Spraque Vitamin Q's and Fisher

Discussion in 'Fisher' started by tube-a-lou, Feb 26, 2017.

  1. tube-a-lou

    tube-a-lou Super Member

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    Hi all,
    Anybody using these with their fisher amps, just wondering how the Fisher amps sound
    with them?

    Thanks
     
  2. heyraz

    heyraz Super Member

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    Oh man...
    This may be the start of a long thread that becomes a "Paper in Oil" Capacitor battle. I've seen it before.

    Vitamin Q is the oil formulation Sprague used in some of their Paper In Oil caps. Vitamin Q is Sprague's PIO "Special Sauce". They've attained some "legendary status" but I can't say they're my favorite.

    To be specific, I'm only talking about capacitor's in the signal path. Not bypass caps, just straight coupling caps.

    I have this huge stash of PIO caps from different manufacturers. If I'm rebuilding an amp and don't like the way one manufacturer sounds, I might pull it and use another. and as I recall, I have a few Vitamin Q's that I've pulled out if favor of another.
    What might I not like? Lack of clarity or coloration. The ideal capacitor should impart nothing to the sound. Of course, there is nothing in the world that's ideal and different people have different tastes, which is why we have choices.
    Personally, I think Westcap made a beautiful sounding PIO cap (CQR series especially) that I flat out prefer. Those are the caps that are in the signal path of my amps.
     
  3. tube-a-lou

    tube-a-lou Super Member

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    4,039
    Received them today and put them in, so far so good need a bit more break in time. P1050641.JPG
     
  4. wcarroll

    wcarroll Active Member

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    I am running the exact same caps in my 800c. They did sound kind of "blah" when I first installed. But, I really like them now. There definitely is a break-in time, but is wasn't very long for mine.
     
  5. tube-a-lou

    tube-a-lou Super Member

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    Your right, when I first put the amp on there was a difference in tone and it was like the amp was out
    of phase but then after a few hour of play everything fell into place.
     
  6. NoTransistors

    NoTransistors AK Subscriber Subscriber

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    I enjoyed a Scott LK-72-B for a long time. When one of the CeraCaps shorted-out, and blew a 7591, I changed out each and every coupling capacitor. Using these fancy P.I.O.s was a mistake, in my opinion, as they muddied up the sound.
    This is why my present Scott, a 299D remains all-original, but for some repairs.
     
  7. gadget73

    gadget73 AK Subscriber Subscriber

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    I think some of those Cera-Caps were a film capacitor of some flavor. A modern film would probably be a closer match to the originals there. My Sherwoods rock original film caps, not for any special sonic reason but because they are in perfect working shape.

    Not everyone digs the PIO sound.
     
  8. tube-a-lou

    tube-a-lou Super Member

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    Actually in the fisher they really opened it up sound quality wise, the soundstage has become wider
    and at times deeper and higher, besides I think the Scotts need a bit more work to get right.
     
  9. NoTransistors

    NoTransistors AK Subscriber Subscriber

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    The issue here is that some of these old coupling caps are time bombs that may possibly make an output tube or transformer go 'boom' some day.
    I suppose that a resistor that is used as a fuse [as discussed here many times] would be the only sane way to use these old caps without fear.
     
  10. NoTransistors

    NoTransistors AK Subscriber Subscriber

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    I always thought that my LK-72-B [stock] sounded better than my Fisher X-202-B [stock]. They were both designed around the same tubes, more or less.
     
  11. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    I never tried them ( i couldn't find adequate quantities at the values i needed)
    I have used the Russian ky40s.
    I suspect (but don't know) that they're similar, only for the reason that i thought they were harsh and then they opened up. I don't know if that's a good thing or a bad thing. It troubles me a bit to think that brand new parts (that meet spec out of the box need to change to sound right. ) i think now I'd just use a good quality (read main brand by known source not boutique) PP film.
     
  12. gadget73

    gadget73 AK Subscriber Subscriber

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    Honestly I wouldn't count on that. The resistor is not guaranteed to open before damage occurs. They usually only go in the event of a dead short. A leaky coupling cap probably won't do it.
     
  13. tube-a-lou

    tube-a-lou Super Member

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    I still want to get a nice Scott amp, I think they are a bit brighter sounding than the fisher with it's smoothness in the high
    end, but when I turn the volume up the Fisher's do hold together better with my speakers.
     
  14. NoTransistors

    NoTransistors AK Subscriber Subscriber

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    My speakers are so efficient, that they can walk across the room [Italian floor tiles] at high volume. And they must weigh at least 120 pounds per side. The Fisher has silicon diode rectification. Scott has a nice Mullard 5AR4 and a bridge rectifier. This might create some differences in sound. Also, Fisher seems to push the tubes to or past their limit. My Scott runs cool, while you can fry an egg on the Fisher.
    Fisher made some really great stuff, but my ears prefer HH Scott.
     
  15. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    In the vein where the conversation wandered,
    I've often thought it might be interesting to get together 4 players (as comparable as possible) a Fisher, Scott, Sherwood, Eico...
    7591 based , 30wpc +/-, either all active or passive tone controls, set them up with same speakers (i had A25s in my head, no reason), play them back to back to back (double blind) and get impressions from a dozen or so peers.
    Totally unscientific, just seat of the pants impressions.
    I've also given some thought to the fact that if you ran same tests with same listeners when listeners were 25 Y.O. and today preferences might be different (compensation for loss of hearing):idea:
    Sorry for the side track
     
  16. tube-a-lou

    tube-a-lou Super Member

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    Sounds like Fun!
     
  17. tube-a-lou

    tube-a-lou Super Member

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    That's what I heard about the Fisher's as well, When I restored the Fisher's I have I lowered those resistor down from
    330K to 220K because they run the 7591 hard.
     
  18. NoTransistors

    NoTransistors AK Subscriber Subscriber

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    The 7591 offered more than double the power of a 6V6GT, in the same size envelope. Fifty years ago, this new tube was being offered for about $2.00 each, so it hardly mattered that they were being pushed to their limit in most applications. When these were available for such an absurdly low price, most other tubes cost three or four times as much, so it seems that the 7591 was agressively discounted at the wholesale level [I read Vacuum Tube Valley magazine].
     
  19. gadget73

    gadget73 AK Subscriber Subscriber

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    The resistor choice really didn't have anything to do with how hard the tube ran. It causes extra stress, but does not produce additional power. Possible it had something to do with the phase inverter though. The higher the value resistor, the easier a job the phase inverter gets. Fisher did put the "noose" on the inverter that reduced it's available voltage swing, so possibly the high value resistor was to help allow it to get the job done.

    The other big sell point of the 7591, besides any price breaks, was the simple driver circuitry required. Its pretty much the same driver as a 10-15 watt amp got to make 25-30 watts. One 12ax7 could take care of phase inversion and voltage gain with no troubles at all.
     

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