Tubes.....and the Jerks that use them.

[fancynapkin 10+ year member]

fzddxfsd

 

[fancynapkin 10+ year member]

Actually, if you get down to the most basic fundamentals, tubes are more linear devices than even the most modern semiconductors.
Tubes and transistors have a property called transconductance... this describes the "gain" available. Put a small voltage in, and it gets amplified to a bigger voltage... in a nutshell, that's transconductance.

However, NO device keeps the EXACT SAME gain over the entire voltage range. To describe the changes in gian vs. input voltages, engineers use what's called a "transconductance curve"... a graph of input voltage vs. output voltage. All devices (tubes and transistors) have the general property that it takes a bit of input to make them turn on at all... they do NOT immediately start to conduct output until there's a small amount of voltage. Hence, there's a "flat spot" on the curve, at the bottom, where things are NOT linear. Also at the top of the curves (at high voltage) all devices start to go non-linear... the output voltage cannot "keep up" with the input anymore.

Between these two extremes, there is a relatively "flat" area, where the output is just a simple multiple of the input. This is called the "linear region", and is where all amplifying devices SHOULD be used.

To avoid the bottom region, most amps use "bias", which consists of applying just a little bit of static voltage to the amplifiying device, to 'prime' it so it's ready to turn on with the least bit of additional input. This avoids the "flat spot"... otherwise known as "crossover distortion", near zero-level.

However, the UPPER limit, is a bigger problem. The more dB (ie, higher range of gain) available between the bottom problem area and the top problem area, the better the device as an audio amp. Smaller linear regions == less available dynamic range and less resolution at lower signal levels.

Now, given that, it's interesting to find that tubes have, in almost every case, a BIGGER linear region (ie, they can go from LOWER to HIGHER output levels than transistors) than any semiconductors. Even the most modern MOSFET devices, STILL can't match the linearity of something like a 6SN7 or 6SL7 tube...not only does the tube have more distance between the lower and higher problem areas, it's FLATTER (ie, the transconcuctance curve is more a straight line) in the MIDDLE of the range than ANY semiconductor, built to date!

To compensate for this solid state amps have to use MUCH MORE feedback than tube amps, which can EXACERBATE time-delay related distortions. Phase shift from feedback, is a KNOWN cause for mis-behaviour in amps... the less needed, the better...

SO, from a fundamental standpoint, tubes still have better inherent behaviour as audio amps than transistors. Until you start getting into pretty exotic solid state designs (such as the pulse-width-modulated output coupled with a "gain cell" variable gain input, as used in the new PS Audio amps, which seem to be the MOST LINEAR solid state amps EVER, but which are UNLIKE ANY other solid state amps on the market) which find innovative, non-standard ways to completely side-step the whole gain/linearity issue, you're stuck with the shortcomings of the transistors in most solid-state amps...

Regards.

Gordon.

Negative feedback in SS amps reduces distortion and noise, lowers output impedance, increases input impedance, strengthens gain control and is implemented quite effectively in modern amplifier designs without many consequences, and for much cheaper than a nice tube amp. People like tube amps because they produce pleasant harmonics when they distort.

 

[JimJ 5,000+ posts]

Jim... I forget what Tubes do you run in that amp?

Svetlana SV811-10's are the triodes, the input tubes are RCA 6EA7's.

 

[GordonW 10+ year member]

Negative feedback in SS amps reduces distortion and noise, lowers output impedance, increases input impedance, strengthens gain control and is implemented quite effectively in modern amplifier designs without many consequences, and for much cheaper than a nice tube amp. People like tube amps because they produce pleasant harmonics when they distort.

A more linear device has less distortion in the first place.

Low output impedence is NOT necessary for good design. Plenty of speakers were PURPOSE BUILT for higher-impedence amps (both tube and solid state), and can work JUST as well as those built for lower output impedence amps. It's a matter of TOTAL DAMPING, not just that of the amp. Speaker drivers CAN be built to DAMP THEMSELVES, very well... just look at most any modern TAD driver, for one example...

