My finished amp

philb · 1st June 2005, 05:38 PM

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).

philb · 1st June 2005, 05:39 PM

pic 2

ble0t · 1st June 2005, 05:41 PM

Nice work!

Any internal pics?

philb · 1st June 2005, 05:42 PM

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

here are the insides

NITRO · 1st June 2005, 06:21 PM

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

Russ White · 1st June 2005, 09:32 PM

Nice amp philb!

Looks good!

philb · 1st June 2005, 09:50 PM

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.

Hugh M · 1st June 2005, 11:01 PM

Thats a sweeet little amp. Nice work Philb.

Hugh

cowanrg · 1st June 2005, 11:53 PM

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.

Leolabs · 2nd June 2005, 03:16 AM

Internal wirings look a bit messy.Try to tidy them up

1st June 2005, 05:41 PM	#3
ble0t diyAudio Member Join Date: May 2004 Location: Milwaukee, WI	Nice work! Any internal pics? __________________ gravity always wins

1st June 2005, 09:50 PM	#7
philb diyAudio Member Join Date: Feb 2004 Location: Canada	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.

1st June 2005, 11:01 PM	#8
Hugh M diyAudio Member Join Date: Sep 2004 Location: Saint John NB	Thats a sweeet little amp. Nice work Philb. Hugh __________________ Lots of Fun and Good sound too - Who could ask for more?

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1st June 2005, 09:32 PM	#6
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	Nice amp philb! Looks good!

1st June 2005, 11:53 PM	#9
cowanrg diyAudio Member Join Date: Apr 2002 Location: Lafayette, CO	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.

2nd June 2005, 03:16 AM	#10
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Internal wirings look a bit messy.Try to tidy them up

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