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Old 26th October 2005, 05:13 PM   #1
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Default Wim's DC EL84 amp

EW published several d.c. coupled EL84 amps designed by Kees Heuvelman and Wim de Haan in January 2001. Wim has a link on his page to the design. Here's the link:

http://www.wdehaan.demon.nl/tubeamps/el84dc/index.html

Here's a first cut at a pcb

Click the image to open in full size.

i'm open to suggestions -- i am sure there are probably some glithces in the above.

will furnish the Gerber files to anyone who asks -- I am only going to burn one board for my own use.
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Old 26th October 2005, 10:44 PM   #2
moamps is offline moamps  Croatia
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Hi Jack,

At first sight:
The cathode resistors dissipate a lot of heat. I think a heatsinked version would be a better choice. Anyway, the footprints look too small.
The heaters' tracks for the ELs might be thicker and routed "one on top of another" with the same current flow direction.

Regards,
Milan

P.S. Nice article in AudioXpress.
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Old 26th October 2005, 11:18 PM   #3
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Quote:
Originally posted by moamps
Hi Jack,
At first sight:
The cathode resistors dissipate a lot of heat. I think a heatsinked version would be a better choice. Anyway, the footprints look too small.

Yes, they should dissipate ~ 10 W.

The tracks for the heaterers are mostly 60 mils -- will have to give this some thought -- for the boards I do myself I like to have as much as possible on the bottom layer.

The EL84 DC amp is going to power my St. Emillion Horns (in a modified wooden Bordeaux wine-box.)

Thanks for the compliment -- National did all the heavy lifting, however.
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Old 27th October 2005, 03:37 AM   #4
kopite is offline kopite  New Zealand
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Hello Jack, nice job.
Which version of the ECC85 is it? I think Wim goes on to say that the version with the better ccs doesn't need feedback. Is yours it?
Thanks,

Phil.
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Old 27th October 2005, 06:49 AM   #5
arex is offline arex  France
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Hello jackinnj

I'm working on the same schematic, without PCB. So, this is my version: (I used ecc 83 instead of ecc85). I'm still working on the box. (I don't know the english word, "chassis" in french).
Ciao!
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File Type: jpg elb4cir1.jpg (51.4 KB, 1057 views)
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Old 27th October 2005, 08:32 AM   #6
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Quote:
Originally posted by moamps
The heaters' tracks
Best not to put heater wires on the board at all. Use a twisted pair and run it as far from the board as you can and then just reach up to connect to the heater pins.

dave
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Old 27th October 2005, 12:35 PM   #7
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Quote:
Originally posted by kopite
Hello Jack, nice job.
Which version of the ECC85 is it? I think Wim goes on to say that the version with the better ccs doesn't need feedback. Is yours it?
Thanks,

Phil.
This is version 4 -- with the ECC88 current source -- but I am going to outboard the -150V/+206V supply -- so both halves of the ECC88 are used for two amps on one board.

Dave -- I agree, the 60 mil trace width will poop out under the pressure of 7 tubes in parallel.
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Old 27th October 2005, 03:55 PM   #8
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OK, here's a 3D view -- I changed the resistors to the TO-220 style (Ohmite or Caddock, non-inductive) with heat sink -- they now take up a lot more space. I also removed the heater traces. Note that I try to take the grounds to the center of the board. I also use a "via" for connecting the top-layer traces -- helps when you are DIY'ing a board to have the darned hole there.

Click the image to open in full size.

here's the PCB:

Click the image to open in full size.
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Old 27th October 2005, 06:32 PM   #9
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A very tempting design with all the ECC85s & EL84s i'm sitting on...

dave
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Old 27th October 2005, 06:48 PM   #10
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Quote:
Originally posted by planet10
A very tempting design with all the ECC85s & EL84s i'm sitting on...

dave
i hate to think of pulling the shards out ---
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