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.
An externally hosted image should be here but it was not working when we last tested it.
Another option:
An externally hosted image should be here but it was not working when we last tested it.
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.
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.
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.
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
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
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 airflowanatech said:
And yes, the cores are all 90° relative to each other. 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.Drewaudio said:
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....
With a project list containing a 832PP, 2A3SE, 12A6PP, 6AQ5PP and a 6L6PP (I've got the tubes at least), I am interested in knowing how the schematic looks like.
I would propably go for a stereo-amp, but from the 2A3-project I notice that stereoamps are tending to be BIG, especielly with big transformers.
I would propably go for a stereo-amp, but from the 2A3-project I notice that stereoamps are tending to be BIG, especielly with big transformers.
the 193J, according to Angela's website (I think mine measured a tiny bit under this), has a DCR of 82 ohms. I figured that 200mA is enough headroom for most purposes. Don't forget that the choke can pass higher current, just at much reduced inductance.salas said:
soundbrigade said:With a project list containing a 832PP, 2A3SE, 12A6PP, 6AQ5PP and a 6L6PP (I've got the tubes at least), I am interested in knowing how the schematic looks like.
I would probably go for a stereo-amp, but from the 2A3-project I notice that stereoamps are tending to be BIG, especially with big transformers.
first, i'd definitely recommend monoblocks. channel separation is pretty much as good as it gets, power supplies are easy to derate, etc etc. the williamson topology is pretty classic but here's pretty much what I'm going to use as a schematic, albeit with some minor changes in the 6L6's biasing network. I'm going to use a 5W 420 ohm resistor per tube into a 100 ohm 5 watt pot, the middle leg of which goes through another 100 ohm pot to ground. adjust balance and total current
An externally hosted image should be here but it was not working when we last tested it.
the caps i'm using are a bit different from this schematic, from an Acrosound catalog. .047 and then .47uF for the couplers and the PSU ones are a bit bigger, see above. Morgan Jones has a good discussion about the Williamson topology in his book Valve Amplifiers (edition III) which I recommend that EVERYONE get
I will dig out a few 6L6 ideas I have been looking at. I will show them tomorrow as comparison.
I really have to a have a medium power amplifier and I am assured the 6L6 will do the job. Please tell us all about your project (loads of pics!!) as I certainly will follow this thread and grab inspiration for a upcoming construction.
I really have to a have a medium power amplifier and I am assured the 6L6 will do the job. Please tell us all about your project (loads of pics!!) as I certainly will follow this thread and grab inspiration for a upcoming construction.
Some schematics I have been considering because of their simplicity and low parts count. Well that are factors that I find important to me - fewer components, less chance of messing something up.
ECF8 + 6L6
6SL7 + 6L6
This looks intriguing with a LM317 as CCS on the cathodes of 12AT7:
12AT7 + 6L6
More complicated and not even close to PP but PSE ... Intriguing but I am not even considering this one, just enclose it for the sake of it:
PSE 6L6
ECF8 + 6L6
6SL7 + 6L6
This looks intriguing with a LM317 as CCS on the cathodes of 12AT7:
12AT7 + 6L6
More complicated and not even close to PP but PSE ... Intriguing but I am not even considering this one, just enclose it for the sake of it:
PSE 6L6
This should be my final layout. A couple more motor run caps along with a little choke are hidden beneath, chassis size is looking to be around 17x9x2.5".
An externally hosted image should be here but it was not working when we last tested it.
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