Project files: The EL2k headamp

What is it?
The PCB files for the EL2k headamp in the previous post (here)

How big are the boards?
The board measures 3.95″ x 3.0″ (app. 100 x 76 mm.) and contains one channel.

What is the status of the boards?
The files are v1.1 of the board. I corrected a few minor issues in the prototype such as the footprint of the input capacitor and the package dimension for the CRD.

Does it use any special/expensive/hard-to-find parts?

  • The Elantec buffers (EL2008/EL2009) that for the basis of the EL2k have been out of production for a long time. You can find them in various places online, both as pulls from scrapped equipment and as unused new-old-stock (NOS) ones. I bought a single pair of EL2008s from a long time diyaudio-user and member of the headphone community who was cleaning out parts so I have no doubts that mine are genuine, but if you do try to source from elsewhere always beware of fakes or substandard parts.
    That said, demand for 15-year old analog video buffers in TO-220 packages probably isn’t at an all-time high now, so I would judge the chance of getting genuine ones as quite good. Unlike various power transistors and small signal JFETs that are regularly counterfeited – even in channels where you would never suspect it – there probably isn’t a lot of money to be made from faking these in the first place.
  • The heat sink is not hard to find as such, but it must be a specific one (the SK68/75 from Fischer). It’s quite common in Europe with Reichelt and TME both stocking it, but I am not really aware of any other sources.

Anything else I need to know?

  • When you mount the buffer as shown, the heat sink will be grounded (because the tab-pin is grounded on the PCB). Not a problem in itself, but it does mean you should be careful of flying PSU leads 🙂
  • Mounting the buffer is a bit of a hassle, firstly because the electrolytics can get in the way unless you wait with mounting those (I didn’t…) and secondly because it doesn’t line up 100% true with the grooves in the heat sink. You can either have the buffer sit flush with the board as I did and use the M2.5 slot, or you can use the M3 slot and have it raised quite a bit above the board. In the first case, there is barely enough room for the screw and in the second it might be necessary to bend the buffer leads a bit to make them reach the holes. It works, but it isn’t as elegant as I would have liked 🙂
  • The PSU for this board should be +/-12 to +/-15V. 15V is recommended unless you are using an opamp that doesn’t tolerate 15V. In theory, the PSU should be capable of at least 2A output currents, but in any normal audio application 1A should be more than enough.
  • If used, the recommended value for the CRD is app. 2mA. I used a J508 because I had a pair left over, but there are other options out there. You can also use a resistor instead or skip this entirely. See this page about class A bias of opamps.

Download design files here

Edit May 5th 2016: Download a BoM from here.

Related information:
See the two original posts for some more information and links.
Note: Always read the “intro post” for additional important information about my designs.


5 Responses to Project files: The EL2k headamp

  1. John says:

    Very interesting article I really like what you have done with the Buffers, now the good news is that I have a ton of these EL2009 buffers going up for sale. I have about 2k of these I purchased from a company that was scrapping them. they will be going for 10-12$ each. if anyone is interestred I will be posting the auction on Ebay within the week.

  2. Pingback: Evolution of a design… | theslowdiyer

  3. Pingback: Project files: The (modified) EL2k headamp | theslowdiyer

  4. Pingback: Project files: The last of its kind… | theslowdiyer

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