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What transformer should i choose for a 19" rack preamp?

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  • What transformer should i choose for a 19" rack preamp?

    Hello!

    What transformer should i choose for a 19" guitar preamp ?

    There is also Kit that i could start with?

  • #2
    We're gonna need much more info than that. Tube preamp or solid state? What is the expected current draw? If tube, how many tubes (filament supply current)? How many rack spaces/How much room do you have? etc., etc. Can you post a schematic?
    "Yeah, well, you know, that's just, like, your opinion, man."

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    • #3
      Originally posted by The Dude View Post
      We're gonna need much more info than that. Tube preamp or solid state? What is the expected current draw? If tube, how many tubes (filament supply current)? How many rack spaces/How much room do you have? etc., etc. Can you post a schematic?
      Hello Dude!

      Im thinking in building a guitar preamp tube for a 19" rack, im thinking in the smallest preamp to fit a 1 unity of heigth space of a 19" preamp rack.

      For Current drawm im thinking something near a modded jcm800, as for number of preamp tubes, maybe around 5 or 6 preamp tubes for a clean channel with is own circuit path and a crunch and lead sharing some preamp tubes.

      As soon as i finish the preamp schematic i will post it here.

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      • #4
        Here's an existing JCM800 pre. You'd have to modify for your requirements.

        http://www.pisotones.com/GORG/Pabloc..._por_gak_2.pdf
        "Yeah, well, you know, that's just, like, your opinion, man."

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        • #5
          I have a friend who had to replace a PT in an Ampeg SVT IIP, which is a 1U tube preamp and there were very few options, I think he had to use a very pricey one from Mercury Magnetics. He may have had more space constraints than you might have though.

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          • #6
            ^^^^^^^^ Agreed. Hard to find something with correct specs that will fit in something less than 1 3/4" tall. It can be done, but I'd consider making it at least 2 rack spaces to give yourself more options.
            "Yeah, well, you know, that's just, like, your opinion, man."

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            • #7
              Just thinking aloud: you might split the job, so split size requirements.

              Main constraint is height, no big deal in fitting 2 (or even 3) smaller transformers.
              Search for a 6.3VAC transformer with current enough for those filaments and another to feed +V

              You might even use a small 2 x 120VAC primary, 2 x 120VAC secondaries "isolation" transformer, wire secondaries in series for 240VAC and use a voltage doubler, you can get almost 600V DC which you can filter and tame down approppriately, or even simple bride rectify it for some 300VDC which might be enough.
              Juan Manuel Fahey

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              • #8
                Antek has some toroids such as this https://www.antekinc.com/as-05tc300-...v-transformer/ that might work. The nominal height is given as 1.6", so it may or may not fit in a 1U enclosure. Remember proper mounting- don't put a metal bolt through the centre connecting both sides of the chassis.

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                • #9
                  Will preamp tubes need to be mounted horizontally to fit in a 1U? Maybe use a narrow chassis and mount them out of the back panel.

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                  • #10
                    19" rack size preamp - toroidal transformer FLAT size. Any transformers shop can offer the same transformer in at least three sizes: flat, normal or tall.

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                    • #11
                      It looks like this one will be able to do 6 preamp tubes in 1U rack:

                      https://www.tube-town.net/ttstore/to...30va-8808.html

                      Use voltage doubler for anode voltage.

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