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Williamson 6L6 Monoblocks (Finally)
Williamson 6L6 Monoblocks (Finally)
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Old 4th March 2007, 08:22 PM   #1
sorenj07 is offline sorenj07  Germany
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Default Williamson 6L6 Monoblocks (Finally)

Well, I finally got all 99% of all the parts to put together a pair of 6L6 monoblocks, probably with a Williamson topology. Here's a tentative layout:

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The tubes are 4 Sov 6L6WXT+'s, 4 Sov 6SN7GT's, and 2 NOS 5U4GB's (forget which type..)

The big cylinders are 80uF 370VAC motor run capacitors for the first L filter with the 193J. The wide, flat caps are 40uF 330VAC motor run caps for the second
L filter, in conjunction with a 156G (9H 40mA, left out of picture). Finally, the white plastic cylinders are 22.5uF 280VAC film capacitors for the input and splitter stages.

One of my concerns is that the 80uF caps are only rated to 70C (the 40uF is 90C and the 22.5's are 100C) so I'm a bit leery of putting tubes so close to it. Is that far enough?

I'll probably have to have a 3" tall chassis (boo) to fit the 40uF and 22.5uF caps and the small choke. I have most of the nitty gritty coupling caps and resistors and whatnot, and am just waiting on picking up a pair of aluminum 17x10x3" chassis. I'd love to be able to sub in KT88's or something given that each chassis gets its own 282X, and the 6.6K 60W OPT would probably work decently.
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Old 4th March 2007, 09:38 PM   #2
EC8010 is offline EC8010  United Kingdom
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I'm not sure which magnetic lump is which. I'm guessing that the biggest is the mains transformer. I'd move them all a little further apart, half an inch, or twelve millimetres. I'd also make sure their coils are all at 90 degrees to one another.

Don't worry about the temperature rating of the capacitors. Keep the valves towards the edge of the chassis (where they can cool easily) and away from the capacitors. Your first layout is better.
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Old 4th March 2007, 10:08 PM   #3
anatech is offline anatech  Canada
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Williamson 6L6 Monoblocks (Finally)
Hi sorenj07,
It also helps to drill a circle of holes around the tubes. That way the chassis can ventillate as well and you encourage air flow around the tubes.

Turning the cores 90 keeps them from coupling to each other. Distance will help as well.

-Chris
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Old 5th March 2007, 12:27 AM   #4
grhughes is offline grhughes  United States
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Williamson 6L6 Monoblocks (Finally)
Default Why don't you follow Marantz, McIntosh?

I would arrange the transformers in a straight line (power transformer, then choke, the output transformer) but with their axes alternated along one edge of the chassis and the tubes arranged in a staight line on the other edge of the chassis. I would locate the input tube as far away from the power transformer as possible. I would locate the rectifier close to the power transformer and right next to the the two audio power tubes. So divide the chassis into three parallel lines, one in the center for the filter caps, the one near the right edge for the tubes and the one near the left edge for the iron. The star ground could be in the geometric center of the chassis near the filter caps. If you use a 3 inch high chassis then I would cut oversize holes for the three high heat tubes and maybe recess them into the chassis or cut numerous holes around them for ventilation. Ray Hughes
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Old 5th March 2007, 05:33 AM   #5
Drewaudio is offline Drewaudio  New Zealand
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Could you tell me where you got the output transformers from (their their cost)?

Cheers!
Andrew
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Old 5th March 2007, 02:23 PM   #6
sorenj07 is offline sorenj07  Germany
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Quote:
Originally posted by anatech
Hi sorenj07,
It also helps to drill a circle of holes around the tubes. That way the chassis can ventillate as well and you encourage air flow around the tubes.

Turning the cores 90 keeps them from coupling to each other. Distance will help as well.

-Chris
I'm considering finding some metal grills and cutting out a rectangular section from the chassis, mounting the grill, and putting the tube sockets on that. It has been nicely implemented in some amps I've seen and probably allows for more airflow. Heck, I could even put some Vantec Stealth 60mm 12VDC case fans in the 3" tall chassis for real airflow And yes, the cores are all 90 relative to each other.


Quote:
Originally posted by Drewaudio
Could you tell me where you got the output transformers from (their their cost)?

Cheers!
Andrew
Hi, the transformers I'm using are Edcor CXPP60-8-6.6K's. They're very reasonably priced at just under $60 each, and have a 60-watt 20Hz-20KHz power capability. I don't expect to need all of it for 6L6 tubes but it's nice to have that much headroom, especially if I experiment with bigger tubes like the 6550/KT88.
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Old 5th March 2007, 02:25 PM   #7
sorenj07 is offline sorenj07  Germany
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Quote:
Originally posted by EC8010
Don't worry about the temperature rating of the capacitors. Keep the valves towards the edge of the chassis (where they can cool easily) and away from the capacitors. Your first layout is better.
I should probably mention that the capacitors on the right in the second picture aren't meant to be included on top of the chassis, they'll still be tucked away beneath the plate.
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Old 5th March 2007, 05:18 PM   #8
crispycircuit is offline crispycircuit  United States
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The 40 ma choke is only good for the driver/input stage due to the low current rating. If your going to use a choke in the B+ supply it will need to be 500 ma. if your going to try to run 6550 tpye outputs.... And to have enough current for 4 - 6L6s you will also need 2 - 5U4 rectifiers, especially if 6550 tubes are used. Big amps need big current and that's espensive, heavy, & blah, blah....
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Old 5th March 2007, 05:23 PM   #9
crispycircuit is offline crispycircuit  United States
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Opps... Your using 2 6L6s per amp. Please excuse my earlier post. My coffee hasn't kicked in yet... The 40 ma choke is still not big enough current wise to be used in the main B+ supply... Now where's my coffee???
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Old 5th March 2007, 08:21 PM   #10
sorenj07 is offline sorenj07  Germany
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it isn't, there's the 193J for that (200mA). the 40mA choke is for the input, splitter and driver stages.
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