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  »  New  An ultimate transformer for narrow bandwidth?..  Re: ...apply similar tactics to the power supply......  Melquiades Amplifier  Forum     14  71619  02-03-2005
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07-14-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 1
Post ID: 1200
Reply to: 1200
Ultimate HF output transformer?

This thread is a derivation from the thread:

An ultimate transformer within a narrow bandwidth?

Since my Super Milquades is up and running I’m wondering what can I do with the output transformer at HF channel in order to push the envelop of “possible” in SET further then it has been already pushed in this amp.

The HF channel in Melquiades operates from 3.7hz and the output stage is sits being a coupling capacitor of 420pF. The output transformer is made for me by Lundahl, 10:1 Amorphous core,  ~1H, 250mA. It does fine but the question is why at this frequency I would ever need a cored transformer and why an air core transformer might not be used?

CV made air core OPT in past and reported positive results. From a different prospective I have heard some comments in the past that my output stage (I use a half of 6C33C) with coreless transformer might experience some “issues”…

Anyhow, I see Bud is hanging around; he is a magnetician, “an applied magnetics designer”, which in the contemporary world makes his profession more like magician. Perhaps Bud, Chris, Thorsten, Joe, Dima and whoever else might my share their considerations of the subject of air core OPT for HF channel. Or perhaps someone could point out a place when I can get a pair, at least to try…

I wonder: if I have an amp that push the full SET power down to 7Hz then why should it have full power up to 150kHz? I have to note that what my current HF transformer does serves fine and do not bother me, BUT I would like to find out if conceptually air core (in this case) would be a fruitful direction to go. My extended experiments with the crossovers coils indicate that it should be but I do not know how about the output transformers…

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-16-2005 Post mapped to one branch of Knowledge Tree
Bud
upper left crust united snakes
Posts 87
Joined on 07-07-2005

Post #: 2
Post ID: 1204
Reply to: 1200
The usual, overlong post/reverse paristalasis response.

Romy,

Air core is ok, but.

1. Self inductance in an unmitigated field clumps. You can easily see this by unwinding a hockey puck style air core inductor and measuring the inductance with each turn removed. Never will you have the smooth loss of inductance that model / theory of Maxwell promise.

2. Amorphous, metglass, core is not an answer I would propose for anything but the huge power station devices it was designed for. Especially if it is combined with the usual massive amounts of mylar in the coil, as is typical Lundahl practice. What follows is hotly denied by individuals whose calculators are much more active and refined than their senses.

The core provides the potential of a magnet, each sheet or turn making one potential field strength magnetic map. The coil provides a bunch of turns of wire that act in three discrete categories.

1. First is to carry the constituent parts of the voltage signal, this signal goes through numerous stops and starts with each change in tangence of that signal. With every stop, called static electricity by some, called an E Field print by me, a complete magnet is formed in the window of the core inwhat ever shape it holds. When this occurs the electron cloud, that all of the electrical names really are, prints across dielectric membranes, air, water, vacuum, etc., to find place holder electrons that are free to accept an opposite charge. If the various members of this dielectric / E Field circuit have too high a linking threshold some of the E Field print will be lost  If the E field print reaches too far afield, the print will be distorted in time / phase in its reconstitution and B Field activity, towards the next change in signal vector. This finding of free electrons gets easier as the initial charge threshold is breached. This is the only ageing that occurs in a transformer. (here come the quiet and calm refutations that this is not proven and does not follow accepted models of electomagnetic behaviour) Bah!!

These E Field print and B Field release characteristics are essentially occurring within the entire confines of the amplifier and if connected by Litz cables to a fast preamp, there also. The time boundary for a good amplifier is under 2000 nanoseconds so one E Field print happens at a time, for a given signal trace, within the amp. Of course, there are an impossible to comprehend number of signal traces, in different stages of their activities, during a moment of a symphony passage.

