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Champ Circuit into Vintage Radio Body

Discussion in 'Amp Tech Center' started by Blutack, Jan 16, 2021.

  1. Blutack

    Blutack TDPRI Member

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    Hi Folks,

    I really fancy building a wee Champ kit (probably the Ampmaker WF55), and since I'm not much of a woodworker, I had the crazy notion of housing it inside an old vintage radio.

    The best candidate I've found so far is a Pye P75 (see attached photos). These aren't rare, so I'm not destroying anything particularly valuable, and a non-working one would be cheap enough to try. I also reckon I could re-use the original chassis for the amp kit, and possibly even the transformers (though I'd need to do more research on this).

    So what do you think folks? Fun project, or best avoided?

    One problem I found immediately is that the original speaker is 6.5" diameter, so it's going to be tricky to find a guitar speaker to fit. There would be room for a 6"x9" in there, but they seem really rare in the UK, and I don't know how they sound. Again, any hints and tips would be most welcome! :)

    Thanks!


    pye-p75-cambridge-vintage-valve-radio_360_fd7888440f846eb5ad735074cacdc9cf.jpg Pye P75 inside.jpg
     
    Last edited: Jan 16, 2021
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  2. maj34

    maj34 Tele-Meister

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    Looks like a cool project. If you have the skills to make it fit I'd say go for it!

    6x9 speakers have been used to great effect by RobRob I think? Are they really uncommon in UK? You typically find them in cars... Often automotive garages (the type that have a small junkyard out back) have a stockpile of them.

    One suggestion: Go for a 5f2a circuit so you can use that second knob as a tone. It's just another pot and another couple of passive components.

    Alternate advanced suggestion: instead, use the 2nd knob to control a built in attenuator.
     
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  3. Peegoo

    Peegoo Poster Extraordinaire

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    Heck yes that's a fantastic project!

    If that were sitting on my bench and I planned on playing it at home, I'd go with the speaker that's already in the radio--if it's working. I'll bet it'll sound really great. You want little amps like this to growl and bark. They're not known for "loud and clean."

    If I were planning to record with it, I'd install a switching jack on the rear of the amp chassis that takes the little front speaker out of the circuit and allows me to plug in a proper guitar speaker to poke a mic into.
     
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  4. Asmith

    Asmith Friend of Leo's

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    This has done my GAS no good! I've just ordered a 1950s PYE P31MBQ case radio for £27 untested but the visible iron I can see looks very clean for 60+ years old. It won't be easy to service, point to point and lots of replacement parts needed but hopefully the PT, OT and valves are in working order making it a pretty cheap project.
     
  5. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    You just have to work out how to fit everything in. It looks like you might be able to shoehorn an 8 inch speaker in there if you are creative. A 6 inch or 6x9 will work as well.

    I found this late '30s Philco cab locally. It didn't include the chassis or speaker. It was cheaper to buy than building a cabinet. It ended up housing a 5E3. It originally had a 10 inch speaker. I fashioned up a 12 inch baffle.
    I didn't want to go through the hassle of making the original knob locations control the 5E3. I made the front knobs stationary and for looks only.
    I installed a flickering led behind a makeshift radio dial as an *on* indicator. It has a red jewel in the back as well.
    A 5E3 chassis is intact in the back. I made some back panels to finish it off.

    DSCN1319.JPG DSCN1316.JPG

    Have fun with your project.:)
     
    Last edited: Jan 16, 2021
  6. Blutack

    Blutack TDPRI Member

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    Thanks for the encouragement, everybody! I'm definitely going to go for it.

    @Peegoo - yes, that's a great idea to install a switching jack. That way I could compare the original speaker with another guitar cab, and see what I like best.

    @maj34 - that's a great idea to put in a tone knob too. What you can't see in the photos is that there is already a knob on the right hand side of the cabinet (you can see the pot that attaches to it at the RHS of the chassis). I don't know what its original function is, I reckon that's crying out for an L-Pad attenuator anyway!

    I had discounted 6x9 car speakers as I thought they'd sound crap for guitar, but I have one in the shed as it happens, so I could give it a go and see. Though I haven't found a 6x9 guitar speaker in the UK yet, I've found a few 6" ones which would be a direct fit, so that's there as a backup.

