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OTL Asylum OTL, Output Transformerless Amplifier User Group. |
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OTL Asylum OTL, Output Transformerless Amplifier User Group. |
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In Reply to: A comment posted by Lew on January 24, 2005 at 07:06:36:
Hi,> you should know that the Atma-sphere amps operate well
> (in my system, optimally) with no NFB whatsoever.Good on you. Compatibility will always depend. I also note that I did not remember correctly the amount of NFB on the M60, or maybe it has been reduced in recent revisions.
> Moreover, there are fundamental differences between designs
> based on the circlotron (Atma-sphere et al) and those based
> on the original Futterman circuit,Absolutely. I much preferred the Circlotron type Amp's over the SEPP (aka Futterman) versions.
> Also, I hesitantly would say that the use of an autoformer
> at the speaker-end of cables, to boost the impedance seen
> by OTL amps on the order of 2X does not present the problems
> inherent to the design of a transformer-coupled output stage.Sorry, transformers are transformers. They have magnetic cores which do all the hard work. These cores are subject to certain issues, as are the actual windings. Autoformers do not change this in the least. It is still a magnetic coupling device. It may be easier to make a decent low ratio autoformer, but it is not that hard to make a good higher ratio transformer.
> In other words, the autoformer/OTL strategy is potentially
> less "harmful" to the signal than the OTC strategy.Moreso actually, when compared to a good SE Design. Simply because the bias current in an SE Amp and the Airgap make the transformer core very linear. The key problem in SE Transformers is at very low frequencies, where the hearing and perception is a lot less acute then in the midrange.
Ciao T
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Follow Ups
- Re: A comment - Thorsten 11:44:43 01/24/05 (0)
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