A wine red dual-mode Clementine

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

A wine red dual-mode Clementine

Postby Olof » Sat Apr 23, 2016 8:26 am

Finally got the time to finish her, and the sound is every bit as good as you guys have claimed it to be! [:)

I made the modes switchable by putting a toggle switch from the screens to either UL taps or through resistors to plates. Also put in a switch for feedback on/off. Didn't make sure everything would fit before drilling so the coupling caps had to go on their own VIP balcony... whoops. Chassis is the standard hammond aluminium 12"x8"x3".
The paint was done by wet sanding the chassis with 120, 240, 400 and finally 800 grit, then several layers of spray primer, paint and clear coating. Transformers same procedure except I only used 400 to get the clear coat off and used no primer.

Front.jpg
Front
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Back.jpg
Back
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inside.jpg
Inside
inside.jpg (218.84 KiB) Viewed 1600 times


switches.jpg
Mode and feedback switches
switches.jpg (195.18 KiB) Viewed 1600 times


Caps.jpg
Coupling cap balcony
Caps.jpg (200.17 KiB) Viewed 1600 times


I will listen to her for a while before I do any measurements on the actual performance. I did measure the power consumption though, loaded with KT88s the input effect is around 75W, with 6L6GCs it's around 60W.

Had a blast building this, the PCB made it super straight forward. Hats off to Shannon!
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Re: A wine red dual-mode Clementine

Postby Geek » Sat Apr 23, 2016 11:23 am

Oooo, like that (love)

Some time ago, a guy who owned a hot rod shop did a chassis in true multi-layer candy apple red. Been hooked on the colour since :))
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Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Re: A wine red dual-mode Clementine

Postby croudyj » Sat Apr 23, 2016 11:42 am

Hi Olof,

That looks really nice. It's a real shame about the lamp getting in the way of the capacitors. I am in the early stages of a Clementine 6L6 and I've been obsessing about parts placement ahead of time because that is exactly the kind of thing that would happen to me. I keep measuring stuff and making mock-ups before I order the parts. The board placement does kind of limit where you can put things. I would like the volume knob in the middle but it's so big that it's not going to fit there, which explains why everyone puts their volume knob right at the edge. I'm also going to use a 2" high chassis so it will be even more cramped in there.

Unfortunately I ordered the chassis before I realized how tall the 120uF capacitors are. Because of the 2" limitation, I had to find some smaller ones that would fit. I see you used 100uF capacitors instead of the specified 120uF ones. May I ask the reason? I don't think you had a height problem like I do.

I recall that you were the guy who got stuffed by Edcor when they didn't ship your transformers but made you pay the shipping anyway. I was horrified to read that and almost reconsidered using them. If you don't mind me asking, what happened? Why wouldn't they ship to you?

Congratulations on a job well done!

John
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Re: A wine red dual-mode Clementine

Postby TomMcNally » Sat Apr 23, 2016 1:14 pm

Very nice !
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Re: A wine red dual-mode Clementine

Postby Olof » Sun Apr 24, 2016 2:26 am

@ Geek, Yeah I've seen a few really good looking red ones here on the forum too. I didn't have access to powder coating, but I'm pretty happy with the result anyway.

@John, The caps are switched to ones with higher voltage rating, I found the 450V ones a bit too close for comfort. The change in value was probably just because I couldn't find any 120u ones that would fit.
Yes I had a bit of bad luck with ordering from Edcor. The things never arrived and neither Edcor nor the dutch post (I lived in the Netherlands at that time) would take responsibility for it. Long story short, in the end I got them from Don Audio in Germany instead. More expensive but fantastic service, would recommend.
Thanks for the kind words!

@ Tom, Thanks! Got plenty of inspiration from your builds as you can probably tell (y)
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Re: A wine red dual-mode Clementine

Postby croudyj » Mon Apr 25, 2016 12:43 pm

I see -- it seems they got 'lost' in the post then. That happened to me once with £100 worth of knobs and jacks, but the post office did at least refund £30. Still, I lost £70. That was when I lived in Europe and ordered from the UK with my dad's help.

About the caps -- I have an unforeseen space problem which means I have a limited choice, so I'm choosing some 100uF as well which are a bit smaller, and I can get 450 or 500 volts in that size, so I might as well get the higher voltage ones too.

Thanks!

John
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Re: A wine red dual-mode Clementine

Postby Olof » Tue Apr 26, 2016 9:15 am

I will never get tired of seeing this! (lol)

Clementine front.png
Clementine front.png (270.38 KiB) Viewed 1526 times


clementine side.png
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clementine side 2.png
clementine side 2.png (443.77 KiB) Viewed 1526 times
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Re: A wine red dual-mode Clementine

Postby Geek » Tue Apr 26, 2016 12:00 pm

Desktop wallpaper! Thanks! :))
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Re: A wine red dual-mode Clementine

Postby Olof » Sat May 07, 2016 12:09 pm

So after some listening I am convinced that triode sounds way better than UL. Didn't understand why, so I did a quick frequency response test:

frekvenssvar.png
Frequency response
frekvenssvar.png (51.28 KiB) Viewed 1451 times


Is the UL mode meant to look like that? I don't like the look or sound of that low-end resonance..

@ Geek, I'm flattered :)) here's the full res ones!
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Re: A wine red dual-mode Clementine

Postby Geek » Sat May 07, 2016 8:19 pm

Thanks! :))

That low end hump is caused by the NFB loop cutting off due to the transformer... the LF response limits the amount of feedback, therefore causing the gain to skyrocket. In a ST-70 with one of my driver boards, the hump is invariably at 4Hz.

Can be cured by using smaller coupling caps, limiting the LF gain of the circuit.

I use a cap box while sweeping and choose a cap that makes it a proper rolloff without cutting into the sonic range.

Cheers!
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