aikido headphone amp
Jul 11, 2006 at 1:38 PM Post #34 of 70
John has a sale on the boards and the stepped attenuator kits right now too!
cool.gif
 
Jul 31, 2006 at 6:53 AM Post #35 of 70
some more photos tonight. the case/transformer and other parts has arrived. some tubes for the voltage regulator has arrived as well 2 weeks ago but I was too lazy to take photos.

some serious work should be happening soon.
 
Aug 6, 2006 at 1:17 PM Post #36 of 70
completed the soldering the amp.

the green resistors are kiwame and the red one are PRP.

All resistors and bypass caps were matched.

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photos of the completed amp

http://img93.imageshack.us/my.php?im...9mediummp5.jpg

http://img123.imageshack.us/my.php?i...8mediumlc0.jpg
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one of the capacitors was damaged while soldering. it's not a critical one (use to connect the internal shield between the triode to ground) so I could use something other than solen.

the gray tubular components are russian teflon caps. and the green ones are russian paper-in-oil caps. These make up the bypass caps.

The teflons uses magnetic leads which I have removed and I am using the internal stranded wire as leads. I have use jbweld to reseal it.

The red rings are tube dampers which are useful for capacitor damping.

The capacitors are somewhat loose so I'll use some blutack to hold them.
 
Apr 26, 2007 at 11:51 PM Post #37 of 70
after a long delay due to priorities/commitments, I've almost completed my aikido

Here are the pics:

http://img404.imageshack.us/my.php?i...4mediumns7.jpg - In this photo you can see the amp PCB and the DC heater supply for the tube. The tubes used at the moment are RCA 8CG7 cleartops and 6H30. I got other pairs of 6CG7/8CG7 that I can roll.

The volume pot is a cheap-o switch but the Vishay-Dale resistors has been handmatched by myself. In case this one sucks (I bought cause it was cheap and I want to try), I have a stand-by Elma with handmatched resistors to use. I'll be using an extension bar so I can have the volume knob at the front.

The green caps are Russian 2.2uF 400V PIO and the silver looking ones are 0.1uF Russian teflon. The black ones are Solens. They were used in places that are not as important

The caps used in the DC supply are CDE 381LX 56000uF and 4700uF. Very long life and size is smaller than others.

The heatsink is used to cool down the LT1083. It's similar to LM317 except that it has a lower voltage drop-out and it's rated up to 7A. I

Also as you can see the headphone jack has not been mounted. I still need to work on the front panel. It need a 45.5mm hole for the volume knob.

Wires has been color coded as well. blue is right channel while white is left. Except for the AC mains wires, all wires are teflon coated. 18AWG for the B+ and heater supply. 20AWG for the NE555 delay supply and LED. 22AWG for the left and right channels.
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Another shot of the amp from a different angle: http://img259.imageshack.us/my.php?i...5mediumpj0.jpg

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Here's the photo of the B+ circuit: http://img138.imageshack.us/my.php?i...6mediumqq2.jpg

It's choke-input and the capacitor is a 10uF Solen + a 2.2uF Russian PIO. it's not big at all but since it a regulated supply, other people have said it's not much of an issue. The SS parts you see are for CCS. Output current can be set by adjusting the trimmer. It's set at around 82mA at the moment. It was designed by Gary Pimm. He has remove all the DIY stuff from his site but I have a copy in case you're interested.

There was a change of PSU from series to shunt. And then the intended shunt design doesn't seem to work with the tubes that I have. So I decided to buy a few VR tubes just in case.

In the end, I went with the VR tubes bypassed with 2x 0.1uF Russian teflons (the silver tubes in the photo). It has the added benefit of not needing a heater and it glows!

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Here's a shot of the chassis top (though it's upside-down since I am testing it): http://img259.imageshack.us/my.php?i...7mediumor2.jpg

The silver tubes that you see are 100uF 430VAC ASC motor run caps. The coke-bottle tube is the VR tube while the straight bottle tube is a 5AS4 (which will be replace by a coke-bottle version just because coke-bottle = sexy!)

