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Old 18th July 2008, 02:42 AM   #171
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It is probably as much inferior as I/P coupling cap. While in some cases coupling cap is neccessary, Ci cap is usually less of a requirement.

Besides, input cap needs to be much smaller value, so choosing better sonically type is much easier.
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Old 18th July 2008, 01:35 PM   #172
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Hi Peter,

I finished building my first chip amp last night, using your 3875 premium kit , running on 300VA 25V-25V power supply. Thanks to your invaluable instructions here, everything went smoothly and i got it working the first time i turned it on. No humming, no noises. pure silense when no input source connected.


Sound clearly exceeded expectations and i was flabbergasted to hear sheer musical sound produced by this little wonder. Bass is phenomenal and vocals do not loose emotions in reproduction. Overall the sound is very smooth and musical, could listen to it forever without any fatigue.

However, to my ears, i feel it lacks a bit in trebel. I was wondering if theres any possibility to tweak some components to accentuate the trebel a bit more? would appreciate your inputs on this.

Cheers
Mubeen
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Old 18th July 2008, 05:07 PM   #173
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Yes, you can further accentuate trebles by adding 0.1uF polypropylene bypasses to main filter caps. You can do it directly underneath the board or by replacing 10uF caps on rectifier board with those (part suggestion from DK): http://search.digikey.com/scripts/Dk...?name=P3104-ND
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Old 18th July 2008, 06:07 PM   #174
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Thanks for quick response Peter. I understand that i would need to replace or bypass caps on rectifier board only, no changes to amp circuit? Let me know if i am wrong. Sorry, electronics is a bit unfamiliar territory for me. Is there any diagram or instruction on here for this task?

cheers
Mubeen
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Old 18th July 2008, 06:17 PM   #175
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That would be correct, but you may also try soldering those small additional bypass caps directly to pins of 1500uF Panasonic caps, underneath the amp board.

This is probably most recomended approach and depending on final result, you may as well remove 10uF caps from rectifier board, whatever works best for you.
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Old 18th July 2008, 08:41 PM   #176
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Thanks mate that worked like a charm. Though the effect is subtle, or may be its not but i would not be able to know as i cant do A-B comparison at the moment. So i am content with 0.1uF caps for now.

I just cant stop music once i start playing through this amp its so much 'alive'. I became a believer in simplicity and minimalist approach when i first heard a NOS DAC and this is the second time i have been amazed and it has only firmed my belief further, rather it has become my guiding philosophy in hi-fi now

Mubeen
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Old 19th July 2008, 05:56 PM   #177
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Thumbs up LM3875 rocks!

Well done Mubeen!.and yes,these fellas when they are build properly they sound really good. They produce very clean and fast sound.They can beat easily some of the good "commercial"ones out there. Enjoy your LM3875 amp!
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Old 20th July 2008, 11:34 AM   #178
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Default Re: LM3875 rocks!

Quote:
Originally posted by lanchile07
Well done Mubeen!.and yes,these fellas when they are build properly they sound really good. They produce very clean and fast sound.They can beat easily some of the good "commercial"ones out there. Enjoy your LM3875 amp!
Thanks mate! Its already beaten my 450 quid worth of 'commercial' amp
'commercial amp' definitely has clearer trebel and thats where it excels, buts thats where its excellence ends. It lacks everything else. It clearly does not have the flow and dynamics of chip amp. It seems rather 'choked/clogged' compared to chippy. I am simply amazed!

This despite the fact that i used ordinary wires and volume pots for assembly, with bit longer signal path due to large case.

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Old 21st July 2008, 02:36 AM   #179
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Thumbs up Lm3875!

'commercial amp' definitely has clearer treble and thats where it excels...

Well,I have noticed and compared that these amps are NOT fatiguing as some commercials ones.You can listen to them all day long. I believe is because it's "delicate" trebles.
Some people like a lot treble,but if you are going to listen to it for a long period of time the sound becomes fatiguing.
I had so many amps like:
Marantz,Luxman,Adcom,Arcam,portal panache etc. but I still like the LM3875 GC better.
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Old 21st July 2008, 05:12 PM   #180
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Default Source selector

Hi Peter,

finally I can start to build my first amp with the kit you sent me.

But I am a real beginner so please, can you address me where I can find instruction on the net about how to connect the input selector you sent me together with the kit? Even Decibel Dungeon on his beautiful pages dedicated to gainclone beginners shows a rotary input selector but seems that he did not explain how to do it.

The switch has 4 position and 12x3 pins but how to connect them?


Thank you

Renato
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