Gain control isn't really an issue, when the amp is more LINEAR in the first place. And the ONLY place where solid-state amps have a distinct advantage in this area, is they "variable gain cell mated to PWM" methodology used by PS Audio (patented). NOBODY else builds amps this way yet... they're ALL either based on total-PWM (which has higher filtering requirements, ie noisier) or ALL class-AB/class A (which is NOT variable gain, and therefore has a compromised noise floor compared to the hybrid design above).

"Without many consequences" is a polite way of saying "it doesn't screw up TOO much". //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

The one thing that solid state amps CAN boast about, is DEFINITELY lower cost. It's impossible to build tube amps cheaply... no one will dispute that. BUT... that's not really the issue here... there's a claim that SS INHERENTLY sounds better than tubes... but except for the RARE EXCEPTION, there's pretty few inherent reasons for this to be so, and some VERY VALID reasons for the opposite to sometimes happen!

And the more "benign" clipping behaviour of tubes? Part again, of the better linearity...

Regards,

Gordon.

 

[GordonW 10+ year member]

BTW: A tube amp, with a noise floor LOWER (ie LESS NOISE) than pretty much ANY conventional solid state amp. And I'm including pricy stuff like Krell, and the like.

http://www.vac-amps.com/Phi_Beta.htm

I'm sitting here listening to one right now, at the store... //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Regards,

Gordon.

 

[ballstothewall 10+ year member]

Thats a sexy amp.

 

[Beat_Dominator 5,000+ posts]

BTW: A tube amp, with a noise floor LOWER (ie LESS NOISE) than pretty much ANY conventional solid state amp. And I'm including pricy stuff like Krell, and the like.
http://www.vac-amps.com/Phi_Beta.htm

I'm sitting here listening to one right now, at the store... //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Regards,

Gordon.

Any graphs of the amp's distortion??

 

[JimJ 5,000+ posts]

BTW: A tube amp, with a noise floor LOWER (ie LESS NOISE) than pretty much ANY conventional solid state amp. And I'm including pricy stuff like Krell, and the like.
http://www.vac-amps.com/Phi_Beta.htm

I'm sitting here listening to one right now, at the store... //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Regards,

Gordon.

Beautiful...pictures of setup now //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Digital or analog source? //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[fancynapkin 10+ year member]

BTW: A tube amp, with a noise floor LOWER (ie LESS NOISE) than pretty much ANY conventional solid state amp. And I'm including pricy stuff like Krell, and the like.
http://www.vac-amps.com/Phi_Beta.htm

I'm sitting here listening to one right now, at the store... //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Regards,

Gordon.

I don't know how many people consider a 20,000 dollar amp conventional...

 

[joetama 5,000+ posts]

Me like KT-88's.... Like them much better than 6550's.... Even though they are pretty much the same thing....

 

[Beat_Dominator 5,000+ posts]

I'm a pentode fan myself.

 

[thylantyr 10+ year member]

As night falls, Jim finds peace and harmony as he puts in his favorite music

and listens to his tube amp system...... unbeknownst to him as to what is about to take place...

Beat Dominator.... slams open Jims' house door holding a 100 pound

solid state amp cradled under his right arm and yells .......................................

...............................................................

.............................................................. I'm The Juggernaut B*tch!!

reference;

http://video.google.com/videoplay?docid=-3934651591022114445

 

[joetama 5,000+ posts]

Oh shit son.....

 

[JimJ 5,000+ posts]

Naw, I'd have the candles already lit, some Diana Krall spinning on the 'table, the soft filament glow emanating through the room...

Evan would find it irresistable.

//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[joetama 5,000+ posts]

Naw, I'd have the candles already lit, some Diana Krall spinning on the 'table, the soft filament glow emanating through the room...
Evan would find it irresistable.

//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Are you going to try to seduce him?