mini amplifier with tube sound

A small mini amplifier, which generates the typical tubes sound.

This amplifier adds to the signal even-numbered harmonious frequencies.

Measurement results of an amplifier, which generates the typical tubes sound.

I catch here a very hot iron in the audio world. I try to discuss it objective without an pro or contra.
What is a electrotechnical definition of an ideal amplifier?

The amplification of an electrical voltage by a desired constant gain. Phase response and distortion of the output signal should be the same like the input signal, only a gain applies.

Ideal means in particular:
  • frequency response equal over all frequencies
  • no phase shift over all frequencies 
  • same frequency and phase plot for all amplitudes under all loads
  • no generation of new frequencies, whether with periodical character (e.g. distortion) or another characteristic (e.g. noise)
  • absence of reaction to the input signal
  • no performance variation vs. temperatur and ageing.
with "in particular" I don't talk about things like: the influence of gravitation from the moon to the amp, or the constellation of  Jupiter to Saturn. In our world there are many Technology Paper Shuffler, who compare every single word, every definition or phrase with gold. This is exactly what they want to do, but they do anything positive to do something better.

Typical tube sound: many, however not all amplifiers with tubes have also the typical tube sound, a warm sound. Many specialists maintain it exactly to hear, probably can it however only the few. I pull the hat for humans with sensitive hearing. The results depend always strongly on the person and the amplifier, loudspeaker etc.. But naturally also interaction and the weighting of the parameters of the many boundary test conditions. Some feel this sound characteristic as pleasantly, others however disturbing. The sound results primarily from the composition of the frequencies in its sound spectrum. Some tube amplifiers (not all), have the lion's share of their distortion factor in the second harmonious one. Often bad transistor circuits tend to odd-number harmonious. Hearing attempts confirm that again and again. Odd-number harmonious ones are clearly more audible than even-numbered harmonious ones, which are only noticed if they are already relatively large. Why is it like that? That is a question - for which I have a theory, which I would not like to discuss however. Whether even-numbered harmonious ones sound also good or not, which must decide everyone for itself. They are not a component of the original signal. They do not correspond completely to the ideal amplifier, a ideal amp have no distortions. Why however do some records with a tube amplifier sound simply better than with a very good amplifier and output system? Don't ask the amplifier developer, ask the sound engineer! In many cases the hifi developer held to be responsible, it's wrong. The musician makes the music, and under logical aspects it's the sound engineer's task to be responsible for a good sound. For answer of this question you must ask the tone engineer of the recording technology and not the amplifier developer, he often made an excellent work and for it he receives as thanks the bad black buck. The musician makes the music. From theoretical view the record studio must optimize the records, so that using of the best hifi rendition also everything sounds good and is felt by the listener as pleasant. The industry is aware of it, only it cannot satisfy all. It can take up only CD and tries these in such a way from logical aspect to take up (I must unfortunately speculate now) that it feels the majority of the listeners as pleasant - that would be understandable also from economic view.

Three examples, which have all their authorization

Case A: there are humans, who wish themselves a (warm or whatever special) sound of the record, with large investigations they trimmed  the loudspeakers and rooms exactly their special conceptions to correspond so long. The conception, the music is to sound not in such a way as in an anechoic area, but e.g. as a musician, who plays in a living room its violin and sits directly in front of him. An anechoic record is then played also in such a way with it to sound as in a living room. A live record sounds then possibly also after living room. But how sounds then only a record, which was noted in the living room? - I do not know it. Case A decides also subjectively with well-being feeling.

Case B: the purist in the loudspeaker art, which trims its loudspeakers so long according to all rules of the art, instrumentation and also after hearing up to everything in every detail is correct, the adjustment to the rooms and also the exact location in the room. If it places the loudspeaker into another room or against a changed location, it sometimes even worsened its special trim. Case A has the same problem. In the case B the result is with correct tuning a fascinating hifi rendition with total dependence on the record. An anechoic record sounds also anechoic with it, an record from the living room would also in such a way sound. It puts the sound characteristic totally into the hands of tone engineer.

Case B goes out of logical aspect the technically correct way.

Case C: the loudspeaker manufacturer does not decide for one of the two extremes. The manufacturer must often go out of economic view another way. The products must be adapted to the multiplicity of the possible rooms of the customers. The loudspeakers should make an optimum rendition possible in all rooms. The manufacturer cannot afford it to let be after-said the loudspeakers sound badly or only well e.g. between 40 and 50 square meter. To realize such a thing, that is true art. How far manufacturers can reach individually case A or B or to want, I can not judge. Now tone engineer is added, and asks by right: for whom am I to take the admission now?

Back to the tube amplifier: a tube amp can reach even the case B. A condition is a correct technical design (is not easy). In many cases however the tendency goes to case A. Many tends even consciously to case A. The characteristic of a tube causes a dominance of the second harmonious ones, which experiences a shift toward case B, these are statements of many audio listeners. That disturbs the purists, since it destroys the perfect rendition. The purist wants a crystal-clear amplifier and no well sounding music instrument. The sound purist of the entire rendition chain puts the characteristic into the hand of the record and very pleasant and unpleasant surprises will completely experience. It is evenly matter of opinion who which would like and both sides should themselves accept also mutually and respectful. Take care with a tube amplifier, ask critical: designed for which case? A,B,C or a mix, or only because of the lovely and beautiful looking red glowing tubes? The circiut in this application note was developed to convert a clean case B amplifier in a case A amplifier. It's easy now to switch the tube sound on or off, even in a adjustable mode.
Applications: Preamplifier for a adjustable typical tube sound

Das_ist_alles.jpg (16150 Byte) K2_Spektrum.jpg (28091 Byte)
That's all. Gain of one, some semiconductors, resistors and capacitors - finish - easy to get an adjustable sound varying from pure up to tube or even guitar sound. Yes, here is the distortion poti setted to pump up to a higher second harmonic level. Sounds powerful and warm. The distance from K2 (20kHz) to K3 (30kHz) is incredible high. Measured with the audio analyzer HP3580A

How are things going on? I don't need this amplifier. I prefer a pure clean sound. I want a amplifier not a music instrument. Again: that's a matter of opinion, decide yourself. Believes not always only those with ties and needle, it gives also bad boys (in addition, very many property). Yes, those with the rhetorically beautiful language. - considers - those must earn themselves thereby their money and many tell you which you gladly hear. I, I cannot carry it for me out - I go working completely normally for 7 hours on the day and earn no tired cent at which I write there. Therefore, fits on into which shop you go. Let you demonstrate the results of measurement and spectra of a hifi amplifier of your choice. A well equipped manufacturer has such a thing - a good audio dealer, who holds something good from itself - should in addition also be able to do a measurement. Please do not let you tell that you do not need such a thing.Know you, hearing is naturally important, it is only unfortunately subjectively and neither measuring nor objectively comparable. Hearing comparisons make enormous fun, but only to talk about "sound, music, softly, seifig, strongly in the bass, transpararente in the middle etc.." is subjectively and easily influenceable. My dear friends, let you the parts for alternation before your eyes comparatively measure - all with same test and boundary conditions. Bad amplifiers varnished with words is noticeable immediately. I love the truth and live for it.

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