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GREAT Tube Magazine [message #495] Tue, 01 June 2004 17:38 Go to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18794
Registered: January 2001
Illuminati (33rd Degree)
Last week, after visiting with Eric and Charles, I ordered a subscription to Vacuum Tube Valley, the new sponsors here. Today, I found a magazine in my mailbox and I must say, I'm very impressed.

Folks, this is one fine publication. Great looking photos, excellent articles both in writing style and content. The magazine is also put together nicely with quality paper and covers. I usually refer to magazines as rags, but this one is more like reference. These are keepers, destined to be kept for life right along side my 1970's Byte magazines and other collectable periodicals.

One thing I like about this magazine is that it combines technical content with editorials and reviews. To tell the truth, I prefer magazines with interesting tech talk to those that are heavy in reviews and editorials. Really anyone can go on and on about their opinions, but it takes something more to discuss things like why a particular grid geometry is chosen in certain situations and things like that. The guys at VTV are capable of this kind of informative discussion, and I like that.

I tended to always prefer tech-talk style magazines to review rags. You would find me completely bored with Car and Driver, for example, except to look through the great photographs. But some of the old Hot Rod magazines were just great. Sure, they have the same old articles every few years, the Holley rebuild, the intake shootout, the gears for Nine-inch Ford. But it's all pretty good information for the new guy entering the hobby. It will wet his whistle. Car and Driver is a fine magazine too, but it is really more for sitting in the dealership floor or in the dentists office. No one really reads it.

Same thing goes for electronics magazines. I'm not saying that I think one is better than the other. But I do prefer a certain style, which is a little more technical, and describes how's and why's and maybe gives a little bit of interesting history. If that's what you're looking for in a tube hi-fi periodical, I suggest you give Vacuum Tube Valley a try. It's really a great magazine.

On a related tubey note [message #497 is a reply to message #495] Tue, 01 June 2004 19:38 Go to previous messageGo to next message
Mike.e is currently offline  Mike.e
Messages: 471
Registered: May 2009
Illuminati (1st Degree)
Hi wayne, do you have the URL for that PDF regarding new ways of measuring amplifiers,superseding simple THD ?

It was rather good,but ive changed pcs since!

and im really interested in how Theory turns into reality,and how measurements dont display always good sound,but sometimes :P

Im lookn at simple designs,like DoZ and alternatives like mosfets,just to hear the difference.

Id like to get a SB live card for my pc,to ensure low distortion source! (integrated everything on mobos thesedays MUST have drawbacks!)



Another link [message #499 is a reply to message #497] Tue, 01 June 2004 20:08 Go to previous messageGo to next message
Mike.e is currently offline  Mike.e
Messages: 471
Registered: May 2009
Illuminati (1st Degree)
From our knowledge of Fourier analysis, we can be confident that the waveform tells the whole truth and nothing but the truth.

'The waveform contains no 'secret' information as to whether it was produced by a tube amp, a solid-state amp, a digital waveform generator or hundreds of sine wave generators operating in parallel, for that matter," he said.

"The mathematics of Fourier assures us of this. If we can make a solid-state amp produce the same waveform as a tube amp when it clips - including duty-cycle modulation - then we have successfully simulated the tube amp with solid-state components."


A Taste of Tubes [message #500 is a reply to message #499] Wed, 02 June 2004 10:27 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18794
Registered: January 2001
Illuminati (33rd Degree)
I can think of a dozen links that discuss various measurements and their importance. But I can't recall exactly which one you mean. Most tube enthusiasts tend to say that high amounts of low order distortion aren't annoying and they place emphasis on high order artifacts. Some get into the proportions of various harmonics and what not.

Personally, I'd expect that low amounts of distortion are best. But since speakers almost always generate over 1% second-harmonic content, I can see why maybe a tube amp making 0.5% might not be really noticable. Solid state amps can bring this down to 0.001% and figures like that.

As long as the amp isn't clipping, neither amp generates a lot of high orders, but when an amp is clipping, the transistor amp makes a sharp edge as the signal hits rail voltage, and that is equivalent to saying it generates multiple harmonics, including high order ones. A tube amp rounds the edges, so while the waveform produced is still artificial and distorted, it isn't quite a raspy sounding and harsh.

So my suggestion is, no matter what kind of amplifier you have, don't push it into clipping.

