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Old 17th March 2006, 09:54 PM   #1
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Default Impedance matching


I have speakers with impedance of 6ohms. My PP amp's OPT's have taps for 4 and 8 ohms. What should I do?

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Old 17th March 2006, 10:12 PM   #2
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Default Re: Impedance matching

I have speakers with impedance of 6ohms. My PP amp's OPT's have taps for 4 and 8 ohms. What should I do?
Technically, the 4 Ohms tap should be better suited. But just chose the tap that sounds best to you. Chances are that it would be the 4 Ohms tap, too, since it would give a somewhat better damping factor (and a bit less output power, but you won´t notice that by ear w/o measuring the actual Po).

If in doubt, just measure.
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Old 17th March 2006, 11:48 PM   #3
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You don't mention in what mode your OP tubes are connected and this makes a difference, as I'll try to explain below:

* With triodes or triode-strapped beam tetrodes/pentodes, it's better to err on the side of a higher impedance than a lower impedance, so use the 4 ohm tap with a 6 ohm speaker.

* In tetrode/pentode mode, the opposite is true, i.e. it's better to load them with a lower impedance, by using the 8 ohm tap with a 6 ohm speaker.

* For ultralinear connection, there is more leeway and it probably doesn't really matter which tap you use. However, in general with UL, using a higher load impedance (the 4 ohm tap) will give less power and less distortion, while using a lower impedance (the 8 ohm tap) will have the opposite effect.

The above is just a general guideline and what works best for you may depend very much on your actual speakers. As you're probably aware, the nominal impedance of a speaker is an average that sometimes doesn't mean too much; the actual impedance can vary all over the place with frequency, depending on speaker design.
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Old 18th March 2006, 12:55 AM   #4
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Thanks for your answers

It's wired ultralinear, I've had it running on 4ohms and it was load enough; I was just worried about damaging something.
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