My new old amp project: SE46 monoblocks

Discussion in 'DIY' started by Redboy, May 28, 2014.

  1. Redboy

    Redboy a few good watts Subscriber

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    I figured out a couple years back that the thing I like most about this hobby is making stuff, specifically single ended tube amplifiers. It's good mental exercise for me, to research different circuits and topologies, theories and tube types, ideas and plans. If I progress beyond the research phase of things, then I might start buying parts and working on a layout. A very few projects make it even beyond that point to actual building of things, with metal shavings and wire strippers and solder fumes...

    Here's the stuff I've been working on lately - a pair of monoblock single-ended tube amps based on Gordon Rankin's Bugle 45 amplifier project as found in an old Sound Practices article.

    Unfortunately, at this point there is only one of them built...

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    Last edited: Oct 11, 2017
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  2. Redboy

    Redboy a few good watts Subscriber

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    I really appreciate the aesthetic of a good old vintage tube amp, especially those built for our government - that old mil spec iron especially is some amazing stuff!

    I was shooting for a "black n' metal" aesthetic here, and I'm pleased with how it's turning out.

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    Last edited: Oct 12, 2017
  3. Redboy

    Redboy a few good watts Subscriber

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    The mate will be a mirror image of the first, on a matching chassis. I used Hammond cast aluminum boxes that I've built several other amps on - these things are really nice to work with.

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    Last edited: Oct 12, 2017
  4. Redboy

    Redboy a few good watts Subscriber

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    Somewhere along the line, I got the idea to see how these things would polish up. I really like the effect.

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    Last edited: Oct 12, 2017
  5. Redboy

    Redboy a few good watts Subscriber

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    Some pretty nice parts went into them... Chicago PT and choke, ASC poly-in-oils, Cerafine filter cap.

    There's something perverse in me that makes me wonder how much I can cram into a 7"x7" box...

    I think I could fit more in there!

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    Last edited: Oct 12, 2017
  6. Redboy

    Redboy a few good watts Subscriber

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    The original Bugle was a stereo 45 amplifier. Aside from modifying the power supply a little to make use of these beautiful potted Chicago transformers, I wanted to see (hear) what the 46 tube could do in this circuit. This isn't new ground - our own Gary Kaufman did this years ago - but I figured the voltages would come out about right, and besides... I have these gorgeous globe 46s to try!

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    Last edited: Oct 12, 2017
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  7. eddantes

    eddantes Drone, Sector 7-G

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    Very cool! I will love to see you complete the pair and tell us how they sound
     
  8. marantzfan

    marantzfan ... Subscriber

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    Now I need to go do some reading on 46's now. I always learn a lot from your builds Nate. :yes:
     
  9. Redboy

    Redboy a few good watts Subscriber

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    Thanks fellas. Anthony, a lot of 45 fans find they like the 46 quite a bit, too. Some of them prefer it.

    The output transformers are from ElectraPrint, and I had Jack wind these with a little special somethin'.

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    Last edited: Oct 12, 2017
  10. cubdog

    cubdog banging through drywall Subscriber

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    Damn! You do such fine work. I'd love to own one of your creations. Maybe someday. :sigh:

    cubdog
     
  11. gadget73

    gadget73 junk junkie Subscriber

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    The 46 is a tetrode, right? Is that wired as a triode, or are you using it as a tetrode? Just curious because I seldom hear much good about tetrodes as audio tubes. If its triode wired, is the screen going to filament(cathode) or did you tie the grids together? Just curious as its not a tube I know anything about.

    Nice looking amps. Pretty good amount of stuff under the hood without being overly crowded. Any hum problems due to the close quarters ?
     
  12. Redboy

    Redboy a few good watts Subscriber

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    No real hum issues so far, but I'll know better when I get the second one done.

    Yes, the 46 is wired triode, with G2 tied to the plate. The tube was actually designed to be operated that way - it's a pretty neat one.
     
  13. rogerfederer

    rogerfederer AK Subscriber Subscriber

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    speaking of tetrode, i recently bought a lance cochrane single-ended 6L6 amp on barter town and emailed lance to get some background.

    he explained the amp was set up to run the 6L6s (or many other similar tubes) as tetrodes: "I've never really liked triode despite the mystique. Just too bland. Tetrode has the bite required a lot of the time and triode is too smooth and lifeless."
     
  14. Markus111

    Markus111 Big Horns & Many Tubes Subscriber

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    Very Nice! I've been wanting to do a 46 build for years. I have the tubes, the iron, the sockets..... Now all I need is the time. I did build the Bugle 45 years ago (with 45s) and that was a fine sounding circuit. Unfortunately I also got rid of the amp years ago. I wish I would have kept it.

    Mark
     
  15. guiller

    guiller Toscaninichus Australis

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    Wonderful amp and restoration job!
     
  16. dodog

    dodog Addicted Member

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    Love it!

    Never been a tube guy but always wondered.... do you guys wear cotton gloves when inserting the tubes or do you meticulously wipe them down if you don't? Never see finger oils on the tubes (and can't image that being a good thing). The closeup of that globe looks cleaner than anything I've ever eaten off of.
     
  17. Redboy

    Redboy a few good watts Subscriber

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    No gloves. Tubes will operate just fine covered in all sorts of grime, but I usually try to get the worst of it off before heating them up...
     
  18. PRM

    PRM Active Member

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    SE 46 Monos

    Hi Nate, Happy birthday to you my friend. The 46's will be sweet. I have a stereo 46 and I couldn't be happier. Good luck with the project. Keep the photos coming.
     
  19. Redboy

    Redboy a few good watts Subscriber

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    Thank you! It's a good day. :)

    Hoping to work on the second amp a bit today. More pics to come!
     
  20. Billfort

    Billfort Addicted Member

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    Very cool Nate.

    It'll be interesting to hear how this works out for you.
     

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