I see Gryphon and NAD both use them in their amplifiers. What is so unique and advantages of using the Holmgren toroidal transformers with internal magnetic shielding?
I have a Holmgren toroid I rescued from a NAD. Don't see anything special about it. have spotted the "Toroid" hedgehog symbol on it...
Probsbly just
1. An inter screen winding
2. A belly band
Both of these things can help reduce noise significantly - I spec them on all my transformers.
1. An inter screen winding
2. A belly band
Both of these things can help reduce noise significantly - I spec them on all my transformers.
"Internal magnetic shielding" would stop it from working as a transformer! Sounds like incoherent marketing-speak for ordinary technology, as Bonsai says.
There is a thick band covered in white insulation round the circumference of the toroid.
There are no extra conductors that would not be expected present.
Given the general standard of components that were in the amp you would not expect the transformer to be anything special either. Just something for the marketing types to get their teeth into as suggested previously.
The band around the outside (external) of a toroid is a gauss band.
It can be done as a ring cut from a section of steel pipe that fills the gap from floor to roof of a steel chassis.
There is an equivalent in an EI (framed type).
The internal screen, between the primary and the secondary is an electrostatic block.
It conducts HF interference from the primary to the Chassis.
This attenuates the HF interference that gets to the secondary, IF the HF route to Chassis is low impedance.
I am still waiting for a link to
It can be done as a ring cut from a section of steel pipe that fills the gap from floor to roof of a steel chassis.
There is an equivalent in an EI (framed type).
The internal screen, between the primary and the secondary is an electrostatic block.
It conducts HF interference from the primary to the Chassis.
This attenuates the HF interference that gets to the secondary, IF the HF route to Chassis is low impedance.
I am still waiting for a link to
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The Gryphon Mephisto blurb sheet refers to "internal magnetic shielding" in the product feature list but the text says "static shielding isolates primary and secondary windings...". Given this may be self-translated from Danish, the author could well be interpreted as meaning "electrostatic" shielding rather than "static" shielding.
Gryphon Mephisto Solo
Gryphon Mephisto Solo
it was there on the gryphon website. I dont understand what is so unique about that feature. What is the use of the electrostatic shield?
I have sent an Email complaint to Gryphon alleging they are breaking the consumer protection act.
I don’t see what the problem is. No one needs protecting!!
I am sure the “internal magnetic shielding” is just referring to the fact that it is part of the transformer itself and not applied externally or separately. This is clearly just a standard gauss band around the periphery of the transformer (in toroids, usually just made from a few turns of the same material the core is wound from) and “internal” because it is under the final tape wrapping of the transformer and there part of it. Engineering heads will see through the sales hype, non-engineering heads will just think that it is a plus, which it is as it allows Gryphon to mount components closer to the transformer with less chance of induced hum.
The electrostatic screen is just a normal electrostatic screen.
There is no clear reference to a gauss/bellyband nor further use of the term "magnetic", only for the electrostatic shield which is quite a cheap option anyway.
Like most advertising, it is intentionally vague but sprinkled with a lot of buzzwords and phrases as a hook for impressionable buyers. Since we are DIYs, you could assume we wouldn't fall for the mumbo-jumbo but I guess we all did at least once or we wouldn't scrutinize it.
Like most advertising, it is intentionally vague but sprinkled with a lot of buzzwords and phrases as a hook for impressionable buyers. Since we are DIYs, you could assume we wouldn't fall for the mumbo-jumbo but I guess we all did at least once or we wouldn't scrutinize it.
In you opinion, what is the best transformer costruction core/winding topology arrangment that reduces either type of HF interferences? (primary to secondary and to chassis)
Any technique or core geometry that reduces inter winding capacitance between the primary and the secondary is a good start. So, R cores and split bobbin EI cores are good. You can see some of these in high end audio products, and JC is a proponent. However, the stray field (50//60 Hz) is higher than in a torroid. You can still fit a belly band around these types to reduce this though.
Torroids are generally smaller and more efficient and an intertwining screen is very effective in blocking mains noise and HF hash from getting across to the secondary. The radiated field is much lower on a torroid, and the addition of a belly band makes them very quiet.
I've had about 6 or seven Torroids wound for my projects over the last 8 years, and always spec an inter winding screen and a belly band.
If you include these, the radiated field is certainly well bellow anything an R core or an EI core can achieve, and the inter winding noise coupling a non issue.
If you want to experiment, wind a few turns around the outside of the transformer and connect a pair of headphones to compare the radiated field performance.
Yes, but they are not the norm on transformers on consumer equipment; and the off-the-sheld toroids from Avel, MD toroid, and Plitron do not include either the screen or the band.
Can you share the info on your custom toroid winder?
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