Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups darrenriley.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

Dukane Intercom Tube Amp Conversion

Discussion in 'Shock Brother's DIY Amps' started by ArcticWhite, Jul 8, 2018.

  1. Platefire

    Platefire Friend of Leo's

    Age:
    70
    Nov 3, 2003
    North Louisiana around Many
    Didn't you say in another thread you had a bunch old Hammond amps? or was that someone else? If so, you could snatch the OT out of a Hammond that had two 6V6's push/pull and use it which would probably have 4/8/16 Ohm taps.

    Regarding cosmetics, I would really try to build my new amp in that existing Chassis. I think those old Dukane chassis with the perforated covers are so cool. Just me!! I would leave all those push button controls abandoned in place and install the new amp input jack, volumes and tones controls in the panel above where you already have holes for pots. I would also remove that rear panel with all the speaker run connectors/terms and replace it with a solid metal plate where you could install a 1/4" speaker jack to connect to your OT speaker taps,
    hopefully 8 Ohm most common.

    That's just my thoughts but I'm big on preserving the old vintage
    amp appearance---so that's just my thinking and take it with a grain of salt:>) Platefire

    BTW-Here is a couple of pics of my Dukane Project
    DSC00412.JPG
    DSC00414.JPG
     
    Last edited: Jul 11, 2018 at 11:13 AM
    ArcticWhite, RoscoeElegante and D'tar like this.

  2. ArcticWhite

    ArcticWhite Tele-Meister

    265
    Apr 14, 2009
    Portland Oregon
    Oh, I am definitely going to use the existing Metal Cabinet. Just going to clean it up and polish it. These things are cool as hell.
    I like the idea of putting a bias meter in the old 4 "speaker panel too.
    I plan to test the original OT because I think you're right about it having an 8 ohm tap. It has several extra wires going to ground for no good reason.
    I'm in the middle of it right now!
     

  3. ArcticWhite

    ArcticWhite Tele-Meister

    265
    Apr 14, 2009
    Portland Oregon
    20180712_003554.jpg This seems like an awful lot of stuff on the EF86 in V1.
    A 20 mfd electrolytic from the g3 pin to ground? With a domino type capacitor in parallel, also to ground.
     

  4. Platefire

    Platefire Friend of Leo's

    Age:
    70
    Nov 3, 2003
    North Louisiana around Many
    I like the idea of a Bias meter in the old speaker opening. I've installed external bias test points along with external bias pot, but never a bias meter? I'd like to hear more about how that works.

    On the EF86. I have never had any experience with those. From what I've seen the hook up for a Guitar preamp is quite different or more complex than a normal 12AX7 but everybody seems to agree that produce great tone. Also I know in the old PA and intercom amps they tend to put a lot of extra components and circuitry not needed on a guitar amp. IMHO I would follow the example hookup of a well known EF86 guitar amp and use that as a model. Everything in the EF86 hookup that didn't resemble the model, I would tear out and get rid of. Seems ever EF86 Pre example I've looked at has had a Triode/Pentode swictch or control including a Vox AC15CC I looked at.

    Here is an interesting example schematic I looked at that has a EF86 in V1 and very similar tube configuration as yours but the two 6V6's are running in parallel instead of Push/Pull. I never have done that but always wondered what it sounds and operates like. But this might give you a good idea of EF86 hookup for guitar including the type input jack to tube you might want to install. Platefire
    EF86 Pre Amp.jpg
     
    ArcticWhite likes this.

  5. RoscoeElegante

    RoscoeElegante Friend of Leo's

    Feb 19, 2015
    TooFarFromCanada
    SSL9000J and ArcticWhite like this.

  6. Platefire

    Platefire Friend of Leo's

    Age:
    70
    Nov 3, 2003
    North Louisiana around Many
    ArcticWhite

    Take a look at the old AC15 schematic(attached pdf). I think this is the simplest Input/pre-amp set up for your EF86 that also has plate voltages that gives you a good idea of DCV to shoot for. I personally would just have one input jack and use a 33K grid resistor. I would never use that second input, but that's just me. To me the only advantage of having the extra input is if you want to hook a second amp in parallel, all you have to do is run a cord from the unused input to the other amp---that's kinda nice to have.

    Again this is just my thinking. Trying to be helpful. I realize not everybody approaches this kind of stuff like me:>) So whatever you decide, it will be good. Platefire
     

    Attached Files:


  7. ArcticWhite

    ArcticWhite Tele-Meister

    265
    Apr 14, 2009
    Portland Oregon
    That's extremely helpful Platefire. I really appreciate your interest and support.
    I'm really excited about using the EF86 in this Amp. It's a weird tube, supposed to be very nice, but highly microphonics and sensitive. More work planned tonight.!
     

  8. ArcticWhite

    ArcticWhite Tele-Meister

    265
    Apr 14, 2009
    Portland Oregon
    Hey Platefire, do you have a better copy of that Schematic, or maybe a link? It gets blurry when I zoom it.
    Thanks AW
     

  9. Platefire

    Platefire Friend of Leo's

    Age:
    70
    Nov 3, 2003
    North Louisiana around Many
    The best thing to do is right click on it on the thread schematic and do a "Save As" to your computer.
    Then I was able to enlarge it to a lot bigger size. It's still fuzzy but you can read it if you look close.

    I did some searches and turned up that schematic from where I originally found it. Here is the Link. Maybe you can save and manipulate it to what your want to see. Platefire
    http://www.tdpri.com/threads/any-schematic-for-ef86-pre-and-6v6-output.339799/

    See if this copy is any better!!
    EF86 Parallel 6V6 Single-Ended Amp.jpg
     
    Last edited: Jul 13, 2018 at 10:52 PM
    Nickfl and ArcticWhite like this.

  10. Nickfl

    Nickfl Tele-Holic

    963
    May 24, 2016
    Florida
    Part of the reason it is known for having issues with microphonics is that it was setup for very high gain in the classic vox amps it was used in. If you read that thread Platefire linked to you'll see that this is discussed along with the Valvewizard circuit values for a more "appropriate" level of gain that reduces these problems.

    Check out my "AC 4 inspired" build thread, and take a look at my schematic, it uses a 5879 pentode input in a very similar way to the EF86 in that Tubeswell schematic. The 5879 is a comparable tube to the EF86 (a good bit cheaper though) and I've used it, and liked it a lot, in one other build so far. I think you'll be happy you decided to try a pentode preamp.
     
    SSL9000J likes this.

IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.