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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
    Interesting. I guess if I wasn't so busy at work, I might go for the IRF. I might still, so thank you for that pointer [​IMG]
     
    The Sylvania and GE 12AU7 tubes I have tried, are only marginally better than the stock Shuguang tubes. The GE 5-star 5963 was noticeably better. Long black plate tubes, even better than that. Of the old American tubes, I'd have to say the Tung-Sol tubes are probably tops. You need to go to Amperex, Telefunken, or Mullard tubes to improve over those. The quality among those three European makers is tops; the only choice is whether you're looking to brighten something up, or tone it down.
     
    I had to distract myself from some family issues over last summer, so I did what some might consider foolish, and started collecting 12AU7 tubes (and its plug-in variants like 5963's and 5814's). And rolling them in my stock Bravo V2 [​IMG][​IMG][​IMG] I left some tube rolling notes in this thread, along with another member's impressions. That may help you decide, should you continue that effort.
     
  2. DefQon
    The IRF510/530/610/630 are all pretty much the same, if you replace the IRF630 with 510 you're just wasting time and money.
     
    IRL or go home.
     
  3. UmustBKidn
     
    Hmm. Ok, that is also good to know. Thank you sir.
     
  4. mcandmar
     
    That was a great read thanks.  Of the tubes i picked up the Sylvania would be my favorite, its a long black plate where as all the rest are short grey plates.  Interesting nobody likes the stock Chinese tube, i found it smoother than the others, and more neutral. Curious as i was expecting it to be tiny and harsh sounding.
     
  5. Evshrug
    With tubes, even ones sold with "strong" or "good" or "like new" ratings, I've found it to be kind of a luck game to get really good samples. That said, of the 8 tubes I've bought, only one seemed to be so dark that I think it could be "poor quality."

    So far the Sylvania JAN 6DJ8 I tried was my favourite, but it may be very close to the very balanced Voskhod I am using now.
     
  6. UmustBKidn
     
    Indeed. It's just amazing how many variables there are with tubes...
     
    - Age of the device;
    - Test measurements (indicating how "new" or how "used" a tube is);
    - Balance between triodes (in the case of tubes like the 12AU7);
    - The synergy (or lack of it) between the tube, the amp, the cans, the DAC, and your ears;
    - The type of music being listened to (some will highlight "tube" sound more than others);
    - Circuits that auto-bias vs. those that do not (like the Bravo's)
     
    I'd say the 4th bullet above is probably the most important. Like all pairings in this hobby, the pairing of a tube with everything else in your system is what seems to count the most.  After all, the exercise of tube rolling is an attempt at finding a tube that makes everything else in your system, sound it's best, to you. Pairing a bright tube like a Telefunken with a set of bright cans, a bright amp, a bright DAC, and music with a lot of treble in it, might make you scream in pain, or at least wonder why someone thought so highly of Telefunken tubes.
     
    So, yeah. I know I'm not hearing top quality while listening to a cheap amp like a Bravo. I've probably spent enough money on tubes to have bought myself a Bottlehead Crack by now, lol. Which is why I stopped buying them. I've heard as much as I can hear for now. But I am holding on to those tubes, because I know I will want to use them again when I do buy the Crack, or when I do finally mod one of my Bravo's.
     
  7. Evshrug
    If you decide to mod your Bravo (or Indeed?), look back through this thread for JudgeBuff's posts. It's fun to read through his explorations.
     
  8. HOWIE13
    I must say I am rather sceptical of some of the claims made by some tube web-sellers regarding their test measurements. These testing machines are nowadays very expensive to purchase and just about impossible to obtain in Europe. Sellers in the USA  nearly always refuse to ship internationally, presumably because of the risk of loss and damage. So where do these myriad of sellers obtain their putative measurements from?
     
  9. UmustBKidn

    Good question. I would presume that some of them do in fact own their own test machines. Some of those sellers do a significant business in vintage tubes. So it really isn't much of a stretch to imagine that some are using vintage test machines. If reputation is a top concern to you, and you don't want to deal with eBay, I highly suggest Brent Jesse, at www.audiotubes.com. His tubes are not cheap, but I trust him. I've bought from him, and I have had good luck using him.
     
    That being said, there seems to be quite a variety of these machines, that also seem to measure different characteristics. Some ads just say the tube was tested, offer a "percent good" reading, and that's it. You need to ask the seller what that means, because lots of them don't want to tell you. And I agree, some of that seems like snake oil to me. I dont think there is a way to be absolutely sure. If you have access to a similar machine and can verify the measurement after receiving the tube, that would be your best bet.
     
