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What Can I Build With These Transformers?

Discussion in 'Shock Brother's DIY Amps' started by Jim Lahey, Jan 26, 2021.

  1. Jim Lahey

    Jim Lahey TDPRI Member

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    Several years ago, I bought Heyboer replacement power and output transformers for my Marshall JMP 2203 100W.

    I didn't end up installing them and they've been collecting dust ever since.

    My question is:

    What sort of amp can I build using these transformers that isn't a 100W amp?

    Would they work for a 20 to 50W build?

    Would they work in a bass amp circuit?

    Does anyone have any other creative ideas to put these transformers to use?

    Thanks in advance!
     
  2. Jesco

    Jesco TDPRI Member

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    I think if you post the specs of both transformers, you will get some input. You probably wouldn’t want to use the output transformer for a 20 watt amp, though it would “work”.

    I gigged weekly for 5 years with a 1972 Fender Super Bassman 100 watt for bass. It was great. I don’t have the schematic in front of me, but I believe it is essentially a twin reverb without the reverb and an added dedicated bass channel. I don’t see why you couldn’t build something in that vein.
     
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  3. Nickfl

    Nickfl Friend of Leo's

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    Do you have spec sheets or links to the specific transformers you got? You potentially could make a lower output amp with the 100-watt transformer set, but exactly what you can do is going to depend on the specs of the transformers and question and their versatility is going to hinge on the details like weather or not they have multiple voltage options on the power transformer and multiple taps on the output transformer.

    My first thought would be that a good direction might be to consider building something along the lines of a Dumble or Trainwreck that is characterized by a very beefy transformer set where using a 100 watt set for a 50 watt amp would be in the spirit of the design.
     
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  4. 2L man

    2L man Tele-Meister

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    A 100W guitar OPT should be fine for 50W bass amp.

    You can use higher power OPT for smaller amp when you make impedance match for example using double loudspeaker impedance which doubles OPT impedance.
     
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  5. Jim Lahey

    Jim Lahey TDPRI Member

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    Thanks for the replies!

    Here are the spec sheets...at least as much as I could find.

    PT.png
    OT.png
     
  6. David Barnett

    David Barnett Doctor of Teleocity

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    Of the options you've listed, a bass amp would be a good fit. ~100W from a quad of 6550s could make a nice punchy bass sound.
     
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  7. LightningPhil

    LightningPhil Tele-Meister

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    There’s nothing wrong with an over sized power TX. And yours has such a vast array of taps that it could power all sorts.

    I’d probably use it to push power through a multistage filter, which would greatly reduce hum and hiss at the expense of burning a bit of voltage. Then a parallel triode input for (there’s a Marshall that did this) leading to a 2 channel preamp (a characterful clean and a lead) and a 25ish watt output. This is just me musing. All my electrics are now in Finland and I’ll not see them till I move there in a couple of months.

    The output TX should be good for lower power usage too. If you put an 8 ohm speaker on the 4 ohm tap, the reflected impedance would be 1750x2 = 3500 ohms. The low resistance of the nominally 4 ohm tap would likely be good for the dampening factor of the speaker and the large amount of iron good for bass. Both seem like a win to me.
     
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  8. NTC

    NTC Tele-Meister

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    See Sunn 2000s. Voltages from that PT are LOW. 185V-0-185v? That would only be 262V after a full-wave rectifier with the CT. 524 V if you don't use the CT and use a diode bridge (that is more like it).
     
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  9. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    A lot of other options with that trannie. Without the CT it delivers 370 VAC or 304 VAC. A bridge rectifier will take care of putting the B+ in most of the desired ranges. It has plenty of power for most any configuration desired.

    It can used with four tube configurations for 100W or 50W. It can be used in two tube configurations for 40W - 50W. With the right OT, it can get down to the 20W area.

    The PT and OT should be able to handle anything from tweed style 2 x 6L6 to bass amps with four tubes. Many many choices. :cool::):D
     
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  10. NTC

    NTC Tele-Meister

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    Or a stereo amp with two push-pull outputs - but you will need another OT.
     
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  11. Jim Lahey

    Jim Lahey TDPRI Member

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    Do you have any schematics (or know where to find them) for a bass amp as you're describing? Thanks for the recommendation!
     
