Posted on Monday, 29th December 2008 by Jimmy Auw

From my previous Aikido project, I’m still thinking of improvement of my B+ PSU. Well, I still hear a small hum. There are several possibilities to be tried, but I’m thinking of improving my B+ PSU first. If it fails, then I will think another way

From the LC-LC filter used before, I’m moving into a more filtering. Well, I’m talking about another stage of LC, creating LC-LC-LC filter. Previously, I used two Samhwa 220uF/500VDC capacitors. It’s a nice price/performance capacitor - I have to admit that. But, I need to change into a higher level (to see how much the improvement).

First I remove two Samhwa capacitors. It was a tiring job to remove those two capacitors (phewww). Then, I change the first capacitor with Korean “Motor Run” Oil Capacitor (60uF/400VAC), second capacitor with Mundorf M-Lytic 560uF/400VDC, then finally with another Korean “Motor Run” Oil Capacitor (40uF/400VAC).

Well, don’t ask me why I use this Korean “Motor Run” Oil Capacitor. It’s simply because I have no budget. If you have enough bucks in your pocket, go with ASC Oil Capacitor then

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Tags: Aikido, Capacitor, HV, power supply, preamp, PSU, tube
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Posted on Monday, 29th December 2008 by Jimmy Auw

I went to my friend’s house to test my “old” Knight 600 Tube Tester. It was old, I got from eBay. I didn’t have step down transformer on hand, so I need to try it elsewhere.

It was a nice unit. Some rust on the screws, but overall all the functions were functional. The roll chart was working completely, no sign of jammed or stucked. This “simple emission tester” could check most tubes, from classic 4 pins to Octal and Nuvistor tube.

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Tags: Amplifier, Audio, tube, tube tester
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Posted on Saturday, 13th December 2008 by Jimmy Auw

A Gainclone challenge? Why not? Solid state? Why? Why? Why? Why? Why? Wise man says ask “Why” five times. But I think I will end up with same answer Sorry! Just consider this as a small killing time, boredom destroyer project uh…

But remember, we are on crisis, so no budget!!! So, I also don’t want to spend any budget… Well, small budget is ok, but really-really small.

Let’s straight to the point and back to the topic: I want to try a LM1875 Gainclone Amplifier. This is not my first time building a Gainclone, but first time with LM1875. Gainclone becomes famous because this “simple chip amplifier” could sound beautiful - in 47 Laboratory 4706 Gaincard (retail price near US$ 3000) and Jeff Rowland Concentra (retail price around US$ 6500). FYI, Gainclone family has some models, like LM1875, LM3875, LM3886, etc. Each has different specifications, especially for power rating and speaker load impedance - but all amplifier with this chip will be called as “Gainclone”.

I’ve received the PCB from my friend at local DIY forum. Now, it’s time to pick my “agents” - I mean my components

“As always, should you or any of your IM force be caught or killed,, the Secretary will disavow any knowledge of your actions. This tape will self-destruct in five seconds. Good luck, Jim.”

Well, just suddenly remember those classic Mission Impossible warning on every end of its mission tape. Now I’m starting to pick my agents. Let’s open my shelves and see what I can find. A Gainclone only need very small amount of components, around 10 pcs each channel. I think I still have some in my drawers.

Some capacitors on my drawer. Umm… I’ve collected these for quite long time.

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Tags: Amplifier, Audio, Capacitor, DIY-Audio, gainclone, resistor
Posted in Collectible Stuff, DIY Audio, Personal | Comments (74)

Posted on Monday, 8th December 2008 by Jimmy Auw

Finally, I put my Aikido Pre Amp on the chassis. Well, was a tough job since normally I didn’t do such thing (e.g. putting my DIY work on “little bit” neat chassis).

I separated inside the chassis into 3 chambers. The first one was for the main transformer, the second was for the power supply unit, and the last one was for the Pre Amp parts itself. I used 5 mm MDF wood covered with thick aluminum foil. The foil then grounded to minimize the interference.

Actually, I planned to put this Pre Amp to the Blind Test Session last week. But, the White Cathode Follower used in my Pre Amp seemed have some trouble when connected to higher impedance load (e.g. the input volume control on amplifier). I need to check it to find and confirm the problem later.

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Tags: Aikido, Audio, chassis, DIY-Audio, pre amp, tube
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Posted on Sunday, 7th December 2008 by Jimmy Auw

Last week, located at Audio Lifestyle Magazine office (also known as TubeLover showroom), held a Pre Amplifier Blind Test Session. If I could recall my brain correctly, we have 38 contenders, from Aikido 6SN7 Pre Amp, to antique #26/#27 Pre Amp. Well it was so nice and crowded session, from 10 am to 10 pm. Over 12 hours, 8 preliminary sessions (5 Pre Amp each) + 1 final session. I was sooo tired to judge in all those sessions (except session III where I need to receive some phone calls). We have 5 judges and some audience to pick favorite/people’s choice Pre Amp.

Enjoy some pics here. So many Pre Amp, so many design! The equipments was Consonance CD Player 2.2, Jadis Defy 7, and Tannoy Stirling full range speaker (with extra Fostex super tweeter).

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Tags: Audio, Blind Test, pre amp, Pre Amplifier, tube
Posted in DIY Audio | Comments (7)