Why SE in SET amps? [message #11382] |
Mon, 03 September 2007 23:41 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
granch
Messages: 118 Registered: May 2009
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Viscount |
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Could someone succinctly explain to an old duffer like me why it has to be "SE" in Triode amps. In my youth that was asking for even order harmonic distortion which a push-pull would cancel. My first big project involved replacing a push-pull parallel 2A3's amp with another to get more power in a high school auditorium. I must have been committing a terrible sacriledge (unintentionally, of course). I was so innocent in those days I even tried to explain negative feedback by going around the loop and got myself lost. Granted even order distortion is less objectional to the ear than odd order. But wouldn't less be even better? Please no cursing, folks. -Dick
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Re: Why SE in SET amps? [message #11383 is a reply to message #11382] |
Tue, 04 September 2007 08:46 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18752 Registered: January 2001
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Illuminati (33rd Degree) |
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It's probably not something you'll be able to discuss in terms of math. If you look at the numbers, you're right. Push-pull offers lower distortion. Well-executed solid state even lower distortion. But to a SET purist, push-pull is "flat and uninvolving" and there is no such thing as well executed solid state. They're lured by the warmth of SET magic.There are two things that may explain some of the reasons why people prefer SET. For one thing, Class A amplifiers have no crossover distortion. The entire audio signal is handled by one amplifying element. And for another thing, the distortion that is made is largely low-harmonics, mostly second and third. This is mostly due to the fact that the tube conductivity isn't perfectly linear, and doesn't have anything to do with more complex things like feedback nonlinearity. A tube clips gracefully too, not with sharp harsh-sounding square edges but almost sounding like it just won't go any further. So without resorting to romantic adjectives, you can see some things that may be part of the SET magic.
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Re: Why SE in SET amps? [message #11386 is a reply to message #11384] |
Wed, 05 September 2007 07:12 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
SteveBrown
Messages: 330 Registered: May 2009
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Grand Master |
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Dick, while it isn't exactly a kit, there is a really nice design called the SETH that you can find info on at the Magnequest website. This is a PP triode design using 2A3's. I built it using PP iron salvaged from a Fisher 500C receiver, 6550's strapped in triode mode, and in a stereo chassis. I have to say, it sounded great. The secret here is the phase splitting transformer, which provides a very elegant way to split the phase, is easier to implement than tube splitters, but costs more. At any rate, others who have heard my PP amp agreed that it was one of the better PP designs they'd heard. I've built lots of PP and SE amps and they each have their charms. The PP stuff definately seems to control the bass better, and the SETh design maintains the integrity of the mids and highs as well - without making them sound strained or dead, as many amps using feedback seem to do. Anyway, hope that helps. The MQ site has extensive info on building one of these, and again, you don't have to be stuck using just MQ iron (though it is very good). I believe Jack at ElectraPrint also makes a splitter like this. Best of luck!
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Re: Why SE in SET amps? [message #11388 is a reply to message #11382] |
Fri, 21 September 2007 22:59 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
RC Daniel
Messages: 18 Registered: May 2009
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Chancellor |
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Hi Dick I have not posted over here for a long time; anyhow... I am thinking that (within reason) some folks may be more sensitive to the ratios of odd : even harmonc distortions, rather than absolute levels. Could a reduction in 2nd harmonic distortion expose odd-order artifacts or somehow make them more obvious / offensive? Hmmm, perhaps this is analagous to dietary intake of omega6 : omega3 fatty acids or blood HDL : LDL ratios and their effects on health? Got to run Raymond
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