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Scott Nixon power supplies

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  • jim@fmtunerinfo.com
    Quite a few folks who own Scott Nixon DACs, locally and around the web, have asked me if I worry about them always being on. I never did but decided on a
    Message 1 of 5 , Dec 2, 2004
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      Quite a few folks who own Scott Nixon DACs, locally and around the
      web, have asked me if I worry about them always being on. I never did
      but decided on a solution anway. The current home page photo show two
      I've rebuilt. My two original SN Dacs now have these modified power
      transformer sections. The new trannies I bought at Tanners. I've
      added line filtering, an on/off switch in the rear and an "on" LED.
      Pics of both below. One in a aluminum box and one in wood cigar box.
      jim..
    • Dennis Boyle
      With regards to operating tubes, RCA operated all their studio equipment in the so-called “Stand-By” mode. The filaments were always on and the B+ was
      Message 2 of 5 , Dec 2, 2004
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        With regards to operating tubes, RCA operated all their studio equipment in the so-called “Stand-By” mode. The filaments were always on and the B+ was switched on for operation. Tremaine’s Audiocyclopedia references this and tests proved the tubes operated longer and over time became quieter. This was also standard on radio transmitters that used directly heated power tubes.

         

        Cycling tube filaments and heaters, on and off, does significantly reduce tube life. When cold the materials used to construct filament and heaters has very low resistance. Due to the current surge on turn-on, over 50 amps on a 211, the heater/filament material is mechanically stressed and will eventually fail.

         

        A much worse condition is called “Thermal Stripping”. This occurs when a B+ is applied to a “cold” tube before the filament has reached operating temperature. In this case the cathode or filament material that emits free electrons is stripped away and the tube degrades fairly rapidly. Might be the reason why so many modern tube amplifier manufacturers only warrantee their tubes for 90 days. There are very few modern amp designs that use separate filament and B+ power supplies. Since filament transformers are cheap and readily available, DIY builders don’t have to answer to the accountants on keeping costs down.  

         

        The simplest solution is a separate filament transformer that allows you to either leave the filaments on all the time or to turn on the filament supply on first. In this case you can put a readily available and cheap Thermistor or Current Limiter on the primary (120VAC line) leads. You can use these devices with an RC network in the B+ Supply for soft start, although a 5AR4/GZ35, 5V4 or 6CA4 or any other Soft Start rectifier diode is perhaps a better choice. The 5AR4 is a good choice because it has very low dynamic output impedance which helps transient performance and current production units sound good and are cheap.

         

        If you are going to use a filament winding on the B+ supply for the rectifier tube, make sure the is at or slightly below the tube’s rated filament voltage. Use Ohm’s Law to determine the correct value for a couple resistors or even better some Thermistors/Current Limiters to prevent current surge.   

         

        These types of power supplies should extend the life and performance of your tubes for a very long time. If you are operating the tubes at 80% or less of maximum ratings (voltage and current), they should last well over 5 years, in the case of power tubes, and voltage amplifier tubes may outlive you.            

         

        Dennis

         

        -----Original Message-----
        From: jim@... [mailto:jim@...]
        Sent: Thursday, December 02, 2004 7:57 AM
        To: dallasaudioclub@yahoogroups.com
        Subject: [dallasaudioclub] Scott Nixon power supplies

         


        Quite a few folks who own Scott Nixon DACs, locally and around the
        web, have asked me if I worry about them always being on. I never did
        but decided on a solution anway. The current home page photo show two
        I've rebuilt. My two original SN Dacs now have these modified power
        transformer sections. The new trannies I bought at Tanners. I've
        added line filtering, an on/off switch in the rear and an "on" LED.
        Pics of both below. One in a aluminum box and one in wood cigar box.
        jim..






