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Old 28th October 2013, 10:42 PM   #1
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Default Work In Progress... Leach Based Amplifier

Here is my work in progress. I thought I'd share this too.

Based on the leach amp, just slightly modified. 3 output pairs of MJ15003/4. input changed for balanced input on XLR plugs with no wiring. Protection circuit and power supply on one single board. The goal is to reduce wiring to the strict minimum possible. The toroidal transformer is right below the pcb and it's wires come straight to the pcb. A power on delay also sits below the pcb near the transformer. The case and mains power cord is the only thing linking each amp, as each amp is a totally independent module.
Attached Images
File Type: jpg ampli rear.jpg (557.2 KB, 916 views)
File Type: jpg ampli.jpg (537.9 KB, 794 views)
File Type: jpg ampli top.jpg (691.7 KB, 757 views)
File Type: jpg amp module top.jpg (666.6 KB, 792 views)
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Old 29th October 2013, 08:17 AM   #2
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Dude your software rendering is so realistic
Quote:
Originally Posted by spookydd View Post
Here is my work in progress. I thought I'd share this too.

Based on the leach amp, just slightly modified. 3 output pairs of MJ15003/4. input changed for balanced input on XLR plugs with no wiring. Protection circuit and power supply on one single board. The goal is to reduce wiring to the strict minimum possible. The toroidal transformer is right below the pcb and it's wires come straight to the pcb. A power on delay also sits below the pcb near the transformer. The case and mains power cord is the only thing linking each amp, as each amp is a totally independent module.
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Old 29th October 2013, 08:45 AM   #3
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Quote:
Originally Posted by OnAudio View Post
Dude your software rendering is so realistic
It's bluffing ain't it?

Nice to be able to fully design and visualize everything before actually making it.

Here's the pcb and sch:
Attached Images
File Type: jpg eagleUp_leachamp3pairsMJ_board_top.jpg (1.07 MB, 784 views)
File Type: jpg eagleUp_leachamp3pairsMJ_board_bottom.jpg (853.6 KB, 415 views)
Attached Files
File Type: pdf leachamp3pairsMJ_sch.pdf (87.0 KB, 243 views)
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Old 29th October 2013, 09:50 AM   #4
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by spookydd View Post
It's bluffing ain't it?
The first 3 pictures look real to me.
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Old 29th October 2013, 10:11 AM   #5
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Quote:
Originally Posted by Jay View Post
The first 3 pictures look real to me.
That's the idea behind "rendering". I made them in high res so I could get the best feel possible and life like.

I am doing the design from the pcb all the way to the case in every detail, so then it can be built with all the proper parts professionally manufactured. I have a good contact in china who can make all this metal stuff properly, with the laser cutting table and the whole shebang. I only need to find a good place to get the screen printing done. I will also have the aluminum parts anodized black, in the same way the heatsinks are, for a good overall impression. The theme is black, with most parts, including most screws in black color.

I want the amp to "breathe" and not enclose its heatsinks in an airtight case. So that's the reason why the case is full of holes. Plus there is plenty of space below the amp modules for the air to circulate coming from the sides and going up in the center in case the amp is sitting on a flat surface instead of a rack. I didn't show the feet on those renderings, but there are 4 rubber feet below, which add a little more space for airflow.

It's not forced cooling, so the convection must not be hampered too much, and I think with the oversized heatsinks, the cooling should not be an issue.

Those heatsinks are the SK479 from Fischer. I carefully chose each part of this design.

I am designing it so some variations can be made without having to change everything. For example I plan to make a stronger version with higher rails and more powerful outputs. which would use 2 toroidal transformers, with the same power-on delay and everything about the case would remain the same.

That existing design with the MJ15003/4 can easily be changed for the MJ15024/25 or MJ21193/4 for example.

I want to avoid "exotic" semi, so the japanese transistors aren't an option.
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Old 29th October 2013, 10:15 AM   #6
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Quote:
Originally Posted by Mircea Crisan View Post
Everything that you see on these pictures has been DIY'ed:
-Amplifier based on LME49810 power amplifier driver. (PCB layouts done by myself).
Output stage-3 pairs matched NJW4281 & NJW4302 ON semi.
-The power source is a full-bridge power converter based on ETD49 core.
+/-60Vcc 800W. (PCB layouts done by myself)
- The aluminum case done by myself.
Very easy to work with this LME driver and the sound astonish in a pleasant way.
Unfortunately, I made a mistake with inscription from front panel.
Clip left is repeat twice. This is it.
Look great! But I prefer the black theme!
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Old 29th October 2013, 10:24 AM   #7
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by spookydd View Post
I want the amp to "breathe" and not enclose its heatsinks in an airtight case. So that's the reason why the case is full of holes.
looks great, and I like the idea
but it is also a somewhat dangerous design

might be a good idea to put a lid on the heatsinks of each amp module (inside the vented box)
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Old 29th October 2013, 10:29 AM   #8
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Default more on work in progress

Posting a few more renderings.

This is just one module. 2 modules in the case, 100% separate, all the way to the power cord.
Attached Images
File Type: jpg amp module input end.jpg (458.5 KB, 456 views)
File Type: jpg amp module top.jpg (666.6 KB, 344 views)
File Type: jpg amp module top all.jpg (634.6 KB, 254 views)
File Type: jpg amp pcb module top.jpg (545.2 KB, 369 views)
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Old 29th October 2013, 10:31 AM   #9
tinitus is offline tinitus  Europe
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is it for professional use ?
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Old 29th October 2013, 10:43 AM   #10
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Quote:
Originally Posted by tinitus View Post
looks great, and I like the idea
but it is also a somewhat dangerous design
I don't see how this could be dangerous in any way. Can you explain what you mean?

Quote:
Originally Posted by tinitus View Post
might be a good idea to put a lid on the heatsinks of each amp module (inside the vented box)
The heatsinks are at ground potential, galvanically isolated from the DC in the amp, no voltage applied to them, so there is no issue there, and no hands can go inside touching the transistor cases, which do have potentially lethal voltages, unless someone purposely opens the case and goes fooling around inside, but then there is nothing to do about such stupid behavior.
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