  12. Jim Lahey

    Jim Lahey TDPRI Member

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    If I built a Tweed Deluxe using these transformers, what, if any, impact to the tone of the amp would change (compared to stock Tweed Deluxe transformers)? Thanks for the recommendations!
     
  13. NTC

    NTC Tele-Meister

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  14. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The power transformer would be able to provide the voltage a tweed deluxe. The OT would not quite get there. The amp would not have the distortion grind/growl the 5E3 circuit is known for.
    One of the 5E3 kit versions (Boothill Amps, iirc) supplies a Princeton OT. Your OT, with a 16 Ohm speaker plugged into the 4 Ohm tap, would be in the ballpark with that kit. It is not an unpleasant sound. It doesn't break up as soon. I have described it as being more of a gentleman than the iconic Tweed Deluxe sound.
    Perhaps a 2 x 6L6 or a 4 x 6V6 version with a 16 Ohm load would distort with more of a 5E3 vibe.
    I like these ideas. The big transformers would be right in line.

    Another direction I might go would be a two speaker version of the 5E7 Tweed Bandmaster. With the 16 Ohms on the 4 Ohm tap, the OT primary is at 7K which is what the 5E7 with three speakers runs. With a pair of 6L6G or even 5881 tubes, it would have a little less power than 6L6GC but you could run any of them. Not many 5E7 clones around. Have a listen to the 5E7 on youtube and see if that sound might be on your radar.

    EDIT: Correction. The 5E7 OT is not a 7K primary.
     
    Last edited: Jan 29, 2021
  15. Old Deaf Roadie

    Old Deaf Roadie Friend of Leo's Silver Supporter

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    I thought this was going to be about Optimus Prime & Bumblebee starting a construction company...
     
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  16. NTC

    NTC Tele-Meister

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    I thought the 5E7 used the same OT as a 5F4 Super, which apparently was 6K to 4 ohms. With a 2.67 ohm load of a 5E7, you would get a 4K load on the primary. IF what everyone says about the 5E7 OT is correct.
     
  17. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Thanks for pointing this out... It was my mistake. I have been interested in a possible future build of a 5E7. This thread,
    Other considerations 5E4 5E5 5E7 amps
    Discussion in 'Glowing Bottle Tube Amp Forum' started by powerwagonjohn, Dec 19, 2020.,

    had me searching for possible OT candidates. The thread questioned the Merc Magnetics 5E7 OT ratio. The MM may have a 6K primary??? The Hammond 1760JB spec'd for the 5E7 lists a 6K primary with 2.67 secondary.

    I have an OT on hand that would be 7K at 2.67 secondary. The one brain cell I have left must have associated the 5E7 with that 7K.:oops:

    I will edit the earlier post.

    So now I want to know if the 5E7 used a 4k or 6K primary OT. More searching.:cool:
     
  18. 2L man

    2L man Tele-Meister

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    I think 6k is better impedance for 5E7. 4k would have made it too powerful for three 10" speakers what were available then. Using 4k operative voltage should be lower. 7k should be good as well.

    H1760JB is versatile when three 8 ohm speakers parallel makes 2,67 ohms and it has also 4 and 8 ohm outputs.
     
  19. NTC

    NTC Tele-Meister

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    The Hammond 1760JB has a 6K primary and 2.66, 4 and 8 ohm output taps. The 2.66 is not traditional if all of the discussions are correct. A 5E7 or a 5F4 would use the 4 ohm tap, and a 5E5A Pro would use the 8 ohm tap.

    I have a 1760JB one the shelf, waiting for me to decide if I want to try it in my 5E7, but that is another thread.
     
  20. NTC

    NTC Tele-Meister

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    2L Man, it becomes a matter of "what makes sense" vs. "What did Leo do?" If the 5E7 and the 5F4 used the same OT, and if that OT was 6K to 4 ohms, then using the 4 ohm tap in a 5E7 is the "right" thing to do. Add to that the fact that most later Fender amps had 4K primaries (or therabouts) on 2x 6L6 amps. 4K to 2.667 ohms makes a lot of sense.

    And we are not answering the OP's question.
     
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