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Regarding EDCOR Transformer Data

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#41
Just some observations on the question of specs:

1) Given a full set of specs as in this thread, a competent magnetic designer can pretty much copy a design, guessing with a high degree of confidence the number of turns, interleaving, wire gauge, etc.

2) So, either you make a high priced product and keep specs secret, or you make a product so low priced that the copiers can't make any money. This problem is exacerbated if you are manufacturing in the USA.

3) In order to keep prices low, you don't do unnecessary things like measure all those parameters on every unique design. Look at the size of the Edcor catalog, and understand how small an operation it is, to see the force of this.
 
#43
Paul Joppa said:
Just some observations on the question of specs:

1) Given a full set of specs as in this thread, a competent magnetic designer can pretty much copy a design, guessing with a high degree of confidence the number of turns, interleaving, wire gauge, etc.

2) So, either you make a high priced product and keep specs secret, or you make a product so low priced that the copiers can't make any money. This problem is exacerbated if you are manufacturing in the USA.

3) In order to keep prices low, you don't do unnecessary things like measure all those parameters on every unique design. Look at the size of the Edcor catalog, and understand how small an operation it is, to see the force of this.
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An interesting viewpoint, however:

1) A competent magnetic designer shouldn't need to copy an existing design, if truly competent they can design and build from scratch. It's usually easier to copy, but I don't see that large a market for cheap clones, much less stating I sell Edcor replicas for less.

2) I think Hashimoto make some of the best iron money can buy (I know, I have a large number of them... and none are inexpensive) and they publish a pretty full set of specifications. I also can't see how manufacturing in Japan could be less than the USA, likely just the opposite, but their fit, finish, quality and consistency are excellent.

3) I have to disagree on this point, as Edcor do publish additional specifications for their SE OPTs... like Inductance, DC resistance (primary and secondary) and maximum (primary) specified current. It's just strange that they just gloss over this on their PP OPTs, what is the point? They don't cost any more than their SE counterparts and I'm certain the specs are on hand, how could they not be?

Granted, I think Edcor do a great job for the price... I can't see anyone building equivalent for less and turning much of a profit. I've only had one unit with a QC problem. By building to order, they can keep a fairly large catalog of designs and not worry about having a lot of inventory, plus they offer custom units too. I do use them for certain projects and have recommended to others as well.

Regards, KM
 
#44
Let us first get certain matters clear. I notice a constant defense of Edcor products; nobody ever said their products are poor - at least not from what I read. This 'debate' is not about that, so let's leave that there?

The point is about a manufacturer providing a product and leave you hanging regarding essential parameters required for proper design.

Paul Joppa said:
Just some observations on the question of specs:

1) Given a full set of specs as in this thread, a competent magnetic designer can pretty much copy a design, guessing with a high degree of confidence the number of turns, interleaving, wire gauge, etc.

2) So, either you make a high priced product and keep specs secret, or you make a product so low priced that the copiers can't make any money. This problem is exacerbated if you are manufacturing in the USA.
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Paul,

As already said, OPT design procedures are well-known (RDH 4 et al), software has been generated for the same ..... why would any competent designer be tempted to take a particular product and try copy it? Any purported superiority lies in simply following the principles and properly executing them - full stop! There is no 'black-magic', and bringing here some semblance of conspiracy/industrial espionage is just ludicrous.


3) In order to keep prices low, you don't do unnecessary things like measure all those parameters on every unique design. Look at the size of the Edcor catalog, and understand how small an operation it is, to see the force of this.
Click to expand...

Giving parameters unnecessary?? Again, with respect, how would you go about designing an amplifier using an OPT? As I asked before: Thumb-suck, go buy a range, listen to each in turn to find "the best sounding one" (only to discover later that you have a degree of 'motor-boating'; should have used that other transformer then - oh, no wait ....)

In practice, if a product design is anywhere near decent, one needs to check the parameters only once (and a few samples now-and-then: it is called 'quality control'). No one asks for a test of each individual product. Time necessary for testing maximum wattage, frequency response, primary inductance, secondary leakage reactance, voltage insulation, equivalent capacitance, weight - some 5 - 7 minutes in a custom set-up. Say once every 50 transformers. Price implications?

