13 Responses

  1. David
    David at |

    Would you please tell me what you used for a choke?

  2. Connor
    Connor at |

    Hey John, can you do a write up on selecting a new (or NOS) transformer for an amplifier?

  3. Bruce Kunakov
    Bruce Kunakov at |

    Love the build,been looking to build a one tube single end amp . Do you have a lay out and parts list will pay thanks John you should sell this in a kit it would do good for us over 60 crowd we want little that sounds real but 18 watts are too much.and have had or tried most amps ever made

    1. Martin Baker
      Martin Baker at |

      I agree about wanting to build this but needing a parts list. Is one available?


      1. Sandra @ thetubestore
        Sandra @ thetubestore at |

        You will find the parts used throughout the 3 part article, but given that it was a personal project there is no layout available. Thank you for the inquiry though.

        1. Martin Baker
          Martin Baker at |

          Thanks Sandra. If John is available do you suppose there’s any way to get him to do a layout for this?

          It’s almost like letting us smell the meal cooking but never letting us in to eat! :-)

  4. Bruce
    Bruce at |

    Hi john I ordered transformers two month wait.I have a lot of parts on hand. My question if you can ,I see a bias switch with 2 yellow wires going to ? I think to a resistor and maybe a different cap Can’t tell switch tabs 4 or 6 ?. And white wire on power tube pin 4 is on one pic and cut on a different pic … Any help you can give would be a big help I only have a few builds and this is first none kit I have to try this one it is dead on to what I was looking for … If you answer these comments I would love to talk about this build… They don’t mass build this type amp …but someone should

  5. Gabriel
    Gabriel at |

    Would it be possible to have the schematic and parts list of this little marvel? (For Christmas!) You make it seem like quite easy to do but I guess I’d rather buy it new though, as I’ve never built an amp …
    If you already have one extra amp that’s built, I would be interested to buy it! Please contact me!

    Merry Christmas!

  6. Alberto Plasencia
    Alberto Plasencia at |

    Dear John,

    I am really glad to find this tutorial, it will help me enormously with my amp project… it seems to be just what i was looking for.

    There are two aspects I would like to ask you about. I am toying with the idea of covering all the amp with a wood case. Just to make it look great, but i don’t know if that would be a problem, perhaps this amp requires heat disipation.

    The other question is: had I have to install an analogic vumeter with lamp, where it’d go in the diagram?

    For me, the vumeter is a must! just it looks mega cool and kind of steampunk…

    If it is possible, i would love to be warned by email if you respond to this note, just not to forget to check if you have answered.

    best regards!

  7. Dave
    Dave at |

    Great series and great build. But for a cathode biased amp you left out the most important part. What did you decide on the the cathode resistor? The bypass cap is labeled on the schematic,but the resistor is not. It does show you want 25V, but not how to get it. I’m guessing you had to experiment a little with that never got back to labeling the schematic.

    1. Vaughn
      Vaughn at |

      Dave, Take a look at the Table above where he breaks down the test results for various tubes. Column Rk shows the Cathode resistor. 500 ohms for all tubes except the 6V6 which used 1000 ohms (1K).

      1. John Templeton
        John Templeton at |

        You are absolutely correct. Many schematics of vintage amps show a given value for cathode bias resistors. Unfortunately you’ll find that today those values will not work and usually run the tube way too hot. I experiment and take readings of idle current to determine the final value for the bias resistor as the inherent current each tube draws is variable as is your local line supply voltage.

  8. Der
    Der at |

    Very nicely done, this design build process tutorial.
    After building a few SE amps (all EL84 powered), I decided to build one using the EF86 preamp tube instead of the usual 12AX7’s.
    Your design is very much like mine – except for the EL84 output and using a full-wave bridge rectifier instead of the rectifier tube. I prefer the more precise response of the solid state rectifier, though one of my amps I decided to add some of the proverbial ‘sag’ by adding a resistor immediately after the bridge which really gave that amp a different character than the others – so I kept it like that.
    But I still like knowing that there is almost no chance of the bridge failing like a tube sometimes can. So I opt for the resistor sag method instead.
    Also, I have found great advantage (and no down side yet) to rectifying the heater power to DC rather than having 6.3V AC traipsing all around inside the chassis.
    One other thing I did was to mount the socket for the EF86 on a separate, small aluminum plate that was shock-mounted to the chassis using a couple of rubber grommets. I can’t say for sure that this made a difference as I didn’t have a comparison to having mounted the socket directly to the chassis. (Why bother!?) :-)
    Again, I like your blog post. Informative, yet not overly verbose nor overly detailed technically.


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