Where to find EF86 ultra-linear schematics for inspiration?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Rollie, Nov 12, 2004.


  1. Rollie

    Rollie Guest

    I've started building amps recently and love it. I'm addicted and obsessively dream about this now.

    My next build is intended to be a high-headroom clean amp.

    Anyone have any thoughts on where to look for schematics for an EF86 driven, ultra-linear output amp? Maybe something with 6V6's... ?

    Other suggestions welcome, too.

    Thanks,

    Roland
     
  2. hasserl

    hasserl Member

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    Maybe an EF86 isn't the best choice for high headroom clean amp. I'm not familiar with any EF86 amps that also used an ultra linear power section.

    EF86's also tend to be noisy tubes, lots of microphonics. Any reason in particular you want to use that tube?
     
  3. loverocker

    loverocker Member

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  4. loverocker

    loverocker Member

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    <later> Actually, I've just got one of my old Mullard circuit books out and in the chapter on the 10Wer, there's a simple variation for 'distributed loading' which I think is "oldtimer-speak" for UL. Anyways, it shows the screens connected to the extra tags on the OT's primary, and a slightly higher R in the power supply to drop the B+ for the PI and preamp.

    Of course this is a 2xEL84 amp, so I guess it may not have enough volume for gigging? :) Maybe just double-up on the output valves (in a similar way to the 36Wer over at www.18watt.com)?
     
  5. Kiwi

    Kiwi Silver Supporting Member

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    My (very) limited understanding is that the Dr Z Route 66 amp combines an EF86 pre-amp with an ultralinear output. Some of his other amps may as well - the 6545, and the Delta 88 possibly too.

    The Matchless Clubman runs an EF86 front end and the resulting amp has punishing amounts of clean headroom.

    I'm no techie - just run a search here on the term "ultralinear" and see if the discussion threads that result cover the topic.

    Kiwi
     
  6. hasserl

    hasserl Member

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    The Clubman 35 is not Ultra Linear. But beyond that, while I hve never played a Clubman myself, I have a homebrew amp I built with inspiration from the Clubman. Although it uses a 6AU6 for the pre-amp rather than an EF86, so it likely sounds a bit different, it in no way resembles anything close to high headroom. It has a beautiful clean sound, but with the volume turned up beyond ~4 it starts to get dirty quick and at 7 it distorts very nicely, thank you very much! A beautiful sounding amp, but not much headroom at all. If a real Clubman does have I would be suprised. But hey, it's possible.

    Other amps using the EF86, like Vox, are also not known for amazing headroom.

    Personally, when I think of an amp with a lot of headroom I think of a Twin Reverb. That tends to be my yardstick for a high headroom amp, and if I was looking to build one that would surely be my inspiration.

    Just my $.02 YMMV, and all that sort of stuff. :)
     
  7. Rollie

    Rollie Guest

    Thanks for the posts, guys. And yes, it is actually the Dr. Z's that were initially piquing my interest in this area.
     
  8. Blue Strat

    Blue Strat Member

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    The NEW Russian EF86s tend to be noisy and microphonic, NOS EF86s tend to not have these problems.
     
  9. TieDyedDevil

    TieDyedDevil Member

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    Thought I'd resurrect this thread. Last month I built my first amp. Well, my first in about thirty years...

    You might be interested because of the design:

    - EF86 preamp
    - low-loss tone stack driven by the triode side of a 6BM8
    - single-ended driver (the pentode side of the 6BM8) pushing a transformer phase splitter
    - a PP pair of ultralinear-connected 6V6s in a cathode-biased non-NFB output stage
    - pushing a Jensen P15N in a large combo cab

    I wasn't going for a high-headroom amp; I wanted excellent note definition, extended frequency response, great touch sensitivity (check the clip), low weight (36 lbs) and a sane stage volume. Running flat out, this amp pushes 105 dB at 1M (A weighted, slow). It stays totally clean up to about 97 dB.

    All the details, schematic and a clip are here:

    http://psg.com/~dlamkins/Articles/amp-1-build-narrative.php?cat=amps
     
  10. Blue Strat

    Blue Strat Member

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    Cool amp! Funny, because I'm about to build something very similar but very different!;)

    I'm using a 1950s PA amp chassis (which looks very much like your chassis) which originally used a pair of 6V6s, a 5Y3 and 2 12AX7s. The transformers are quite large for an amp with such modest potential power output....quite a bit larger than 5E3 transformers.

    My intent is to build an amp with an EF86 front end which will break up early. Mine, of course, won't be ultralinear and will use a tube rectifier.

    Should be interesting.
     
  11. Rollie

    Rollie Guest

    Oh man, thanks for posting that! Looks like a really neat amp. I couldn't get the sound clip file to work, though.

    Any chance you would post your layout diagram and the parts list that you created?

    I love the tone stack also. Are there any current manufacturers that use that type of tone stack or did you completely generate that on your own? If so, I'm totally impressed. I've always felt like there was something "wrong" with the way that traditional tone stacks are configured to rob the signal of bass to "get" treble, or the reverse.

    If its ok with you, I'm going to use your schematic to build one. I'm dying to see that tone stack in action.
     
  12. TieDyedDevil

    TieDyedDevil Member

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    Go for it. Let me know what you think when you're done with your build. Feel free to send email (address on my web page) if you have questions.

