Posted on Saturday, 19th May 2012 by Auw Jimmy

Please go back here if you haven’t read the first article. On this second part, I’m about to create the potting ingredients to pot my Lundahl choke. I have several experimental ingredients, so some of them might not be exposed in detail as the result is still beyond my imagination.

One of important thing that we have to remember is beware of the chemical and its effect. Some of this chemical could be dangerous if exposed with fire. The solution is to use temperature controlled electric stove or for a ‘poor man’s tools’ – I would prefer a simple double boiler. You can use candles (note the ‘s’, means you need more candles to reach your needed temperature) or you can use gas based stove. FYI, double boiler would be safer (if you can’t get a temperature controlled stove) as the temperature mostly would not exceed 100 degrees Celcius.

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Tags: Alcohol, Choke, Double Boiler, Potting, Shellac, Wax
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Posted on Monday, 14th May 2012 by Auw Jimmy

It’s been a while since this idea came to my head few months back. Now it’s time to make it happens. As you might also know that Lundahl is one of the good transformer maker. They use their own C-Core most of the time for their production, included this Choke.

Though I believe they don’t have issue with their “open” design, some people prefer to have it potted to minimize any vibration possibility (included me). So here I come, a potted choke project with this Lundahl.

First problem came to me few weeks back was how to find appropriate enclosure to house this choke. Definitely not easy. Doing custom made housing would be my last resort. After spending few weeks searching, I found a chassis from Hammond which was quite OK for my purpose. I tried to contact nearest Lundahl agent which located on Malaysia (Octave) but they didn’t have it. I also planned to give a visit to Martin Electronics located in Singapore as they carried quite a lot of Hammond stuff, but unfortunately, I was so busy in other thing and have no schedule to fly to Singapore. And last resort, I gave an email to Chris (Partconnexion) and his assistant as usual quoted me with best pricing. Well, I hated to spend almost the same with my goods price for shipping, but got no choice this time. Canadian post is always too expensive for me

After the Hammond came few days ago, it’s time to start drilling…

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Tags: Choke, Lundahl, Potting, transformer
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Posted on Sunday, 8th April 2012 by Auw Jimmy

Tamura’s iron is not new kid on the block. They have been here for a quite long time. Even Westerner also admits the quality of Tamura (well, we can see some contenders from West side but hardly to beat Japanese Iron). I’m interested to try some of Tamura’s Choke. I’ve used the A-4004, which currently a top of the line Choke from Tamura (actually, Tamura doesn’t have Choke line-up as much as Hashimoto or Tango) and quite satisfy with its performace. But I was tempted to try their other two Choke line-up: The Amorphous and The Vintage series.

Amorphous currently available in 2 variants. I take the A-4006 which capable to deliver 200mA on 10H or 400mA on 2.5H. Should be enough for most of your Single Ended or Push Pull application. For the Vintage series (this is the name that I use to call, not official from Tamura), I take the A-395 which will hold 120mA on 10H.

All those three Chokes are similar in size and weight. ‘Similar’ doesn’t mean 100% exactly same, right?

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Tags: Amorphous, Choke, Tamura
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Posted on Sunday, 18th September 2011 by Auw Jimmy

As  my Sowter Choke Input was acquisitioned by my friend. Then I have to consider some replacement. Actually my friend was interested with Hashimoto or similar, but as most of the Choke Input was designed for power amp, instead of preamp, so the specification and requirement (especially for minimum current demand) were different.

Luckily, as my preamp uses quite big current, then I can consider some Choke Input for power amp usage. One of them is the Hashimoto C-25-150CH. This choke is designed for Input application, rated at 25 H and 200 mA maximum current. DCR is claimed around 205 Ohm. Spec wise, it’s all very good to best. As material, Hashimoto is quite confident with its Orient High B core (forget Permalloy or Amorphous). Internally, this choke should be a C-Core type, with extra electrostatic shield. Oh, Hashimoto also put extra work to make this choke as a magnetic shield type. I think they do understand that Choke Input could radiate enough flux and/or electromagnetic things. Definitely, a magnetic shield design will be a nice addition. Build quality of this choke is also quite superb. With around 2.4 Kg weight, this is a heavy weight championship (remember, this is only a choke!)

The second one is a Tamura A-4004. Although it’s rated only 10 H and 200 mA maximum (or 2.5 H at 400 mA), this choke only around 10% lighter than Hashimoto Choke Input above. Physically size, this Tamura also a little bit smaller than the Hashimoto. Before, I was considering A-4006 (Amorphous) also. But due to some other consideration (as my Aikido Preamp already has Duelund CAST Ag Silver Capacitor inside), then I think non-Amorphous core will give a nice combination with it. Right or wrong? We shall prove it later…

Tags: Choke, Choke Input, Hashimoto, power supply, Tamura
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Posted on Saturday, 23rd July 2011 by Auw Jimmy

This is the final choke upgrade that I’ve been waiting for quite long time. After some discussion on the phone with Brian (1 day before his birthday), finally I finalized the order. Custom made from Sowter UK, a Choke specified for Input position. Spec wise, it should be 30H with 75mA current capacity. Rated at 500V as this one will be placed in input position – so safety first!

