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Old 23rd December 2013, 09:47 PM   #1
50AE is offline 50AE  Bulgaria
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Default D3A - 6P45S/El519 SE "The staircase" my first h-end amplifier.

Hello people,

In my previous thread I mentioned about my system and I described my amplifier, but it wasn't finished cosmetically. It was an enclosure designed from plywood which was thought to be veneered for later, but with the time I realized it was not worth it, because the enclosure didn't suit me. It was very uncomfortable to change parts inside, it was lacking space for high end bulky stuff and the main issue was with the cooling. As a beginner I didn't know some parts would dissipate heat so greatly.

So I designed to remake an enclosure of open nature and also stylish.

I started the project about a week and a half ago. Today I finished it technically and it sings. There are some more cosmetic problems that I will easily remedy later.

The schematic consists of a battery biased triode strapped D3A into 18mA, 190 Ua, driving the 6P45S (it's 6P42S) for now, capacitor coupled. I will have an interstage tranny soon. The 6P45S is triode strapped, it drives a 2,4k load, biased at 120mA, -60Vg, 325 Ua, dissipating 39W. These russian equivalents of EL519 are very rugged and can go to 45W of dissipation, the plate starts going red at about 50W.

There's a separate filament tranny.

There are separate power supply for the driver and power stage
-power stage - 2x6D22S rectification, cap input bosch mp 7uF , then 10H choke DCR 160 and Rifa PEH169 3300uF
-driver stage - EZ81, cap input KBG-MN 4uF, 15H choke DCR 240, arcotronics polypropylene motor runs, choke 10H DCR 220, arcotronics again.
-The fixed bias is rectified via 1N4007, but will be tubed soon. RCRCRC filter with arcotronics propylenes.



The remaining holes are for sockets I will find some use. Remember that this enclosure is made to be very DIY friendly and this is my personal amp that I won't stop upgrading soon.

The parts for the enclosure cost me no more than 20$. Believe it or not, I paid more for the wiring inside (Neotech OCC).
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Last edited by 50AE; 23rd December 2013 at 09:51 PM.
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Old 23rd December 2013, 11:38 PM   #2
kevinkr is offline kevinkr  United States
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Interesting construction technique.. Please get some plate caps for the rectifiers and the EL519 - this is a safety hazard.
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Old 23rd December 2013, 11:46 PM   #3
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That's pretty cool, I like it a lot.

Upgradeable too, great idea.

It's like a finished 3D breadboard.

A few sheets of glass or acrylic might be a good idea.
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Old 24th December 2013, 08:33 AM   #4
50AE is offline 50AE  Bulgaria
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I'm glad you like it.
I don't plan putting removable plate caps, because they degrade the sound. I will keep the solder joint and put just a protective cap instead.
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Old 24th December 2013, 08:45 AM   #5
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Plate caps cannot effect the sound. Thats just silly.

Shoog
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Old 24th December 2013, 09:07 AM   #6
50AE is offline 50AE  Bulgaria
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I had the same thought before trying it personally. The same way as cable directions, fuses, power switches.
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Old 24th December 2013, 09:12 AM   #7
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Well done 50AE.
I like very much the idea to have separate powersups for driver and powerstage. My amps are allways like this. 6D22S is a great rectifier- one of the best.
Thanks a lot for showing us your work.
Hilmar
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Old 24th December 2013, 09:20 AM   #8
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They are in the signal path so you can "hear" them.

Quote:
Originally Posted by Shoog View Post
Plate caps cannot effect the sound. Thats just silly.

Shoog
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Old 24th December 2013, 09:47 AM   #9
MartinR is offline MartinR  Germany
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Hello 50AE,

nice one

But be careful with the operating point of the D3a. Ug2 max is only 180V. You´re 10V above it. The datasheets recommends Ua=Ug2=150V.

Best regards,
Martin
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Old 24th December 2013, 10:02 AM   #10
DF96 is offline DF96  England
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Quote:
Originally Posted by Shoog
Plate caps cannot effect the sound. Thats just silly.
They won't affect the signal to the speaker. If loose, they might rattle a bit - just like any other loose object in the room.

However if the OP needs to omit them for good sound, as a sportsman needs to wear his lucky socks, then so be it.
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