Clementine 6l6 completed

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

Clementine 6l6 completed

Postby vvelt » Mon Sep 09, 2013 3:35 pm

clem-front.jpg
Front view
clem-front.jpg (508.84 KiB) Viewed 2621 times

Finally finished my 6l6 Clementine and absolutely love it! Compared to my solid state amp this is much more live sounding with great presence - I guess I'm hooked on tubes now! I haven't made any electronics project since I was a teenager building Heathkits. Thanks to Separks for such a great project!

I decided to build this with a switch for NFB just to hear the difference, so I added the 680 ohm resistors and 6800pF caps noted in Separks' Ultra topic to my Mouser order. I ordered the 1/2 watt size resistors to fit the board but when I received them they were large, more like 1 watt. Then I decided to add a 4p3t rotary switch with an additional resistor so I could vary the feedback from none to medium to maximum. I took a guess on the additional resistor value at 1.3k ohm, 1 watt. These came in really small, more like 1/4 watt size, so now I'm really confused. Anyway, are these resistor sizes OK to use without burning up? How about using the switch, is it safe to use while the amp is running, or should I power down before changing it? See close up below of the switch and wiring.

I also followed the additional grounding scheme posted in an earlier topic, grounding the outputs to the board and chassis (thanks highflyin9). And Tom McNally's post on the spark test for filament windings came in handy, now there's plenty of heater current to roll tubes at some point. Just pure luck, I found that the mounting holes for the choke lined up exactly with the front end of the power transformer. Across the back end of the transformer I added a small mending plate and terminal strip to hold the power connections. I used a Powercon inlet to avoid needing a rectangular hole in the chassis.

The amp chassis is from eBay seller hma60, and I like it a lot so I hope they make these available again. I had it powder coated in silver vein and it looks sharp. There are times when I like have one stereo channel louder than the other so I used 2 pots to control volume since I couldn't figure how to add a balance control. Does anyone know how to add balance? Anyway, it was a good excuse to go all out on the retro Fender look, and the chicken head knob on top is for the feedback switch.

clem-inside.jpg
Inside view
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clem-nfb-switch.jpg
NFB via 4p3t rotary switch for Off, Medium and High feedback
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clem-rear.jpg
Rear view
clem-rear.jpg (457.75 KiB) Viewed 2621 times
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Re: Clementine 6l6 completed

Postby Shannon Parks » Thu Sep 12, 2013 9:24 am

Great looking amp! All these Clementine pix are making me want to build another. Your adjustable feedback switch is A-OK. Their ratings are fine. Of the top of my head, I see no reason why you you can't adjust the feedback on the fly. If there was any switch popping noise, just turn down your volume first. As far as balance, I think your dual mono volume pot seems fine and simple to me.

Shannon
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Re: Clementine 6l6 completed

Postby highflyin9 » Tue Sep 17, 2013 9:28 am

That's a real beauty, nice work! ;)
My DIY Electronics Blog: DIYAudioBlog.com
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