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RE: [dallasaudioclub] Scott Nixon power supplies

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  • 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 1 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 2 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 3 of 5 , Dec 2, 2004
        • 0 Attachment

          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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          Incoming mail is certified Virus Free.
          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 4 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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