    If you spend any time chatting with the sellers, they bring up another problem: some buyers purchase vintage tubes for big bucks, then attempt to return the tubes - but what they send back isn't the original tube ... its a similar tube with the same date code, but inferior measurements. So, some buyers attempt to scam legitimate sellers in this way. One guy I chatted with in England, was so adamant about not releasing the exact mullard date codes on his tubes, that he was willing to risk ticking off potential customers, instead of revealing the date codes. I guess it's hard to blame him. Clearly, he has been burned.
     
    Other sellers refuse to sell to certain countries (Italy seems to come up a lot, also South Korea). Personally, I refuse to buy from most other countries, because if something goes wrong, you have no recourse. That eBay store front gives the illusion that every seller and buyer can be trusted. That really isn't the case. I got burned way back when eBay was brand new, and didn't use it for a long long time because of that. It's better now than it was in the 90's, but there are still scams.
     
    So, yeah. Buyer beware. There really are no guarantees (except maybe what you can get from ebay itself). Personally, I've only come across 2 wonky tubes, out of about 3 dozen. That's not such a bad record.
     
  10. Evshrug
    Audiotubes.com and Tubemaze.com
    What other sellers have you found to be of good repute? I have a web tab open to Cryoset.com right now.
     
    money4me247 likes this.
  11. UmustBKidn
     
    Never heard of them. I tend to avoid anything with "cryo" in it - that's more snake oil IMO.
     
    Not personally tried, but here's another vendor: tubedepot.com. They are insanely expensive, $299 for a Mullard 12AU7. You're better off taking your chances on ebay lol.
     
    Another vendor, not personally tried, but cheaper than the above: www.vacuumtubes.com. His prices seem a bit more in line with reality.
     
    Evshrug likes this.
  12. money4me247 Contributor
    lol... well, when you die in a few decades & i get unfrozen by future technology, we can discuss snake oil vs real science [​IMG]
     
    ...oh wait, we won't b/c you were not cryogenically preserved [​IMG]
     
  13. HOWIE13
    @ UmustBKidn: 
    Fascinating and very helpful reply. The Audiotubes website has lots of information. It's all very bewildering though, especially when there are different ways of assessing tubes, different machines measuring different things, and on top of all that there is the question of whether the machine is up to date with its calibration.
    I guess in the days when tubes were ubiquitous as an electronic component people were used to all these measurements. Today, it seems to me that the machines may be useful if well calibrated and interpreted correctly, but could also be grossly misleading. I think I will go for what looks like 'reasonable value' tubes and keep my fingers crossed that they will sound OK.
     
  14. money4me247 Contributor
    help w/ this query. I read the following:
    I was wondering if this statement has any bias in truth as I compared the specs for both amps & their impedance is about the same:
    Bravo V3: Out-Put Impedance: 20~600 Ohm
    Little Dot 1+: Suitable Headphone Impedance: 8 - 600 ohms [Note: they do NOT state the actual output impedance]
     
    If someone can answer this question, it would be much appreciated! :) I was curious b/c the poster claims that the HE-400 won't work well w/ the V3, as the HE400 are low impedance, high efficiency headphones (Impedance: 35 Ohm, Sensitivity: 92.5 DB).
     
    In Put PowerDC24V
    Input Sensitivity100mV
    Input Impedance100KOhm
    Out-Put Impedance20~600 Ohm
    Gain30dB
    Frequency response10Hz-60KHz +/- 0.25dB
    Signal/Noise Ratio>90dB
    Dynamic range84.6dBA(300 ohm) 89.8dBA(33 ohm)
    THD0.016%(300 ohm) 0.45%(33 ohm)I
    MD + Noise:0.045(300 ohm) 0.42(33ohm)
    Dimension79mm (D) X 130mm (W) X 44mm (H)
    InputStereo RCA x1, Stereo 3.5mm x1
    OutputStereo 6.35mm x1

     
    Frequency Response: 10HZ - 50KHz (-3 dB)
    THD+N:
    0.2%: 1Vrms @ 1000Hz
    0.6%: 3Vrms @ 1000Hz
    1.0%: 5Vrms @ 1000Hz
    Signal-to-Noise: 92dB
    Suitable Headphone Impedance: 8 - 600 ohms
    Input Impedance: 50K ohms
    Power Output:
    150mW @ 300 ohms
    300mW @ 120 ohms
    800mW @ 32 ohms
    User variable gain settings: 6.5x or 3.25x
    Power Consumption: 15VA
     
  15. mhamel
     
    The issue with the Bravo amps and high sensitivity cans is that it has a ton of gain (+30dB), where the gain on the LD 1+ is both lower and adjustable.  With high sensitivity and a fixed line level input, you'll barely have any adjustment in the volume pot on the Bravo.
     
      -Mike
     
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