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Old 1st March 2004, 01:14 PM   #1
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Question LM3876 Gainclone, Bass shy

Hi,
I just built the inverted gainclone using LM3876. The changes were as follows
1> I used a 15-0-15 5 Amp transformer for the supplyand
2> I used 4700 uf capacitors as power supply buffers.
3> I even tried to paralleling 47uf at input making it 94uf but to no avail. Even my TDA2009 amp gives more bass.
Pls help.
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Old 1st March 2004, 01:17 PM   #2
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Hi, what circuit are you using for this one, is it the reference design from the NAtional data sheet, or some other variation that you have found around here. If we could get a better look at what you have built any limitations in there may become a little more obvious.
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Old 1st March 2004, 01:20 PM   #3
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What are the speakers? GC is not suited for all speakers.
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Old 1st March 2004, 01:22 PM   #4
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Question Link provided

I used the design found at

http://www.decdun.fsnet.co.uk/gainclone.html
Please go to 'Building the amp' section for the circuit.

Regards,
Goldy
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Old 1st March 2004, 01:24 PM   #5
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Default Speaker info

The speakers are self made two way with drivers of BPL origin which is a local brand here in India. I can undestand difference in sound but the bass is simply missing. How can this be?
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Old 1st March 2004, 03:29 PM   #6
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You did adjust for the different pinout of the LM3876 from LM3875? You did use a suitable resistor in your mute enable/disable wiring?
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Old 1st March 2004, 03:42 PM   #7
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Don't forget that chip amps need a few days to 'break in' and all areas of performance, expecially bass, will improve a great deal within the first 100-or-so hours of use. Also, have you got a big enough heatsink attached as a bigger sink means more bass

BTW, Nuuk's site (Decibel Dungeon) has schematics for amps based on the LM3875 chip - I presume this is what you mean...
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Old 1st March 2004, 03:51 PM   #8
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Question I am surprised

"You did adjust for the different pinout of the LM3876 from LM3875? You did use a suitable resistor in your mute enable/disable wiring?"

Yes I did.



"Don't forget that chip amps need a few days to 'break in' and all areas of performance, expecially bass, will improve a great deal within the first 100-or-so hours of use. Also, have you got a big enough heatsink attached as a bigger sink means more bass"

Does 'break-in' really have such a huge difference? Let me admit that I did not have a huge heatsink (I am running off a 15-0-15 supply). But how can heatsink affect bass. The heatsink were not too hot to justify a bigger one.
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Old 1st March 2004, 04:06 PM   #9
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Yes, breaking in new components, solder joints, wiring, etc always takes time. On my first IGC I noticed a very big improvement in sound from one day to the next (leaving it on overnight) for about three days.

A big heatsink really does give a different sound - this is one of those things I have tried and can say worked for me. Using just a couple of small pc chip heatsinks the igc ran fine (not too warm) but changing just the heatsinks for larger 6mm thick aluminium L-sections gave a much more solid sound. Some people have done quite a lot of work into this - those that agree seem to think that it is to do with the lower resonance of more massive heatsinks having less of an influence on the chip (making it more stable).
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Old 1st March 2004, 04:09 PM   #10
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The same thing goes for your case, the feet your amp sits on, your shelf/support system - they are all part of the cumulative effect on the amplifier components so try to make sure each part of the 'chain' is well made and stable.
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