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New here and looking to build a tube amp

Discussion in 'Shock Brother's DIY Amps' started by CBMorgan91, Jan 19, 2021.

  1. CBMorgan91

    CBMorgan91 TDPRI Member

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    Good morning everyone,

    This is my first post, so I'll start with a short introduction and then my question.
    My name is Christian and I am new to the world of tube guitar amps or amps in general. I have dabbled with tube radios with mixed success, but I get the basics of circuitry.

    I have a chassis from a tabletop RCA radio with octal tubes. The tube sockets are all in good shape as is the output transformer which drove an 8 ohm 6 inch speaker. The tube lineup was 35z5, 12sq7, 12sk7, 12sa7, and 50L6. This was a transformerless set.

    I have it in my mind that I could use some of these tubes, chassis, output transformer, and maaaaybe the speaker to build my first amp.i would like to add a main transformer.
    My goal would be to build a guitar amp with a very clean sound. If I want distortion and reverb, I'd add accessories such as pedals.
    I have lots of questions so I will try to make this as simple as possible. With this old radio chassis be something that would be practical to build on to? Can someone provide me with a schematic and possibly a parts list for the type of amp that I am trying to build? Did anyone recommend a good source for a man transformer? I want this amp to be pretty simple. An on/off switch, volume, and tone. I don't know if I would use the original potentiometers or not, but I do have them still. I may also want to swap out the original speaker for a 15 inch 8 ohm. Thank you for any information and help you can give me.​
     
    TeleUpNorth likes this.
  2. lathoto

    lathoto Tele-Meister

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  3. Nickfl

    Nickfl Friend of Leo's

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    The chassis? Sure, the rest of it not so much... You can't just add a power transformer into a transformerless amp, the filament voltages are very different from tubes used with a power transformer and while you can run it through an isolation transformer that is still problematic.

    For the same reasons, standard guitar amp schematics are not going to be easy to adapt to those tubes, so you're going to need to design this amp from the ground up if you're insisting on using the tubes and output transformer from your tabletop radio and that is it's not going to be a simple task and therefore probably does not lend itself well to a first project.

    A kit, or at least building a clone of a classic amp, is probably a better place to start for your first build unless you want to spend a lot of time learning what you need to know to design a circuit from the ground up.
     
    dan40 likes this.
  4. Mongo Park

    Mongo Park Tele-Afflicted

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    I would find a radio with a transformer and some more guitar amp like tubes. It would be way easier. Radios out there with 6v6 6k6 power tubes. And 6sn7 and tubes of that family for preamp.
    Hammond organ conversion is a well tracked path. I think it would take a lot of research/learning to go with what you got. I don’t know where you live, for me lots of old radios and such on kiji/Craig’s list for 25-45$ That are a easy slide int a guitar amp. Easy to learn what is guitar friendly.
     
  5. CBMorgan91

    CBMorgan91 TDPRI Member

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    Thank you all for the very quick replies. After reading your comments, I now realize that it is a bad idea to try to make the existing tube complement work. I do however plan to use the chassis to mount a transformer and the correct tubes. I like the idea of a kit, but all of the prices that I'm seeing are approaching $200 and up. Now, if there is some diagram from an existing tweed tube amp with a parts list, I could work with that. Maybe one of the early 1950s fender amps? I do apologize for all of the newbie questions. As far as the cabinet goes, I plan on building that myself.
     
  6. Mongo Park

    Mongo Park Tele-Afflicted

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    Here is a something I bought for $20 it was a radio. F0BCA457-4356-4069-BD79-60700C421169.jpeg 4623BEF1-F684-445D-8142-D626C48D2B8E.jpeg
    The amp was separate from the radio, this is the amp. Power and output transformer 5y3 rectifier 6v6 power tube. The third sockets had a plug going to the radio. The two wires are the speaker wires Minimally it needs a preamp tube in the place of plug socket. New guts power cord and and a input jack, you are playing guitar. Something like this is the perfect starter radio to guitar project. It is even the right shape to go on a cab for a combo.
     
  7. tah1962

    tah1962 Friend of Leo's

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    Welcome to TDPRI :)
     
  8. gigante

    gigante Tele-Meister

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  9. CBMorgan91

    CBMorgan91 TDPRI Member

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    Thanks again everyone for the responses and links. As far as the amp is concerned, I'm really looking for simplicity. 15 watts or under. The radio chassis dimensions that I have are about 1 ft by 9 inches. Any old radio in my area is hard to come by. More than likely, I'm going to have to buy the correct tubes and power transformer. I just spent a little time looking at diagrams online And I think I would like to try to build a Fender Champ 5C1 or similar. They appear to use octal tubes, which is a plus for me because the radio chassis already has octal tube bases.
     
  10. subgenius_one

    subgenius_one TDPRI Member

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    Having just finished a Bassman Micro as my first build, I can say that Rob's designs and instructions are well documented and sound great. Easily worth the time and effort.

    Having repurposed an old chassis, I learned that you likely need to have a chassis somewhat bigger than you would otherwise need. Any holes that do not line up with the new layout may cause adjustments to how things are mounted. I guess if you are going really old school and not using any boards for your components then this may not apply. I thought my chassis was more than large enough because it had more tubes than the new circuit, however the layout combined with the existing holes for things like a cap can, etc. ended up making for somewhat of a tight fit front to back. One side of my board ended up being right under the pots on the front of chassis. Overall it was worth it to me, because even though it would have been easier and nicer looking to buy an new chassis to use I wanted to use the old combo amp with a 15" speaker.
     
  11. gigante

    gigante Tele-Meister

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    Should be plenty of room for a simple amp in there.

    I built a 1-ish watt amp head with a 6sj7 preamp (different implementation than the 5c1, but same tube) in an old radio. I liked the sound quite a bit.
     
  12. goonie

    goonie Friend of Leo's

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    Here's links to a schematic, layout and parts list for a 5f2a (Tweed Princeton). Great amp, love mine and had fun building it.
    https://el34world.com/Hoffman/files/Hoffman_5F2A.pdf
    https://el34world.com/Hoffman/files/Hoffman_5F2A_BOM.pdf
     
  13. CBMorgan91

    CBMorgan91 TDPRI Member

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    Thank you so much for the link. I look forward to the build.
     
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