RMI-FC100, a single stage audio power amplifier - Page 92 - diyAudio
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Old 5th February 2010, 02:56 PM   #911
roender is offline roender  Romania
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Greetings from Nepal
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Old 5th February 2010, 03:01 PM   #912
Zen Mod is offline Zen Mod  Serbia
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Originally Posted by roender View Post
Greetings from Nepal
good luck , and have a fun !
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Old 5th February 2010, 03:19 PM   #913
Bigun is online now Bigun  Canada
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I spent 2 months there once, in the mountains. Wonderful place, stunning place, amazing place. Looks like you have been both to the Everest Region and to Machapuchare ?
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Old 5th February 2010, 03:32 PM   #914
johnYks is offline johnYks  Australia
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http://magicalplacesoftheworld.files...t-olympus3.jpg

Greetings Roender
Very happy to see you back_I am hoping for
news on the design or even just your thoughts
on it as to where it stands.
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Old 5th February 2010, 06:34 PM   #915
Sheldon is offline Sheldon  United States
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Originally Posted by roender View Post
Hi all,

Sorry for neglecting this tread, I am badly cached with may daily job and mare than that I was in a long trip in Himalaya
I will answer your questions as soon as possible.
Sheldon, don't waste your time with the SE version of fc-100. Is very hard to tell if there is any improvements at all, at least on my MA Gold speakers. Maybe yours are more resolute and will cont.

Thanks,
Mihai
Thanks. Very nice pictures.

I was interested in the SE version, not because I expected better sound, but just because it was a chance to try something a little different. Mostly, it was an exercise in learning the amp a little better. But, I hate unsoldering stuff from a pc board, so maybe I'll just match my outputs better on the second version, and leave it at that.

Sheldon
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Old 8th February 2010, 03:28 PM   #916
roender is offline roender  Romania
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Originally Posted by koldby View Post
Hmm Maybe my questions are too stupid?
I can see a problem in the Vbe multiplier, as the Vbe multiplier transistors own Vbe will be multiplied as well and thereby reduce the influence of the Thermatec diodes, but what if you used an opamp to amplify 1 Thermatec diodes foreward drop five times. You would end up with the same result as a string of five Thermatec diodes in series, right? Of course the active devices has to share the load pretty much equally for this to work, but this amp uses matched devices.

Does any of this make any sense?

Koldby
Koldby,

Could you please show me where you had seen a vbe multiplier transistor in RMI-FC100 topology?
Why complicate the schematics with a opaamp as a single tracking diode multiplier when we have access to all five TT diodes?
Keep it simple

Regards,
Mihai
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Old 8th February 2010, 05:02 PM   #917
koldby is offline koldby  Denmark
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This was actually a comment to my previous post in post 909, where I was wondering if you could use two pairs of NJL1xxx instead of 3 pairs of NJL0xxx and still get the right tempco.
Also I wondered ther if you couldn´t get the same class A bias along with the correct class B with a differen value Re..

Absolutely keep it simple, but if you can´t get the NJL0xxx, maybe a solution could be found with the same performance (Same total Cob )

Koldby
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Old 23rd February 2010, 05:23 PM   #918
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Mihai can I replace 2SC3423Y \ 2SA1360Y with 2SC2705Y \ 2SA1145Y? They are the same but in different package.
I can't find original 2SC3423Y \ 2SA1360Y transistors.
I guess if performance of SE version is no different from original, SE version is cheaper and simpler.
Regards.

Last edited by AndriyOL; 23rd February 2010 at 05:29 PM.
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Old 27th February 2010, 10:55 AM   #919
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Mihai,

Thanks for sharing your good work. I have just been pointed to your amp so this must be it! I am looking for the best sounding class B / AB amp to drive my tweeter with my active speakers and I think this would be the best choice.

The trouble is that I have limited skills and at best could do it using perfboard and am not competent in matching devices, etc.

Are there PCBs, or better, kits available, which will save me a substantially amount of time and efforts and give me better chance of success?

Best regards,
Bill
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Old 27th February 2010, 03:22 PM   #920
Sheldon is offline Sheldon  United States
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Having built two of these, I would say that it's major overkill to use as a tweeter amp. Right now, I use the amp for 300Hz and up, just because that's the way my system is set up - and it's probably overkill there. As it was pointed out to me, the great advantage of this amp is that it can deliver clean power into complex loads, while delivering lots of current. You don't need that to drive a tweeter.

Of course it would work very well. But it's not an easy, or inexpensive amp to build. You don't need multiple paralleled output devices for any normal tweeter. And I certainly wouldn't try an amp of this complexity on perfboard.

I'd take a look at this one, as boards are available: My new SymAsym PCB design Rev_1.3

Sheldon

Last edited by Sheldon; 27th February 2010 at 03:29 PM.
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