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Bravo Audio - funny looking little tube amps

Discussion in 'Headphone Amps (full-size)' started by ear8dmg, Sep 9, 2009.
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  1. Netforce
    My little bear amp has stopped working today :/
    The leds stopped working or flicker a little before staying off again, it only produces a high static sound no matter where the volume knob is turned, the tube glows a little.
    Any ideas what might be wrong or what I can do?
  2. DefQon
    Change your tube? Check the wallwart? 
  3. Netforce
    Only got the stock 12u7 it came with. Tried another wall wart and varies between nothing at all and a slight flicker.
    The blue led remains on when its unplugged, and has stayed on for a few minutes now. I should of gotten the bravo v2 instead of this amp [​IMG]
  4. DefQon
    Think your tube is dead. If you look closely check and see if both filaments glow when the amp is on.
  5. Netforce
    So it looks like it's ranging from no response to barely visible. Both filament does appear to light up if just briefly. So if the tube is dead does the whole amp not power up?
  6. Evshrug
    Net force,
    Indeed, dead tube right at the heart of the circuit and signal path would make the rest of your amp "dead."

    Judge Buff,
    I'll try validating your crystal ball hypothesis later today. Mostly, I've just avoided bumping the table, and things have been fine. There is the other Bugle Boy too, I've just been lazy about getting out the multimeter to re-tune the bias for a new tube. LATER, though, because I've got an interview with Apple Inc this morning in an hour!
    Netforce likes this.
  7. DefQon
    There's 4 ways of tackling this problem.
    1. Buy a cheap replacement tube on ebay should be < $10.
    2. Instead of buying the tube to see if the stock tube is really dead, spend the $10 on a multimeter and measure the pins to see if the heaters getting any currents
    3. If under warranty still, ignore the above 2 and RMA it. If RMA return shipping is not covered and too expensive, persist with either option 1 or 2.
    4. Post some internal pictures here, if option 3 is not valid for the amp, so you don't void warranty.
    Netforce likes this.
  8. Netforce
    Alright, thanks for the help. Ordered a new tube since I don't think the seller is going to rma. I'll post back if it doesn't work.
  9. UmustBKidn
    I scored an old Tung Sol made in USA tube from Ebay over the weekend. Seems like the easiest thing to try first.
  10. draconothese
    hello im new to the forums. I am having issues with my bravo v2 hopefully one of you can help me out.

    the issue is if I plug a cord into the input without anything plugged into it there's a awful hiss sound from my headset it goes away partway when its plugged into a source but its still there. also if I touch the metal plug they gave me and touch the heat sinks for the irl 630's I get a little shock. is it a grounding issue?, how can I fix this its driving me crazy.

    if there's nothing plugged into the amp there's a hum that gets louder if I turn up the volume knob. the hum starts to go away if I grab onto the adapter that came with the amp the 1/4 to 1/8 adapter

    also most of the hum goes away if I lift it just off my desk or tilt it on its side

    is there a grounding issue or something how can I fix this
    also below is a list of mods I have done to help narrow down the problem
    I have changed the irl 630 to irl 510
    did the crosstalk wire mod
    changed tube to a rca black plate
  11. DefQon
    Check that your 510 are soldered properly. The hum is crosstalk and emi with nearby equipment that send radio waves. When I have my Bravo next to my desktop there is this loud background hum which goes awat when I have my hand cover up the amp.
  12. draconothese
    ok I have made sure I have the 510 soldered down good so its not the problem. how can I fix the crosstalk and emi problem without moving the amp  somewhere else ?
    also I still cant figure out why there's so much juice going through the wires that it would shock me. im thinking its a grounding issue but not sure how to go  about trying to ground the amp.
    also it looks as if all the positive connections on my amp go to the ground is that normal thought it would be negative going to ground
  13. DefQon
    Hmm negative should be connected to the circuit ground, not positive to circuit ground. Check for any legs that are not soldered in properly, i.e. a floating terminal. Sounds like something is not soldered to the contact pad properly (or a defect) for it to be to discharge a shock to you.
  14. draconothese
    ok I was able to remove the hum by attaching a wire from the screw on both of the irl 510 to the ground but there's still static that I cant get rid of  its kind of like the static you hear when you cant get a channel on a old TV to come in
  15. DefQon
    Well at least you got the hum fixed which is almost always related with grounding issues.
    High distortion or static usually come from the volume pot, headphone jack or the tube. 
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