Building a guitar amp.. Transformers!

Discussion in 'General Electronics Chat' started by strangedays, Jul 16, 2007.

  1. strangedays

    Thread Starter New Member

    Jul 16, 2007

    I'm about to work on building my own guitar amp, with the help of a friend who has good electronics experience.

    This is more of a fun project so money spent is not wasted in my view.. more for a learning experience.

    One issue we are having though is locating the right transformers. We are trying to copy an orange amp design (80 watt.. 4 el84s valves and 2 12ax7's)

    I was wondering if I could get any advice on this as well, anything to watch out for. Im not too bothered if at first it all goes bang, but of course I would like to have a workable end result that I can just tweak to get perfect.

    but these damb transformers are giving us a headache as we are not sure what to get.

    ps. the schematics of the design can be found here:
  2. mrmeval

    AAC Fanatic!

    Jun 30, 2006
    Which transformer? There are two.
  3. Gadget

    Distinguished Member

    Jan 10, 2006
    Both could be a bear to find, being near obselete technology. The first being the supply transformer supplying the HT voltage (no Idea what the HT is for these...guessing between 150 to 200 ???) and also the filiment volts which I'm pretty sure for those valves is 6.3v.
    Then you need an output transformer.... again no Idea of the impedence on the primary, but with a secondary of probably 4 ohms.
    Another problem may also be finding suitable HT smoothing capacitors.

    May I ask Why valves..???
  4. bloguetronica

    AAC Fanatic!

    Apr 27, 2007
    Valves are not bad at all. They intruduce harmonics, and that's why the sound is so rich.
  5. lightingman

    Senior Member

    Apr 19, 2007
    The HT for these amp's is 400 to 450 volts, the heaters are 6.3 volts at (I think) about 1 Amp for each EL34 and about 300mA for the others.....It may be worth while trying to contact Fender or Marshall, or one of the other back-line amp manufacturers....As there are amp's still being made with valve output stages......Daniel.
  6. nomurphy

    AAC Fanatic!

    Aug 8, 2005
  7. legac

    Well-Known Member

    May 4, 2005
    You search "Tube DIY". There are many suppliers which can provide power transformer and output transformer. If you are in Asia pacific region, there are many suppliers in Hongkong, China, Thailand , Vietnam can supply the transformers at low costs.
  8. subtech

    AAC Fanatic!

    Nov 21, 2006
    A guitar amp isn't a bad project. Data on the tubes you plan to use should be available with a google search.
    Don't overlook the possiblility of separate transformers for the plate/screens/grids. Separate transformers may be easier to find although they will require more physical area for mounting. They can also make troubleshooting easier later. One very important thing to remember about tube type gear is that the voltages are high, and the available current is sufficient to kill. If you are not familiar with tube type equipment, proceed carefully.
  9. Tube Tech

    Active Member

    Jan 11, 2007
    Step 1: Navigate your way to

    Step 2: Search for Gerald Weber

    Step 3: Buy all of his books

    Step 4: Read and heed

    Then build the amplifier.

    Tube Amp Talk for the Guitarist and Tech

    Tube Guitar Amplifier Essentials

    A Desktop Reference of Hip Vintage Guitar Amps

    By another author:

    The Tube Amp Book