2. Second is to charge the potential magnets to their field strength map potential by electrons moving in wires and creating flux. As the flux links to form the actual flux charge, that resonates within the core, any discontinuity in the shape of the field strength map, for each of these thin magnets, distorts that flux charge and changes the vector of those force "lines", which are actually a field gradient, but that gets difficult to think about, so, back to lines.

Regular E/I core, laminated as in a power transformer in a 1X1 alternating pattern, displays a diamond shape of linear transform volume of flux lines rather than the rectangular shape of the window. This occurs because the fringe flux lines balloon, as they cross the E/I gap, and constrict the adjacent E's on both sides. This causes the field strength map potential, from the E Field, to be distorted by a non uniform activity in the core. These flux charge lines cut the secondary and create an instantaneous B Field that also stops and starts.

3. The E Field links to all adjacent dielectric materials and if the barrier between the primary and secondary has a high threshold for electron linkage, large scale, low amplitude signals are going to link elsewhere. This means a slight displacement in time when they release to the resultant B Field and the potential of them not being understood by the correlator in your brain and ignored as noise. High threshold materials can be discovered by rubbing them in your dry hair and seeing how long they will stick to a wall. Mylar and Kapton being among the worst in this sense.

If the dielectric circuit provides a high threshold (dielectric constant number) throughout the primary, very little space not occupied by wire in the secondary, and an abundance of free electrons, but with a low dielectric constant number, in the material used as the barrier between primary and secondary, then the E Field electrons print very clearly and at breathtakingly low field strengths.

When you have an unmitigated primary and secondary and the E Field cannot effectivly print field strength map magnets, the extreme low level, low frequency content, of high frequency signals, is compromised and the position in the time stream of the impact of hitting a Glock, for example, will be compromised, as will the decay of the notes resulting, due to the clumping of unmitigated flux fields in an air core. The E Field will print in the same fashion as with core but again, the low frequency compliment to all transients will go askew in time. This can be obscured to some degree by sharp cut off of signals and careful tuning and driver alignment, but....

The typical amorphous core is a cut, squashed, doughnut shape and this places the gap in the middle of the coil. Means that the potential field strength map is disturbed into a figure 8 shape. This is not worse than the mess with power transformer stacking of E/I core, but, not as good as a gapped core E/I where all E's and I's are butted together rather than interleaved. This core style provides a D or bread loaf shape of linear flux transform. So the cut core has to provide a higher Mu material, with less gap induced ballooning of flux lines, to equal the performance of the Butt gapped E/I core, made of much more prosaic materials. This brings it's own bag of problems as the mu of the field potential has less latency and to stretch out the resultant B Fields so we can, with our electrochemical speed sensors, understand the signals, a "slow" high threshold material must be used for the coil construction.
This brings us to the notorious ageing of Lundahl and other amorphous core transformers. They can sound good.

An important thing to know is that the first half wave of every inductive event is constrained only by the mu of the material and storage mechanisms of the core construction, so they can excurt and overshoot an E Field potential, in a high mu material, to the detriment of the resulting flux transfer between primary and secondary.

Finally, the area under the window of the core has a built in amplification factor of about 1000. This means that the floor where signal turns into uncorrelatable noise will be much lower, in a core coil than an air coil transformer. And, of course, any core induced problems are going to stand right out. My E/I output transformers do not have this non linear flux transform problem, well 4 pieces of lamination do, but they are acting as wave guides for all of the rest and so my potential magnet fields are much more uniform than in other constructions. Since I follow the theory of coil design that admits that there is a differential circuit, in E Field linking, that can be manipulated, I adjust my coil's effective mu to that of my core and get some pretty nice results. Here is an email copied to me, by Island Pink, who is on this and other forums, after replacing a Lundahl PP transformer with one of my PP designs.

