Era of Tubes (Valves) Amplifiers is reviving an more people turning back to them again looking for better sounding Audio Systems .
When you come up with idea of getting a new gear you`ll find vast variety of products on the market.
To be guided in search for right audio device and feel familiar when reading the device parameters list (Specifications) you need to know some basics of what is printed in Manuals or other technical papers. I won't go too deep in technical explanation of each - there are really many and enough boring, but there are few most important ones which you should know and I`ll talk about them in an simple language and you don't need to be graduated in Electronic Science to grasp the idea. So... let's sort what is listener expectations for Top Level audio device and what parameters are responsible for them: |
Ideal audio system has to make listener feel like if he presents in natural sound reproduction whatever it is: rock concert, theatre, opera, beach, forest...no matter what kind of sound source. He has to hear every quiet and loud, low and high tonal sounds and their combinations without fading or suppressing participants. Hes to feel space and location of sources in front of him as we are talking about stereo system.
Together we will go through parameters which are "in charge" of these features:
Together we will go through parameters which are "in charge" of these features:
Tubes(Valves) vs. Transistors (solid state)-
There are many disputes about preferences between them, but in fact: Tubes provide Listening comfort as they have very short row of even harmonics, while transistor`s ones are stretching even up to 14th, with odds prevailing . Human's ear is most sensitive to odd harmonics also causing an aural fatigue. For tube outline can be applied special soldering/assembling techniques which eliminates surface transfer effects between parts, instead of common PCB placement , |
Typica SE tube amplifier deagram
One of most widespread fable about tubes is "they sound warm or soft" or "different"- is just based on failure or ignorance of how to form the right electronic "condition "for the tube.
"Softness or warmness " in sound is just a sign of undesirable distortions presence which tonally stains initial signal .
Can you imagine past century hardrockers playing on "soft and warm" tube amplifiers? Or why we blame tube amplifiers now when we still listen to records made in past century when all professional equipment was tube based?
"Softness or warmness " in sound is just a sign of undesirable distortions presence which tonally stains initial signal .
Can you imagine past century hardrockers playing on "soft and warm" tube amplifiers? Or why we blame tube amplifiers now when we still listen to records made in past century when all professional equipment was tube based?
In fact skillfully finished tube amplifier should sound tougher when tough signal presents, as signal is less "smeared" and "soften" by distortions compared to the solid state based one.
Of Course I'm not saying that all tube amplifiers are good as nowadays market is awashed with manufacturers with no past or expertize.
I think, you have heard that tube amplifier`s owners keep replacing tubes in their devices to get better sound - they are released from manufacturer not being finished properly. Ideally tuned amplifier has to sound naturally (truly, not affecting the sound in any ways) and any not professional invasion in electronics will only damage it's sound quality.
"Experimenters" who arbitrarily replacing the tubes are getting different set of harmonics and accordingly different sound tonality, which makes them think that one tube is better than another. In fact, if comparable tubes are properly tuned there should be no difference in sound.
Of course there is a chance to put finger on the crux and get exact matching with this "method", but its equal to win millions in lottery. Electrical mode for each tube has to be adjusted by its "personal" parameters and even simple biasing is not enough if you are chasing the top parameters. For this tubes in amplifier has to be burned in and only after that can begin the long and meticulous electronic process of tunings and adjustments . I don't believe it can be done in mass production.
"Digital vs. Analog" sound-process of analog signal transform to digital is enough complicated process in math meaning and I would not bring here the Fourier transfer terminology. In picture you can see how segment of signal is processed.(dramatization). Actually, I'm not fan of digital sound as it is artificially transformed from analog to digit and then returned to analog so undergoes conversion respectively two times, which by math means multiplies doubled errors. |
Itself idea if amping is to make "quiet signals louder" and this feature is called:
Gain (amplification) - in specifications you see "how many times output signal is bigger than input signal" . Expressed in dB - higher number - more amplification can provide the amplifier. Always consider that of Max. output Power of amplifier can be big enough to damage your ears by accidentally "big" signal's burst. It is good practice to make sure that amplifier has volume control knob always in Minimal position before it is turned on -especially for powerful Headphone amplifiers like this one! Nominal power - is level of output where parameters like distortions are measured and listed and the level where you expect the best sonic performance . |
One of phenomenons of vacuum-tube amplifiers better sound over transistors ones - tube does not produce wide variety of distortions.
{ High Fidelity Standard admits amplifiers with 1% of distortions based on that they are not aurally noticeable. This standard was developed in tube era and in tube amplifiers 1% is not noticeable indeed. But following parameters will give you certain an idea of particular device or its creator} Distortions - means how much output signal was altered (damaged). Shown in Specifications as ratio of initial signal to excess signals emerged during processing in %%. Mostlikelly you'll find in specification are THD (total harmonic distortion) and IMD (intermodulation distortion). |
THD (total harmonic distortion) -are excess frequencies (any sound is a frequency ) which are produced by amplifier due to nonlinearity in signal processing. In simple terms is how many excess "sounds" was created by the device .
