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Old 18th November 2013, 10:36 PM   #1
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Default Monoblock project

So I am building a pair of monoblocks on a steel Hammond chassis that measures 17" x 10" x 3". The design is similar to the Mullard 5-20 amplifier. I can't fit the choke under the hood so I am going to mount it on top. I went with Edcor iron so the choke looks nice enough to be on top, the blue end bells with the black chassis looks good. I pretty much have my layout done and plan on posting some pics but I have a question about transformer placement I plan on having the cores line up as such:



So the output and power transformer are on the back side of the chassis with the choke up front. The choke will be between the rectifier tube and the preamp tubes. The power tubes will be on the outer side of chassis next to the output transformer.


Does this seem OK? Any advice would be great before I start drilling holes.


thanks
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Last edited by famousmockingbird; 18th November 2013 at 10:48 PM.
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Old 18th November 2013, 10:42 PM   #2
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ok so for some reason what I type in edit mode does NOT appear the same in the thread so I will post a picture ASAP
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Old 18th November 2013, 11:24 PM   #3
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What tubes are you using?
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Old 18th November 2013, 11:36 PM   #4
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From what I read in Morgan Jones book, the choke is the highest emitter of EM fields...that said, it should be tucked into the farthest corner of any chassis, away from everything as much as possible.






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Last edited by Richard Ellis; 18th November 2013 at 11:37 PM. Reason: typo
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Old 18th November 2013, 11:58 PM   #5
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What tubes are you using?


Tubes are EF86 gain stage directly coupled to 12AX7 LTP PI driving KT77 PP/23% screen taps. Rectifier tube is 5AR4.
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Old 19th November 2013, 12:01 AM   #6
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From what I read in Morgan Jones book, the choke is the highest emitter of EM fields...that said, it should be tucked into the farthest corner of any chassis, away from everything as much as possible.






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Thanks I will read up on that and maybe change my layout if it will help.
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Old 19th November 2013, 12:01 AM   #7
smbrown is offline smbrown  United States
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I was looking at some of the mono-blocks now on the Audio Note Kits site: ANK Audiokits - The Authority in High End Audio Kits
The choke on the "ledgend" and "interstage" designs seems very close to the interstage, I'd wonder about that. However, it is as far from the input tube as practical. There are other designs, like Sun Audio 2A3 that wedges the choke between power and output transformers, and much closer to input tubes.
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Old 19th November 2013, 12:03 AM   #8
smbrown is offline smbrown  United States
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Sorry, the Legend obviously does not have an IT, but power and output are very close. I guess my point is, lots of things are possible, but maybe not optimal.
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Old 19th November 2013, 12:27 AM   #9
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If at all possible, mount the choke on the side wall. Doing so allows the coil of the choke to be perpendicular to the coils of the other magnetics. Take full advantage of all 3 spatial dimensions.

If the side wall is not available, mount the choke at 45o to both the power and O/P transformers.
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Old 19th November 2013, 12:59 AM   #10
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If at all possible, mount the choke on the side wall. Doing so allows the coil of the choke to be perpendicular to the coils of the other magnetics. Take full advantage of all 3 spatial dimensions.

If the side wall is not available, mount the choke at 45o to both the power and O/P transformers.
The choke is a hair larger than 3" and the chassis is only 3" deep. I can maybe figure out a way to mount it on the sidewall but it will be TIGHT. I really like the 45 degree idea and might have to go with that if I can't use the sidewall.
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