What makes Dumble style amp sound better?

[Zippy]

God only knows what stress rock-n-roll puts on a transformer.

Would that be HAD or Clapton?

[talbany]

Where is the physical stress coming from?

Vibration..

Tony

Understood. Has that been shown to be true? My degrees are in applied physics and materials science, and I've not read papers regarding high cycle fatigue effects on electronic effects. That doesn't mean they don't exist. In fact, I'm happy to help with a literature search, if someone thinks there is a reason to believe it has a basis.

I think the mechanical stresses and temperatures are too low.



I could believe there is some magnetic order from manufacturing that becomes more random with age, but I don't know how strong that effect could be on the coupling, or whether it would be in such frequency ranges that don't matter in this application.

Zip
I have no scientific data that suggests that physical stress (vibration) on laminates causes a shift in frequency response..Perhaps Smitty can elaborate..

God only knows what stress rock-n-roll puts on a transformer.

Actually a good friend of mine who knew Ken Fisher well said that Ken recommend Jimi Hendrix recordings (Band of Gypsy's I believe) as a good signal generator to break in an output transformer on a Komet amp years ago.. ..No lie

Tony

[67plexi]

Let's look at Transformer , New and Used cycled thousands of times.
Simple as I can explain it. One the metallurgy of copper and Iron
Copper gets softer when heated and cooled down
Iron is just the opposite the more iron is heated and cooled down the harder it gets.
Both factors will change the magnetic properties of a transformer.
http://www.electrical4u.com/joules-law/
I'm a sucker for seasoned transformers or cycled transformers power and output
I have 3 go to guitar amps all have heavily cycled transformers that's my choice.
Question have any of you ever played a guitar amp that sounded it's best just before the output
transformer died due to the insulation failed on the copper windings.
And the application of the insulation of the transformer wire is a whole other dimension
to the equation in the early 1960'S the wire was run through a vat or huge tub of insulation
Now day's they use a felt pressurized with insulation that covers the wire so it's thinner.
One more part on the steel or iron core most of the steel is made in China now and it's less than
substandard in its metallurgy same with the purity of the copper. And trying to get a materials data
sheet from my steel supplier is like trying to get a straight answer out of a politician.
To each his own.

[Zippy]

Let's look at Transformer , New and Used cycled thousands of times.
Simple as I can explain it. One the metallurgy of copper and Iron
Copper gets softer when heated and cooled down
Iron is just the opposite the more iron is heated and cooled down the harder it gets.

The metal just doesn't get hot enough to do what you claim. If it was hot enough to cross the phase boundary of iron or 0.4 homologous temperature of copper, paper would combust and nylon would melt.

If anything is going on, it is in the ordering of the magnetic domains.

[rdjones]

God only knows what stress rock-n-roll puts on a transformer.

Would that be HAD or Clapton?

[img:400:346]http://2.bp.blogspot.com/_pbDWlY7JgwY/S ... 883391.jpg[/img]

[vibratoking]

IMO, the only way one can conclude that output transformers do not have different permeability at different frequencies after break-in is through an inadequate understanding of metallurgy and magnetism.

I have taken several courses on electromagnetic fields and theory, but my understanding must be inadequate. Perhaps you can correct my thinking with something other than bent nails? Maybe you can explain the quantitative theory regarding the frequency dependence of permeability and how it changes after break-in? I assume that theory will also define exactly what break-in is. I am always open to learning.

Because I understand it myself does not mean that I have the ability to 'correct your thinking'. I wasn't aware there was a 'quantitative theory regarding the frequency dependence of permeability and how it changes after break-in'. Sounds like troll bait to me.

I typically don't bite on the deductive-is-the-only-type-of reasoning bait. As a practitioner I don't limit my reasoning to pure deduction. I also include inductive reasoning (seems especially appropriate for transformers).

So if you can accept that permeability is frequency dependent, that permeability is affected by continued physical stress, and that the operation of a transformer applies physical stress to the laminations, you can conclude (though inductive reasoning) that the frequency response of a transformer will change after use.

Which part are you struggling with?

You stated that permeability changes with vibration. I just asked you to back it up with some facts. Your answer is you weren't aware. Circular discussions aren't useful. I don't accept 'magical' thinking, so we can agree to disagree.

I don't accept that there is enough physical stress on the laminations to change the magnetic behavior in any significant way. I am asking you to prove it rather than pontificate. If the depth of your understanding has already been fully demonstrated in this thread, then I have my answer.

[Smitty]

Your first paragraph is pure troll bait. Utter mischaracterizations designed to illicit engagement at the level you wish to play. Not my cup of tea. That you cannot discern between inductive reasoning and circular thinking is a red flag.