"If I was unscrupulous, I'd try to sell you the Lundahl 1620s, saying they're pretty good, not bad for the money, etc. Actually, the O-Netics level 1's are so much better, they are INSULTINGLY good (in the words of 'Romy the Cat' ). It took about 30 sec to realize they were, they had more detail and much more finesse, no usage, straight out of the box and onto the chassis. They got distinctly better for a couple of hours after that, and may improve for a week or two in small ways. The top-end detail, and treble tone-differentiation is astounding, maybe 2 -3 times better than the Lundahls, to the ear. Even the bass tone seems better, bass lines are easier to follow. The overall effect is to reveal new things on every track you play, including basic stuff like lyrics that were muffled and uncertain before, backing vocals you never knew existed, tone on things that were just noises before, etc, etc. For example, on Chieftains stuff, I noticed Derek Bell breathing (huffing and puffing actually) as he worked away on the harp, never noticed it before. The very quiet track 'Small Hours ' on John Martyn's album 'One World' is a revelation. It was recorded at night, outdoors, near a lake (Chris Blackwell's estate ? ) and has lots of lovely ambient sounds including the breeze blowing and ducks honking on the lake. There's loads of extra small sounds, more space and more convincing REALITY going on there, you can just sit there immersed in it, wonderful."

I have chosen this excerpt for it's name dropping cachet ... of course. But I received this long before I had encountered the good sound club and the spontaneous erruptions of laughter..... and knew Romy the cat was not a rude British cartoon.

And, now that I have whipped up your interest, or bored you to death, I only make SE outputs for a guitar amp mfg. I do this only because he is willing to use a spark gap arrestor in the primary circuit, to eat the "carbon tracking across the tube socket"  voltage spike, created by the ultra low storage SE coil and core configuration getting the DC B+ turned off with a switch! The designer claims that the spark gap provides an interesting tone .....

I am about 3 weeks away from supplying 3 Kz ohm to 4,8 & 16 ohm SE outputs for 300b or 2A3 tubes to George Wright, of Wright Sound, and Gary Pimm of Pimm CCS fame (constant current controls to buffer stages from each other in amplifiers). They are going to test and report on the modified and hopefully less violently "high performance" SE Audiophile outputs. If my plan works I will be able to participate in your SE hi frequency OP contest with composure. Unless, you are using a parafeed hookup that blocks the DC from the primary. If that is the case, I can whip up two transformers for a moderate or high price that will help you out without loss of composure or any need to cover my Emporial nakedness.
Bud

 

07-16-2005 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 3
Post ID: 1205
Reply to: 1204
aircores - Re: The usual, overlong post/reverse paristalasis response.

Hello chaps,

Another option thrown in there by Bud; always enjoy your posts even if I don't follow them 100%...
Let me attempt to barbarically distil what you said into 2 aspects which are

1) The dielectric properties of the insulating materials
2) Magnetic properties and distribution of the core

Now, as regards (1), I can well imagine that mylar and other dielectrics suck, particularly if polar (not sure which are). The ultimate aircore would consist of self-supporting coils stacked vertically above each other, with the minimum of glue or whatever to hold their shape. This would almost eliminate dielectric effects, simply because there aren't any dielectrics there (other than the insulation on the coil wire).
I know you are fond of litz wire and paper etc, but I don't see how any conventional cored construction could compete in this regard.

For (2), air does away with core non-linearity, magnetostriction, eddy current losses, hysteresis losses, memory affects and other distortions. Ok, so as you suggest, you get "non-ideal" inductance with turns behaviour, but I wonder what detrimement to peformance that would translate to, when you gain so much more.

Let's not forget here that Romy is talking about 1kHz and upwards and using (half) a 6C33, which is a very nice load impedance of around 200 ohm, maybe less. So, even 1H primary impedance is plenty, and the half-section use means half the normal standing current.

My aircores, which have only seen use on the test bench so far have a mere 0.25H of inductance, an enormous ratio of 90:1 (for driving a 0.5 ohm ribbon tweeter array, ribbon matching transformers removed) yet measure something like 600 to 40k or so (-3db) when driven from 600 ohms.

I'm just getting some suitably non-metallic, non-magnetic chassis material to try and lash up an actual amp around them, although the ribbon array ain't ready yet.

