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Old 20th March 2011, 03:58 PM   #11
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Default Your transformer

I extracted it. It weighs 8.8KG ! Which means it really is 1KVA 52-0-52 . Are you using it (below 1) in your amp ? If you are , it will dazzle you with sub 1V ripple no matter what you do.

Glad I could contribute to the "monster".
OS
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Old 20th March 2011, 07:27 PM   #12
Art M is offline Art M  United States
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Quote:
Originally Posted by ostripper View Post


after reading this : Leach Amp Power Supply I realized that the standard .1uf decoupling was ill conceived

the .1uF does nothing except possibly create a new problem. The nikko in the photo adheres to this observation closely with 2- 10uF's decoupled to chassis ground/HS (just another return path).

OS
Very illuminating, total output board bypass consisting of only 2 small electrolytics. This certainly conflicts with the " common sense "
in other posts.

I see that Eva covered this issue in a more rigorous manner with some
very nice graphics and explanation.

I would like to know if the location of these bypass caps on the power
bus is of issue. From looking at the Nikko board, they did not place them
at the entry to the board.
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Old 20th March 2011, 08:57 PM   #13
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Quote:
Originally Posted by Art M View Post
Very illuminating, total output board bypass consisting of only 2 small electrolytics. This certainly conflicts with the " common sense "
in other posts.

I see that Eva covered this issue in a more rigorous manner with some
very nice graphics and explanation.

I would like to know if the location of these bypass caps on the power
bus is of issue. From looking at the Nikko board, they did not place them
at the entry to the board.

Specifically , they decoupled 2 of the 10uF's to the HS ground and 2 to the zobel/HV supply ground return. The caps were in the middle of the rail busses.
They especially kept the driver/VS/input ground separate from everything else. This is actually anal , as john's amp and mine are already -100db regardless of grounding .. I just thought it was interesting how a room full of Japanese audio engineers approached this issue.

OS
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Old 20th March 2011, 09:34 PM   #14
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The Luxman M-02 has the same - 10uf decoupling on the output stage with 100nF to chassis. The Zobel is tied into this ground as well.
The front supply decoupling ground returns to that supply, which makes sense, since it is a totally separate supply.
For this one, using that big transformer you're sending me ( ), I won't be using a separate transformer for the front end supply. All power and decoupling will return to the main power star ground.
As for my decoupling, I've been doing it that way since I started. I learned it from ESP and Self and I can't find any reason to do it any other way. Output stage gets 220uF plus 100nF, frontend gets 220uF only.
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Old 20th March 2011, 10:10 PM   #15
jaycee is offline jaycee  United Kingdom
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With a 1KVA monster like that i dont think i'd bother with separate transformer supplying the frontend, just a boosted supply like the one used by the Krill amp. I guess it gets a bit complex supplying 6 channels though as that'd mean using large, high voltage caps!
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Old 20th March 2011, 10:21 PM   #16
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Howdy jaycee,
The plan, as of right now is for 1 transformer, 2 main supplies, 2 front end supplies.
The main supplies will have 100nF bypass and 39,000uF smoothing caps per rail.
The front end supplies will be regulated cap multipliers, fed from the main supplies.
Each supply will feed 3 channels - 3 left and 3 right.

Last edited by MJL21193; 20th March 2011 at 10:23 PM.
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Old 20th March 2011, 10:35 PM   #17
jaycee is offline jaycee  United Kingdom
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Yep, sounds about right to me certainly beat the sh*t out of any off the shelf 6ch amp
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Old 20th March 2011, 10:56 PM   #18
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Some chassis work today. Following my own recommendation to add more heatsink area, I cut this piece for the back:

_0331.JPG

This is 7.25" wide and cut to 18" long. The fins are only 1/2" long and tightly spaced but ever little bit helps, as far as cooling goes.

Some machining:

_0333.JPG

_0334.JPG

These recesses are for screw to fasten it to the ends of the main heatsinks. Drilled with a 3/4" forstner bit.
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Old 20th March 2011, 11:06 PM   #19
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I need recesses in the fins for the input jacks and the output banana jacks. I made a pair of templates:

_0335.JPG

to guide the follower bit in the router. The small template is for the input jack recess, the larger one for the outputs and the IEC and power switch.

Routed:

_0337-1.JPG

patience and hearing protection required! It takes several passes to cut away all of the fin. Having the template clamped down tight is critical.

The larger recesses don't go full depth:

_0338.JPG

just deep enough to make it possible to mount the jacks.

It's starting to look like something now:

_0341.JPG

temporarily attached to get accurate measurements of the other parts needed. Jacks installed for dramatic effect.


PS: no, that's not blood on the plank. Red paint.

Last edited by MJL21193; 20th March 2011 at 11:10 PM.
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Old 20th March 2011, 11:08 PM   #20
jaycee is offline jaycee  United Kingdom
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Now here's where you really make me jealous. You have a tool shop and you know how to use it !

The best case I've got for an amp right now, is the guts of an old Teac A919 I got from Freecycle. Should be nice to build a 100W/ch amp into, but the original transformer is stupidly overvoltage for this (especially as it only had 1 pair of outputs!), and there's only 115mm where the transformer is for a toroid, so only ~250VA would fit.
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