    @Asmith - that's hilarious! I'm still at the thinking stage and you've only gone and done it already! :lol: What are your plans for yours then? Are you going to convert it into a guitar amp, or keep it as a radio?

    Oh, and @Lowerleftcoast - NICE WORK!! That looks *really* sweet.
     
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  7. NTC

    NTC Tele-Meister

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    I have a strange little shoebox size amp. It is basically a Champ now. It has a cheap 6x9 in it and it can do a pretty good early Kinks tone with a humbucker guitar and the amp turned way up.
     
  8. Asmith

    Asmith Friend of Leo's

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    No idea but I figured at £27 I'd salvage enough to justify the cost. I've built some point to point amps and I'm fairly confident in my knowledge of valve amp design and safety. So I'm going to pop it open drain the more than likely dead caps check the mains wiring and decide if it's worth the effort to service it or just tear out all the caps and resistors and make some unique out of it.
     
    Last edited: Jan 17, 2021
  9. Peegoo

    Peegoo Poster Extraordinaire

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    How about a shoe-sized amp?

    [​IMG]
     
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  10. RoscoeElegante

    RoscoeElegante Friend of Leo's

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    Check out DLab's YouTube channel. Lots of conversions there.
    https://www.youtube.com/c/dlab500/videos

    Some of his clips are almost exactly what you're interested in:


    I cheated by putting an Ibanez head into my 1936 Silvertone cabinet (the visible "1948" is the model number). I dubbed it the Electromaster since I had this handsome badge from an old water heater.
    SilvertoneAsElectromaster!.jpg


    SilvertoneBack.jpg
    Next is finishing putting my Excelsior Pro into a 1952 Westinghouse TV cabinet.

    Fun stuff! Good luck on your project.
     
  11. NoTeleBob

    NoTeleBob Tele-Meister

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    Maxwell Smart approves
     
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  12. NTC

    NTC Tele-Meister

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    I keep thinking about getting one of those big, beautiful old radios and putting a bluetooth setup into it so it is useful in the modern era
     
  13. Blutack

    Blutack TDPRI Member

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    Roscoe - once again, nice work, and thanks for the videos. The Electromaster badge is the icing on the cake there :D

    That's what got me started on this journey, NTC. When I was a kid, my parents had a 1960s Roberts R200 radio, and I just loved playing about with the dials. Then when I learned to read, I learned European geography by looking up the station names in our atlas.

    20210114_184835.jpg

    Anyway, as a lockdown project, I decided to convert a non-working one into a Bluetooth speaker. I left some of the old circuits inside just as a steampunk kind of thing.

    20210114_184910.jpg

    It sounds great, and was a really easy, fun project.... which got me thinking about a Champ....

    BTW, one of those would also make an amazing shoebox amplifier. I'm really tempted to do another one with a couple of DIY stompbox circuits inside, paired with a Ruby amplifier.
     
  14. Blutack

    Blutack TDPRI Member

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    And so it begins.... :D


    pye.PNG
     
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  15. Asmith

    Asmith Friend of Leo's

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    I hope there will be follow up thread. I hope to do the same and my radio is due to arrive on Friday but I have 3 other projects and a degree to compete first so I won't get a chance to tinker until june
     
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  16. Blutack

    Blutack TDPRI Member

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    Well, it's arrived, and I think this is going to be a fun project!

    amp inside2.PNG

    The first problem is that the chassis is really tight, so I think I'll have to either put the tubes on the far left hand side with the turret board in the middle, or make my own turret board to fit.

    Amp Inside.PNG

    I think that's going to steer me away from a kit, and towards sourcing my own parts according to a schematic, which I've never done before. I'll have to cost up both options and then decide - watch this space! :)

    In the meantime, can anybody tell me how important component separation actually is? Firstly between components on the turret board itself, and secondly between the transformers, tubes and board. I'm sure it can physically be done, but I'm not experienced enough to know whether I'll get noise etc?

    P.S. I even found a dry joint from the early 1950s - how cool is that!? :D

    Dry joint.PNG
     
  17. Deeve

    Deeve Poster Extraordinaire Silver Supporter

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    those cabs look great
     
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