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Old 26th October 2010, 07:24 AM   #1
nige838 is offline nige838  United States
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Default DIY 50C5 mini amp...

Hello all,
Just wanted to share my newest project...

It's tubes are as follows:
35w4
12AT7
12AT7
50c5

It's built into a 6" x 4" x 1" enclosure, quite small...
Sounds amazing, very bluesy, even with a crap 1970s 8" that I dumpster dived for a few weeks ago...ever so slight of a hum, barely noticeable,

All tubes are pulled out of 2 1950s radios,

Total Cost: $35
Tell me what you think...
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Old 26th October 2010, 08:10 AM   #2
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weally qute!
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Old 26th October 2010, 08:17 AM   #3
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I think the capacitor on top will have a very short life..
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Old 28th October 2010, 07:33 PM   #4
nige838 is offline nige838  United States
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Well, just to update...

I left it on for 12 hours to make sure that nothing melted and everything is A OK. I'm about to start working on another design that uses the popular 50L6GT and the 12AX7 (Although I may substitute 2 12AT6 instead)

Took it to the pawnshop and they gave me $100, not bad for a $35 investment...
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Old 28th October 2010, 07:45 PM   #5
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I think you should rotate the output transformer so magnetic fields of power and output transformers would be perpendicular, it minimizes hum.
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Old 28th October 2010, 08:18 PM   #6
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and add a fuse...
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Old 28th October 2010, 08:18 PM   #7
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And ground the chassis...
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Old 28th October 2010, 09:55 PM   #8
nige838 is offline nige838  United States
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Yes, I know that I need to add a fuse, maybe 1 Amp? The chassis is grounded to the negative lead of the capacitor, and all the other grounds ground there too...

It doesn't have a bad hum at all, but next time I will run the output transformer perpendicular.

This is my first amp, so any feedback will be more than welcome. One thing that I didn't count on was the heat generated by these tubes. Now I understand why you can't just pack all of them onto a small chassis. Live and learn I guess.
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Old 28th October 2010, 09:58 PM   #9
nige838 is offline nige838  United States
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Also, should I ground the center tap from the AC in? I used the transfo. backwards to get the dual primaries to run the heaters and the other to run the B+ and B++.

Thanks
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Old 28th October 2010, 09:58 PM   #10
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Wow, congratulations!
Quite good job for the first amp!
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