Sorry I couldn't think of the specific URL you wanted. But here's one you might enjoy:



are ppl clipping? [message #504 is a reply to message #500] Thu, 03 June 2004 00:50 Go to previous messageGo to next message
Mike.e is currently offline  Mike.e
Messages: 471
Registered: May 2009
Illuminati (1st Degree)
is that why people remark on the differences? because they ARE clipping their small valve amps?? so there is warm clipping...

If they WERENT clipping and it did sound different itd really make you wonder


am downloading that pdf :-)



Re: On a related tubey note [message #507 is a reply to message #497] Thu, 03 June 2004 07:23 Go to previous messageGo to next message
Adrian Mack is currently offline  Adrian Mack
Messages: 568
Registered: May 2009
Illuminati (1st Degree)
> Id like to get a SB live card for my pc,to ensure low distortion
> source! (integrated everything on mobos thesedays MUST have
> drawbacks!)

Yep, well at least my onboard soundcard is a LOT worse than my SB live 5.1 sound card. The onboard sounds real dull and lifeless, and also sounds like its frequency response output is crap (it was ages ago but I think I found it had like no top end). The SB Live 5.1 is 100x better.


So what differentiates amplifiers then? [message #508 is a reply to message #499] Thu, 03 June 2004 15:07 Go to previous messageGo to next message
akhilesh is currently offline  akhilesh
Messages: 1275
Registered: May 2009
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Then why do amplifiers sound different?
-akhilesh

Re: So what differentiates amplifiers then? [message #510 is a reply to message #508] Thu, 03 June 2004 18:47 Go to previous messageGo to next message
Mike.e is currently offline  Mike.e
Messages: 471
Registered: May 2009
Illuminati (1st Degree)
The problem i think is,that steady state sine although music contains it and its all music is , it doesnt show the dynamics.

A better way would be a-b testing etc

I havent been rich enough to afford many amps,im stuck with a 2x15w a/b kitset for now ,so i cant possibly comment if amps ive heard sound different!

My two cents [message #511 is a reply to message #510] Thu, 03 June 2004 20:34 Go to previous messageGo to next message
Dean Kukral is currently offline  Dean Kukral
Messages: 177
Registered: May 2009
Master
I haven't listened to as many amps as most of you guys, but I can pretty truthfully say that I haven't heard much difference from one to another. But then, I haven't listened to them A/B nor through very high dollar speakers which might demonstrate differences better.

I Have heard massive differences from one speaker to another, however. The difference between a couple of decent amps is nothing compared to the differences between speakers!

I guess that is one of the reasons I get so bent out of shape reading reviews describing all the differences between speaker cables. I think that if you can actually hear a difference between two cables, then at least one of them is defective. (This assumes that they are of adequate size to carry the load.)

In my opinion, for those of us building a system on limited budgets, most of our money should go into the speakers.

(This applies to home sound, not professional stage reproduction, about which I know nothing.)

Re: My two cents [message #514 is a reply to message #511] Thu, 03 June 2004 23:35 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18794
Registered: January 2001
Illuminati (33rd Degree)
I find there's much more difference between tube amps than between solid state amps. I expect this is because output transformers and amplifier configuration makes a big difference in frequency response, which is the most immediately noticeable quality of a sound system. It's kind of like there's a bit of EQ built-in to some tube amps, and the there is more dependency or interaction with other components too. So there's more noticeable difference between tube amps than between solid state amps.

Take a couple of direct coupled solid-state amps and set them up so that the ouput signal is 10 volts peak to peak. With the same input signal, it is pretty hard to tell a couple good units apart. But take a couple of fine tube amps and do the same thing, and you can often tell a difference right away. One will have a little more bass than the other or something.

Notice I specified direct coupling for the solid-state amps and didn't mention amp configuration on the tube amps. That's a big part of this deal. Many solid-state amps are direct coupled. An exception is Class A amps which are most likely RC coupled. You'll notice some difference between an RC coupled Class A solid state amp and a direct coupled complementary-symmetry solid-state amp. I don't think it is as immediately noticeable as some of the differences in tube amps, but you can still tell.

As for tube circuits, a parafeed amp is likely to be more powerful in the bass than a standard transformer coupled amp, at least if they are about the same power, size and weight. But still, these differences in tubes, configuration and output iron make noticeable differences in tube amps, and you won't generally find such differences between modern solid state hi-fi amps.

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