Tube Amp with the "Good Kind of Distortion"

[dienson]

I just have

Matched Pair (2x) Genalex Gold Lion 12AX7 tube (ECC83) come three hours ago​

just put them in and listen almost 2 hours, it is okie, but sound not clear like stock tubes, a little bit bright not warm like stock, with my ears these Genalex tube sound not good like stock McIntosh 12AX7A , made in USA,
Maybe run on a week then see what it sound, maybe better
Anyway have sound in time waiting replace from Mac
Have A Good Day to all

 

[mhardy6647]

I don't think stock Mac 12AX7A in a modern Mac preamp would be "made in USA". Do they really claim to be, or was Mac using NOS (new old stock) US tubes. There have been no US-made small signal tubes for a long time.

 

[dienson]

I have picture of it included,
It look like Telefunken
Have a Good Night

 

[Ken Tajalli]

Has anybody seen this ?
My eyes popped out, then I laughed out loud.
The killer bit was "Returns not accepted" !

 

[mhardy6647]

Well -- I mean -- used fuses would be right up there with used prophylactics.
You know?

 

[egellings]

Must be a thin line between a burned in and a burned out fuse.

 

[Ken Tajalli]

The things we do in the hope of more resolution !
Tell me, does warm weather reduce high frequency sound wave propagation ?
wait a minute, . . .
is that why the call it warm sound?
I wonder . . .

 

[Kijanki]

Many look for "warm sound" (added even harmonics) - opposite to many SS amps that produce TIM distortions (overshoot in time domain) resulting in added unpleasant higher order odd harmonics (3th harmonic is still euphonic). TIM is produced when deep negative feedback is used. NFB is wonderful, reducing THD, IMD, output impedance and increasing bandwidth. It is possible to design SS amp with deep NFB free of TIM, but bandwidth would have to be reduced at the input, to one amp had before feedback was applied (likely poor). Unfortunately it doesn't look good in specifications, while TIM is undetectable with typical sinewave measurement (tempting to use a lot of NFB). The other approach is to create feedback that is non-recursive using additional error amplifier, that corrects output (instead of feeding signal back to the input of the same amp). That's how it is done in my Benchmark AHB2 amp, that has two parallel output stages - one one for the signal and one for the error.

Any added distortion would make instruments sound false. Clarinet, for instance, has such unique sound because it produces only odd harmonics (complete lack of even harmonics). Passing it thru "warm sounding" amp will change its sound. It might still sound nice (or even nicer), but it won't be original clarinet sound. Piano overtones are stretched. Overtones of given key is not at the double frequency of the octave higher key, but a little bit higher. To avoid beat between such keys higher keys are tuned higher - to overtone of the lower key and not to double frequency. Tuning person plays first key and then stretches octave higher key frequency to stop the beat. After all this is done to avoid beat people play it thru overly warm amps, that add harmonics, that beat with overtones.

When people get used to added harmonics (or distortion) anything clean will sound to them analytical/sterile. Some even claimed that amp "removed" harmonics from musical material (impossible unless bandwidth is inadequate). Distortion adds dynamics, pretty much like distorted electric guitar vs clean Jazz guitar at the same level. Warm sound is not a virtue to me - it is distortion of the sound.

 

[DanielT]

Hm, a power tube amp where tubes get very hot, they are very hot no matter how much the volume changes. Can this constant high heat in itself create an evenness in the sound reproduction? A stability? That compared to a transistor-based amplifier where the heat can vary (it does with tube amps as well but it is constantly very high)? If so, can this high but steady level of distortion be perceived as positive in many people's ears?

Note that this is a question and not a statement.

 

[Ken Tajalli]

Hm, a power tube amp where tubes get very hot, they are very hot no matter how much the volume changes. Can this constant high heat in itself create an evenness in the sound reproduction? A stability? That compared to a transistor-based amplifier where the heat can vary (it does with tube amps as well but it is constantly very high)? If so, can this high but steady level of distortion be perceived as positive in many people's ears?

Note that this is a question and not a statement.

Not exactly true.
Depends on the design of the amp. A class AB tube amp, gets warmer as the volume goes up, a Class A does not.
Indeed that is true with SS amps too, some pure class A SS amps get pretty warm at rest!
The tubes need a heat (filament) in order to work (helps electron flow), but otherwise that heat can cause issues, rather than create stability.
The heat does not create distortions, indeed a well designed and made Tube amp can be comparable to SS in terms of distortions, perhaps not noise, but that has been said a 1000 times before.
Tube warm sound, good distortions is a myth, created by badly designed tube amps, and those who don't know any better.
Ofcourse if one needs to create a distortion box (for Hifi or guitar), then with Tubes it is easier to get a pleasant sounding distortion box.
My 2 pence.

