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Old 19th June 2007, 12:19 PM   #1
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Angry Suggestion for LM1875

Hi,

During the search I got this circuit using LM1875 , can any one told me that can I use the same circuit for 3 Way Active Crossover with combination of LM3886.

Actually why I prefer this because of very small PCB , but I dont know how it function or does it good idea to use this apart from standard circuit present on LM1875 datasheet given by Nationl Semiconductors. This circuit has less n less components and very very small PCB.


And one more thing dear if its an good idea can I use the same circuit with +- 15 Volts or more upto +- 20 Volts.

Please guide me.

Actual Circuit suite is :

http://www.headphoneamp.co.kr/bbs/zb...esc=asc&no=202
Attached Images
File Type: gif lm1875t.gif (35.4 KB, 853 views)
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I am not a technical person in this audio field but its my hobby . I want to make HiFi audio system for my home use. Please any one can help me to make it by providing guidelines.
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Old 19th June 2007, 02:12 PM   #2
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hi makarand_g,

Have a search for zero one threads on LM1875, he's doing something similar, here's one
Tweeter Clone

You should have no problem running the LM1875 on higher voltages using that ciruit, I'm not 100% sure about the rail splitter but it should be OK, but I'd avoid using a rail splitter if possible.

regards
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Old 2nd July 2007, 04:38 AM   #3
Malquis is offline Malquis  Argentina
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I've an LM1875 running with +-32 V 64V and it hasn't burned yet !!
it drives an 8'' subwoofer for my home theater I've made it suffer but he doesn't want to die so don't worry abou it. And about the splitter I would avoid it to it's easier and better to use a split transformer.
Regards.
Malco
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Old 2nd July 2007, 05:01 AM   #4
gootee is offline gootee  United States
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I know nobody except me seems to like rail-splitters. But I've been using one based on the LM1875T for a long time and it works well. Look at the LM675 datasheet, at national.com. Mine is similar to the one they show, there. But I use the LM1875T, instead of the LM675. Mine splits 35V into +/-17.5V. I only draw about 1.5A max, though. So you might need to use one of the other chipamps, if you need more current (or voltages that are too high for the LM1875).

- Tom Gootee

http://www.fullnet.com/~tomg/index.html
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Old 6th April 2008, 11:14 PM   #5
simsim is offline simsim  British Indian Ocean Territory
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@Gootee

I'm also interested in using the LM1875 as a rail splitter (it's half price compared to the LM675 at the only electronics shop here). So far I have been limited to building single supply amps (using the 1875 actually). Do you think I can use it as an exact replacement, keeping the other component values in the LM675 datasheet typical applications? I'm new to electronics and don't want to mess with mains electricity yet.
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Old 6th April 2008, 11:24 PM   #6
paulb is offline paulb  Canada
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I think it should work, but if you're just using it to power an LM1875 power amplifier why not just use the single-supply version of the LM1875 amp? Or, if you speakers are at least 8 ohms, use a bridged version (also called BTL).
Anyway, it should work. Wire it up and try it out.
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Old 6th April 2008, 11:48 PM   #7
simsim is offline simsim  British Indian Ocean Territory
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Hi

I have already built a couple of 1875 amps using the single supply circuit, I would just like to use the split supply circuit to see what the split supply fuss is all about :-)
Also, there is a lot of used power supplys to be found at thrift stores and similar places, it would be nice if you could 'recycle' them, find a new use for them, but a lot of diy audio projects use split supply and I haven't run into one of those.
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Old 6th April 2008, 11:50 PM   #8
simsim is offline simsim  British Indian Ocean Territory
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I will try it out. thanks for your reply!
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Old 7th April 2008, 01:21 AM   #9
Malquis is offline Malquis  Argentina
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The single supply circuit works just fine but it's a bit more complex and if you are also working with active crossovers it gets harder with the ground artificial grounding is not funny to me and it makes circuits more complex also having to add a series capacitor like in class A amps which degrades bass response. but if you are just using and building a simple amp single supply circuits works just perfect.
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Old 7th April 2008, 02:42 AM   #10
simsim is offline simsim  British Indian Ocean Territory
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The single supply amp I built from the datasheet has a 2200 uF capacitor in series with the speaker. You mean it degrades the bass? I didn't know that.
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