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DanX 15th March 2008 05:06 PM

Using split rail supply for single rail DC
I want to add a preamplifier to my LM1876T IC amp using the DC supply available, it seems to work OK when connected to the DC+ and centre tap at the bypass capacitors but there is a loud hum on the audio output, perhaps an earth loop. When connected to the DC+ and DC- rails it blows the AC fuses. I have used the same preamp (LM1036N) in a battery powered portable amp with TB820M with excellent results (single rail setup) the DC goes into a standard 7812 regulator on the preamp board with a 220uf bypass cap before it. Any help would be much appreciated, I'm not einstein I just like to build my own electronic goods rather than buying them.
Thanks all,

TheMG 15th March 2008 05:18 PM

Your preamp requires a single-ended supply. It must be connected to the + rail and ground (center tap) of the power supply.

Hooking it up to +/- shorts the - rail to circuit ground.

The hum is likely a ground loop.

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