Re: Zero Autoformers

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OTL, Output Transformerless Amplifier User Group.

In Reply to: Zero Autoformers posted by bmotorcycle on June 7, 2005 at 09:16:27:

First, you are not defeating the amplifier! Here's why:
The ZERO can do things no other transformer can. That is because of two reasons- first, it does not have to block DC, so it is much simpler and is an autoformer rather then a transformer. Thus there is only one winding, not two. Second, and much more important, a transformer of this capability would not be possible with a conventional tube amp. It is only possible if you start out with a low output impedance (relatively speaking) amplifier to begin with. The M-60 is a good example of that.
As a consequence the ZERO has much, much wider bandwidth then conventional transformers and is full power down to 2 Hz- unheard of in conventional designs!
Does it always work? No. But using the 4 ohm taps, I suspect that it makes your M-60s work much better with the Apogees then without. Apogees are not known for being tube friendly, BTW; this is a good thing.
Your speaker does not 'need' 3 ohms to work properly. What the ZERO is doing is loading the amp at about 16 ohms, and you are loading the 4 ohm tap at about 4 ohms, which is nominal for the speaker. It is not a 3 ohm load. I think you have also noticed that the speaker is not that hard to drive, once the impedance issue is dealt with.
The transformer seems to have a break-in period, and also has about a 1/2 hour warmup characteristic. So you have to allow for those two things as well, and if I were you I would experiment with speaker cables, unless you have the type that has the cables integrated into the unit.
Contact me if you have any other questions.

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Follow Ups Full Thread

Topic - Zero Autoformers - bmotorcycle 09:16:27 06/07/05 (1)

Re: Zero Autoformers - Ralph 10:55:47 06/07/05 (0)

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Re: Zero Autoformers - Ralph 10:55:47 06/07/05 (0)

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