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Building your own gear??

Discussion in 'Pro Audio Equipment' started by trock, Jan 24, 2005.

  1. trock

    trock Active Member

    Has anyone here done this??

    i found this on the web while doing some general research on design and engineering your own equipment and just reading some articles on bill putnam etc

    http://home.earthlink.net/~djahnsen/

    just curious if anyone has and what the results were like??

    thanks
     
  2. trock

    trock Active Member

    before anyone asks about the legality of his design he does say this

    Frequently Asked Questions (FAQ)


    Can I really build an LA2?

    Technically (and legally) no. Teletronix LA2 is a registered trademark owned by the JBL division of Harman International and I certainly don't want to violate their trandmark. However, the patents have run their course and the parts are available so you can build a compressor that sounds identical (because it's built identical) to an LA2a without the Teletronix logo or labeling for far less money than a vintage unit will cost today.



    Is it LA2 or LA2a?

    It's both. Teletronix started with the LA2. (Actually they started with the LA1 but those are virtually impossible to find.) The LA2 was a peak limiter or Limiting Amplifier (LA, get it). The design was later slightly modified to include a compress/limit switch on the back of the LA2a to select between compression (3:1) or Limiting (up to infinity:1) I've used a modified version of the LA2 Layout and functionality of a circa 1969 LA2a.



    Can't I build it with only the schematic (like you did)?

    Sure, it's not rocket science. With an accurate schematic, knowledge of parts suppliers, and a basic knowledge of circuit layout do's and don'ts, you shouldn't have a problem. Though in hindsight, I would have used a book like this if it were available.



    Are all the parts curently available?

    Yes. A few are hard to find but they are all still in production.



    Wait, I thought the transformers aren't made anymore.

    The LA2 and early LA2a's use a HA-100X input transformer which is no longer made. Later LA2a's were equipped with the A-10 which is still in production. All the other parts are still available although I recommend using better quality capacitors and resistors.



    What Does it cost build?

    It can be build for around 500-600 dollars if you don't go crazy buying Telefunken tubes, exotic caps, an expensive enclosure, etc. (Not that there's anything wrong with that.) The most expensive items are the audio transformers at around $100 ea (there are two) and the T4b electro-luminescent module, which is $160.



    Does the book get really technical

    No. There is a chapter explaining the way the circuit functions and the rest is devoted to building the compressor. I wrote it with the project studio owner or musician in mind using a minimum number of tools. A soldering iron and some basic hand tools are all you need. A multimeter is recommended, but not required and you don't need a scope, tone generator, or distortion analyzer, etc.

    he is also doing a fairchild 670
     
  3. Kev

    Kev Well-Known Member

    yep

    I do

    I don't have an LA2 based unit that I am happy with yet
    but
    I have lots of DIY gear

    search this server for DIY and Kev
    or
    search me out on google
     
  4. trock

    trock Active Member

    Hey Kev

    thats very cool, how has it worked out for you?? i am looking at building the LA-2A from this book just for kicks to see ow it comes out

    he also has the fairchild 670 all mapped out as well so i may try and build that.
     
  5. Kev

    Kev Well-Known Member

    how has what/which worked for me ?

    If you contacted Dave recently you will probably have the updated info.
    In the early days there were a couple of mistakes that did seem to confuse some people.

    Dave's is not the only LA2 tubed compressor out there ... there is another KIT available.

    Also there are some good web sites with some turret board layouts that look very good.

    Give this one much time before you take it on AND give Dave even more time to get it sorted out.
    There is a string of people who have had this project on the go for many years.

    I suggest you make something simple first and then move up to these Tubed Units.

    Have you done those searches yet ?

    You need to do reasearch and you may find .... well let's just say ... do the search ... 8)
     
  6. trock

    trock Active Member

    i meant how has the DIY stuff you have made worked for you?

    as for the LA-2A

    i know they make quite a bit of the electroluminescent gain control. That can be replaced with a FET that would have instantaneous response time

    i think alot of the sound can be done with better and faster components that we have available today for much much less

    Looking at the revision history of the LA-2A, it looks like they were still using discrete circuits as amplifiers. Operational Amplifiers really weren't readily available in 1967, so I'm not surprised.

    I have looked at the manual for the LA-2A. The heart of the unit, the electroluminescent panel, can be replaced by better devices. The other components, i.e. the vacuum tubes, are replaced by field effect transistors.

    The most challenging part would be the metering. I'll have to research the vu meter. I think it is just a logarithmic output device, but I'm not sure.

    Packaging would be a separate issue. Most of the electronics should fit inside of a pack of cigarettes, perhaps with the exception of transformers if they are in fact required. Have you ever seen one of these gadgets?
     
  7. trock

    trock Active Member

    sorry Kev

    i also meant to tell you i checked out your website and the stuff you have built and was really impressed.

    there is another guy on a forum i visit and he sent this stuff he has done. you might know of it already or be interested if not

    http://www.fivefish.net/diy/
     
  8. trock

    trock Active Member

    ohhhhhhh

    i seem to have found some interesting DIY pages Kev

    thanks!

    nice site!
     
  9. Kev

    Kev Well-Known Member

    yep
    cool

    keep digging as most of the good stuff is some-what hidden

    the fivefish site does look to have familiar pictures
    can't place the person off hand but I'll work it out

    keep digging and you will find the forum that is currently carrying my old Group DIY name ... although it is not my baby anymore .. do pay it a visit
    ... you may like it
     

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