I stand by my assertion that the plastic deformations (bent nail) cause by the vibrating laminations while not significant in single instance testing (bulk of scholarly articles) plays out over long time scales to reduce the stresses in the steel and changes the permeability. It relieves the stresses created in the manufacturing of the lamination (cutting and stamping).

I am a student, not a teacher. You wish not to learn but to argue. I cannot help you for these two reasons. You must do your own homework.

Here is an article that infers that lower cyclic mechanical strain amplitudes produce slower rates of relaxation (seasoning).

http://www.shotpeener.com/library/pdf/1987127.pdf

I've attached another article more specific to the matter at hand with some measurements which should serve to delight you.

That you disagree with me does not make me wrong.

[Max]

"What makes Dumble style amps sound better?"

IMO: the personal taste of the player / listener.

Cheers,

Max

[Zippy]

I stand by my assertion that the plastic deformations (bent nail) cause by the vibrating laminations while not significant in single instance testing (bulk of scholarly articles) plays out over long time scales to reduce the stresses in the steel and changes the permeability. It relieves the stresses created in the manufacturing of the lamination (cutting and stamping).

I am a student, not a teacher. You wish not to learn but to argue. I cannot help you for these two reasons. You must do your own homework.

Here is an article that infers that lower cyclic mechanical strain amplitudes produce slower rates of relaxation (seasoning).

http://www.shotpeener.com/library/pdf/1987127.pdf

I've attached another article more specific to the matter at hand with some measurements which should serve to delight you.

That you disagree with me does not make me wrong.

There is not sufficient stress induced by vibrations in a transformer to produce plastic strain. I am a materials scientist. My Ph.D. dissertation was a study of the evolution of deformation mechanisms during cyclic fatigue.

[Smitty]

I am interested in reading your dissertation. Can you please post it? Thanks.

[vibratoking]

Thanks for the links. There is good information there. I read the paper regarding cyclic strain and the corresponding change in magnetoelasticity. I noticed that the minimum stress applied to any sample was 115MPa or 17000 psi. I believe that is a stress which is orders of magnitude beyond anything induced in a transformer lamination through magnetic flux. I'll assume 100 laminations in a transformer. I've never counted so I don't know the actual number. That means you would need the equivalent stress of 1.7 million psi in the amplifier transformer to be equivalent with the study. So, I am trying to learn something here. What phenomenon in a guitar amplifer could possibly induce stress on the order of 1,000,000 psi? The paper shows delta changes on the order of about 4x with stresses that are orders of magnitude beyond anything in a guitar amp. The numbers don't seem to indicate that anything could be going on here. This would indicate a change of roughly 4ppm. And that is generous, looking at the plot, the change is probably closer to 1ppm. I wonder if this is enough to be audible?

About the nail analogy: the fatigue limit of iron is about 100,000 psi. The stresses induced on a transformer in an amplifier are significantly below the fatigue limit. This is obvious in that the fatigue limit has never been approached or exceeded during normal operation of any transformer that I am aware of. I am wondering how this analogy applies to the discussion.

[67plexi]

Look at this Doctor Zippy JMP50 1202-118 power transformers one 1969 the other new
Please observe the heat discoloration on the paper bobbin and the steel laminate's
45 years old still works like a champion. What was the cause and effect ???
I bet it was those darn Mullard XF-2 EL-34 power tubes. Nothing to do with Joules Law.
Oh no I just gave away the PT of Mega-plx.

[Max]

Some more opinions:

When alloying, the concentration levels of carbon, sulfur, oxygen and nitrogen must be kept low, as these elements indicate the presence of carbides, sulfides, oxides and nitrides. These compounds, even in particles as small as one micrometer in diameter, increase hysteresis losses while also decreasing magnetic permeability. The presence of carbon has a more detrimental effect than sulfur or oxygen. Carbon also causes magnetic aging when it slowly leaves the solid solution and precipitates as carbides, thus resulting in an increase in power loss over time.

Source: http://en.wikipedia.org/wiki/Electrical ... Metallurgy

If anything in a transformer suffers from aging, it will most likely be the core. Two major contributors cause a negative effect of aging and affect your tone. Before World War II, the science of processing iron was not up to snuff. It was difficult to boil out residual carbon, and even a miniscule amount of carbon in older iron causes it to age. As an iron core ages, its magnetic conductivity begins to poop out, slowing the transformer’s responsiveness with increasing losses. The result is less output with only lower mids breaking through.

During WWII, the war effort created a shortage of iron. So, many transformer companies made cores from sheet metal, like that used to make soup cans! These had the wrong kind of iron and harbored plenty of carbon, to boot – do not confuse iron with steel! Finally, when silicon was implemented to help force the carbon out of post-war iron, transformer iron became stable enough to outlast us all.

Another contributor to transformer aging comes from humidity. Amp owners who live in humid climates have noticed their tone changes over the years, especially if their older amps had transformers built around paper bobbins, which have always run the risk of moisture absorption affecting tone. Conversely, we found that transformers with plastic bobbins weren’t likely to suffer tone degradation via moisture saturation.