So sorry. There are many alternative products available out there.

You giva me no specs on my bottles - I no buy. You giva me no specs om the OPT, I no buy. I goa next-door.
 
#45
kmaier said:
An interesting viewpoint, however:

1) A competent magnetic designer shouldn't need to copy an existing design, if truly competent they can design and build from scratch. It's usually easier to copy, but I don't see that large a market for cheap clones, much less stating I sell Edcor replicas for less.
Click to expand...

There are just a handful of typical winding diagrams applicable for audio output transformer design. So no matter how competent engineer is, whatever he will develop will be derivative of an existing work over half of century old.
 
#47
LinuksGuru said:
There are just a handful of typical winding diagrams applicable for audio output transformer design. So no matter how competent engineer is, whatever he will develop will be derivative of an existing work over half of century old.
Click to expand...

AJT said:
i dont think anyone will ever give away trade secrets, as opt making is more of an art than science...
Click to expand...

??
I must have missed the classes on transformer design magic at varsity. Sure, "existing work over half of century old' - as are Kirchoff's Laws, Ohm's Law....

Not sure I am getting your point here, LinuksGuru. And "OPT making more of an art than science"? Apart from development of better transformer steels (the characteristics of which are known), there is no more art in transformer design typified by its equivalent diagram than in the rest of an audio circuit. If I may again kindly point to the 5th paragraph in my previous post .....

The design requirements have been known ever since the first pre-50s hi-fi amplifiers and conveniently illustrated by Crowhurst in nomographs a few years later. Hosts of successful OPTs with predictable results have been designed along those lines without any 'black magic' involved (though promotion will claim magic here as with many other plain engineering matters). Just for the record, a.o. I have designed and wound OPTs with 3 dB frequency responses of some 6 Hz - 240kHz and < 1% distortion at the target output power of 100W; I am not aware of having involved any art/mysticism/trade-secrets.

So pray, what basics of engineering am I missing here?
 
#48
I agree with Johan... it's not magic, certainly a labor of love to a large degree, attention to detail and consistency and a bit of art in the final cosmetic casings, but the RDH Chapter 5 covers the technology in good detail. Not sure why LinksGuru quoted me instead of Paul however.... I don't need convincing ;-)

Regards, KM
 
#49
Johan Potgieter said:
AJT said:

I must have missed the classes on transformer design magic at varsity. Sure, "existing work over half of century old' - as are Kirchoff's Laws, Ohm's Law....

Not sure I am getting your point here, LinuksGuru. And "OPT making more of an art than science"? Apart from development of better transformer steels (the characteristics of which are known), there is no more art in transformer design typified by its equivalent diagram than in the rest of an audio circuit. If I may again kindly point to the 5th paragraph in my previous post ..... "
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It's a partial quote but all I'm really thinking is, wire tension, insulator material, non-magnetic materials and precision will all make a big difference in transformer quality. Along with the required amount of science.
 
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#50
right, choice of materials, winding techniques, etc....

Patrick Turner in his website gives away all schematics and diagrams....

but i think he said, even doing so, he is not sure how the individual uses his information,
he is not sure the ones using his information will build it the same way he does...

i learned to make OPT's from Patrick's website and from many of the postings here...

i will be happy if OPT makers divulge among others, the physical data of the core,
the dc resistances of both sides or primary winding same with the secondary windings.....
these information gives me a hint as to the quality of their build...
 
#51
Johan Potgieter said:
Let us first get certain matters clear. I notice a constant defense of Edcor products; nobody ever said their products are poor - at least not from what I read. This 'debate' is not about that, so let's leave that there?
Click to expand...

In my earlier post I cited the data I had accumulated on various transformers. Of them all, in terms of primary inductance, Edcor was one of the poorest tested:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/Iron/TransformerInductance.pdf

Cheers

Ian
 
#53
ruffrecords said:
In my earlier post I cited the data I had accumulated on various transformers. Of them all, in terms of primary inductance, Edcor was one of the poorest tested:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/Iron/TransformerInductance.pdf

Cheers

Ian
Click to expand...

