Connect with us

Tube Headphone Amp

Discussion in 'Electronic Basics' started by Dave.H, Mar 9, 2008.

Scroll to continue with content
  1. Dave.H

    Dave.H Guest

    Hi, I'm interested in building a simple tube stereo headphone amp, I
    found a circuit but have a few questions.

    Link to circuit (Site is in Japanese, but schematic is perfectly

    First, the schematic calls for a 117 volt/12.6 volt transformer
    across what I think is the output, I can only find a 115 volt/12.6
    volt 2.5 amp transformer. Will this work? Another question is about
    the numbering of tube pins on the 12AU7A, there's two sets of
    numbers. Which ones am I supposed to read? Last question is
    regarding the 12AU7A itself, will I regular 12AU7 work here? Thanks
    for your help.

    Thanks in advance.

  2. Dave.H

    Dave.H Guest

    Forgot one thing, all the ground connections, are they going to signal
    ground, or B-?
  3. Dave.H

    Dave.H Guest

    Specs for the transfomrer is as follows:
    * Primary 115 VAC, 60 Hz.
    * Center tapped secondary.
    * Enclosed, 4 hole chassis mount.
    * Minimum 6" long leads.
    * Dual bobbin design - no electrostatic shield required.
    * Class B insulation (130 degrees, C)
    * Hi-Pot test of 2,000 V RMS.
    * UL listed (# E50394) & CSA certified (# LR3902).

    Rating: 12.6 VCT, 2.5 A
    Mounting Centers: 1.5" x 1.56", vertical

    Or another transformer I found

    TRANSFORMER, POWER, 125 V, 15 mA

    Primary: 117 volt, 50/60 Hz
    Secondary: 125 V, 15 mA
    Filament winding: 12.6 volt, 0.3 amp
    Mounting centers: 2", U-bracket
  4. Art

    Art Guest

  5. Eeyore

    Eeyore Guest

    Well, it's certainly a close enough match to the specified part for
    sure, but using a MAINS transformer as the output transformer will
    assure truly dismal audio quality.

    Sorry to tell you but many (most) hobby projects of this ilk are truly
    dreadfully designed and will assure at best mediocre results that
    somewhat defeat their original purpose.

  6. Eeyore

    Eeyore Guest

    Hello ! Ting ting ! Wakey wakey ! The 12AU7 / ECC82 is a DUAL triode.
    One set of numbers refers to the first triode and the second to the err
    ... second triode.

    Have you been using valves long ?

    Yes, a 12AU7 works very well in a socket designed for a 12AU7.

    If you mean 12AX7 or 12AT7 then the answer is NO.

  7. Eeyore

    Eeyore Guest

    Read the thread on grounding and star points in It's very

  8. Mike Silva

    Mike Silva Guest

    Yes, it's the same thing. But you might be happier with the results
    if you use real audio output transformers.
    The two numbers refer to the first and second sections of the tube.
    Use the first set of numbers for one channel and the second set for
    the other channel.
    Yes, no problem.

  9. Tim Wescott

    Tim Wescott Guest has audio transformers that'll work much
    better than mains transformers. You can start with mains transformers,
    but as Eeyore so diplomatically mentioned, your sound quality may suffer.

    Tim Wescott
    Control systems and communications consulting

    Need to learn how to apply control theory in your embedded system?
    "Applied Control Theory for Embedded Systems" by Tim Wescott
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day