FYI, most designer will not go with Choke Input approach. First, because the Capacitor rated at higher voltage is so cheap and widely available. It’s easy to get Capacitor rated at 630 VDC and the cost is so far very reasonable. Second, Choke at Input is a kind of “waste” in terms of voltage. It only produces DC around 0.9x from the AC voltage source, compared with Capacitor which could produce DC around 1.414x from the AC source. Kind of voltage waste? Sort of…

Back to the choke, DCR is optimized at Level 2 raised from the standard spec (well, if you know me so well, mostly I don’t go with standard spec). At Level 2, the DCR targeted around 260R from 300R at standard spec (but I got better on real measurement). I could have option up to around Level 4 which could reduce the DCR around 1/5 times lower, but it will lift the height of this choke to 6 Kg. I don’t mind to pay more for manufacturing process and material cost, but I do mind with the 6 Kg shipment cost and the tax!

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Tags: Aikido, Choke, Choke Input, preamp, Sowter
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Posted on Tuesday, 12th July 2011 by Auw Jimmy

Not just Lundahl here, I also ordered custom choke from Jack/Electra-Print. I contacted Jack and asked him to create a Choke, with requirement to be placed in Input position. He offered me a VPI technique which (according to him) enough for Choke Input application. Other requirements was a “jimmyauw.com” standard which mean oversize construction (M6 lamination, 30H/75mA).

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Tags: Choke, Electra-Print
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Posted on Friday, 1st July 2011 by Auw Jimmy

I’m ongoing to rebuild my Aikido Preamp which has been suspended for quite long time. The target is simple: a complete wood chassis and some upgraded parts then we are done (no more upgrade or whatsoever for this Preamp). You can check link above to check the current parts used on the Preamp.

I have ordered new chokes from Sowter, Electra-Print, and Lundahl. Brian (Sowter) and Jack (Electra-Print) needs to custom my order, so they will be delayed around 2 weeks for production times. Meanwhile Per (Lundahl) got a ready to use one (LL1673) then I ordered from Kevin (K&K Audio) and delivered right to my home around 2 weeks with Priority Mail service.

Kevin helped me to match both chokes. Although from the appearance, I think they were not manufactured on same batch (you can see different font size), but from some short measurements, they are indeed quite “matched”.

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Tags: Choke, Common Mode Choke, Lundahl
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Posted on Monday, 13th June 2011 by Auw Jimmy

I need to build small chokes for my AD1865 DAC. After some calculation, it comes to specific wire length, turns, and layers. In order to maintain the stiffness of the winding, I have to use what do I have now (no winding machine here). So it seems that the combination between hands and foot does the job perfectly

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Tags: Choke, DAC, inductor, LCR Meter
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Posted on Friday, 13th May 2011 by Auw Jimmy

My cheap L/C Meter has arrived. With this new tool, I can play and explore more, especially things related with inductance, like Choke or Inductor. Although this is not the most accurate meter, but should be enough for typical daily usage. Before, I plan to take the Tonghui L/C Meter, which costs around 4x more. But this probably later on the future as this Tonghui is not easy to get. So at this moment, this cheap meter should work fine.

Below is the measurement result when measuring our previous DIY Choke.

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Tags: Capacitor, Choke, inductor, L/C Meter, Tool
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Posted on Sunday, 24th April 2011 by Auw Jimmy

I need some small inductor for my DAC power supply section, but finding appropriate one is not an easy job. I have found several ready to use inductor, but whether the construction or the inductance, doesn’t match my needs. So probably, I’m gonna learn myself to wind some.

Actually, consider this one is just for fun (definitely it’s not a neat job, as the winding completely not in symmetry between layers). Anyway, before my inductance meter arrives, practically speaking, I can’t finish this project. I just want to know how long do I need the wire to fully wind this inductor, what is the problem, and the work around to get a nice one. And now, I got the estimated length and some also learn some tricks to make a neat one.

After the meter arrives, I just need to measure how big the inductance and will do some adjustment if needed – either going into smaller wire or need to add some more turns.

And to be honest, it’s very difficult to wind manually without a winding machine. Especially when you are using small wire, as the wire is not stiff enough, so easily loose from its “formation”.

Tags: Choke, inductance, inductor, wire
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Posted on Saturday, 26th September 2009 by Auw Jimmy

It’s a weekend holiday and it’s time to scratch my laziness and doing some audio DIY mods. This time, I will try a capacitor from Jensen, the 4-Pole Electrolytic.

What makes it different from standard electrolytic? Well, it has 4 poles instead of 2 of standard electrolytic (that’s why they call it Jensen 4-Pole capacitor – I wonder why 4-Pole instead of 4-Poles?) But that’s simply out of our discussion here.

Again another question, why it has 4 Poles instead of 2? Keep reading.

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Tags: Aikido, Choke, jensen, power supply
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