Announcement

Collapse
No announcement yet.

Tube amps

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Tube amps

    Attached Files

  • #2
    Re: Tube amps

    The K-501 amp kit is a single channel (mono) version of the K-502 amp kit which is almost identical to the K-12G amp kit. They are a design by Tube Labs (S-5 Electronics). Here is a picture of my K-12G amp:



    These amps sound REALLY good. But at 8 watts they will only drive the Overnight Sensations or any other lower sensitivity speaker well on a bench top or desk top (near field) application. If you want to fill a medium to large room with sound you will need a much more efficient pair of speakers.
    Craig

    Comment


    • #3
      Re: Tube amps

      Originally posted by PWR RYD View Post
      The K-501 amp kit is a single channel (mono) version of the K-502 amp kit which is almost identical to the K-12G amp kit. They are a design by Tube Labs (S-5 Electronics). Here is a picture of my K-12G amp:



      These amps sound REALLY good. But at 8 watts they will only drive the Overnight Sensations or any other lower sensitivity speaker well on a bench top or desk top (near field) application. If you want to fill a medium to large room with sound you will need a much more efficient pair of speakers.
      Thanks for the info! I'm happy to hear that these are good little amps.

      Your tube amp build thread is what inspired me to dig my kit out and start fiddling with a design. In my model, the chassis is just a block, so I can see what might be a pleasing configuration. One thing that occurs is that I think it would look cleaner with the input in the back of the unit. Then maybe put the volume control centered in the front. The transformers are spaced 3/8" apart from the faces of the cores. Is that enough? Also, I've been toying with putting custom made aluminum cans over the caps. Would they get too hot for that?

      Comment


      • #4
        Re: Tube amps

        Since your transformers are so close to each other you will probably need to rotate one of them 90 degrees to reduce interaction. Custom aluminum cans over the caps should not be a problem as the caps don't really get hot.
        Craig

        Comment


        • #5
          Re: Tube amps

          So I wonder how those tube kits would differ from the $600 Carvin tube amp?

          Comment


          • #6
            Re: Tube amps

            Originally posted by PWR RYD View Post
            Since your transformers are so close to each other you will probably need to rotate one of them 90 degrees to reduce interaction. Custom aluminum cans over the caps should not be a problem as the caps don't really get hot.
            I have a little more room to space the transformers out, and I could make my chassis deeper. I like the transformers parallel, will rotate one if I need to. Any idea how far apart they'd need to be in a parallel configuration such that interference wouldn't be an issue?

            BTW: your latest build really is sweet looking.

            Comment


            • #7
              Re: Tube amps

              I've heard of an old trick used by guitar amp builders. Power up the power transformer with no load, and connect a cheap pair of headphones to the output transformers secondaries with the primary windings left open. I haven't tried it, but supposedly you can hear the 60hz EMI from the power transformer as picked up by the output transformer this way. A more scientific approach would be to use an oscope if you have access to one.
              "I have not failed. I've just found 10,000 ways that won't work." Thomas A. Edison

              Comment


              • #8
                Re: Tube amps

                Originally posted by AJ View Post
                I've heard of an old trick used by guitar amp builders. Power up the power transformer with no load, and connect a cheap pair of headphones to the output transformers secondaries with the primary windings left open. I haven't tried it, but supposedly you can hear the 60hz EMI from the power transformer as picked up by the output transformer this way. A more scientific approach would be to use an oscope if you have access to one.
                I don't have an oscope, but I could try the headphones test. Thanks!

                The other thought that occurs is maybe using a Mu-metal shield between the transformers, as in attached image. Anyone know if this may work? I also made the chassis a bit wider and deeper. And I tried modeling some configurations where the transformers sit perpendicular to each other, but don't much like the look. I may try again now that I've made the chassis bigger.
                Attached Files

                Comment


                • #9
                  Re: Tube amps

                  Originally posted by grymster View Post
                  I don't have an oscope, but I could try the headphones test. Thanks!
                  Note that this isn't definitive. The magnetic field could shift when the transformer is under load... But, it's better than nothing.

