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

[atupi]

Thanks for your thoughts Rudi
This evening some friends came to me to listem FC-100 and some DIY speakers and i've used FC-100 without covers and the bias swing was not so big. It remained around 37mV.
Before my new NJL arrives a will optimize the air circulation installing some small fans on the back of the case and i thinks a will survive like this.

Just to show you some quality differences between 2013 transistors vs older production date transistors:
Vf diode for NJL0281:

2013 samples:

0,508
0,507
0,506
0,509
0,509
0,506
0,506
0,507
0,505
0,507

2012 samples or older:

0,518
0,521
0,518
0,548
0,522
0,524

 

[roender]

Just to show you some quality differences between 2013 transistors vs older production date transistors:
Vf diode for NJL0281:

2013 samples:

0,508
0,507
0,506
0,509
0,509
0,506
0,506
0,507
0,505
0,507

2012 samples or older:

0,518
0,521
0,518
0,548
0,522
0,524

This doesn't mean that ONsemi has done something wrong with newest Thermal-Track transistor unless TC is different than -1.66mV/grdC. If it is, then other diode is inside the transistor case, not what was used in the previous production batch.
If the diode Vf is less than 0.52V but TC is the same batch to batch then only a simple adjustment of the series variable resistor into the FC100 diode string will bring the bias to the desired level. If the TT diode Vf is much bigger than 0.5V then nothing could be done if the bias at the zero adjustment point of the variable resistor is greater than designed value.

 

[andreasw]

Hello,

Here are some pictures of my finished amp.
The Lightspeed Attenuator is integrated as well but I have the option to separate it.
So it´s easy to try things like an amp or pre-amp.

Thanks to Rudi for his support!

Regards
Andreas

 

[atupi]

Congratulations on a fine finished project.
Looks gorgeous.
Can you tell what is your case size inside?
I'm facing some heat dissipation problems and i try to how to see how are doing others

 

[bcmbob]

Andreas, that's quite an accomplishment ! Care to share any info on your impressions of the sound it produces?

 

[andreasw]

@atupi
On the picture you can see how it works.
I took 2 Conrad heatsinks (350x150x60mm), 8 Aluminum angles and a plate of 3mm Aluminum.
The plate doesen´t reach the heatsinks there is a 10mm slut.
With the holes in the top plate there is enough air circulation.

At first the amp has to play some hours.
Later I will write something about the sound in comparsion to an Aleph J and Symasym (at this moment ...).

Regards
Andreas

 

[atupi]

I've recognized Rudi's ideas

Smart move with that 10mm clearance. I will post some pictures in few days when i will have everything installed inside.

What about grounding scheme? I know there are different approaches, my case is not connected to the FC-100 right know, what would be the best solution ?

 

[zsaudio]

@atupi
On the picture you can see how it works.
I took 2 Conrad heatsinks (350x150x60mm), 8 Aluminum angles and a plate of 3mm Aluminum.
The plate doesen´t reach the heatsinks there is a 10mm slut.
With the holes in the top plate there is enough air circulation.

At first the amp has to play some hours.
Later I will write something about the sound in comparsion to an Aleph J and Symasym (at this moment ...).

Regards
Andreas

Eager to hear your findings.

 

[Rudi_Ratlos]

Adrian: Andreas is a DIY-friend of mine and to build the case like this and leave a 10mm space in the bottom plate for better air circulation is his idea.
I approve his idea very much.

Best regards - Rudi_Ratlos

 

[Sheldon]

What about grounding scheme? I know there are different approaches, my case is not connected to the FC-100 right know, what would be the best solution ?

Make an AC ground to common, not DC. Connect the common to the case via a film cap - 1uf or so.

Sheldon

 

[roender]

Guys,

Your builds looks gorgeous.
This is mine, more than 5 years old now.
The pictures that doesn't represent RMI-FC100 are from my work in progress project

 

[atupi]

Mihai is a R-core fan

 

[roender]

Mihai is a R-core fan

It does sound much better than toroidal transformers in any audio application.

 

[mlloyd1]

Mihai:

From where do you get your r-core transformers?

thx,
mlloyd1

 

[roender]

Mihai:

From where do you get your r-core transformers?

thx,
mlloyd1

From Paris
SELECTRONIC: Composants Electroniques, Systèmes d?Alarme, Matériel Electronique

 

[miepa]

FC 100 assembly kit for sale

Hi there,
i sell my FC 100 assembly kit - including all parts - not assembled
I have way too many projects and I'm starting to sell some of them.

http://www.diyaudio.com/forums/swap...mplete-including-all-parts-not-assembled.html

 

[Bensen]

From Paris
SELECTRONIC: Composants Electroniques, Systèmes d?Alarme, Matériel Electronique

Thanks for reminding me to Selectronic! They have there R-cores at serious discounts for the moment. I bought myself 2 500VA 2x36Vac beauties for my next toy.

 

[pooge]

Mihai:

From where do you get your r-core transformers?

thx,
mlloyd1

It's VERY difficult to find off-the-shelf R-cores in North America, or even elsewhere with 120v primaries. I even tried doing a custom order several years ago, but quit in frustration with Chinese "English".

I am not aware if the situation has changed since then.

 

[bcmbob]

I made a call to Antek a couple months ago and they said there just wasn't enough U.S. demand to keep R-cores in stock. They knew of no other domestic vendor. Maybe some sort of group buy might influence their view.

 

[mlloyd1]

yeah, you're telling me


i got one for a preamp on "ePay" some years ago and have not been able to find one easily in the USA since.

unfortunately, nothing's changed as far as i can tell.

mlloyd1

It's VERY difficult to find off-the-shelf R-cores in North America, or even elsewhere with 120v primaries. I even tried doing a custom order several years ago, but quit in frustration with Chinese "English".

I am not aware if the situation has changed since then.