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Old 29th November 2012, 10:44 PM   #471
Telstar is offline Telstar  Italy
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Interesting.
Two things come to my mind regarding bass performance.
First, the psu, it needs to be bigger and stiffer. Double transformers size and capacitors bank. I wouldn't do a CLC, though, because is a class AB.
Second check your amp for some wrong value in the networks that define frequency response, maybe you did some mistake.
Third, you should have tried the amp in your friend'd main system with the Ayre preamp. Apples to apples.
Note that the Ayre is a two stage amp without global feedback.
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Old 29th November 2012, 10:56 PM   #472
evette is offline evette  Canada
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I would change your power supply make your power transformer at least 250va or better yet 300va and double your total supply to 40,00 uf per rail. This is a great amp so give it the best.. Just my 2 cents worth. Evette
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Old 29th November 2012, 11:15 PM   #473
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Hi Rudi,

The PGA-2311 is most likely your bottleneck here... It is good but nothing to compare to a good stepped attenuator or high quality pot. I have tried many itterations of PGA-2310 and 2311 and the 2310 is a little better because of the 15V supply it has better swing but it is still a PGA... I would retry this with a better attenuator and it will most likely give justice to the FC-100

Ciao!
Do
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Old 30th November 2012, 06:35 AM   #474
zsaudio is offline zsaudio  Europe
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Thank you Rudi for the interesting test.
I would do the test in a chain where i only change the power amps. The volume control should be the same too.
I use 400VA toroid and added some mor capacitances for my RFI-FC100 and comparing it to my other DIY amps i don't miss the bass, it has a well controlled bass and goes deep in my system.
Thanks again for your findings.
Best Regards,
zsaudio
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Old 30th November 2012, 07:27 AM   #475
Luke is offline Luke  New Zealand
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Thanks Rudi. Just to keep it in perspective, we are talking about nearly 10K euro worth of hifi, not bad this amp scored even a 9/10 against it.
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Old 30th November 2012, 10:44 AM   #476
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Gentlemen,

thank you for your feedback.

When I drove home yesterday night, I had the same impression that some of you expressed in their feedback: my transformers (2 x 160 VAC)
and reservoir-caps (20.000F per rail) are to small for this kind of music (frequencies < 100 Hz).

I can easily replace the digital PGA2311 attenuator by an ALPS Velvet motorized potentiometer.

But the most important: I will not be able to notice any sonic change, unless I will connect a pair of "adequate" speakers to the FC-100.
The pair of Behringer 2031B Truth that I am currently using, conceil too much of sound-information.

So: this will be my next project: a pair of new speakers (DIY-type?), and then I will "upgrade" my FC-100.


Best regards - Rudi
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Old 30th November 2012, 02:13 PM   #477
roender is offline roender  Romania
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Quote:
Originally Posted by Rudi_Ratlos View Post
Gentlemen,

thank you for your feedback.

When I drove home yesterday night, I had the same impression that some of you expressed in their feedback: my transformers (2 x 160 VAC)
and reservoir-caps (20.000F per rail) are to small for this kind of music (frequencies < 100 Hz).

I can easily replace the digital PGA2311 attenuator by an ALPS Velvet motorized potentiometer.

But the most important: I will not be able to notice any sonic change, unless I will connect a pair of "adequate" speakers to the FC-100.
The pair of Behringer 2031B Truth that I am currently using, conceil too much of sound-information.

So: this will be my next project: a pair of new speakers (DIY-type?), and then I will "upgrade" my FC-100.


Best regards - Rudi
Interesting results. What kind of power capacitors are you using? My fc100 has no problem playing low frequencies and having Nikicon KG Gold Tune capacitors and two 300VA R-Core trafos
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Old 30th November 2012, 02:26 PM   #478
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by roender View Post
Interesting results. What kind of power capacitors are you using? My fc100 has no problem playing low frequencies and having Nikicon KG Gold Tune capacitors and two 300VA R-Core trafos
It's more likely the transformers than the capacitors brand
Yours are more powerful.
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Old 30th November 2012, 02:31 PM   #479
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Mihai, I am using 2 Nichicon LQ(M) capacitors, 10.000F/80V, per power-rail.

Best regards - Rudi
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File Type: jpg Nichicon.jpg (85.7 KB, 327 views)
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Old 19th December 2012, 08:31 AM   #480
atupi is offline atupi  Romania
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Rudi,
could you tell me please if the schematic found in build manual FC-100_Eng_V1 is the latest one ?
As i was unfortunate to buy only a part of the entire kit (only pcb's) i will start hunting/collecting the other parts and i need to know the exact parts/values.
Apart those hard to find transistors there are some special/boutique parts recommended ?

I have the emitter resistors (o.1R) only for one channel. Would be a problem to buy 0.12R for the other channel as they are easy to find on ebay ?

Thanks !
Adrian
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