A couple of excellent examples are the original Partridge and Radiospares transformers from England – with the fog and rain they experience, these transformers held up quite well. That may explain why coating paper in wax was attempted early on, and to verify that humidity affected output transformer tone, we flew in transformers from amps made in the ’60s that had never left the U.K., all with paper bobbins, and put through a dehumidifying process, then resealed them in varnish and gave them a full bake. The owners freaked out and thanked us for giving them their original tone back! One called to thank us personally when he realized it was his tone fading over the years, and no this ears! He said that as time passed, he noticed less treble and a lot less note separation and definition. Others had this mastaken belief that their amps were getting too old to play.

Source: http://www.mercurymagnetics.com/pages/n ... mernik.pdf

Cheers,

Max

[Tubetastic]

Some more opinions:

When alloying, the concentration levels of carbon, sulfur, oxygen and nitrogen must be kept low, as these elements indicate the presence of carbides, sulfides, oxides and nitrides. These compounds, even in particles as small as one micrometer in diameter, increase hysteresis losses while also decreasing magnetic permeability. The presence of carbon has a more detrimental effect than sulfur or oxygen. Carbon also causes magnetic aging when it slowly leaves the solid solution and precipitates as carbides, thus resulting in an increase in power loss over time.

Source: http://en.wikipedia.org/wiki/Electrical ... Metallurgy

If anything in a transformer suffers from aging, it will most likely be the core. Two major contributors cause a negative effect of aging and affect your tone. Before World War II, the science of processing iron was not up to snuff. It was difficult to boil out residual carbon, and even a miniscule amount of carbon in older iron causes it to age. As an iron core ages, its magnetic conductivity begins to poop out, slowing the transformer’s responsiveness with increasing losses. The result is less output with only lower mids breaking through.

During WWII, the war effort created a shortage of iron. So, many transformer companies made cores from sheet metal, like that used to make soup cans! These had the wrong kind of iron and harbored plenty of carbon, to boot – do not confuse iron with steel! Finally, when silicon was implemented to help force the carbon out of post-war iron, transformer iron became stable enough to outlast us all.

Another contributor to transformer aging comes from humidity. Amp owners who live in humid climates have noticed their tone changes over the years, especially if their older amps had transformers built around paper bobbins, which have always run the risk of moisture absorption affecting tone. Conversely, we found that transformers with plastic bobbins weren’t likely to suffer tone degradation via moisture saturation.

A couple of excellent examples are the original Partridge and Radiospares transformers from England – with the fog and rain they experience, these transformers held up quite well. That may explain why coating paper in wax was attempted early on, and to verify that humidity affected output transformer tone, we flew in transformers from amps made in the ’60s that had never left the U.K., all with paper bobbins, and put through a dehumidifying process, then resealed them in varnish and gave them a full bake. The owners freaked out and thanked us for giving them their original tone back! One called to thank us personally when he realized it was his tone fading over the years, and no this ears! He said that as time passed, he noticed less treble and a lot less note separation and definition. Others had this mastaken belief that their amps were getting too old to play.

Source: http://www.mercurymagnetics.com/pages/n ... mernik.pdf

Cheers,

Max

I LOL when I read that bit - I'm betting anyone in the UK would too. Fog? LMAO!!

Its not that rainy either. Talk about stereotype!

Anyway I've lost my old romanticism for a lot of unexplained things of whats supposedly the answer to these kind of things that go round. I need concrete proof and consistent example's.

I get where both sides are coming from - I think I've been there on different things. Sometimes you hear/believe what you want to - the Hifi world is full of that stuff until something else comes along and your mind shifts perspective.


MM saying a transformer changes also suits their sales M.O - you get someone who doesn't bother about the mentioned "change" and others who are never going to be happy unless they believe that vintage tone will eventually come from their purchase - though their ears will hear a difference after a while when you become accustomed to something. I've learned to like what I loathed.

I don't think theres a right or wrong answer here. A-lot of belief, which isn't a bad thing.

[Kassie]

I LOL when I read that bit - I'm betting anyone in the UK would too. Fog? LMAO!!

Its not that rainy either. Talk about stereotype!

One finds these discussions in the old car trade all the time... does a particular chassis come from a forgiving climate like southern California? or from moisturised Europe (rust etcetera).

I believe the only difference is.. guitar amps usually are not kept in barns or under a blanket in your garden. Usually they are kept indoors... however it may be that the air humidity can still be higher. (In the Netherlands it can be pretty humid in the summer and autumn).

Great Brittain does seem to catch the biggest showers before they reach the European mainland... Even though I didn't live there for an extensive time. The rainy stereotype is often mentioned in NL.