DC Filter against humming Toroidals - Summary of the most interesting Comments

[tiefbassuebertr]

DC filter - summary of the most interesting comments here on diyaudio - all mentioned post-# from
dc filter
unless otherwise stated:

Basic Descriptions
Theory of Operation (very good explanation): post #20+25+200+199+235
and post #32 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
and post #50 about
DC Blocking Filter for Mains
and post #51 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

white paper of Plitron (11. February 2002) post #38#155#157#226#240 (last URL) and post #76 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

Measurements/Experiments
Measurement (oscillogram pics) from EVA 50mV DC, heater in half-power mode (unfortunately deleted) post #57 + comment post #119 and post #21+26 about
?? DIY PS Audio Humbuster
and post #39 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
DC measurings by post #116 about
DC Blocking Filter for Mains
and post #30 about
DC Blocking Filter for Mains
simulation by post #51 about
DC Blocking Filter for Mains

Current through Capacitor - minimum requirements
Low Voltage capacitors in most cases low current capacitors (EVA) post #73
advice for sufficient current capacity post #18
calculate appropriate numbers for the capacitor value post #134-140 and post #23 about
DC Blocking Filter for Mains

Circuit Topologies
Electrolytic Capacitors: connected in parallel (but anti-phase) vs. serial connection "back to back": post #124+125+132+215+216+227 and post #108+83 about
DC Blocking Filter for Mains
and post 43+46 about
DC Blocking Filter for Mains
Dangerous condition for the caps: post #8 and post#9 about
Thule Audio's Universal Inrush Current Limiter for their Amplifiers - very special?
and post #32 (Bob Cordell) about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
MKP instead polarized cap: post #99 and post #14 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
Advantage of Lars Clausen's single capacitor plus a 4.3 V tranzil post #78 and post #12 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
Advantage of BMW's 850 circuit solution: #159 #202
Advantage of GK's topology (only single capacitor necessary): post #91 about
DC Blocking Filter for Mains
another approach from
Buzzing toroids
go to post #68 about
DC Blocking Filter for Mains
and post #13 about
DC Blocking Filter for Mains
approach from JKoch: post 57 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
new approach without serial dc filter from simon7000: post #73 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

Commercial Solutions
Bryston's solutions: post #56 #141#142#145#148#153 and post #19+24 (Bob Cordell) about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
and
http://bryston.com/BrystonSite05/pdf...28Oct02%29.pdf
Mark Levinson's solution (ML-23) by post #1 about
AC power connection schematic explanation needed
advice to Burmester's solution #88 #91 and post #70 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
PS Audio humbuster post #119 and post #10 about
?? DIY PS Audio Humbuster
Overview finished outdoor DC filter: post #227#240

Other effects (like distortion) than superimposed DC
not only superimposed DC but distortion on the mains is the clue (not removable through the DC filter) post #120 and post #43 (Bob Cordell) about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
other reasons for buzzing toroidals post #36

Local mains conditions
mention of the situation for the mains in London post #44+251
mains impedance post #64 about
DC Blocking Filter for Mains

Audible sonic differences
post #103 about
DC Blocking Filter for Mains

Ultimatest solution against unwanted buzzing effects without serial connected DC filter
twice of the actually necessary primary voltage: post #3 about
noise from transformer
read also in this case post #51 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

Various
only Thermistor (Armeterm NTC) 1-2R N.Pass post #26
only rectifier post #90 about
DC Blocking Filter for Mains
Off-Topic. inrush current limiter circuit post #82#172 and post 66+67 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
Offtopic Cyrus I+II post 29 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

DC Filter Thread Overview
dc blocker test report
dc filter
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
DC Blocking Filter for Mains
DC blocker diode/cap orientation
noise from transformer
Buzzing toroids
Mains DC Blocking help | whathifi.com
Getting rid of transformer hum - Audioholics Home Theater Forums
in German language:
Netzfilter selber bauen: wer macht mit?, Elektronik - HIFI-FORUM
Bryston Endstufe mit Trafobrummen, Frage an die Elektronik-Spezis - Verstärker, Lautsprecher, Zubehör - Analog-Forum
DC-Filter von LC Audio Technology, Elektronik - HIFI-FORUM
Antiparallele Dioden als Gleichspannungsfilter?! - HiFi Heimkino Forum
Gleichstromfilter für 20DM - der Duchbruch - HiFi Heimkino Forum
Stammtisch für HiFi- und Musik-Freunde | Stromversorgung | DC-Offset im Netz: Gleichspannungsfilter
DC-Netzfilter / SymAsym / Projekte / Home - DIY & Hifi
Stammtisch für HiFi- und Musik-Freunde | Stromversorgung | DC-Offset im Netz: Gleichspannungsfilter
and in french language:
ronronnement de transformateur torique - Page 5 - Amplification

