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