As an aside:

I've also played with 100% mumetal devices from Sowter: gapped for 135mA, Lpri about 1.5 or 2H, power handling spec'd from 1k up. Despite singing along with the signal, they sound absolutely glorious (interestingly, I noted similar comments from Colloms in his review of the AN UK "Ongaku" which uses permalloy transformers; not that I pay much attention to what them reviewers say).

If my Sowters weren't wound for 3k:8, which is completely wrong for Romy's amps (they'd work but give about 100 time less power), I'd send a pair to Boston for the competition...

Would be no problem for Brian to whip up a design suitable for the S2 Melquiades amp, would be interesting to see how a mumetal core and traditional winding methods would compare with the O-Netics approach.

Still, I'd be tempted to go with the aircore route and that's what I'm pursuing for myself. The difference between M6 and mumetal OPTs in an old lash up amp was not subtle, so I have to wonder how much damage even the mighty mumetal is doing to the signal given that it is sucking a fair amount of energy out of it, and that in a presumably non-linear fashion.

cheers,
cv
(Bud - you may know me as shinebox...)

07-16-2005 Post does not mapped to Knowledge Tree
Bud
upper left crust united snakes
Posts 87
Joined on 07-07-2005

Post #: 4
Post ID: 1206
Reply to: 1205
further air core heads

CV,
Nicely put.... and thanks for the Rp information on the 6C33. Do you have any thoughts, or a curve trace source, about the Rl ratio? 

Now, since air core's are to be your weapon, here are some thoughts to explore.

1. Wind biffilar or trifillar in each receiving coil and do not be afraid to let the wires wander a little bit. This will help with the clumps where it is important.

2. Think about coupling in two planes. Means surround the receiver with drivers on both top and bottom and inside and outside. You can use polybutadene coated wire to accomplish this, as self supporting windings, made on ever so slightly tapered Alcatel plastic arbors are a breeze, except for the alcohol needed to activate the poly. Use 99.99% pure juice for this, please. The poly wire will give you a tiny bit more dielectric to work with and air around the wires, as opposed to wax dipping or the like.

3. Wind the receiver in a square cross section for this scenario and parallel connect all of the primaries and make them as shallow vis a vis the receiver as possible.

4. Do not overlap primary on primary. You may even need to make E Field shields to enforce their mutual exclusion, except through their connections.

If all of this is just too mad, do make sure your receiver is driven on two opposing sides, to ensure a linear flux gradient, and don't hesitate to extend the primary windings beyond the secondary by 6 to 8 mm, in this scenario only, to kill the bridging capacitance losses. Also, a wide thin winding, for the receiver, is good here.

On another path entirely I think a non saturable reactor style core construction might also be a beneficial exploration. This was pioneered by Peerless in the late 40's for Altec and JBL and just means you take the I's and put them on the bottom of the E core, rather than across the legs. No reason why this would not be valid at this low an impedance and DC offset current should not be a factor at all. We make single coil crossover inductors in this fashion. as replacements for hockey puck, dog bone and foil wound inductors to very good effect, though we do multifillar the windings and pay attention to the dielectric circuit.

Another very good possibility would come from non saturable permalloy powder core torroids. These are used mostly as common mode rejection chokes in switcher power supplies. I do not have any information about their audio behavior with a DC field polarizing current though, and they might need to be rather large.....

I like everything I have seen about Sowters work. They are not afraid to innovate and we have mutual thoughts about the problems gapped cores exhibit.

Bud


 

07-16-2005 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,345
Joined on 05-28-2004

Post #: 5
Post ID: 1209
Reply to: 1204
6C33C: HF trransformer...

