What makes Dumble style amp sound better?

[Max]

"A high rate of manufacturing rejects occur from time to time in production lots of instrument current transformers. This has initiated a systematic search for the causes."

But as you'll know "instrument current transformers" are used for different applications than transformers in a guitar amp: http://en.wikipedia.org/wiki/Current_transformer

So it might be possible, that these results of a "systematic search for the causes" aren't valid 1:1 in regard to the kind of transformers used in guitar amps.

BTW 1.: You'll find countless papers dealing with the aging processes at work in the kind of transformers used in electricity distribution systems (I've attached an example). But it might be questionable how valid the results published in these papers are in regard to the kind of transformers used in guitar amps.

BTW 2.: I've strong doubts, that researching the aging process of transformers used in guitar amps will shed much light on the topic of this thread ("What makes Dumble style amps sound better?"). But of course it might be an interesting topic in its own right.

Cheers,

Max

[talbany]

Long term aging (Steel)
According to Mercury Magnetics this has the largest effect on transformers over time (as it relates to steel in older transformers) and depending on the amount of carbon, sulfur, oxygen and nitrogen...
http://en.wikipedia.org/wiki/Electrical_steel

Silicon significantly increases the electrical resistivity of the steel, which decreases the induced eddy currents and narrows the hysteresis loop of the material, thus lowering the core loss.[1] However, the grain structure hardens and embrittles the metal, which adversely affects the workability of the material, especially when rolling it. 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. For these reasons, the carbon level is kept to 0.005% or lower. The carbon level can be reduced by annealing the steel in a decarburizing atmosphere, such as hydrogen.[2]
[/quote]

Short term effects?
One possibility would be due to magnetic hysteresis effects.
(partial alignment of magnetic domains due to magnetic fields).. which could change the response and coupling in an OT ...Perhaps Zippy can elaborate if this is a possibility?

Here is a paper on aging affects on various insulators (includes Paper)

http://journals.tubitak.gov.tr/elektrik ... 0802-5.pdf

7. Conclusions
A series of accelerated ageing experiments has been investigated for oil/paper cellulose insulation system used
in transformers. Polarization and depolarization currents and recovery voltage of aged cellulose immersed in
oil were measured. The aim of tests was condition assessment of insulation system. The main properties of oil
and paper were studied. Electrical measurements show that both polarization and depolarization currents are
strongly influenced by ageing time and water content of oil and paper. The results have shown that maximum
recovery voltage of oil/paper insulation system and tensile strength of paper insulation in power transformers
vary significantly and consistently with respect to ageing time and ageing temperatures.
Good correlations have been obtained between the tensile strength of insulating paper with recovery
voltage of insulation system, total acid number (TAN), and water content in oil. The tensile strength results
have been used to predict how lifetime of insulating paper changes with temperature and time. Therefore
lifetime of paper has been estimated by using Arrhenius model. It can predict the life of paper for power
transformers at various operational temperatures.

Like Max suggest..The problem with these types of tests is how they actually affect tone in guitar amps will likely never be known without extensive testing and at great expense.. So IMO to ask for scientific evidence and how it effects tone is extremely difficult and due to all the variables involved,

BTW.. Those out there with degrees and doctorates on the subject, it would be nice to at least offer up some of the variables that might contribute to the changes in sound (or NOT) over time since it's been stated here and other sources that they notice it!..Perhaps this would give others some place to look if they want research it further..Also if some of this info I posted does not apply PLEASE state why you think so so we can advance the discussion..

So much for bowing out..Huh!


Tony

[bruce egnater]

Are we still talking about guitar amps here?

[Tubetastic]

Indeed, Bruce - what are your thoughts/experience?

[chikov]

My internet was down, so I missed several pages of a great discussion. To the participants it might be irritating, to have some one disagree with you, but to the observer, like myself, it is a wealth of knowledge to choose from. Thanks guys. Know this, i am reading every word, so do not stop, unless you must.

[bruce egnater]

Well I'm not as much of a scientist as you guys but, every Dumble amp I've worked on had stock Fender transformers (or SVT as in the SRV/SSS). Are you saying the Dumble amps were not "magical" until the transformers reached a certain age?

[talbany]

Are you saying the Dumble amps were not "magical" until the transformers reached a certain age?

NO!!... That's not what we are saying!..It's a totally subjective topic..
Speakers Break in, certain caps have a break in,tubes Break in..No magic there!!...Transformers may take a bit longer but are IMO...No different..Some might not even notice it,some do and others here want scientific proof...

Tony

[bluesy]

.....but is it possible that some of these amps took sooooo long to "deliver" because the iron was being "seasoned" by Mr. D.? Could newer at the time iron be burned in somehow until it was "ready"? Just a thought.

