What exactly is the purpose of a tube in an amp?

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Robertt8

Robertt8

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What exactly is the purpose of a tube in...say an amp or microphone, and is there a huge difference between them?
 
Whay....... back when before the days of 2 cent transistors tubes provided the only form of amplification around. Transistors are simply two semi-conductors set in layers. You get either PNP or NPN, and it all reality they pretty much sound the same...(it has to do with clipping and how they clip or distort)
But tubes on the otherhand are a whole different story. Different types sound different. In all honesty if you are sensitive enough two tubes from the same company, same factory, and same lot can sound totally different based on if the tech built the innards before or after a liquid lunch. Look at the differences of what people pay for same brand tubes because they have "D-getters" or "Ribbed Plates." And just look at the difference in price between a made in China 12AX7 for $3 and a Telefunken Dimond Bottom 12AX7 going for $75 and often more.
There is some BS wrapped up in these things, but a lot of it based on fact.
-k
 
Bottom Line With a TUBE AMP VS Solid State Anything...


Tube = Serious Balls, Punch and Clarity

Solid State = Digital representation of the above....
 
Solid state was around long before didgital my friend. actually Solid state is as about as old to digital as tubes were to solid state. Solid state and digital are NOT the same thing. The Neve boards that everybody freaks out about are Solid State. Tons of high end "Vintage" modeled gear is Solid State. Solid State and Digital are two vastly different things. Not to tout the bennefits or debtriments of either technology but just want to point out that the two are not equivalent.
 
stranglerfig said:
Bottom Line With a TUBE AMP VS Solid State Anything...


Tube = Serious Balls, Punch and Clarity

Solid State = Digital representation of the above....
Click to expand...

ROFLMAO!

Voltage is voltage and current is current, amigo. Neither is digital.

Preamp tubes amplify mic voltage to LINE voltage.

Power tubes amplify the line voltage by many orders of magnitude, enough to drive a speaker and supply the current necessary to do so.

http://www.kbapps.com/tubes.html

"Tubes distort uniquely because as the signal emitting from the plate approaches its maximum potential, the tube gradually begins to react less and less to the original input signal. This results in a types of compression of the signal, and produces a soft clipping. Clipping occurs when the input signal increases but the maximum power has been reached. Thus the signal becomes cut off, or clipped. Transistors, on the other hand, react exactly the same to the input signals rights up to their maximum power; then they stop quickly, creating a sharp clipping. These different types of clipping produce different series of harmonics (overtones). When the transistor amp clips, it produces more odd-order harmonics (and in its worst case can sound hollow and dry), whereas tube distortion produces even-order harmonics. Tube distortion sounds warmer. It should be mentioned that various types of transistor and tube distortion are possible, depending the amp's design."
 
So tubes good clip, solid state bad clip, digital worse clip.
But if you stay below the clip level which is still best.
I would still like tube, but any other opinoins???
-k
 
clipping is a fifteen yard penalty to be avoided at all costs
 
c7, good explanation. Also, in a tube, electrons are flying thru space from one element in there to the other in a vacuum. Just an interesting point. But as far as preference, gotta listen.

But clipping type can't be the only reason for people perfering tube is it?

BWT I could swear the filament my tube in my pre used to glow brighter.

In kilowatt linear amplifiers, tubes are still the only way to go, BTW.
 
Before anyone runs out and buys the latest presonus tubepre because of this thread there is one thing that you have to remember. Good tube equipment is much more expensive to manufacture than good solid state equipment. To a home recordist on a tight budget this means that you will get a lot more bang for your buck out of a solid state pre that costs less than $1000, than you would a tube pre that costs less than $1000. Personally I wouldn't even look at a tube mic pre that costs under a grand; most of them just plain suck, but you can get 4 very nice channels of rnp or sytek for that price.
 
