Williamson 6L6 Monoblocks (Finally)

sorenj07 · 4th March 2007, 08:22 PM

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:

Another option:

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.

EC8010 · 4th March 2007, 09:38 PM

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.

anatech · 4th March 2007, 10:08 PM

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

grhughes · 5th March 2007, 12:27 AM

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

Drewaudio · 5th March 2007, 05:33 AM

Could you tell me where you got the output transformers from (their their cost)?

Cheers!
Andrew

sorenj07 · 5th March 2007, 02:23 PM

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.

sorenj07 · 5th March 2007, 02:25 PM

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.

crispycircuit · 5th March 2007, 05:18 PM

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....

crispycircuit · 5th March 2007, 05:23 PM

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???

sorenj07 · 5th March 2007, 08:21 PM

it isn't, there's the 193J for that (200mA). the 40mA choke is for the input, splitter and driver stages.

4th March 2007, 08:22 PM	#1
sorenj07 diyAudio Member Join Date: May 2006	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: Another option: 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.

4th March 2007, 09:38 PM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	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. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

4th March 2007, 10:08 PM	#3
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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 __________________ "Just because you can, doesn't mean you should" © my Wife

5th March 2007, 12:27 AM	#4
grhughes diyAudio Member Join Date: Mar 2005 Location: Cubicle Sweet Cubicle, SW, MO, USA	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 __________________ "The gift of imagination is the gift of the gods imparted to a few for which they receive innumerable kicks in the a$$ their entire life." Le Corbusier (Edward Jenneret)

5th March 2007, 05:18 PM	#8
crispycircuit diyAudio Member Join Date: Feb 2007 Location: Near Buffalo NY USA	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.... __________________ The stuff you don't know always humbles us.........

5th March 2007, 05:33 AM	#5
Drewaudio diyAudio Member Join Date: Mar 2006 Location: New Zealand	Could you tell me where you got the output transformers from (their their cost)? Cheers! Andrew

5th March 2007, 05:23 PM	#9
crispycircuit diyAudio Member Join Date: Feb 2007 Location: Near Buffalo NY USA	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??? __________________ The stuff you don't know always humbles us.........

5th March 2007, 08:21 PM	#10
sorenj07 diyAudio Member Join Date: May 2006	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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