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Hi,
I am searching for DIY power filter/balanced power to upgrade the power to my gears. Search in this forum revealed that the Hammond (193L or 193M) would be a good power supply tweak. I have searched through a number of posts but still not able to identify How I can use the choke for power supply tweak. How is the choke be wired and used? WOuld those with experience with these chokes asvise or point me to some link on how to use these chokes for PS filtering.
In addition, these chokes are not available locally. Can I use standard chokes for tube gears with similar specification for this tweak? I am a tube DIYer adn am able to source different chokes locally with similar spoecification.
I have used the search function and read through lots of posts but still not able to determine how to use these chokes. Sorry for my low level question.
Thanks
Andy
Follow Ups:
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This tweak works because the inductance of the power supply filter chokes in question, 5 henrys or 10 henrys, is enough to limit the 60 Hz current when they are connected to the 120 volt mains. If you are located where the mains voltage is 240 volts, be sure to use at least 10 henrys to avoid drawing excessive current.
Be sure the alternative chokes you use are rated in henrys, not millihenrys. There are large chokes in the millihenry range, and connecting one of the these to the mains will result in a spectacular test of your circuit breaker.
Hi Sekela,
Thank you for your information. Is a choke in the 10h - 20H rane suitable for this application? I have read some old post that the DC resistance value of the choke sholdbe close to the supply main frequency. I.e For 50 hz area, prefer to have dc resistance close to 50 ohm while in 60 hz area prefer to have the dc resistance close to 60 ohm . Is this correct? If this is true, I may need to custom made a choke with 10h - 20h inductance and close to 50ohm dc resistance as I am in Hong Kong with 50 hz supply main.
It would be easier for me to get alternative choke locally and Hammond is not available in the generl consumer market in Hong Kong. Shipping it across the ocean will be prohitly expensive compared with the price of the choke.
By the way, how do you find this choke tweak compared with a well implemented ac filter (e.g a diy Risch filter).
Thanks
Andy
The reactance of the choke limits the current it draws at the mains frequency. The DC resistance should have some relationship to the resistive part of the choke impedance at high frequencies.
The purpose of the choke in this application is to provide a dissipative load to high frequency electrical noise (RF noise). If the choke reactance (ie, the value of inductance that is specified for it) applied to all possible frequencies, then it would be essentially an infinite impedance to radio frequency noise. However, the choke has parasitic capacitances that allow the RF noise current to flow. There will be some resistance associated with this parasitic current path that is higher than the DC resistance. For one thing, the RF current only flows on the outside skin of the winding wire. Thus, there will be some relationship between the resistive part of the RF impedance and the DC resistance, but the relationship will depend on the details of the wire and winding methods.
I used a large transformer instead of a choke and got a benefit in noise reduction. I get better performance from R-C networks. I did not pursue the Hammond choke tweak because I was making progress with AC filters made with resistors and capacitors. If you would have to spend a lot to make a suitable choke, I suggest experimenting with Wima metallized paper suppression capacitors (MP3 type) and Precision Resistive Products (PRP) half-watt resistors. The caps are rated for use with your AC mains, so there would be no safety concern.
Hi Sekela,
Thank you for your response and advices. Would you advise some link or design on the RC filter. The RC filter will be a better idea.
I may aslo search your old posts to see if I can find an answer.
Thanks
Andy
The design is proprietary and involves others, so I can't post it. However, you can easily do some experiments and come up with a design you like without spending a lot for parts or shipping.
I use a set of different capacitor values, with all the R-C strings in parallel. Each cap has a self-resonance frequency above which it acts like an inductor. Using a set gives broader frequency coverage for damping the noise.
Use only suppression capacitors that have AC voltage ratings. These come rated as "X" for line-to-neutral and "Y" for line-to-ground service. The different ratings reflect different test conditions and approvals by safety agencies. "X" caps can fail to short or open under the expectation that the circuit protection device (fuse or breaker) will operate to kill the power in the event of a short. "Y" caps should only fail to open-circuit, as energizing the safety-earth could cause a lethal condition. It is perfectly proper to use a "Y" cap for line-to-neutral, but not proper to use an "X" cap for line-ground.
Suppression capacitors come with a variety of dielectrics. The only ones I like for use with an audio system are the Wima metallized paper, MP3. Rifa metallized paper are also available, but these use plated steel wire leads, while the Wima are non-magnetic. This seems to matter.
You can use flame-proof resistors or the PRP resistors encased in flame-proof Teflon tubing. The filter should be constructed so that it does not start a fire if one of the capacitors should fail to a short-circuit.
Use a symmetrical construction of -R-C-R- instead of a simple resistor and capacitor in series for each string.
Experiment with higher values of resistance. Each different cap size seems to prefer a different amount of series resistance.
Hi Sekela,
Thank you for your advices and I will start from Here.
Regards
Andy
Alan published extensively on this particular tweak in the archives here. I believe Alan was the one who surfaced and promoted this particular method and mechanism.
Also, Al Sekela posted briefly on how to use a transformer similarly at one point.
Both methods are simple parallel filtering, using a plug to have the choke (or transformer) take current from the hot to the neutral lines; the transformer tweak adds an R-C load on the secondaries, and I cannot help you there. I have one of the latter and it works, but I don't know how to calculate the load for you.
I use mine exactly as Chris O described.
There are numerous sources for Hammond products including the 193L.
RayBan
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Long Live Dr.Gizmo
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