White Paper AES/Plitron
http://www.dalitech.com/Resources/Me...ansformers.pdf
Low Noise Technology | Plitron (torodials without hum/buzz)
Low Noise Power Transformers for Solid State Amplifiers | Plitron
Plitron’s patented “Narrow Bandwidth Technology” | Plitron

Commercial Products
Kempelektroniks (NL) Power DC X-Terminator
KempElektroniks
KempElektroniks
http://www.kempelektroniks.nl/FilesC..._plus__eng.pdf
Vibex VR-1 (Spanien)
:: VIBEX ::
HIFI-Studio Wittmann: Vibex VF Linie
Vibex Reference Power Filter V1R Rhodium - die nadel - Ihr Onlineshop fuer HiFi-Zubehoer und mehr
and post #75 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
Horch (D) Line Silencer
http://www.horch-gmbh.de/Produkte/Line%20Silencer.pdf (Deutschland)
go also to post #61+69 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
OMTEC
http://www.dienadel.de/cosmoshop/artikelpdf/27871_d.pdf
PS-Audio (USA) Humbuster III
http://www.loftsound-shop.de/loftsho...III::3065.html
PS Audio - Humbuster III
Diyaudio-Mitglied "paulmc" (Chief Executive Officer/ CEO = Generaldirektor) bei PS-Audio)
schreibt zum Gleichstromfilter "Humbuster" von PS-Audio unter post #11:
?? DIY PS Audio Humbuster
Privat „Bucht“ - PS Audio DC-Filter Humbuster III - HiFi Forum
TK Audio Gleichspannungsfilter (no longer available)
Warum ein Gleichspannungsfilter (nicht mehr lieferbar)

Finished DC Filter PCBs (Kits)
L C Audio Technology / DC Filter (from Denmark)
Comment from Mr. Nelson Pass by post #2 and #26 about
dc filter
DC Filter (Erläuterungen zu den Ursachen des Brummens)
JTD Audio - Soft start and Anti-hum module (from U.K.)
DEXA Soft Start + DC / RFI Filter (from Korea)

DIY DC Filter
DC Filter für 10€
Mains DC and Transformers (Grundlagenartikel)
DC-Blocker - Scintilla-buizenversterkers
Netzfilter selber bauen: wer macht mit?, Elektronik - HIFI-FORUM
and post #73 about
Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

[Nico Ras]

And your conclusion?

[tiefbassuebertr]

Originally Posted by Nico Ras

And your conclusion?

No conclusion;
read the last by post #3 from Nelson Pass about
noise from transformer
This is for me personally the best exist solution - unfortunately not suited for existing devices, only for new projects.
Nevertheless I work on a circuit to determine the threshold of DC current for hum/noise at various toroidals.
To comment a short conclusion is impossible, because I still want to evaluate the overview themselves.

[Bonsai]

I did not go through each link above, so if I am repeating what you have already linked to apologies:-

Rod elliot has a great description of the whole issue around DC on the mains, and circuit to block it (similar to Bryston). Take a look on his site.

When I was still in Japan, I was playing my sustem and it started to make a terrible buzzing noise from the transformer. I discivered that it was caused by the tumble dryer. When I turned it off, the noise went away. So DC on the mains is quite an issue. I will build a mains isolator in a separate box sometime. might be interesting to actually detect the DC, and then switch in the DC isolator when needed.

[AndrewT]

He has referenced westhost in his list.
A high proportion of those links are connected to commercial offerings.
I doubt any of these are useful to builders who want to solve the problem themselves.

[Ron AKA]

Originally Posted by Nico Ras

And your conclusion?

My conclusion is to use a standard laminated core transformer.

[AndrewT]

They hum and buzz as well.
It's not just a toroid trait.

I have found EI to be noisier than toroid in general (by my averages of my stock and experiences).

[Ron AKA]

Quote from Bryston:

"Because toroidal cores are so efficient, they sustain magnetic flux easily. DC offset on an AC line will eventually cause the toroidal core to go into saturation by continually driving the core into one direction. This sounds bad both literally and figuratively...An EI transformer core has unavoidable gaps. These gaps are generally bad, both for stray magnetics and for overall efficiency. But, they do help here in a passive way. An EI core can’t sustain a magnetic field for long and any additional flux is sprayed out of it’s many gaps."