Mathematically it looks like input frequency (sound) multiplied by natural number times 2,3,4... And as better is the amplifier- shorter set of extra frequencies . |
IMD is most aurally noticeable and you have to be attentive if manufacturer is confident enough to show them in Specifications.
Signal-to-noise ratio -this parameter means how big is difference between maximum rated signal compare to no-signal state.
Also it tells us how clearly can this amplifier deliver the quietest sound, not covered (masked) by its own noise . Device with good Signal- to- Noise is quiet ratio gives you feeling of Musical scene depth . It is not annoying with hum and buzz in musical pauses and is not modulating low level signal . There are different methods how to measure this factor, the most honest is "not weighted". Manufacturers confident in their product represent this parameter measured by this method and mark it "not weighted". |
Knowing signal-to-noise range and Maximum output level we can determine :
Dynamic range -which is ability of Device to deliver the tinies at the same time with sound of loudest sounds. It is range between level of amplifier's noise and maximum signal level could be reproduced by amplifier. In the same time, ability to distinguish barely audible sounds while extremely loud sound presents depends on both range of Dynamic range and low total distortions. No matter is it percussions , gunshot in videogame or thunder in a movie soundtrack we want to hear all these in the way is if we are direct witnesses of the event, naturally. If you had mentioned that in audio system thunderstorm sounds almost at the same level like human voice - Consider that amplifier can not reproduce it's full rumble because of its low dynamic range. |
Knowing possible weakness of amplifier (dynamic range limitation) audio engineers developed concession called "voice compressing" ,somehow to avoid "shearing" or inflating of sound .
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Musical scene width (crosstalk)- is how good is horizontal location of sounding objects (instruments) by width - stereo effect which is described by Crosstalk parameter (in dB units) and means how much one channel "enters" into another, thereby narrowing the scene It feels like as if all musical instruments moved to the centre in front of listener |
"Negative Feedback controls what happens" on the other end of the rope.
No negative feedback - stout-harted climber is left to her own .
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Negative FeedBack -as tube based amplifiers are tended to have relatively high output impedance, negative feedback reduces it to acceptable range.
It watches how your speaker or headphone "describes" the signal and "brakes" membrane (cone for speaker) movement when signal ends. This electronic "mechanism" works like Traction Control in off road vehicles and in amplifier to prevents speaker's membrane (cone) from "hanging out" and from producing loose sound (especially in bass-es part). It controls behavior of all circuitry and also prevents amplifier to "fall off the rope"- into oscillation, It reduces induced hum and total distortions level. There are endless disputes between audiophiles about using NF. One of their argument states - "triode tube amplifiers sound exceptionally without any negative feedback". Not devoted don`t know that triode tubes already has negative feedback inside the tube by their own topology. |
" Why tube amplifiers use transformers ?"- Transformer is heart of tube amplifier and it's parameters mainly determines entire Amplifiers quality.
Generally tubes work under high voltage and low current. Conversely ,Speaker (or headphone), which has low impedance, needs low voltage and relatively higher current. In this case we have conform tubes specifics to load's impedance and transformer here works like conditioner. Or like "travel voltage converter" in our trip abroad. One of difficulties in transformer building is it's ability to evenly perform signal transformation on different frequencies and expertize of fulfilment determines it's quality. |
On the picture you can see in circles junction point 3 different parts made in point-to-point technics. All they are directly, "end to end" coupled and their legs are in contact to each other. Drawing shows signal path (in red) from part A to part B in case of PCB mounting. As we can see,signal from part A goes through solder (in yellow) then follows layer`s copper (in green) and again enters solder before it reaches leg of part B. To create simple connection of 3 parts, as shown on picture above, we need generally 3 connector lines on PCS board and respectively 6 soldering points. |
Thereby signal path getting longer. Besides, connection of 2 different metals causes surface transition effects (for e.g. can work as a semiconductor) and we really don't want any extra "effects " in signal line .
Besides, proper point-to-point soldering allows to minimize amount and length of wires .
Besides, proper point-to-point soldering allows to minimize amount and length of wires .
In case of Point-to point soldering part`s connectors (legs) are directly attached,like so called wire wrapping , which reaches metall diffusion level. Solder (tin alloy) here works like the cement in construction reinforcement.
Point-to-point correctly built audio devices always have to sound better than assembled on PCB. |
Electrostatic and Electromagnetic shielding - this is important when interfered signals from air can access the audio signal path and merging damage the base signal, causing specific hum ,hiss e.g.
Electrostatic fields are is easy enough to "cut off" as they flow over the metal surface and can be shielded even with aluminum. Unlike are Electromagnetic fields, they are mostly generated directly from close placed transformers and can with no fade enter all the signal paths . This is why is important to shield Top Level amplifiers with steel as only steel has ferromagnetic properties capable to withstand them. All antic iconic amplifiers have been built in steel chassis based on these considerations. |
There are much more other signal parameters describing phases, multitone interaction, slew rates e.g..... but i think that above is enough for this time. Later I can add more information here respectively to questions.
I hope this brief review of primary Audio parameters would be helpful for visitors.
I hope this brief review of primary Audio parameters would be helpful for visitors.
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