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Old 1st June 2005, 06:38 PM   #1
philb is offline philb  Canada
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Smile My finished amp

Here are some pictures of my new amp, it uses the national semiconductor lm3875 chipamp. It is the second amp i build and find that the bass response on this amp is not nearly as strong as the lm1875. Why is this? the schematic is the same as the brian gt ones, no z-network or snubber caps. The supply caps are 2200uf for each board and i am using a bridge rectifier and a 150VA torroid transformer that I modified slightly to get the proper supply voltages.

Anyway hope you enjoy the pictures. Oh yeah this amp cost nothing to build beside the shipping on the lm3875's, i had everything lying around already, and even borrowed from an old broken sony tuner (The speaker jacks).
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Old 1st June 2005, 06:39 PM   #2
philb is offline philb  Canada
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Smile pic 2

pic 2
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Old 1st June 2005, 06:41 PM   #3
ble0t is offline ble0t  United States
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Nice work!

Any internal pics?
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Old 1st June 2005, 06:42 PM   #4
philb is offline philb  Canada
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Default pic 3

your very quick i didn't even have time to post the last pic.

here are the insides
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Old 1st June 2005, 07:21 PM   #5
NITRO is offline NITRO  Turkey
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Default Re: My finished amp

Quote:
Originally posted by philb
it uses the national semiconductor lm3875 chipamp. It is the second amp i build and find that the bass response on this amp is not nearly as strong as the lm1875. Why is this?

I encountered same situation too.First i build a 1875 amp then a PA100 with LM3886.Both amps builded same as with national semi's datasheets included.Suprisingly LM1875 amp (with a tiny 30 VA transformer) sounded basses powerful and deep instead of PA100.Then i changed some component values (input coupling caps and especially feedback caps called Ci in datasheet) and finally amp sounded good.

Türker
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Old 1st June 2005, 10:32 PM   #6
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Nice amp philb! Looks good!
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Old 1st June 2005, 10:50 PM   #7
philb is offline philb  Canada
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Smile thanks nitro

I'll try changing some of the components, after all i did just use things that i already had. Maybe some panasonic fc caps would be a nice touch. If i get to it anytime soon i'll post back on the difference.
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Old 2nd June 2005, 12:01 AM   #8
Hugh M is offline Hugh M  Canada
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Thats a sweeet little amp. Nice work Philb.

Hugh
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Old 2nd June 2005, 12:53 AM   #9
cowanrg is offline cowanrg  United States
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nice job. i like the incorporation of wood. its something that needs to be done more often i think. i like the organic look of some electronics.

one of my next projects is to revisit the chip amp and see what i can make of it. i like the freedom it allows you in the design aspect.
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Old 2nd June 2005, 04:16 AM   #10
Leolabs is offline Leolabs  Malaysia
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Internal wirings look a bit messy.Try to tidy them up
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