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Old 11th December 2008, 08:59 PM   #1
athos56 is offline athos56  United States
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Default My SE KT-88 Build thread

Ok here it goes, I got all the parts I need to build a SE KT-88 amp. Its based off of this schematic posted by you know who on the Tubecad.com site. It has an Aikido front end. The PSU is supplied by a hammond 278CX, and I'm using 6D22S diodes for rectifiers. The PSU is a CLCLCRC. The Chokes are 2 massive 193Q's and my caps are all solen 47uf/600v, except for the first cap which is a Solen 4.7uf cap. This PSU arrangement is the same as I used in my Buffer just beefed up a notch. My opts are 5k Edcor's (CXSE25-8-5K). As usual I went way overboard, I'm thinking of calling it the Iron Man. Now I have to go work out so I can lift it.... Pictures of the proposed layout to follow.
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Old 11th December 2008, 09:03 PM   #2
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Old 11th December 2008, 09:06 PM   #3
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Old 11th December 2008, 09:08 PM   #4
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Very interesting!

I've been looking for SE KT88 schematics, in the end a design based on Mikael Abdellah's amp pleased me most, to be found here:http://diyaudioprojects.com/Tubes/KT88/

This is all still in the 'planning' stage, so I'll certainly follow this thread! Good luck with it
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Old 11th December 2008, 09:23 PM   #5
athos56 is offline athos56  United States
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Quote:
Originally posted by Miniwatt
Very interesting!

I've been looking for SE KT88 schematics, in the end a design based on Mikael Abdellah's amp pleased me most, to be found here:http://diyaudioprojects.com/Tubes/KT88/

This is all still in the 'planning' stage, so I'll certainly follow this thread! Good luck with it

I also looked at this one, and in hind sight I might have went with it because it was less complicated. Yet here I am. I'm thinking that with the bones of what I got here I can tweek, tear down, and rebuild and what not in the future. I have enough juice to run it at a higher operating if need be...

Or it could turn out to be as sweet as I hope and I'll keep it as is.
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Old 11th December 2008, 10:03 PM   #6
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Default KT88 build

Athos:
Great supply of components there......Hoping you haven't dedicated yourself to that chassis....not meaning to rain on your parade but, I do so believe your chassis is too small.
Morgan Jones' book describes layouts of chassis' & notes tubes should be spaced at minimum one and one half envelopes width apart.
Your outputs as I see it, are well below that minimum. Further as you have selected some premium iron.It would seem they are really cramped for space........I'm worried that they will induce onto each other despite the cores being correctly rotated.
_____________Sheepishly asking....Got another chassis kickin around??________
___________________________________________Rick... .........
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Old 11th December 2008, 10:22 PM   #7
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That thing has got to weigh at least fifty pounds... probably more. What keeps the chassis from bending? Nice photos. Let us know how it all works out.
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Old 11th December 2008, 11:02 PM   #8
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Default Re: KT88 build

Quote:
Originally posted by Richard Ellis
Athos:
Great supply of components there......Hoping you haven't dedicated yourself to that chassis....not meaning to rain on your parade but, I do so believe your chassis is too small.
Morgan Jones' book describes layouts of chassis' & notes tubes should be spaced at minimum one and one half envelopes width apart.
Your outputs as I see it, are well below that minimum. Further as you have selected some premium iron.It would seem they are really cramped for space........I'm worried that they will induce onto each other despite the cores being correctly rotated.
_____________Sheepishly asking....Got another chassis kickin around??________
___________________________________________Rick... .........
I totally agree... Well see what happens Maybe I'll start on a PSU chassis and order another Chassis for the amp...

Quote:
Originally posted by Ty_Bower
That thing has got to weigh at least fifty pounds... probably more. What keeps the chassis from bending? Nice photos. Let us know how it all works out.
More... Each one of the chokes weights ~20 pounds, the same for the Power transfomer, maybe 10 each for the Opt's, plus 2 for the filament transformer...

The chassis is steel, however, if it all goes in one case then I'll have to use a board to move it... two chassis is looking better all the time...

Can you tell I got the fever of a mad scientist??
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Old 12th December 2008, 01:43 AM   #9
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Seeing as how you've already got a pair of the 193Q, I'd cut the PSU down to one choke and buy another 278CX. Then build monoblocks.

I built one of Tubelab's Simple SE amps. It's single ended, and will run KT88. I've only got one choke in the power supply, and it's a relatively lightweight 159Q (7H). Hum is virtually impossible to detect. I can't imagine how you'd actually need two chokes in the power supply.

By the way, why the 193Q? Where are you going to put 500 mA of B+ with only a pair of KT88?
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Old 12th December 2008, 02:04 AM   #10
athos56 is offline athos56  United States
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Quote:
Originally posted by Ty_Bower
Seeing as how you've already got a pair of the 193Q, I'd cut the PSU down to one choke and buy another 278CX. Then build monoblocks.

I built one of Tubelab's Simple SE amps. It's single ended, and will run KT88. I've only got one choke in the power supply, and it's a relatively lightweight 159Q (7H). Hum is virtually impossible to detect. I can't imagine how you'd actually need two chokes in the power supply.

By the way, why the 193Q? Where are you going to put 500 mA of B+ with only a pair of KT88?
Interesting question, the simple answer is that it was a mistake... I was choosing between a 845 and a SE kt-88 and a PP Kt-88. Well, in all three of my PSUD sims I modeled using the same chokes. When it came time to buy I just bought what I simed the PSU with. So they were rated with the 845 in mind. But the added benifit of the huge chokes are the low DCR. I can teach myself how to put this together but I constantly make little mistakes like that That Mono-block idea is a good one...

About the two chokes, I tend to do things that worked for me before. The CLCLCRC worked for me once really well, so I'll tend to want to use it again, if I don't and it doesn't sound as good then I'll kick myself, just a little OCD... But I agree, they are way big
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