 

[DanielT]

Not exactly true.
Depends on the design of the amp. A class AB tube amp, gets warmer as the volume goes up, a Class A does not.
Indeed that is true with SS amps too, some pure class A SS amps get pretty warm at rest!
The tubes need a heat (filament) in order to work (helps electron flow), but otherwise that heat can cause issues, rather than create stability.
The heat does not create distortions, indeed a well designed and made Tube amp can be comparable to SS in terms of distortions, perhaps not noise, but that has been said a 1000 times before.
Tube warm sound, good distortions is a myth, created by badly designed tube amps, and those who don't know any better.
Ofcourse if one needs to create a distortion box (for Hifi or guitar), then with Tubes it is easier to get a pleasant sounding distortion box.
My 2 pence.

No, I know the myths about the "good distortion" in tube amps. I was more interested in this:

Bias current in the output stage, and the stability, which according to this youtuber is good with tube amps. I do not know technically how, or where the possible benefits would lie. Do not know if what he claims is true. Watch a few minutes of the video and he will mention it, at the beginning of the video.

 

[charleski]

compared to a transistor-based amplifier where the heat can vary

This is true for class A-B designs. But any decent amp designer knows that and integrates bias-compensation that eliminates this factor. If you look at any textbook on amp design you'll find a chapter on thermal stability.

 

[Ken Tajalli]

No, I know the myths about the "good distortion" in tube amps. I was more interested in this:

Bias current in the output stage, and the stability, which according to this youtuber is good with tube amps. I do not know technically how, or where the possible benefits would lie. Do not know if what he claims is true. Watch a few minutes of the video and he will mention it, at the beginning of the video.

There is some truth in what he is saying.
He is pointing to an issue about SS devices, in that the characteristic changes according to temperature. But as the previous post indicates, this is true about calss AB amps (most SS amps).
There is no denying that tube amps are simpler, and once you find the sweet spot in class A operation (most quality hifi tube amps these days), then the bias circuit can be a simple one, and need not be temperature compensated.
SS amps can be very complicated, the designer can use many devices, as they are small and cheap, so servo units, correcting secondary amps sections etc. can be cheaply implemented to make the final product measure and sound very good.
But on the whole, this phenomena is but one small corner of the answer, mostly put forward to sell his own amps.

 

[DanielT]

I thought the sweeping statement in the video in my post no 196 regarding transistor-based amplifiers was strange. Certainly a poorly constructed transistor-based amplifier can of course sound bad. It goes without saying, poorly constructed -poor sound. BUT transistors and their development of heat and how it should be dissipated, all designers of amplifiers should know that. It's like basic course 1A. Just study the data sheet for each transistor. Then, based on that, construct suitable heat sinks that leads awayt he heat, or use fans.

 

[Ken Tajalli]

I thought the sweeping statement in the video in my post no 196 regarding transistor-based amplifiers was strange. Certainly a poorly constructed transistor-based amplifier can of course sound bad. It goes without saying, poorly constructed -poor sound. BUT transistors and their development of heat and how it should be dissipated, all designers of amplifiers should know that. It's like basic course 1A. Just study the data sheet for each transistor. Then, based on that, construct suitable heat sinks that leads awayt he heat, or use fans.

There is a time delay thought.
The instant the junction gets higher, for the heat to transfer from the die to heatsinks and final temperature equilibrium.
For that a class A amp, would dissipate as much power regardless of signal, so this issue won't happen.
But you need a beefed up system for that, and it is wasteful.

 

[charleski]

There is a time delay thought.
The instant the junction gets higher, for the heat to transfer from the die to heatsinks and final temperature equilibrium.
For that a class A amp, would dissipate as much power regardless of signal, so this issue won't happen.
But you need a beefed up system for that, and it is wasteful.

Quoting from Doug Self's book, "drivers and output devices have relatively large junctions with high thermal inertia" (Chapter 10). If this were a factor then you'd see 2nd and 3rd harmonics rising at low frequencies (i.e. 10Hz) in a class B design as the dissipation varies over the cycle. He tested a class B design and found no change in distortion that couldn't be attributed to his analyser's own variation.