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      • jim@fmtunerinfo.com
        Hi Dennis, All good stuff and you know I ve learned that and much more from you, John, Walter and others over the last 17 years. And thanks for sharing your
        Message 3 of 5 , Dec 2, 2004
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          Hi Dennis, All good stuff and you know I've learned that and much
          more from you, John, Walter and others over the last 17 years. And
          thanks for sharing your knowledge with us all. I did forget to
          mention the IEC socket. The IEC socket and an EMI/RFI network. I also
          didn't say I installed a current limiter and John's snubber circuit.
          As said I never worried about leaving it on but so many guys kept
          worrying even though I told them it would be OK. Many guys will only
          be happy when you tell them what they REALLY want to here! :-) Of
          course my "alternatives" can and will be left almost always on but
          has the benefit of filtering the AC from the wall a bit more. By the
          way, the single 6DJ8 doesn't supply gain but is used as a cathode
          follower only. I've listened to a SS Nixon and the tube+ version and
          prefer the tube+ version. More harmonic richness in the midrange. The
          great thing about the SN DACs is the price. I love the sound better
          than ANY DAC I've owned, borrowed or whatever. I know someone with a
          high dollar Audio Note 3.1? It's also a zero sampling DAC. Hopefully
          I can A/B them soon. No matter the outcome, I'll stick with the $475
          version Nixon and NIX the $$$$ Audio Note. 8:-) jim...
          --- In dallasaudioclub@yahoogroups.com, "Dennis Boyle"
          <chimeraone@w...> wrote:
          > With regards to operating tubes, RCA operated all their studio
          equipment
          > in the so-called "Stand-By" mode. The filaments were always on and
          the
          > B+ was switched on for operation. Tremaine's Audiocyclopedia
          references
          > this and tests proved the tubes operated longer and over time became
          > quieter. This was also standard on radio transmitters that used
          directly
          > heated power tubes.
          >
          > Cycling tube filaments and heaters, on and off, does significantly
          > reduce tube life. When cold the materials used to construct
          filament and
          > heaters has very low resistance. Due to the current surge on turn-
          on,
          > over 50 amps on a 211, the heater/filament material is mechanically
          > stressed and will eventually fail.
          >
          > A much worse condition is called "Thermal Stripping". This occurs
          when a
          > B+ is applied to a "cold" tube before the filament has reached
          operating
          > temperature. In this case the cathode or filament material that
          emits
          > free electrons is stripped away and the tube degrades fairly
          rapidly.
          > Might be the reason why so many modern tube amplifier manufacturers
          only
          > warrantee their tubes for 90 days. There are very few modern amp
          designs
          > that use separate filament and B+ power supplies. Since filament
          > transformers are cheap and readily available, DIY builders don't
          have to
          > answer to the accountants on keeping costs down.
          >
          > The simplest solution is a separate filament transformer that
          allows you
          > to either leave the filaments on all the time or to turn on the
          filament
          > supply on first. In this case you can put a readily available and
          cheap
          > Thermistor or Current Limiter on the primary (120VAC line) leads.
          You
          > can use these devices with an RC network in the B+ Supply for soft
          > start, although a 5AR4/GZ35, 5V4 or 6CA4 or any other Soft Start
          > rectifier diode is perhaps a better choice. The 5AR4 is a good
          choice
          > because it has very low dynamic output impedance which helps
          transient
          > performance and current production units sound good and are cheap.
          >
          > If you are going to use a filament winding on the B+ supply for the
          > rectifier tube, make sure the is at or slightly below the tube's
          rated
          > filament voltage. Use Ohm's Law to determine the correct value for a
          > couple resistors or even better some Thermistors/Current Limiters to
          > prevent current surge.
          >
          > These types of power supplies should extend the life and
          performance of
          > your tubes for a very long time. If you are operating the tubes at
          80%
          > or less of maximum ratings (voltage and current), they should last
          well
          > over 5 years, in the case of power tubes, and voltage amplifier
          tubes
          > may outlive you.
          >
          > Dennis
          >
          > -----Original Message-----
          > From: jim@f... [mailto:jim@f...]
          > Sent: Thursday, December 02, 2004 7:57 AM
          > To: dallasaudioclub@yahoogroups.com
          > Subject: [dallasaudioclub] Scott Nixon power supplies
          >
          >
          > Quite a few folks who own Scott Nixon DACs, locally and around the
          > web, have asked me if I worry about them always being on. I never
          did
          > but decided on a solution anway. The current home page photo show
          two
          > I've rebuilt. My two original SN Dacs now have these modified power
          > transformer sections. The new trannies I bought at Tanners. I've
          > added line filtering, an on/off switch in the rear and an "on" LED.
          > Pics of both below. One in a aluminum box and one in wood cigar
          box.
          > jim..
          >
        • Dennis Boyle
          Jim, As you might remember, my ears don’t like the 6DJ8/6922/ECC88 tubes. They have an edge that I think it due to their distortion ratios…too much higher
          Message 4 of 5 , Dec 2, 2004
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            Jim,

             

            As you might remember, my ears don’t like the 6DJ8/6922/ECC88 tubes. They have an edge that I think it due to their distortion ratios…too much higher odd order harmonic distortion. I am sure this is minimized in a cathode follower application. It might be interesting to try some vintage E88CC European types just to see if they make a difference. They sound much more musical.