                  Originally posted by grymster View Post
                  The other thought that occurs is maybe using a Mu-metal shield between the transformers, as in attached image. Anyone know if this may work? I also made the chassis a bit wider and deeper. And I tried modeling some configurations where the transformers sit perpendicular to each other, but don't much like the look. I may try again now that I've made the chassis bigger.
                  Just the one wall you have there probably won't do much. The power transformer would need to be encased in steel to reduce any radiated EMI.
                  "I have not failed. I've just found 10,000 ways that won't work." Thomas A. Edison

                  Comment


                  • #10
                    Re: Tube amps

                    Originally posted by AJ View Post
                    Note that this isn't definitive. The magnetic field could shift when the transformer is under load... But, it's better than nothing.



                    Just the one wall you have there probably won't do much. The power transformer would need to be encased in steel to reduce any radiated EMI.
                    Thanks! So a steel case would help? It wouldn’t need to have a Mu-metal liner?

                    I really like seeing the transformers. Maybe I could make a steel case that looks like a transformer, and I could even line it with Mu-metal foil.

                    Comment


                    • #11
                      Re: Tube amps

                      Originally posted by grymster View Post
                      Thanks! So a steel case would help? It wouldn’t need to have a Mu-metal liner?

                      I really like seeing the transformers. Maybe I could make a steel case that looks like a transformer, and I could even line it with Mu-metal foil.
                      Mu metal, or a case made from the same material the transformer laminations are made, will be superior to simple steel. Steel would be better than nothing, which is about what aluminum or copper are like. A Mu-metal foil lined case would be the way to go.
                      R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
                      Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

                      95% of Climate Models Agree: The Observations Must be Wrong
                      "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                      Comment


                      • #12
                        Re: Tube amps

                        Mu metal, or a case made from the same material the transformer laminations are made, will be superior to simple steel. Steel would be better than nothing, which is about what aluminum or copper are like. A Mu-metal foil lined case would be the way to go.
                        Cool. That might be fun also. Thanks for the suggestion. Maybe a foil lined, copper cover would look nice.

                        Comment


                        • #13
                          Re: Tube amps

                          Mu metal, or a case made from the same material the transformer laminations are made, will be superior to simple steel. Steel would be better than nothing, which is about what aluminum or copper are like. A Mu-metal foil lined case would be the way to go.
                          I believe that the way to do it, is to wrap the transformer winding themselves with some sort of shielding like copper foil or such.

                          Toroids are easy to shield, just a band of (ferrous?) metal about the same height as the transformer wrapped all the way around the periphery. That's the way AVEL told me to do it.

                          Comment


                          • #14
                            Re: Tube amps

                            I believe that the way to do it, is to wrap the transformer winding themselves with some sort of shielding like copper foil or such.

                            Toroids are easy to shield, just a band of (ferrous?) metal about the same height as the transformer wrapped all the way around the periphery. That's the way AVEL told me to do it.
                            Wrapping the windings with copper foil will not help reduce magnetic flux leakage. To do that you need a magnetic material like Mu-metal. Copper foil does help reduce electrostatic fields though.

                            The nice thing about toroids compared to EI transformer cores is that magnetic flux leakage with toroids is quite a bit lower. They need much less shielding than their easier to wind counterparts.
                            R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
                            Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

                            95% of Climate Models Agree: The Observations Must be Wrong
                            "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                            Comment


                            • #15
                              Re: Tube amps

                              "...Any idea how far apart they'd need to be in a parallel configuration such that interference wouldn't be an issue?..."

                              I looked above for an answer to the distance question, perhaps I've missed it; but, does anyone know how the distance that would eliminate or sufficiently limit interference is calculated, rather than using a barrier. I ask because I've started collecting parts for a Dynaco Mark III KT 88 mono amp, and also prefer a parallel orientation of the transformers.

                              Comment

                              Working...
                              X