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Old 11th February 2006, 03:38 AM   #1
arnoldc is offline arnoldc  Philippines
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Default Simplest flea-powered amp?

I have always wanted to make something really small I can bring to the office (and also use at home) and 0.5W - 1W is all I need.

I have been reserving my 12B4 for this but I was side tracked and made a 12B4 preamp instead, which I really liked. Besides, I don't think that the 12B4 can be run without a driver.

I wanted the purest (sic) single triode amp (duh) that can be driven from a CD player.

From the tubes available with me, it seems that the 417A is capable of producing some watts with a 5W plate dissipation, so I was thinking of putting in a 5K load and drive it around 25-30mA. Bias it around 2V and I should be fine? Maybe?

Are there any triode candidates out there? Maybe I can beg friends if they have any that you may suggest
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Old 11th February 2006, 03:46 AM   #2
Sheldon is offline Sheldon  United States
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With ss power supply, this would be one tube:

http://www.sempermusica.com/

Search under "spud amps" for more examples of the genre.

Sheldon
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Old 11th February 2006, 03:51 AM   #3
arnoldc is offline arnoldc  Philippines
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Hi Sheldon, I like that! Can we ditch the input transformer?
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Old 11th February 2006, 04:05 AM   #4
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by arnoldc
Hi Sheldon, I like that! Can we ditch the input transformer?

I don't see any reason you couldn't sub in a cap for the transformer, or no cap. Note that I haven't looked up that transformer to see if he's getting any gain there. But here's one with the same tube and just a pot on the input:

http://digilander.libero.it/paeng/projects_frame.htm

Edit: Actually, no pot shown, but could be one. Should be no problem as long as the source has no DC.
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Old 11th February 2006, 04:26 AM   #5
arnoldc is offline arnoldc  Philippines
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Great!

Now I'm fired up I'm taking my amp prototyping chassis from the storage and make one, now!

Thanks Sheldon.
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Old 11th February 2006, 04:35 AM   #6
Sheldon is offline Sheldon  United States
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These always looked cool to me, and I might build on some day. Curious to see what you think.

Sheldon
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Old 11th February 2006, 08:30 AM   #7
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How about an ECL82/PCL82 amp - cheap and plentiful and a one tube amp.
Even better try an ECL86, slightly better tube but slightly more popular.

Shoog
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Old 11th February 2006, 09:26 AM   #8
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Default Tube amp kit

Hi all,
I cheated and took the easy way out.

Got the amp kit from Antique Electronic Supply and it works. Each morning I get into the lab and turn it on. It runs a full 12 hour day, every day.

It gets coments and always brings a smile to visiting brass who come here.

I don't have the 'ears' any more to know good from great, but it keeps me happy and it was a snap to build.

Good luck on this project, perhpas I will order parts for one of these as well.

Later dude
Jack Crow
tdy
Camp Arifjan, Kuwait
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Old 11th February 2006, 02:53 PM   #9
jane is offline jane  Norway
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Quote:
Originally posted by arnoldc
Hi Sheldon, I like that! Can we ditch the input transformer?
You probably can. The output tube (6S45P-E) needs 2V peak for full drive, quite close to line level.
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Old 11th February 2006, 04:05 PM   #10
arnoldc is offline arnoldc  Philippines
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Done!

The picture shows the amp in testing in the kitchen (yeah, I assembled it in the kitchen as my workbench has another unfinished project on it) with Kenwood car speakers.

This amp sounds great with the cheap Hammonds on it I like the tone so much! So this is how a real single triode amp sounds like It's so pure, I'm listening to Hayley Westenra's Pure album.
It's now driving my DIY Altec speakers.

I like it, I like it!

Click the image to open in full size.
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