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Old 6th November 2011, 07:38 PM   #1
Haz is offline Haz  United Kingdom
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Default Any thoughts on the LM3875?

Hello

I would like to know what people here think of the LM3875 from national semiconductor. I ask as I want to build an amplifier based on the chip with the many bare PCB's on ebay.

I know that their is more to an amplifier eg. pcb layout and design, and the components used, But what does it sound like?

Thank you.
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Old 6th November 2011, 07:40 PM   #2
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If constructed well, and used within thier limitations, they can sound quite nice.

Mike
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Old 6th November 2011, 11:54 PM   #3
! is offline !  United States
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It sounds like a moderately detailed class A/B amp chip. Whether you like that more or less is something only your ears can compare. Most who build with it are satisfied with the result although people tend to feel more elaborate, more expensive amps sound better but that is to be expected, people need to feel their time and money are invested well and in some cases something else really does suit the application better so the real question is, does that particular chip seem well suited for an amp with the parameters you desire?

To put it another way, the best amp is not one where you fixate on one chip then build an amp around that chip, rather than you decide what kind of amp you want to build then pick components suitable for it. Unless the only priority is keeping price low, there are other PCBs for other chips too or even having a PCB house make a board for you... it might cost a few dozen dollars but if you are spending a lot more than that in total it is a reasonable expense to get exactly what you want.
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Old 7th November 2011, 07:57 AM   #4
Haz is offline Haz  United Kingdom
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Join Date: Oct 2010
Quote:
Originally Posted by ! View Post
It sounds like a moderately detailed class A/B amp chip. Whether you like that more or less is something only your ears can compare. Most who build with it are satisfied with the result although people tend to feel more elaborate, more expensive amps sound better but that is to be expected, people need to feel their time and money are invested well and in some cases something else really does suit the application better so the real question is, does that particular chip seem well suited for an amp with the parameters you desire?

To put it another way, the best amp is not one where you fixate on one chip then build an amp around that chip, rather than you decide what kind of amp you want to build then pick components suitable for it. Unless the only priority is keeping price low, there are other PCBs for other chips too or even having a PCB house make a board for you... it might cost a few dozen dollars but if you are spending a lot more than that in total it is a reasonable expense to get exactly what you want.
Thanks for your post.

I pan to use high quality components. and if I'm not satisfied with the result I
will just build something else I choose the LM3875 due to its simplicity and parts needed to get a working amp. As I'm trying to build up more experience.

So far ive built 3 headphone amps including a cmoy, But ive always liked listening to music though bookshelf speakers. The amp will be up against my arjenhelder TK2050!!
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Old 7th November 2011, 08:40 AM   #5
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Location: South East. UK
Quote:
Originally Posted by Haz View Post
Hello

I would like to know what people here think of the LM3875 from national semiconductor. I ask as I want to build an amplifier based on the chip with the many bare PCB's on ebay.

I know that their is more to an amplifier eg. pcb layout and design, and the components used, But what does it sound like?

Thank you.
With the amount of external components needed to get a working amp, I would recommend building it 'point to point'.

Have built several this way, and the benefits are they are easy to modify without the PCB. Built this way a very good amp can be built, for not a lot of cash.

The 3875 is my favourite out of 1875,3886,4780, it seems to produce very good audiable results.
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Old 7th November 2011, 09:43 AM   #6
AndrewT is offline AndrewT  Scotland
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Location: Scottish Borders
Do not omit input filtering.
Do not build DC coupled.
Do not omit stability enhancing components.
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regards Andrew T.
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