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OTL Asylum OTL, Output Transformerless Amplifier User Group. |
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In Reply to: Negative Feedback in Atma-Sphere amps posted by Rushton on January 23, 2005 at 16:17:42:
Hi,> The M-60s have about 0.5db of negative feedback if I recall
> correctly (hardly a huge amount).The current M60 lists as follows:
Output Impedance: ~4.1 Ohms
Feedback: 1 dbIt seesm the feedback has been reduced from earlier versions (good idea), if at the cost of an output impedance a bit on the high side for the real world.
> The MA-1 and MA-2 have always had ZERO negative feedback.
> The newest ver.3 of the MA-1 and MA-2 now includes
> switchable negative feedback for 0, 1 or 2db.So NFB was added.
I agree however that these leves are much less than what memory told me, especially on the subject of the M60.
Still, it would seem that M60 has around 5 Ohm Output Impedance without NFB which makes using it with conventional speakers a little difficult. The 6db or so NFB I remembered would have brought this down to a more usefull 2.5 Ohm, now more less on parity with a typhical SE Amp on the 8 Ohm Tap.
However, these fairly low levels of NFB (as also found in the Graaf) underscore why I listed them among my favourites, strictly on sound, as I did not dive too deeply into their designs. And why the SEPP OTL's I have heards all where much worse.
It's probably worthwhile for people considering OTL's to read carefully the various specifications found on AtmaSphere's website.
So my recommendation to djn remains as written, try a M60 Clone, there is enough info out there to do that.
Ciao T
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Follow Ups
- Re: Negative Feedback in Atma-Sphere amps - Thorsten 00:27:21 01/24/05 (1)
- PS.... - Thorsten 00:52:09 01/24/05 (0)
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