Two LM1875 MARKAUDIO CHR-70 8ohm computer audio - diyAudio
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Old 29th December 2015, 06:21 PM   #1
Nag is offline Nag  United Kingdom
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Default Two LM1875 MARKAUDIO CHR-70 8ohm computer audio

Dear All,
I am planning to build stereo Mark audio chr-70 (8ohm) speakers with lm1875 for desktop use only.
I am always listen low volume. I am struck at power supply.
I am planning to buy 18-0-18 36VAC toroidal transformer.
36VAC is enough for low volume usage ?. (low price for budget build)
Can I go with official circuit diagram for computer usage ?.

Thanks for your help.
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Old 29th December 2015, 07:03 PM   #2
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18-0-18 will give you close to maximum B+ for the LM1875. You might consider a slighly lower voltage. What is the VA of the former?

dave
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Old 29th December 2015, 08:24 PM   #3
Nag is offline Nag  United Kingdom
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Dear Dave,
Thanks for your quick reply.
Primary Voltages: 1 x 230V
Secondary Power: 18VA each (Total two).
one transformer to power two LM1875 chips.
any changes required in official circuit diagram?.
I am connecting computer on board out put to amplifier input.

Thanks.
Nag
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Old 29th December 2015, 10:52 PM   #4
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What is the rated VA? All the rest we knew.

I used 225VA 18-0-18 trafos on my LM3875. For an LM1875 you likely want a minimum of 80 VA per stereo amp, twice that would be better.

dave
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Old 30th December 2015, 11:26 AM   #5
Nag is offline Nag  United Kingdom
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Dear dave,
As per your suggestion I am going with Transformer 3A 15-0-15V (EI low budget). So total 90VA for sterio amp.
Thanks.
Nag
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