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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. UmustBKidn
    Well, if you're using a computer fan, likely it's running on a DC power supply. That ought to produce less noise, if any. I use a Thermaltake USB fan, and I do not hear any RFI noise as a result of placing the unit behind my amp. (I don't remove the top of my stock amp for cooling purposes - the fan blowing from the rear is sufficient).
  2. UmustBKidn
    Hahahaha nice [​IMG] Yeah, its kind of amazing how much improvement you can get just by rolling tubes in the stock amp. I've been posting about that for about the last year.
    Now if you rewind about a year and read how many tubes I ended up buying and rolling through this little amp, you'll probably get a good laugh. Or maybe just understand why I did.
    What I'm still kind of curious about though, is the loss of bottom end on the modified amp. Not sure what to think about that yet. I may end up changing the output caps back to better quality 1000 uF units just to see what happens.
  3. UmustBKidn
    The only component that requires heat to run properly, is the tube. Part of the reason for the short delay on startup of a tube amp, is for the heater within the tube to reach operating temperature. That happens pretty quickly (10-15 sec), so the circuit kicks in and starts producing sound after that happens.
    That being said, I don't think you could cool it enough with the fan setup above to degrade tube performance. I didn't go to quite the same effort to cool mine - the fan I linked above stands alone behind my amp (I use two of them, one for each amp), and I keep the output control set to about 2/3rds. Thats enough to bring the heat sinks down to a temp that allows me to touch them while operating. So mine probably operates somewhat warmer than yours does. Just get some air moving over the amp seems to be plenty.
    I think your setup is pretty awesome (even if it was a quick job), but it's probably overkill... for those considering a fan, the aforementioned Thermaltake USB fan is probably plenty (and it keeps my modified amp cool also, with the stock heat sinks).
  4. UmustBKidn
    My bravo's are both susceptible to RFI. The only thing I keep near mine that causes noticeable RFI is my cell phone. I can tell when I have an incoming phone call or text, because I start to hear curious noises, lol [​IMG]
    I'm sure that occurs for lack of any shielding on the amp.
  5. UmustBKidn
    I don't own a V3, but I would suggest adding a cooling fan - especially if it seems to make the amp work.
  6. UmustBKidn
    I haven't attempted bias mods on mine yet.
    Every thread I've read on modding includes the caution that the FETs will get hotter. Some people use bigger heat sinks, some mount the chips off the board on huge heat sinks. I'm just not that ambitious. I prefer to use that Thermaltake USB fan. For $11 bucks its the cheapest easiest fix, and doesn't introduce any noise that I can detect.
    Not sure why the tube is hotter, unless perhaps it's just proximity to everything else being hotter. But the little fan would put that all to rest.
  7. UmustBKidn
    I have mixed feelings about that mod. I could not hear a difference after performing that mod. And I had already replaced the FET's and caps by the time I did that one.
    The only mod that has a really noticeable impact is replacing the MOSFETs. The rest of them seem rather subtle.
  8. rwpritchett
    Hello all,

    I've been a V1 owner for about a month now and I've rolled about a dozen tubes so far. I've balanced the left-right pots to ~13.5V. Two quick questions:

    #1 Is it normal that the blue LED remains lit after powering off the amp?

    #2 I get a slight buzzing in my left channel when music is not playing. It's probably there while music is playing too, but gets drowned out by the other sounds coming through. What component causes this and any recommended fixes?

    BTW, some tube notes: my favorites are a 1970 Amperex orange globe A-frame and a 1985 6N23P Voskhod Rocket logo, ECC86 works in this amp, ECC85 does not work
  9. Didhefocus
    How long dues the LED stay on? A few seconds is normal while power supply caps discharge.

    I found that hum or buzzing can be from nearby electronic devices. Try moving the V1 around to find the best spot. A bad cable could also be the problem.
  10. rwpritchett
    The LED stays on for a few minutes. Maybe 5 min? I think the LED drains the caps eventually and that's the only way to get it to go out. If I take the tube out after turning the amp off the LED turns off, however the thing will stay charged: If I put the tube back in, say 24h after being turned off, the blue LED will illuminate until it discharges everything.

    For the buzz, it's not from an electric device as I've used the amp here, there, and everywhere and it always has it. Maybe the switching PSU is to blame?
  11. rwpritchett
    Ok, now that I'm home, I timed it and the blue LED remains on for over 10 minutes, slowly dimming as it drains whatever power is feeding it.

    I take it this is abnormal?
  12. Didhefocus
    I'm home now also and It's definitely not normal. Mine is a V3, the same except for the EQ, stays on only briefly but goes dim quickly. Maximum 5 seconds.
    I would now tend to believe your hum problem and the LED are related. I would guess that the external power supply is not the culprit or you would have heard the hum in both channels.
    Have you done any mods yet? if not... replacing the power caps would be a good starting point for your repair and simultaneous mod.
  13. rwpritchett
    No, haven't done any mods yet. I don't have any experience in electrical de-soldering or cap replacement. I wouldn't know where to start in tracking down what makes that LED stay on after turning off. Anyone familiar with the PCB traces?
  14. mcandmar
    The amount of time the led runs really depends on the amount of capacitance in the power supply and the current the LED consumes.  What power supply are you using?
  15. Didhefocus
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