             

            The best tube buffer stage I ever heard was 71A DHT in a cathode follower configuration or better yet after it was modified to use   output transformers with the tube operating at a gain of 1. This was the tail end of a line preamp that use a 6J5 for the amp stage.

            Built by a Doctor in New Orleans who was nice enough to come up and let me listen to both versions after I sold him the output transformers to replace the ones he was using. They were some single ended transformers made by James, that cost very little and sounded pretty good. They are made in Taiwan and are sold on e-bay.

             

            Dennis Boyle

            Chimera Laboratories

            Website: http://www.chimeralabs.com/

            Website: http://home.att.net/~chimeraone/index.html

             

             

            -----Original Message-----
            From: jim@... [mailto:jim@...]
            Sent: Thursday, December 02, 2004 11:43 AM
            To: dallasaudioclub@yahoogroups.com
            Subject: [dallasaudioclub] Re: Scott Nixon power supplies

             


            Hi Dennis, All good stuff and you know I've learned that and much
            more from you, John, Walter and others over the last 17 years. And
            thanks for sharing your knowledge with us all. I did forget to
            mention the IEC socket. The IEC socket and an EMI/RFI network. I also
            didn't say I installed a current limiter and John's snubber circuit.
            As said I never worried about leaving it on but so many guys kept
            worrying even though I told them it would be OK. Many guys will only
            be happy when you tell them what they REALLY want to here! :-) Of
            course my "alternatives" can and will be left almost always on but
            has the benefit of filtering the AC from the wall a bit more. By the
            way, the single 6DJ8 doesn't supply gain but is used as a cathode
            follower only. I've listened to a SS Nixon and the tube+ version and
            prefer the tube+ version. More harmonic richness in the midrange. The
            great thing about the SN DACs is the price. I love the sound better
            than ANY DAC I've owned, borrowed or whatever. I know someone with a
            high dollar Audio Note 3.1? It's also a zero sampling DAC. Hopefully
            I can A/B them soon. No matter the outcome, I'll stick with the $475
            version Nixon and NIX the $$$$ Audio Note. 8:-) jim...
            --- In dallasaudioclub@yahoogroups.com, "Dennis Boyle"
            <chimeraone@w...> wrote:
            > With regards to operating tubes, RCA operated all their studio
            equipment
            > in the so-called "Stand-By" mode. The filaments were always on and
            the
            > B+ was switched on for operation. Tremaine's Audiocyclopedia
            references
            > this and tests proved the tubes operated longer and over time became
            > quieter. This was also standard on radio transmitters that used
            directly
            > heated power tubes.

            > Cycling tube filaments and heaters, on and off, does significantly
            > reduce tube life. When cold the materials used to construct
            filament and
            > heaters has very low resistance. Due to the current surge on turn-
            on,
            > over 50 amps on a 211, the heater/filament material is mechanically
            > stressed and will eventually fail.

            > A much worse condition is called "Thermal Stripping". This occurs
            when a
            > B+ is applied to a "cold" tube before the filament has reached
            operating
            > temperature. In this case the cathode or filament material that
            emits
            > free electrons is stripped away and the tube degrades fairly
            rapidly.
            > Might be the reason why so many modern tube amplifier manufacturers
            only
            > warrantee their tubes for 90 days. There are very few modern amp
            designs
            > that use separate filament and B+ power supplies. Since filament
            > transformers are cheap and readily available, DIY builders don't
            have to
            > answer to the accountants on keeping costs down. 