    I'm still tweaking... you may have noticed that the narrative is growing.

    I don't yet have a BOM or a layout suitable for the web. At some point I may upload the chassis drilling guide, which you could use to get started. But... I'm kind of hesitant to recommend my layout. On the one hand it's really good for minimizing coupling and strays because everything runs direct from lug to lug and there are only a few wires. It's almost an RF-style layout. On the other hand, working in that chassis got to be a bit trying. When I do it again, I'll almost certainly build a jig so I can do most of the tight wiring outside of the chassis. That's assuming that I stick with that chassis size.

    I don't know any manufacturers that have ever used that tone stack design. I do remember seeing some old schematics of amps that used a fixed bridged-T to get their mid-dip.


    Re: the clip... I'm trying to write standards-compliant HTML and some browsers (notably IE, dependent on its settings) choke on MP3s in <OBJECT> tags. There's a direct link to handle the case of the browser not being able to handle MP3 at all, but you probably don't see that. I'll add a separate link.

    Meanwhile, try this link: http://psg.com/~dlamkins/Articles/apics/Amp_1_Demo_1.mp3
     
  13. Rollie

    Rollie Guest

    That link works great--thanks. I like the sound of that amp. I know its hard to get a good dry clip recorded, but some of those plucked chords ring like a bell. It also sounds touch sensitive--that overdrive you're getting is all pick-attack, right? I like it. I'm definitely going to build one. Can you tell me what trannys you used? Everything else I can wing. :)
     
  14. TieDyedDevil

    TieDyedDevil Member

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    The iron is all Hammond. I guess I should note that on the schematic.

    I love the way those chords ring. Everyone who's played the amp remarks about that.

    And yes, the overdrive is all pick (actually finger) attack. It sounds like I bumped up the volume about ten seconds into the clip, during the single note lines. There may been some others: this is an excerpt out of about 20 minutes of recording. Listening to the clip, though I can't hear any other changes. As far as I recall, that's all one pickup (neck) and (except for the volume bump near the beginning) one setting.
     
  15. Rollie

    Rollie Guest

    Man, that is great. I'm definitely building one. It will have to wait until 10-K and proxy statement season is over, though. This summer I'm all over it.

    By the way, what is your professional background? I thought I saw a reference to a chip design software in your web page--are you/were you an EECS guy or a circuit designer or something?

    I've got a couple friends who are RF circuit designers who have helped me with amps, layout, parasitic capacitance issues, etc. and those guys have been *really* insightful into debunking and sometimes reinforcing some of the tube amp mythology that floats around the web. Sometime I wish I had finished my engineering degree.:D
     
  16. TieDyedDevil

    TieDyedDevil Member

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    I learned electronics hands-on at a very young age. I literally started when I about four years old. While other kids were reading comics, I read things like the ARRL Handbook and the RCA Receiving Tube Manual. I built a lot of gear as a hobbyist - mostly audio and later digital. Never did get the hang of RF, but learned a lot about layout in the process. I spent a couple summers in high school as a bench technician, repairing TVs, stereos, tape recorders, etc. Mostly tube gear at that time, although transistors were starting to make inroads.

    I thought I wanted to be a computer designer, but Intel released the 4004 right after my first year of college. I saw the handwriting on the wall: there weren't going to be any more Seymour Crays in that field. So I focussed on Computer Science and took a bunch of EE courses. Through a special program I was able to replace most of my liberal arts courses with courses that I really *wanted* to take, so I was able to get about five years' worth of CS courses and two years of EE courses in the span of four years.

    I spent about a year between my first and second half of college doing tech work for a video game manufacturer. I worked as an EE during my last two years of college and for four years afterwards, doing instrumentation, process control and automation using both digital and analog techniques.

    After that I decided to actually do something (besides firmware) with my CS degree and got into the early days of video games (Parker Bros. and Activision). The home videogame industry tanked around `83 or `84 and I moved on to doing more traditional software development work. I eventually became interested in AI, and have developed a lot of practical applications in that field. I wrote a book on Lisp, self-published it on the web, and released it in hardcopy this year.

    Now I'm working as a software engineer for a growing self-funded company and looking forward to getting into amp building as a retirement career.


    Sorry you asked? Sometimes I'm not good at the short answer... ;)
     
  17. Rollie

    Rollie Guest

    Not sorry at all--that explains a lot. :)

    Good luck with the new company. I'm seeing a lot more private company investment these days and we're more optimistic now for liquidity events for startups than we've been since 2000. So it looks like its a good time to be in a startup again.

    Back to amps, though--(amps are far more interesting than work, work, work). Thanks for the help, schematics and advice on this one. A Berkeley engineering dropout like me can use all the help he gets. Its all I can do to remember what electricity is. :D
     
  18. saros141

    saros141 Guest

    David, that is a very cool design and it sounds excellent, thank you for sharing!
     
  19. TieDyedDevil

    TieDyedDevil Member

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    Thanks. I'm still tweaking the design. I hope to have some more clips up soon.
     
  20. guitarcrazy2004

    guitarcrazy2004 Member

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    ef86 ?? kcanostubes just sent me one i order with no pins?? after spending 78.00 for a gec ,and yes i have pictures of the tube and invoice....bad business-be carefull...........after spending 78.00 u would think the tube would at least have pins to put itin the amp.......damn shame...
     

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