Halve Impedance When Replacing 2 OTs with 1?

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The New Steve H
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Halve Impedance When Replacing 2 OTs with 1?

Post by The New Steve H »

I built an amp with two OTs in parallel. Don't ask me why. I want to build a similar amp with a single OT, feeding the same number of tubes.

Question: to get the same sound, should I get an OT with half as much impedance? I assume that's right, since the other OTs were paralleled.
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Firestorm
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Re: Halve Impedance When Replacing 2 OTs with 1?

Post by Firestorm »

If primaries and secondaries were both parallel, the reflected impedance doesn't change. Inductance and winding resistance are halved.
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The New Steve H
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Re: Halve Impedance When Replacing 2 OTs with 1?

Post by The New Steve H »

Thanks!
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Zippy
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Re: Halve Impedance When Replacing 2 OTs with 1?

Post by Zippy »

What are you going to do with the speakers? Put them in parallel, series, or just one?
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The New Steve H
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Re: Halve Impedance When Replacing 2 OTs with 1?

Post by The New Steve H »

I don't have the amp in front of me right now, but somehow or other, I connected both OTs to the same set of speaker jacks. I use it with a 1x12 8-ohm cabinet. It has a 2-gang PPIMV, so you can run one OT at a time. I thought this was a great idea, but it really isn't all that exciting in practice.

I love the amp's tone, but the PT is too small for the current draw, so it gets hot. I have some concerns about burning it up. I want to put a bigger PT in it (Edcor EM0827). If I'm going to go to all that trouble, I figure I might as well get rid of the two-OT setup, which is a bit weird. I am figuring that when I make the new chassis, it will be easier to avoid hum if I only have one OT to deal with.

I was afraid that going to a single OT would mess up the tone, but it sounds like I'm safe. I would like a little more bass, but other than that, it's very nice.
Relax. It's SUPPOSED to smoke a little.
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