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On Sat, 06 Oct 2012 17:19:57 -0500 |
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Dale <rdalek1967@×××××.com> wrote: |
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> Alan McKinnon wrote: |
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> > I've promised myself for years since my apprentice days that I would |
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> > one day built a valve amp from a kit. There's something about the |
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> > warm glow from the tubes on a winter night that is appealing :-) |
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> > I'd better hurry up and get on with it, I read that decent quality |
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> > valves are becoming scarce and are generally only available from |
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> > (what used to be) the USSR. |
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> |
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> Found a few sites for ya: |
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> |
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> http://tctubes.com/about-us.aspx |
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> |
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> http://electrontubestore.com/index.php?main_page=contact_us |
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> |
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> http://www.tubesandmore.com/customer_service/about_us |
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> |
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> I found that by typing 6gh8a in google. That's a old tube that I used |
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> to have to replace pretty regular. I think it was used in the audio |
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> section and would usually work fine when cold but get a bit weird when |
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> it gets good and hot. They got replaced a LOT back then. Anyway, two |
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> are in the USA but one is in Canada. |
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Cool finds, thanks! |
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Maybe I should go-ahead and build an amp and be done with it. No more |
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mucking about putting it off :-) |
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> Maybe you got more time than you think. ;-) I do think the old tubes |
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> have better sound tho. I can't explain it but they just sound |
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> different. |
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You're not imagining things. Valves do sound better and you can measure |
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it and see why. |
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Valves and transistors both distort sound to some degree as all |
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electronic systems will. The difference is in how the distortion |
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happens. |
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Semiconductors are prone to even-harmonic distortion, so if you have a |
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100Hz sine wave, it will produce distortion at 100hz, 400Hz, 1600Hz and |
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so on. Valves produce odd-harmonic distortion, at 200Hz, 800Hz and so |
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on. |
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If you are now thinking "Fourier" and wondering if transistors try to |
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make square waves, you are bang on the money because that is exactly |
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what is happening. To the human ear, a square wave sounds like gross |
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horrendous distortion, even at very small percentages. At it's worst, |
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this is "clipping" and happens because a transistor will happily pass |
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current until the voltage drop over it hits the supply voltage and it |
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clips. Bingo, one square(ish) wave and horrible sound. |
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Valves deal with this in a more "analog" fashion, as the voltage drop |
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nears the supply voltage it passes less and less current, rounding the |
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waveform and never actually clipping it. Which sounds far more pleasant |
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to the human ear. |
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Modern circuitry tries to avoid the transistor problem using "soft |
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clipping" and other tricks - basically trying to make the transistor |
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behave in the same way a valve oes. This does make a huge difference, |
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but you can never completely eliminate the device's inherent |
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characteristics, it is what it is and this leopard doesn't change it's |
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spots. |
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> I think that is why some places still have tubes. Some |
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> people just like them more. I think they make great heaters. lol |
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> |
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> Dale |
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> |
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> :-) :-) |
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> |
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-- |
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Alan McKinnon |
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alan.mckinnon@×××××.com |
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