In a orig AC15 circuit nothing beats a EF86 but

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Groovey Records, Jan 29, 2008.


  1. Groovey Records

    Groovey Records Member

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    With all the Microphonic ding a ling ching even on great sounding NOS tubes what can you do.

    Does dampening an EF86 tube take away any of the qualities that they are sought out for. Would using a Silicone ring damper change the character of the tube, masking the chime and bell tones it can give? Does dampening muddy the tube?

    What are acceptable ways to chill out and stabilize the microphonic resonances of an EF86 without impinging on its true nature and excellence?

    Is that even possible without losing the character only the EF86 brings to the original late 50's or 1960 Vox AC15 circuit?

    Thanks
    Groovey Records
    listening to Memphis Underground- Herbie Mann w/ Steve Cropper, Reggie Young, Larry Coryell. and Sonny Sharrock on Guitar.
    on Vinyl of Course
     
  2. phsyconoodler

    phsyconoodler Member

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    a dampener on an EF86 is the only way to go.I don't think it alters the tone,just helps the rattle.
     
  3. hamfist

    hamfist Member

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    I'm pretty new to EF86's, but my amp (AC30HH) is a head. I've had two EF86's in it with no microphonics at all.
    I would assume that isolating the amp from a cab's vibrations is a very good way of solving this problem.
     
  4. chaz

    chaz Member

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    I saw Weber has a spring mounted tube socket available now on their amp parts page. I have no idea if that would work or not but can't imagine it would hurt. Between that and the dampers what else can you do?
     
  5. ruger9

    ruger9 Supporting Member

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    Some manufactures put rubber sleeves around them... totally encased...I wonder if you could dip the tube in that rubber coating used to protect tools?
     
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  6. Blue Strat

    Blue Strat Member

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    Interesting idea! Anything that adds weight/mass might help.
     
  7. Groovey Records

    Groovey Records Member

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    I heard Vox is using a encased EF 86 tube on one of their signature Amps. I wonder who makes it for them? It should improve reliability problems but to get the best sound inside a mummy shroud?

    I've put the Head on a granite slab next to the Cabinet. That worked well, still I needed to put the amp back up on top of the cab so I could run a 4x12 next to it. I have eggshell foam under the head ontop of the cab now.

    Any experience with a Halo Ring?

    Regards
    Groovey Records

    Listening to Memphis Underground- Herbie Mann
    on Vinyl of course

    [​IMG]
     
  8. hamfist

    hamfist Member

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    Yes, the new AC30HH has one of these. I've no idea what tube it is though, as I don't think you could get the casing off without ruining the tube.

    [​IMG]
     
  9. AL30

    AL30 Member

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    What's the temperature rating on that stuff? Are the rubber tubes on the tube itself or on a tube shield?

    AL
     
  10. DanD

    DanD Member

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    Hamfist,
    Looks like regular heat shrink tubing.
    Use an x-acto knive to remove it.

    DanD
     
  11. hasserl

    hasserl Member

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    I experimented a bit with coverings and dampers on microphonic 6AU6 miniature 7 pin pentodes. Not the same thing as an EF86, but a similar situation. I found that basically the first thing you need to do is to sort thru the tubes to remove those that are noisy to begin with, it doesn't matter what you do you won't be able to quiet them down. I did try some heat shrink tubing, I don't think it did a damn thing. BUt what I did find that helped was some rubber grommets made for insulating holes in metal chassis to preven chaffing of wires passing thru it. I found some that the I.D. was a nice sng fit on the tube, then I wrapped a strip of solid solder (about 1/16" dia) inside the groove around the outside of the grommet. (I also insulated the tube socket with a rubber o-ring under the base of the socket and one under each mounting screw) I've gigged with the amp about four times now and so far the microphonics are under control.

    I think Mike hit on the key thing in his reply above, changing the weight. You've got to add some weight to get any benefit. Just adding a thin layer of rubber as a sleeve isn't going to do any good, just an o-ring isn't going to do much better, you have to add enough weight to change the resonant frequency the tube is vibrating at. Like adding weight to the ends of handlebars on a motorcycle to reduce vibes, it's the same effect.
     