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here's a photo of the other equipment used for testing: http://img404.imageshack.us/my.php?i...9mediumes9.jpg

it's our Sony DVD player and a cheap headphone. These were used just because my main CD player is at work and I wouldn't used good headphones when testing a newly built amp!

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photo of ground-loop breaker and ne555 delay circuit: http://img259.imageshack.us/my.php?i...0mediumzu0.jpg

In my experience, ground-loop breaker helps in eliminating/minimizing noise. the NE555 circuit is used to delay the AC supply of the B+. So when the 8CG7 and 6H30 are already hot when the full B+ kicks in.

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another photo: http://img138.imageshack.us/my.php?i...2mediumnp8.jpg

In this photo, the 2 resistors and orange drop are used to reference the DC heater ground to B+. I believe this extends the life of the tube. (Tubes has a maximum rating for heater-cathode voltage)

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just a close-up of the DC heater supply: http://img138.imageshack.us/my.php?i...3mediumzc2.jpg
 
Apr 26, 2007 at 11:54 PM Post #38 of 70
what needs to be done:

I need to drill 2 holes on the front panel for the volume knob and LED.

I am hoping for a black paint mirror finish on the chassis. I've downloaded some guide used to paint computer cases so I'm hoping that is applicable too. I've bought the supply and a buffer to help. In case this fails, there is a place near where I live tha powder paints metal!
smily_headphones1.gif
 
Apr 27, 2007 at 12:14 AM Post #39 of 70
results: take note that I'm using a cheap headphone

Initially, only the right channel has sound. So I thought it must the headphones. I installed it on my PC and there was no problem with it. I think it is the adaptor I'm using.

I then connected the jack to the output by putting it beside the wires (not sure if the description is clear but I had to do something to make it work. Think McGyver for the older folks
smily_headphones1.gif
)

I was very surprised with the sound. soundstage is amazing. possibly some a little harshness but that could be because it still needs break-in or due to the headphone. bass is okay. I was playing something that doesn't have much bass.

Tonight, I'll be using my everyday phones (Beyer DT880) and using the usual selection for testing:

- Metallica's and justice for all and one
- beethoven's 6th symphony (1st movement)
- tschaikovsky's 1st piano concerto (2nd movement)
- vivaldi's 4 seasons (one of the movements in either summer or autumn)
- chemical brothers
- prodigy
- mariah carey - not sure of the title. but it's the 1st track of her "best" CD.
 
Apr 27, 2007 at 2:27 AM Post #41 of 70
Quote:

Originally Posted by AndrewFischer /img/forum/go_quote.gif
Are you running with the White cathode-follower or the standard Aikido output?

I'm about 4 months behind you. Just finished my power supply. I'm ordering boards for the amp in a few days.



When I bought the PCB, there was no white cathode follower.
 
Apr 27, 2007 at 2:40 AM Post #42 of 70
Quote:

Originally Posted by jarthel /img/forum/go_quote.gif
When I bought the PCB, there was no white cathode follower.


That's what I thought. You might have cut up the board though.



I'm leaning towards getting the Octal mono boards as they are on sale right now. Downside is the smaller range of tubes.
 
Apr 27, 2007 at 3:04 AM Post #44 of 70
Quote:

Originally Posted by jarthel /img/forum/go_quote.gif
can I ask why?


To make the outputs a White cathode follower. I'm not suggesting that you should have. I was just wondering what you did.

Have to decide how I'm going to configure mine.


a.
 
Apr 27, 2007 at 3:11 AM Post #45 of 70
Quote:

Originally Posted by AndrewFischer /img/forum/go_quote.gif
To make the outputs a White cathode follower. I'm not suggesting that you should have. I was just wondering what you did.

a.


most of the replies I've seen in AA and Diyaudio pertains to the old design. and the feedback has always been great. I am not sure if considerable number of people have built the white cathode follower. so I guess, the original version is safer of the two.

ps. you can't cut the single board because there are things that are shared between the two.
 
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