provide a stable supply voltage for the frontend, ...
This SYMASYM is powered by a 2 x 25 VAC / 300VA transformator and the DX PSU.
The attenuation is done by the "Lightspeed Attenuator", which is controlled by a BOURNS motorized 100K potentiometer.
The attenuation can be controlled remotely.

The SYMASYM is a Christmas present for my brother, and I have done my very best to give it a good sound.
I have invited several friends in the next week, and I will perform a "shootout" between the FC-100 and this SYMASYM then.

I will keep you informed.

Best regards - Rudi
Attached Images
File Type: jpg SIM 001.jpg (375.3 KB, 651 views)
File Type: jpg SIM 007.jpg (468.8 KB, 559 views)

Last edited by Rudi_Ratlos; 19th November 2012 at 11:14 AM.
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Old 19th November 2012, 03:44 PM   #462
evette is offline evette  Canada
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Looks great Rudi, Evette
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Old 19th November 2012, 06:49 PM   #463
lucylu is offline lucylu  England
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Default Parts

Hello Rudi Do you have any of the shunt transformers 4 x 34 vac left also 2sk170bl matched pairs available thanks regards john
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Old 19th November 2012, 07:50 PM   #464
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Yes I do. I will send you an EMail tomorrow.
Best regards - Rudi
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Old 20th November 2012, 08:24 PM   #465
atupi is offline atupi  Romania
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Hi Rudi,

any chance to have some extra pcb's left?

Regards,
Adrian
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Old 21st November 2012, 09:02 AM   #466
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Adrian:

I am currently doing a group-buy for the German DIYers. The group-buy is already closed, but I think that I will have 1 set of FC-100 PCBs
and "hard-to-get" components left.

The set consists of PCBs, 4 x 34VAC transformer, 2SK170BL pairs, authentic Toshiba 2SA1360/SC3423,
MJE15034/35, NJLs, MPC74 emitter resistors, ...
All transistors are closely matched according to Mihai's specifications. For example: the 2SK170BL have an IDss > 9mA and are
"VGS - matched" at ID 6.2mA (best that I could).

I can tell you tomorrow, after I have packed all the parcels for the Germans.

I will never do a 3rd round of group-buy for the FC-100 as is, even though the FC-100 is the most-beautiful DIY-AMP, I have ever listened to.
I congratulate all of you, who have their DIY-kits and will build it. Do it carefully, please: this AMP is being worth your carefulness.

The reason for never offering a 3rd round: it is extremely difficult to order/buy NJL0281DG/NJL0302DG !
MOUSER will offer them again in October 2013 (!), FARNELL, DIGIKEY, RSONLINE, ..., do not have them on stock, ...
I was really happy to finally find a supplier of the NJLs (150 of each) for the German group-buy!
Moreover: if you take a look at the FC-100 technical threads, you will notice that the build of the FC-100 is not always "DIY foolproof"
due to some anomalies (maybe) of the integrated ThermalTrak diodes.

It is the backend of the FC-100 that is causing me headaches.
The FC-100 frontend is IMHO above any reproach!

I will ask Mihai (and my favourite German DIY mentor), if he will assist in a re-design of the backend, in something like Groner-triple,
like KRELL did, ... But it will take quite a while, before I will be able to present you the FC-100 MKII - if ever.

Best regards - Rudi_Ratlos

Last edited by Rudi_Ratlos; 21st November 2012 at 09:04 AM.
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Old 21st November 2012, 11:32 AM   #467
Telstar is offline Telstar  Italy
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You dont have to do a full kilt for the next GB, just the PCBs and whatever you have left.
I know the NJL are a PITA to match, and this before the diode issue.
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Old 21st November 2012, 11:48 AM   #468
atupi is offline atupi  Romania
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Thanks Rudi ! I'm looking forward to be part of this beautiful project.

Adrian
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Old 22nd November 2012, 05:26 PM   #469
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Whoowh!

I received a feedback from Mihai (Mihai: "Enjoy your holidays! Have a very nice time and do not break any of your bones!"),
in which he signalized to provide me an alternative to the "NJL0281/NJL0302" (very hard, near to impossible to get these
transistors nowadays) backend.

I am looking forward to his proposal.

Best regards - Rudi_Ratlos
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Old 29th November 2012, 09:48 PM   #470
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Default Sound Comparison

I have just returned from my friend Christian, who invited me to do the "sound-comparison" between the FC-100 and the SYMASYM at his home.
The reason for not performing this comparison at my home was: my speakers (Behringer 2031B Truth) "do not sound", are not able to reproduce a stage.

Here are the 2 competitors:

Click the image to open in full size.

On the right side on the floor, with the ALU front-plate: the SYMASYM.
Details of the SYMASYM: one transformer, 2x25VAC / 300VA, one PSU with 20.000F per power rail, each channel having 2 pairs of NJW0281/NJW0302 as output transistors.
As attenuator I use the George Stantscheff's "Lightspeed-Attenuator".

On the left side: the FC-100 (you know it for sure), having two transformers, 2 x 25 VAC /160VA each, the backend power-supply of each channel being "backed-up" by 20.000F per power-rail. As attenuator I use a PGA2311-based attenuator developped by the German Stefan Dreyer.

A pair of Infinity Kappa 400 (6 Ohm impedance) serves as speakers.

We listened to 2 CDs: "George Benson - Weekend in L.A." and "Depeche Mode - Remixes 81-11"

First the SYMASYM:

Christian was very impressed by the SYMASYM. It plays very "lively", very dynamically and offers at lot of soul.
The sound of the SYMASYM immediately reminded him of the old-school NAD3020 with a lot of power.

Then the FC-100:

First: listening to George Benson.
His first remark: "Whoowh". Ultra-fast, perfect resolution (you can hear George Benson's voice 50 cm above the guitar that he is playing),
very wide stage,really astounding, "leave this AMP here".

Then: listening to Depeche Mode.
Christian played a track with very deep going bass, as low as 60-70 Hz.
At these frequencies the FC-100 showed some kind of "weakness" and was not able to reproduce these frequencies "in a controlled, superior way".
My FC-100 does not "play" these frequencies; it "pushes / shoves" them. It is not bad, but could be done better.

Christian then took me into his living-room, where we listened to the same Depeche Mode track, this time playing on his AYRE K-5xe / V-5xe
and a pair of B&W 801D. I noticed the difference.

I asked him: "If I would give your AYRE - amplifier 95 of 100 possible points for sound reproduction: how would you rate the SYMASYM / the FC-100?"
His answer: "I would give 80 points to the SYMASYM. I would give 90 points to the FC-100, if it could reproduce the very low frequencies better.
It is perfect to play Jazz and mainstream POP.
Knowing about its deep-bass weakness, I give it 88 points."

This has been the result of the "shoot-out" - and I agree.

How can the FC-100's weakness to reproduce very low frequencies be improved? Has it to do with my specific build?

Best regards - Rudi_Ratlos
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File Type: jpg competitors.jpg (215.5 KB, 308 views)

Last edited by Rudi_Ratlos; 29th November 2012 at 09:52 PM.
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