  12. Groovey Records

    Groovey Records Member

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    Hasserl,

    A very unique and original approach -
    Let me see if I've got this right-
    Two small O ring under the socket screws
    one under the socket base (between the chasis and the socket?)
    Then on the tube itself a grooved rubber grommet filled with a strip of solder.

    Are you using one or two?
    Could you shoot a picture of this ?

    Thats thinking out of the box
    best thanks
    Groovey Records
    Listening to Robben Ford - The Inside Story
    on Vinyl of course
     
  13. jazzguitar

    jazzguitar Supporting Member

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    My BadCat has rubber grommets mounted between the tube sockets and the chassis. The sockets are floating and move when you touch them, it was quite a surprise when I first went it to swap a tube out! It does seem to help though.
     
  14. Swarty

    Swarty Member

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    The heat shrink looks like a decent approach. In the old amps Vox dealt with it a different way; the early versions had the tube wired as a pentode, but later ('61?) ones had it wired as a triode, making it much more stable... but also losing a lot gain/honk/pizazz... A customer had me convert a triode version to a pentode version and man, what a difference... It went from sound very nice to sounding huge and mean!
     
  15. hasserl

    hasserl Member

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    I'm out on the road right now. I'll try to post something later this afternoon.
     
  16. hamfist

    hamfist Member

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    The Ac30HH (yeah, I know I'm getting really boring going on about this amp !!) has a little switch where you can switch between triode and pentode on the EF86. As expected the triode has a lot less gain. The pentode configuration is where the goodies are at ! On Pentode, it's a "badass mutha !!" (in a nice Voxy way of course !).
     
  17. kiteflyer

    kiteflyer Member

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    I tried out the Weber 9-pin shock mount for the EF86 in my AC30 build. Works really well IMO. The noval socket is mounted to an alluminum bracket with rubber washers and that's mounted to the chassis with vibration dampening springs. I don't get much microphonic ringing at all in the channel.

    The only downside is the pain of using the damn thing. It may not be obvious at first, but with the socket sitting outside of the chassis, the pins are difficult to get at; and extremely close to grounding out on the chassis. I used heat shrink tubing to prevent it, but what a PITA.


    [​IMG]

    [​IMG]
     
  18. Groovey Records

    Groovey Records Member

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    Hello Friends

    EF86 PROBLEM SOLVED!

    The RFT EF86 (Tesla) ops checked very well.

    First I tried it with the Halo and the wire tube cage- Very Sstable no ching or rattle. No microphonics

    Second just the tube and the wire tube cage. just the slightest ring very very minor on sustained notes at 3pm on the amp volume. 7 on the guitar with two overwound HB pups.

    Went to Just the Halo next and ran it all maxed out guitar tone, vol and 3pm on the amp

    All good thats where it will stay until I test the NOS Mullards, These RFT Tesla EF86 where a good buy about the same as current modern manufacture.

    [​IMG]

    Best
    Groovey Records
     
  19. Groovey Records

    Groovey Records Member

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    Dear Friends,

    I'm not going to take anything away from the RFT EF86 (Tesla) tube that I got from Mike K. (What a gentleman BTW) In fact I am going to buy a few more. They are a great sounding AND stable NOS tube for a very resonable amount of money in todays market.

    I wonder if Nikoli Tesla had anything to do with this company. I read his biography and recommend it for people who are interested about the wizards, magicians and con artists of the modern electric age. Tesla's thoories and practices are behind things just now coming to be. He was a visionary.

    Now yesterday I said I also ordered a NOS Mullard EF86 from Mike and that I would try it today. It is special. River Deep, Mountain Wide Special.

    The TopHat Supreme 16 is now all genuine Mullard except the EZ81 rectifier tube. V1, 2 and 3 are ANOS Mullard 12ax7's and the EL 84's matched NOS Mullard's. All tubes measure above original NOS spec's by a large margin and this NOS Made in England Mullard EF 86 is the last trick in the deck.

    Just look at this beauty no ring no ping no stabilizer just chain saw motor growl and bell note round tone. It's a real Jewel. Thanks Mike

    [​IMG]

    Best Regards
    Groovey Records
    Listening To The Firebird Suite-Igor Stravinsky-Antal Dorati conducting The London Symphony Orchestra
    On Original Living Sound Vinyl
     

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