Need advice - 25 volt transformer with LM3875

[commoncollector]

I have an LM3875 kit from audiosector.com and I happen to have an Avel 250VA 25v transformer kicking around. Looking at the datasheet and reading in the forums here, it appears as though 25v is the upper end of what will work well for an 8 ohm load. I thought I had 8 ohm speakers, but checking the impedance graph and reading the plans, it appears as though the nominal impedance is more like 4 ohms. See the attached graph.

So my question is, should I get a lower voltage transformer or use the 25 volt one I have?

[Nuuk]

Yes, get an 18v traffo, or use a regulated supply to bring down the voltage on the one that you have.

[AndrewT]

that looks like it might be a 4ohm Bass/mid driver and an 8ohm treble with a Zobel on it to reduce HF impedance.

This style of 4 to 8ohm has become very common. A chipamp must be designed as a 4ohm capable amplifier to drive these effectively.
18Vac, as Nuuk says, is about right.

[commoncollector]

that looks like it might be a 4ohm Bass/mid driver and an 8ohm treble with a Zobel on it to reduce HF impedance.

Heh, you nailed it!

Thanks for advice! I'll get an 18v xformer.

[sandyhooker]

Originally posted by commoncollector


Heh, you nailed it!

Thanks for advice! I'll get an 18v xformer.

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