            > The simplest solution is a separate filament transformer that
            allows you
            > to either leave the filaments on all the time or to turn on the
            filament
            > supply on first. In this case you can put a readily available and
            cheap
            > Thermistor or Current Limiter on the primary (120VAC line) leads.
            You
            > can use these devices with an RC network in the B+ Supply for soft
            > start, although a 5AR4/GZ35, 5V4 or 6CA4 or any other Soft Start
            > rectifier diode is perhaps a better choice. The 5AR4 is a good
            choice
            > because it has very low dynamic output impedance which helps
            transient
            > performance and current production units sound good and are cheap.

            > If you are going to use a filament winding on the B+ supply for the
            > rectifier tube, make sure the is at or slightly below the tube's
            rated
            > filament voltage. Use Ohm's Law to determine the correct value for a
            > couple resistors or even better some Thermistors/Current Limiters to
            > prevent current surge.  

            > These types of power supplies should extend the life and
            performance of
            > your tubes for a very long time. If you are operating the tubes at
            80%
            > or less of maximum ratings (voltage and current), they should last
            well
            > over 5 years, in the case of power tubes, and voltage amplifier
            tubes
            > may outlive you.           

            > Dennis

            > -----Original Message-----
            > From: jim@f... [mailto:jim@f...]
            > Sent: Thursday, December 02, 2004 7:57 AM
            > To: dallasaudioclub@yahoogroups.com
            > Subject: [dallasaudioclub] Scott Nixon power supplies

            >
            > Quite a few folks who own Scott Nixon DACs, locally and around the
            > web, have asked me if I worry about them always being on. I never
            did
            > but decided on a solution anway. The current home page photo show
            two
            > I've rebuilt. My two original SN Dacs now have these modified power
            > transformer sections. The new trannies I bought at Tanners. I've
            > added line filtering, an on/off switch in the rear and an "on" LED.
            > Pics of both below. One in a aluminum box and one in wood cigar
            box.
            > jim..
            >







            ---
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            Checked by AVG anti-virus system (http://www.grisoft.com).
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          • jim@fmtunerinfo.com
            Hello Dennis, You may know that I ve always agreed with you on the 6DJ8 issue. I even talked with Scott about that before I bought my first DAC. It doesn t
            Message 5 of 5 , Dec 7, 2004
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              Hello Dennis, You may know that I've always agreed with you on the
              6DJ8 issue. I even talked with Scott about that before I bought my
              first DAC. It doesn't seem to be an issue as the cathode follower in
              the Nixon's application. I've "rolled" a few tubes and have been
              happiest with a Mullard. I picked up a Telefunken this weekend and
              plan on trying it. Maybe some day I'll build a different audio stage
              but I'm as happy as can be for now. I really enjoy music through this
              DAC. I'm using a one meter pair of the interconnect you loaned me
              between the Nixon DAC and my preamp. That was a nice improvement. You
              won't be getting those back! Sorry. 8:-) I didn't figure there would
              have been an improvement but there was. I was already using Vampire
              Wire. But of course your winding, materials and RCAs are all
              different. jim...
              --- In dallasaudioclub@yahoogroups.com, "Dennis Boyle"
              <chimeraone@w...> wrote:
              > Jim,
              >
              > As you might remember, my ears don't like the 6DJ8/6922/ECC88 tubes.
              > They have an edge that I think it due to their distortion ratios…too
              > much higher odd order harmonic distortion. I am sure this is
              minimized
              > in a cathode follower application. It might be interesting to try
              some
              > vintage E88CC European types just to see if they make a difference.
              They
              > sound much more musical.
              >
              > The best tube buffer stage I ever heard was 71A DHT in a cathode
              > follower configuration or better yet after it was modified to use
              > output transformers with the tube operating at a gain of 1. This
              was the
              > tail end of a line preamp that use a 6J5 for the amp stage.
              > Built by a Doctor in New Orleans who was nice enough to come up and
              let
              > me listen to both versions after I sold him the output transformers
              to
              > replace the ones he was using. They were some single ended
              transformers
              > made by James, that cost very little and sounded pretty good. They
              are
              > made in Taiwan and are sold on e-bay.
              >
              > Dennis Boyle
              > Chimera Laboratories
              > Website: HYPERLINK
              > "http://www.chimeralabs.com/"http://www.chimeralabs.com/
              > Website: HYPERLINK
              > "http://home.att.net/~chimeraone/index.html"http://home.att.net/~chi
              mera
              > one/index.html
              >
              >
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