noiseportrait said:
Before anyone runs out and buys the latest presonus tubepre because of this thread there is one thing that you have to remember. Good tube equipment is much more expensive to manufacture than good solid state equipment. To a home recordist on a tight budget this means that you will get a lot more bang for your buck out of a solid state pre that costs less than $1000, than you would a tube pre that costs less than $1000. Personally I wouldn't even look at a tube mic pre that costs under a grand; most of them just plain suck, but you can get 4 very nice channels of rnp or sytek for that price.
Click to expand...
And how far under $1000? dbx 286a for $199? or is that sucky too?
 
junplugged said:
And how far under $1000? dbx 286a for $199? or is that sucky too?
Click to expand...

i think most peoples problem with cheap tube preamps is that they aren't 100% tube and they're a starved plate design (i think that's what it's called).......which to be completely honest with you, i dont really understand..........but i think that it means that the tube isn't recieving enough power. plus the signal going out to tape is going through a solid state amp rather than a tube. power tubes are where you get the bulk of your tone and the best sounding clipping/distortion.

disclaimer: this is the way i remember it, but i have a terrible memory, so do a search......i've seen a few people talking about this in the past.....i dont know what you would search for though.

i've just decided that i'm not going to buy cheap tube gear based on the fact that tube gear is more expensive to build therefore a solid state pre amp will probably give me "more bang for the buck."

hopefully one of the guys that knows more than me will jump in and clear up any of my misinformation/clarify anything that i said that doesn't make sense.
 
SSL? Doesn't that stand for Solid State Logic...I think it does ;)

Sorry, just thought I would add to the notion that solid state is not some red-headed stepchild. Actually there is probably a lot more high quality solid state gear than there is tube gear (unless you're talking about guitar amps) for exactly the reason that noiseportrait stated.
 
donkeystyle said:
i think most peoples problem with cheap tube preamps is that they aren't 100% tube and they're a starved plate design (i think that's what it's called).......which to be completely honest with you, i dont really understand..........but i think that it means that the tube isn't recieving enough power.
Click to expand...

The starved plate design provides less voltage to the tube than intended. This results in the tube saturating more rapidly than normal. The associated sound is often referred to as a caricature of a 'real' tube sound.

There is also the frequent criticism of cheap tube pres as not actually using the tube at all. I haven't used all of the cheap tube pres, but that is certainly not this case with the one I have. The sound might be cheesy if it's cranked, but the tube isn't just a gimmick.

The combination of tube & solid state gain in a single amp is no big deal. Part of that is that with the starved plate design you can't generate as much gain without sounding totally ridiculous. So to add more gain, there's a solid state stage or two. Again, no big deal.

As for the tube vs. solid state argument I think it's rather silly. I will say that I have to have tubes for guitar amps, but other than that I use whatever works, which tends to be solid state for mics.
 
Nobody mentioned the fact that a good tube is a lot faster than solid state, a really fast tube can do the job in about 4 nano second, which can be a thousand times faster than a transistor.

Besides that, the well designed tube can handle very high frequencies, up to gigaherzes, that's why you can find tubes in a F16 fighterplane (radar)
 
hmmm...well, i'm not really sure if anyone REALLY answered what I was looking for (although, I always enjoy heated debates)... I'm curious as to what a tube IS... What's in there that amplifies stuff and why does it look like a little light bulb. That's all. Forgive me if i didn't read a thread close enough that might explain this.

Thanks!
Tait :)
 
Robert,
C7 pretty much said it. Tubes have two basic purposes. They are used to amplify weak signals, and to rectify A/C from the wall outlet to DC, which most electronics run on.

So in guitar amps and microphones, tubes serve the same purpose. They amplify the weak input signals from instruments or microphones up to a usable level.

Check this out. I did a google on vacuum tube.

How a tube works

Wikipedia vacuum tube page

Check these out and post back if you have any questions.
 
Thanks, B-man and C7; I can sense another brain wrinkle building. Pretty soon I'll have to learn some math, if I'm not careful. Whowouldathunkit.
 
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