I've read a number of articles on primary inductance and it's role in low frequency response.. I never seem to see anything about potential negatives to high primary inductance though.

Have you seen this article? A Consequence of The Quest for 20Hz Roll Off | Cascade Tubes

Because of the distortion in a tube, there is a shift in bias current driven by the magnitude of the even term harmonic distortions. This change means that when the output tube is being driven hard, the dynamic bias point (and current) can be significantly different than the dc bias point (and current). What this means is that there must be a transition between bias currents when there is a transition between drive levels. So what does all this mean?
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Lets look at the example of a rapid transition in volume. In classical music this could be a trumpet blast or the crash of cymbals. In both cases, the level of the music, and hence tube drive and load current, changes suddenly. This sudden change is the crux of the problem. When the current in an inductor suddenly changes, there is an induced voltage in the inductor proportional to the inductance and the rate of current change. The magnitude of this voltage is to oppose the change in current.

This voltage acts to oppose the B+ voltage and hence limit the plate current in the output stage. Once this happens, the current begins to increase exponentially until the steady state dynamic operating point is reached. In effect, this phenomenon limits the transient dynamic response of the output stage. And because of the relation above, it can be seen that the larger the primary inductance of the output transformer, the slower the transient response will be
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A trumpet blast in classical music is an example of a marcato fortissimo or very strong, marked transition in the music. Such a transition will markedly shift the operating point current from one value to one much higher. This transition cannot occur instantaneously but will take time to occur dependent on the size of the primary inductance. The effect of this phenomenon is one of blunting, or slowing the transition. Additionally, the nonlinear nature of the exponential ramp will increase distortions as the transitions take place. The net effect being that a transition which is intended to be sharp and crisp, becomes muddled and distorted. In some cases, the effect is minor. But in large transitions, the effect can rob the music of important dynamic character.
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There are more technical details and the mathematics at the link.
 
#54
#57
I did read it but i guess you forget what you wrote...

"Edcor XSE 10-50-8K output transformer:
This transformer is intended for single ended tube amplifiers to drive a 50 ohm load"

And for the other transformers: it makes no sense to measure it with a handheld lcr meter and make conclusions about a transformer (low frequency) response. Permeabilty swing is very large so it depends very much on the signal level.


ruffrecords said:
If you had read the article you would have realised that the transformers tested are NOT gapped so they are not intended to carry dc.

Cheers

Ian
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#59
esltransformer said:
Because i think he don't know what transient response means.
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Why do you say that? I looked up the definition of transient response
the response of a system to a change from equilibrium
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Isn't that exactly what he's talking about?

when the output tube is being driven hard, the dynamic bias point (and current) can be significantly different than the dc bias point (and current). What this means is that there must be a transition between bias currents when there is a transition between drive levels.
....
When the current in an inductor suddenly changes, there is an induced voltage in the inductor proportional to the inductance and the rate of current change.
....
This voltage acts to oppose the B+ voltage and hence limit the plate current in the output stage. Once this happens, the current begins to increase exponentially until the steady state dynamic operating point is reached. In effect, this phenomenon limits the transient dynamic response of the output stage. And because of the relation above, it can be seen that the larger the primary inductance of the output transformer, the slower the transient response will be.
Click to expand...

I've been endeavoring to understand primary inductance in output transformers, and what effect that has to my listening experience. So I'd be interested to understand what transient response is in your opinion.

Also, if that isn't the correct term for the phenomenon caused by large primary inductance of an output transformer in this application, isn't it still an effect that exists? (whatever you would call it?)

The effect of this phenomenon is one of blunting, or slowing the transition. Additionally, the nonlinear nature of the exponential ramp will increase distortions as the transitions take place. The net effect being that a transition which is intended to be sharp and crisp, becomes muddled and distorted.
Click to expand...
 
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