Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: llama on May 30, 2013, 11:51:57 am
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Hi All. Well I'm on build #3 - an AX84.com October Club Ver9, but instead of going with the layout plans, I'm using another re-purposed chassis. Its a 20Watt PP 6V6 amp.
I'm trying something new on this one, but want to know your knowledgeable opinion of the location of the power tubes.
Do the power tubes being close to the PT cause noise issues? or is it more a matter of heat?
I've included a pic of the top of the chassis here: http://www.llamatone.com/wp-content/uploads/2013/05/ML20-mock-layout.jpg (http://www.llamatone.com/wp-content/uploads/2013/05/ML20-mock-layout.jpg)
I'm ready to move on, but i want to be sure.
Thanks Again - Scot
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I would personally not use that layout. Also, that 380-0-380 PT is likely to cause you some grief in a 6V6 amp.
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Your PT will give you about 530VDC unloaded. Trying to drop that to 350 is going to generate a LOT of heat, or at least I would think so. Just my 2 pennies. :smiley:
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If you want 350vdc, work backwards.
350vdc + ~30v (presumed rectifier voltage drop) = 380v
380v / 1.414 = ~269vac
So you want a 270-0-270v transformer, or something near that.
For me, I'd keep the rectifier and multi-cap can right next to the power transformer. Choke may go between power transformer and output transformer. I would keep the 6V6's right next to the OT. I'd keep the bias pots near the 6V6's, but perhaps on a side of the chassis instead of the top face (though my latest amp had them on the top face). I'd probably want meter pin jacks near the pots and 6V6's to insure I didn't have to open up the chassis.
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Thank you all. Back to the drawing board and build it as I should.
Thanks~
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Hi there, sorry for my absence, Summer was quite a lot of fun, but now back to fun.
Thanks for all of your comments, as far as the PT, I'm going to start with what I have now and maybe go for a power scaling option or new PT.
I have completely restructured my layout. Here are two pics of the rough layout which includes the power amp (PT, Rec tube, OT, 6V6's CapCan, bias pot and PI tube). http://www.scotpresant.com/2013-08-24_17.51.37.jpg (http://www.scotpresant.com/2013-08-24_17.51.37.jpg) & http://www.scotpresant.com/2013-08-24_17.55.11.jpg (http://www.scotpresant.com/2013-08-24_17.55.11.jpg)
The preamp section will occupy the front section of the chassis, where it is bare in the pic.
Does this layout make more sense? :dontknow:
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kinda but not really.but i have no builds under my belt so listen to the pros.move the cap can over to your rec and pt.move the output tubes across the back of the chassis.if the guys are saying that pt is going to be an issue then it's going to be an issue.
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Does this layout make more sense? :dontknow:
Yes, it's just a little confusing to look at with all of the old holes there......
You should tell the guys that you will be making a new bottom plate from aluminum to cover all of the existing holes....
You should also let them know that you are re-using a certain chassis for a reason,,,,,i.e.,,it fits in a really cool enclosure, and that's what will make it unique.
When you are a trailblazer (as you obviously are),,,,sometimes you must walk down the new trail alone and come back to tell the others that there was nothing to be afraid of.....
And other times you will walk alone and get bitten by a snake and die alone..........the price of being a trailblazer :icon_biggrin:
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Thanks Tim,
I have moved the can cap to the other side, thanks. I expect to have trouble, that s the only way i learn. If I buy the correct PT now, I may miss some important lesson in V=IR or something along those lines. I need to see things myself for a fuller understanding. This build is more of a learning tool build, rather than a club blaster, but can travel easily.
I will likely buy a new PT anyway, but sometimes its the journey that is important.
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Does this layout make more sense? :dontknow:
Yes, it's just a little confusing to look at with all of the old holes there......
You should tell the guys that you will be making a new bottom plate from aluminum to cover all of the existing holes....
You should also let them know that you are re-using a certain chassis for a reason,,,,,i.e.,,it fits in a really cool enclosure, and that's what will make it unique.
When you are a trailblazer (as you obviously are),,,,sometimes you must walk down the new trail alone and come back to tell the others that there was nothing to be afraid of.....
And other times you will walk alone and get bitten by a snake and die alone..........the price of being a trailblazer :icon_biggrin:
Thanks SilverG!
I forget that all this exists only in my head and is not common knowledge. Trailblazer...no.
I am re-purposing a 1960's Sig gen that produced 3 watts at 600 ohms. When it worked, it used two 6V6's and a few others as well. The chassis is housed in a big steel enclosure and looks unique.
Not sure of the current ratings, but the PT is rather large and high in HT. My purpose of this build is to have removable pre amp stages so i can build and design new Preamp circuits while still playing the amp. I figured that the ax84 October was a good Power section and interesting place to start.
The latest layout is very close to what HBP said in May. Thanks everybody!