Net result - EI standard transformers do not have this high susceptibility to DC.

[Nico Ras]

Originally Posted by AndrewT

They hum and buzz as well.
It's not just a toroid trait.

I have found EI to be noisier than toroid in general (by my averages of my stock and experiences).

Hi Andrew, you are right that EI cores can be noisy as well, but you will find some bad manufacturing qualities, they are either missing a few laminations, windings are not tightly wound due to incorrect slack adjustment on their winders and the core is not vacuum impregnated to fill the air gaps and keeping the laminations from vibrating. Toroids can also suffer from the same bad manufacturing practices as EI cores.

When we took over Hawkins a few years ago, I had an interesting experience. The was a black gentleman who has wound toroidal cores in the company for some 37 years - that is is job. But while he wound the core he continually tapped it with a hammer. Let me assure you he is not a scientist he never went to school.

In my varied and wide stretching engineering intellectual approach I asked him why stuff up the core like that. He looked at me and said when you learn about my job you will see I am doing the right thing.

He explained that when he taps the coil as it rotates he is arranging the magnetic particals in one diredction as well as stress relieves the material - so where is the magic, I asked him to make on core without performing this stupid ritual and made two transformers. The one he tapped was less noisy, magnitizing current was 9 mA while the untapped one was noisy with 110mA magnetising current - I was bowled over.

[tiefbassuebertr]

.................................................. .................................................. .................................................. ..

Originally Posted by Quote from
[url

http://www.dalitech.com/Resources/Measuring%20Acoustic%20Noise%20Emitted%20by%20Powe r%20Transformers.pdf[/url]
(If the URL don't go open, go to post #155 and #157 about
dc filter
for the completly article)

WHY AND HOW POWER TRANSFORMERS PRODUCE ACOUSTICAL NOISE ??
Transformer noise has two sources:
- winding vibrations and
- core vibrations.
The single most effective way to reduce windings noise is by having a good quality controlled winding process when assembling them.
This research focusses on the cores of normally silent transformers, which make noise under adverse mains conditions. Transformer cores can become noisy as well under specific secondary load conditions which can be translated (transformed) into the adverse mains conditions at the primary as discussed in this paper.

There are three physical phenomena that produce noise in the magnetic core:
[1-16, Tadashi Sasaki et al, "Magnetostrictive Vibration of Electrical Steel Sheets under a Non-Sinusoidal
Magnetizing Conditions, IEEE Transactions on Magnetics, Vol. Mag-23, No. 5, September 1987, pp. 3077-3079]

1. The movement of the 90-degree Bloch walls inside the magnetic domains, frequently called Magnetoacoustic Emission (MAE); see Figure 1.
2. The rotation of the magnetic domains, that is responsible for the bulk magnetostriction; see Figure 2.
3. The Lorentz Force Acoustic Signal (LFAS) causing mechanical forces between laminations of the core; see Figure 3.

MAE occurs in the steep section of the hysteresis loop; see Figure 4. Not much sound is emitted and the bulk magnetostriction is small. The rotation of the magnetic domains is dominant near saturation in the hysteresis loop.
The magnetostriction becomes "large" and the core laminations move considerably, thus generating acoustic noise (see Figures 4 and 5).
The rattling of laminations of the core (LFAS) depends largely on the construction of the core. The EI-type cores are more prone to make noise due to their many separated pieces of lamination which mostly are only sturdy clamped at the four corners.

In toroidal cores the long role of core band is sturdy clamped everywhere due to the mechanical rolling tension and the pressure caused by the winding tension.
In general: magnetostriction, occurring near saturation of the core, is the main cause of the acoustical transformer noise, while LFAS largely depends on the construction of the core. Due to magnetostriction the core vibrates at the fundamental mains frequency and its harmonics and at core resonance frequencies. In this regard it is important to notice that a noisy transformer means that
a) the transformer is badly constructed -or-
b) that the transformer is forced to operate in a magnetic region close to or at core saturation.

The main reason why the transformer is noisy may be a combination of the above given causes.

Anyway, the device has become noisy and the amount of acoustical noise produced should be measured to determine whether or not the produced noise level is acceptable.

.................................................. .................................................. .................................................. ......
Who can post the paper from Tadashi Sasaki, mentioned above ??