[bruce egnater]

I understand. Are you guys saying that all amps (including Dumble) will sound "better" (subjective) as they age? Clearly aging filter capacitors are not a good thing I assume, so at what point does one determine that some components are properly/adequately broken in and others are not. Is there a scientific/controllable/measurable method to break in capacitors, resistors, transformers etc. (not speakers) to speed up the process and also quantify/qualify the effects of component aging? I believe just because a component is old (used or NOS) that it is necessarily better. There were plenty of parts that were bad when they were new and are still bad now that they are NOS.

[martin manning]

There are a number of possible effects being discussed here. I'm generally skeptical about this whole subject, as most of the evidence is anecdotal and from a very small sample size (often of one!) with no control.

1) Old parts sound better than new parts because the materials and processes used to make them were different.
Examples of this are CC resistors vs. CF vs. MF, and PIO vs. film/foil vs. metalized film capacitors. Old resistors of the same type (MF e.g.) have been said to sound better than new ones of the same type due to the differences in construction and materials used.

2) Old parts sound better than new parts because the materials in them have changed with age.
An example of this is the electrical steel used for transformers as discussed above. The steel used in old transformers is both aged and likely to be of a different composition than modern steel. I have no idea how anyone could know what an old transformer sounded like when it was new. It's more likely that the old parts were constructed differently to begin with, and identical new parts would sound the same as old ones.

3) New parts sound better after a period of break-in.
This claim seems most often to be made with regard to coupling and tone shaping capacitors by companies selling boutique parts, and the necessary break-in period is said to be on the order of 100 hours. It is conceivable that the properties of dielectric materials could change with applied voltage, and some amp manufacturers believe strongly enough in this to spend time and effort "burning in" new amps for a period of several hours. I have noticed that newly built amps seem to lose some brightness after a few hours of use.

4) New parts manufactured by one company sound better than parts of the same type manufactured by another company.
This claim has been made in the case of capacitors of the same type made with nominally the same type of dielectric, and in the case of metal film resistors.

[talbany]

I understand. Are you guys saying that all amps (including Dumble) will sound "better" (subjective) as they age? Clearly aging filter capacitors are not a good thing I assume, so at what point does one determine that some components are properly/adequately broken in and others are not. Is there a scientific/controllable/measurable method to break in capacitors, resistors, transformers etc. (not speakers) to speed up the process and also quantify/qualify the effects of component aging? I believe just because a component is old (used or NOS) that it is necessarily better. There were plenty of parts that were bad when they were new and are still bad now that they are NOS.

Bruce
At this point the effects of transformer aging are really just a theory some amp manufactures have devised based on listening tests..Some (including myself) have noticed tonal alterations while either changing transformers or having amps come back in the field years later and notice a difference..IMO..I would never use the term "BETTER' and certainly NOT magical to describe the aging effects,especially when using old used and possibly abused iron (especially with output transformers).. I have an original output transformer from a 1959 Bassman that sounds like ass!!! and have replaced old iron in some amps where I thought the new iron was an improvement,IMO...It also depends on the type of amp,since some people seem to prefer the slightly "smoother" tone of aged transformers especially in an amp that has built in overdrive..

Since you manufacture many amps perhaps you might start your own listening tests...What do you hear when you change out an older for newer transformer (of the same type)or take an amp that has been in the field for several years and compare it to a fresh amp off the line..Do this over a dozen or so amps of the same model of different time frames and see if you can devise your own theory on the effects of aging on your transformers

As far as the aging process, and controlled break in period..

Like Martian mentions the initial break in period is considered 100 hrs..Caps and other components might shift as well...
As far as long term break in there is no set time frame..It really depends on the type of transformer, how it was used,quality,design and materials used...
I do think there is a point however where aging and abuse can have negative effects and become,dark,lifeless,fuzzy, and sloppy low end...Like my 59..
I couldn't agree more on the NOS is 'BETTER" thing..Although I do believe if you want to get as close as you can to the 'Classic" Dumble ODS sound one should use the same parts in critical spots (signal path) as Dumble used..

BTW..."smoother" usually just means not as bright or strident, whatever!

Tony

[vibratoking]

Like Martian mentions...

I used to think of Martin as a nice looking fellow with a black dog. That has been replaced by something far different...

[martin manning]

Like Martian mentions...

I used to think of Martin as a nice looking fellow with a black dog. That has been replaced by something far different...

How so? Maybe there is some misunderstanding re my post above? Items 1) to 4) are claims I have heard regarding old parts, not what I personally believe.

PS: Most women seem to be more attracted to the black dog than to me.

[vibratoking]

Martin, I understood your post completely. I guess my joke wasn't really that funny. Notice how Tony spelled your name.

[martin manning]

Oh, I see. Tony does that all the time so I just ignore it!