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My Singlepower Supra Experience - Why mine almost blew up like a Hand Grenade (and yours might too)

Discussion in 'Headphone Amps (full-size)' started by tyson, Jul 30, 2009.
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  1. Tyson
    I've had the Supra SE for a while now, and have quite a collection of 6sn7, 7n7, 12sn7, 2c51, vt-231's, 12at7's, 12au7's, 6922's, ecc99's, 6bl7's, etc... to "tube roll" in the amp. I also use Lawton Audio (Denon) LA-2000's, which are a pretty difficult load, being down in the 25ohm area.

    I was never super happy with the sound I was getting. Hence the purchase of all the various tubes.

    But, no matter what tubes I used, it always sounded a bit weak and there was that intermittant noise (faint, but noticeable during quiet passages).

    I figured it was just a poor match with the very difficult Denon's, even when using the 6bl7's and the high voltage setting on the amp.

    Finally, I decided I'd just go ahead and sell the amp and get the Zana Deux Transformer amp instead. But I wanted to give the Supra a check-up with a good tech before selling it to anyone.

    So, I called someone I trusted, Wayne Waananan at Bolder Cables - Store for The Bolder Cable Company - to have a look at it. He worked with Kevin Gilmore and Mike Galusha (a couple of genuine tube circuit guru's). They asked me to take some pics and send them to him. Pics below:






    As can be seen, those are not premium quality parts, far from it. But here's the rub - those 2 big @ss soup can sized capacitors? They are rated for 450v. Not bad, except the voltage from the transformer is 530 Volts! Now, even though they are connected in series, there is not a leveling resistor(s) in place between them. That means there is a high degree of danger that they will blow up, Yes, BLOW UP LIKE HAND GRENADES!!!!.

    So, obviously this thing needs extensive repairs to get fixed. The power transformer is putting out WAY TOO MUCH voltage for this circuit. And the (cheap) parts in there are not rated to handle anywhere near this level of voltage. And because of the way voltage, current, and low impedance loads work, that means it's putting out 2.5mW of power to the Denon's (and only 1.2mW in Class A). That's pathetic. And there's 500v in the case just waiting to escape and kill your @ss. Grrrr. When I think about the fact that my 2 year old daughter likes to listen to my headphones it enrages me.

    Back on topic - the changes needed are 3 fold - 1) Get a new input Power Transformer that's better quality and is half the voltage of the current one. 2) Replace the cheap, incorrectly spec'd parts in the power supply with better, appropriately spec'd ones (ie, get some HEXFRED diodes, and some Solen Film caps to replace the cheap electrolytics). 3) Optimize the output to be transformer coupled and use much better quality caps in the output circuit (ie, Obbligato film in oil caps and Sowter & Lundhal transformers).

    The cost in parts alone adds up very, very quickly.

    In the meantime, I suggest ANYONE that owns a Single Power amp to contact Wayne at Bolder Cables to see about getting it checked up. These amps ARE NOT SAFE.

    Wayne was able to identify several major problems on mine just from an understanding of the circuit, combined with hi-rez pics I sent of the internals, and telling him the values of various parts on the board.
  2. spritzer
    Thanks for making this public. These amps have serious design issues and do pose a danger, not only to the user but also to the very expensive headphones connected to them.
  3. NWRain
    First, Spritzer's thread, and then your thread. I can't believe that I wanted to buy a Single Power amp on the for sale forum at one point.

    If this level of neglect and poor build quality is a constant among all Single Power amps, then what will happen to people who have the Ornate Single Power amps that drive their Sennheiser HE-90s?
  4. spritzer
    I assume you are talking about the ES-2 amps in the huger boxes? They have all the same issues or even much worse as the other ES-1 amps. Same circuit but with some truly insane stunts by Mikhail. [​IMG]
  5. scootermafia
    Dear God. What a rat's nest. If one of those caps blew, it really would be epically bad. That does make me sick, especially as you said young children are near these amps. It's only a matter of time before Mikhail's work actually hurts people, not just their wallets. He should recall all of his stuff.
  6. iriverdude
    What a mess.
  7. jpelg
    Two words come to mind...

    "Drawn" and "quartered"
  8. Currawong Contributor
    I wonder if he was trying to emulate Tube Research Labs "random wiring technique". If I had an amp that looked like that inside, I wouldn't switch it on.
  9. Uncle Erik Contributor
    Wait a second. You're going to replace the power transformer, all the caps and add output transformers? Why?

    Aside from the case and the pot, you'll have to build an entirely new amp. What would be the point of that?

    Personally, I strip the thing, sell the parts, and put the money towards a new amp. I wouldn't be able to sell that to someone else in good conscience.
  10. kevin gilmore
    Just for a bit of perspective here. The 2 juice cans wired together are about 1600uf
    at 530 volts. at (C*V*V/2) thats about 225 joules. Each is 3 inches diameter
    by 5.625 inches high. Mikhail has been known to use capacitors 2 or 3 times
    this big in the past.

    These caps are wonderful if you are driving an argon laser directly from 3 phase
    440 volts at about 75 ampres. In fact i have a laser that has 8 of these inside.
    (actually those are 3 sizes bigger)
    But for a home headphone amplifier that puts out at most 1 watt, its more than
    even silly.

    In a hospital setting, a heart defibrillator usually has the following settings.
    (0, 2, 3, 5, 7, 10, 20, 30, 50, 70, 100, 150, 200, 300 and 360 joules) and by
    the last 3 settings you are already desperate and the patient is already likely

    I almost sent mikhail a pair of these to build into an amp. I'm now glad that i
    did not.
  11. Spareribs
    Wow, its a shame. Thanks for the info. This sounds like a mess though.
  12. Pricklely Peete Contributor
    Wow Tyson, sorry to hear of this misfortune with your SP. I'm glad nothing bad happened to you or your family members.

    Good luck with whatever you decide to do with it going forward !

  13. vcoheda Contributor
    and yet people claimed and some still claim that the SP amps are the best sounding. to say that i am having a hard time reconciling those views with the above, as well as the other recent threads on this, would be a massive understatement.
  14. TreAdidas
    Can someone break this down in layman's terms? Joules volts etc. mean very little to me. Not a technical fellow just a music lover.

    Ok mismatched power supply and caps... I got it. Not sure how this equates to something blowing up like hand grenades and a headphone amp being dangerous to use.

    Just curious. Thanks.
  15. tintin47
    If you feed a cap a voltage higher than its rated input, it can overload the cap and cause it to explode. When you feed a cap 25% more voltage than it is rated for, it can explode violently.
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