 Bud wrote:
I am about 3 weeks away from supplying 3 Kz ohm to 4,8 & 16 ohm SE outputs for 300b or 2A3 tubes to George Wright, of Wright Sound, and Gary Pimm of Pimm CCS fame (constant current controls to buffer stages from each other in amplifiers). They are going to test and report on the modified and hopefully less violently "high performance" SE Audiophile outputs. If my plan works I will be able to participate in your SE hi frequency OP contest with composure. Unless, you are using a parafeed hookup that blocks the DC from the primary. If that is the case, I can whip up two transformers for a moderate or high price that will help you out without loss of composure or any need to cover my Emporial nakedness.
Bud, perhaps what you suggest does make send. I do not know as my expertise in the subject somewhere between the expertises of Neanderthal. I appreciate your offer to try your transformer but I kind of have my own pattern how I approach the things. I need to identify what dissatisfies me in my current sound and then, only then, I can expose myself to something else, for instance to change a transformer and to see if it moves me to the direction where I identify I should move. So far my Super Melquiades is too knew and too raw in order to me be able to practicly demead any "evolved" burden to the HF transformer. So far I am teaching it and the Macondo to sound properly together… Probably I will be able to say anything defiantly how the current output magnetics in Super Milq perform in a couple weeks…

For a time being here is the data for 6C33C.

Rgs,
Romy the Cat

 


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-17-2005 Post does not mapped to Knowledge Tree
cv
Derby, United Kingdom
Posts 173
Joined on 09-15-2004

Post #: 6
Post ID: 1215
Reply to: 1206
Re: further air core heads
Hi Bud,
Thanks for the pointers; I already have a pair of vertically sectioned cores wound from a while back, on white nylon (ugh?!) . Not remotely optimal, but if the concept works I will definitely have to try something along your lines. The tip regarding the polybutadene is just what I was wondering about, thanks.

I also wonder if a sectioned toroid might be better - just curling the vertical core into a donut, slinky spring style. Anyway, all conjecture til I build the blasted thing.

Romy beat me to posting 6C33 data; from the "Super Melquiades" thread, looks like just one section as far as the treble amp goes.

Best,
Chris

PS Just saw you mention the Horenstein Mahler 3rd - coincidentally, a friend lent me the very same (though on CD) a few weeks ago - loved it.
07-17-2005 Post does not mapped to Knowledge Tree
jamesrm618
Posts 5
Joined on 05-18-2005

Post #: 7
Post ID: 1218
Reply to: 1215
Re: further air core heads
This site may be of some interest
http://xoomer.virgilio.it/efhco/

regards
James
07-18-2005 Post does not mapped to Knowledge Tree
Bud
upper left crust united snakes
Posts 87
Joined on 07-07-2005

Post #: 8
Post ID: 1219
Reply to: 1218
Leads to further air core heads
Thanks James.
Do you read Italian? I would be interested in knowing what exactly those air coils are for, I assume interstage but the picture is not worth a thousand words. It appears that the formers are plastic, but, could they be wax? That would be very interesting. Anyway thanks for the pointer, shows us that Chris does have his head on straight.... not that there was ever any question ...
Bud
Page 1 of 1 (8 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  An ultimate transformer for narrow bandwidth?..  Re: ...apply similar tactics to the power supply......  Melquiades Amplifier  Forum     14  71619  02-03-2005
  »  New  Fun with transformers?..  Re: An amplifier is not a subject but a service.....  Melquiades Amplifier  Forum     7  56553  10-21-2005
  »  New  An amplifier for Tweeters..  The 7721/D3A as the tweeter diver....  Audio Discussions  Forum     17  113772  09-03-2006
  »  New  RAAL “Water Drop” tweeter for Macondo...  Your comment takes me by surprise...  Horn-Loaded Speakers Forum     77  543666  02-16-2007
  »  New  The one-stage Melquiades...  Tubes vs. Speakers vs. FR...  Melquiades Amplifier  Forum     73  374874  04-21-2007
  »  New  A DSET is better then an expensive SET..  DIY Stradivarius...  Audio For Dummies ™  Forum     41  194505  09-21-2007
  »  New  Entry level DSET Melq?..  Look outside the Lundhal if you need more current to dr...  Melquiades Amplifier  Forum     10  61645  01-25-2008
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