if tubes are more linear than SS then from where does the high THD come from ?
is it the low gain ? the output transformer ? unwillingness to design a proper circuit because it would be too expensive to implement ? an actual craving to have an amp with tons of THD ? something else ?
is it the low gain ? the output transformer ? unwillingness to design a proper circuit because it would be too expensive to implement ? an actual craving to have an amp with tons of THD ? something else ?
It depends on what your definition of high is. Most solid state designers think they can hear distortion less than 1%. Some think even less. There are plenty of tube amps out there that do less than 1% at normal listening levels.
John
John
Usually, this. Plus outright laziness or lack of ability. Some of the best tube amps, or at least those held in high regard, have distortion rivaling solid state. A Citation II is in the 0.008% range at 1 watt / 1 kHz.
As an addendum, some amps are designed with relatively high distortion in mind, because it allows discernibility when compared with normal amplifiers. Some $$$ customers would rather something sound "different", than actually sound "better" - hence a slight subjective preference for added distortion. This I don't get, but people are welcome to do as they please.
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1% distortion is "peanuts" !
Do you have distortion values for your loudspeakers ?
If so, wich manufacturer does dare to publish ?
Do you have distortion values for your loudspeakers ?
If so, wich manufacturer does dare to publish ?
The answer is simple: THD don't reflect directly cleanness of sound reproduction. It is well known fact repeated again and again, but still needs to be repeated, because some people keep thinking that THD directly reflects the sound quality...
In order to sound clean usual tube amp don't need so deep feedback as typical class AB opamp requires, that's why an opamp to sound well needs much lower THD.
However, the myth exists that the people who call reproduced by tubes sound clean and accurate are schizophrenics; this myth helps those who can't afford a properly built tube amp to feel better, and proudly use modern mass-production.
In order to sound clean usual tube amp don't need so deep feedback as typical class AB opamp requires, that's why an opamp to sound well needs much lower THD.
However, the myth exists that the people who call reproduced by tubes sound clean and accurate are schizophrenics; this myth helps those who can't afford a properly built tube amp to feel better, and proudly use modern mass-production.
there are many ways to build speakers.
in most cases distortion could be slashed by an order of magnitude but the designers don't bother.
if i had unlimited resources i could design a speaker that would have no more than 0.1% THD. by unlimited resources i mean design every transducer from scratch. it would probably end up costing about $100,000 though.
most $100,000 speakers though will probably have more than 1% THD though.
What high THD? Are you comparing like-with-like?
I would guess that a line-level signal amplified x 15 by a single triode such as a 6H30 would have less distortion than the same signal amplified by a single transistor. It may be that only by using multiple transistors and negative feedback would you reduce the distortion. But then you could add feedback to the triode circuit and reduce the distortion also.
THD (the single number version) is totally useless as a specification so why care?
You need to look at the spectrum to get any clue... 2nd & 3rd (particularily if 2nd is higher) are quite benign. Higher order harmonics are very unnatural and stand out like crazy...
And then you have to consider the HD content at different power levels and frequencies and how it changes as a function of these.
Your question could be classified either as trolling or a significant lack of understanding of the basics.
Tube amps do do have inherently higher distortion, and even those with high single figure numbers often have lower distortion where it counts.
dave
You need to look at the spectrum to get any clue... 2nd & 3rd (particularily if 2nd is higher) are quite benign. Higher order harmonics are very unnatural and stand out like crazy...
And then you have to consider the HD content at different power levels and frequencies and how it changes as a function of these.
Your question could be classified either as trolling or a significant lack of understanding of the basics.
Tube amps do do have inherently higher distortion, and even those with high single figure numbers often have lower distortion where it counts.
dave
nowhere probably.
u can think of a speaker as 3 parts:
1 - motor
2 - diaphragm
3 - suspension
each will produce its own distortions and will need different techniques to reduce them.
motor distortion is effectively reduced by using underhung topology and a copper shorting sleeve.
diaphragm distortion is reduced by using ultra-stiff materials like ceramic, beryllium and diamond
suspension is a bit of a mystery. i am trying to figure that out myself.
In respect of a single triode stage the thd is caused by the imperfection of the operating curves. This generally creates higher 2nd harmonic but much lower higher order distortion. Many designers (and commentators) believe that this is not particularly noticeable and hence make no attempt to reduce it.
And you would have wasted your efforts & a whole lot of money, Geddes' research has shown that there is no correlation between THD in speakers & sonics. THD as high as 25% is tolerable.
He even tells you to completely ignore the entire chapter on speaker distortion in his earlier book.
That one can hear thru a loudspeaker and here fractional distortions in amplifiers and other upstream kit goes miles towards illustrating how resolving and how adept 2 ears plus a brain are.
dave
hm that amp is 40 years old, and it doesn't look all that complex. shouldn't we be able to do even better today ?
where are the 0.001% THD tube amps ?
I don't have an answer for you, but I remember seeing several text books on speaker design so surely the information is available. I guess the guys in the Speaker section of this forum will be able to advise you from experience, and I bet they love to talk about it!
that is true. you could hear 0.1% THD in a bad transistor amp through a speaker with maybe 5% THD.
but a speaker can have nice or mean distortion as well. JBL designs their drivers in a way that would make them pretty heavy on low order distortions but everybody thinks they sound good.
on the other hand many people can't tolerate the sound of plastic cones even though the amount of distortion caused by the plastic cone is probably minor.
in SS amps distortions are reduced by several orders of magnitude using NFB.
what would it take to reduce distortion of a tube amp to say 0.001% THD ?
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