Sansui Output transfomers from a SM-30

Discussion in 'Tube Audio' started by battradio, Oct 7, 2017.

  1. battradio

    battradio Electron trainer Subscriber

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    http://www.tube-amps.net/images/SM30/SM30_07_600.jpg
    http://www.tube-amps.net/Sansui_Tube_Era_Products.htm

    I just purchased a pair sansui output transfomers from a Sansui SM 30 , one of the best vintage 6BQ5 PP output transfomers that can be had .

    I'm early in in the build planning stage and wanting suggestions on circuits to use , the original used a 6AN8 which i'm not enamoured with or 6GH8's

    Have a nice potted power transfomer that is 610 volts CT at 225 Ma , a 5 volt 3 amp winding , and two 6.3 volt windings and several potted chokes to chose from .
    So a 5AR4 or 5V4G would both work for the power supply .

    Also have a nice pair of fisher power transformers from 610-st's i want to go mono blocks .

    Looking for them to arrive tuesday
     
  2. primosounds

    primosounds AK Subscriber Subscriber

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    Hi Battman, are you going to be running the amp in cathode bias ? I just completed building a PP EL84 stereo amp based on the EICO HF86. It turned out extremely good. The circuit is fairly simple, and my power supply was CLCLC. I also used film caps for 2 of the Cs.The front end is supposed to be 2 x 12DW7 but i "cheaped" out and use 1 12ax7 and 2 12au7 instead. only 1/2 of each 12au7 is used. You could just use 1 12au7 and split the duty but i preferred to keep the 2 tubes seperate. I think having the 2 phase splitters separated may help the amp perform or sound better. I was actually going to use 2 6c5 as the splitter tubes but since i was recycling an amp chassis that already had the 2 9 pin sockets i went with half of a au7 instead. The amp seems to be operating conservatively so i suspect that increasing the voltage a little may give you more power.
     
  3. battradio

    battradio Electron trainer Subscriber

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  4. whoaru99

    whoaru99 Epic Member

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    Dunno where it rates in the scheme of things but I think I'm going to base my next EL84 amp on the HK 20. Looks like your power transformer would be a good fit.

    Schematic here: EL84/6BQ5 circuit recommendations?
     
    Last edited: Oct 7, 2017
  5. battradio

    battradio Electron trainer Subscriber

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    That is one to consider ,was also looking at this one .

    [​IMG]
     
  6. battradio

    battradio Electron trainer Subscriber

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    [​IMG]

    Another candidate
     
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  7. battradio

    battradio Electron trainer Subscriber

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  8. battradio

    battradio Electron trainer Subscriber

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  9. AmadeusMozart

    AmadeusMozart Member

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    Hashimoto was the manufacturer of the Sansui transformers and is still making them 40 years later. Not cheap but are about the best that are still available today and are financially (just) affordable after some other high end manufacturers closed their doors / prodcution lines. I am presently in the middle of building a clone of the Audio Note kit four but if I had to start over again I would build a clone of the Sansui HF-V60. Main reason is that the tubes are Octal based which longer life expectancy than their Noval equivalent ones. (The kit 4 has a 12AX7 as input tube).
     
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  10. battradio

    battradio Electron trainer Subscriber

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  11. kward

    kward AK Subscriber Subscriber

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    I've built two amps recently that were nearly identical except for the output tubes--one with 6V6's and the other with EL84's. The 6V6 in my opinion is more neutral sounding, whereas the EL84 is warmer (everybody probably knows that already). A scaled down HF60 for either a 6V6 or EL84 output stage I think is going to give too much frontend gain to be used as a straight power amp. However that exact combo is magic if you want to add a volume pot directly on the power amp and drive it with digital frontend sources.

    For a power amp only for EL84 outputs, my vote would be a 12AX7 gain stage and a 12AX7 split load inverter. For power amp only with 6V6 outputs, I'd go a 12AX7 gain stage and 6NS7 or 6FQ7 split load inverter. I know...nothing new under the sun in those suggestions, but it works so well.
     
  12. arts

    arts Super Member

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    I have always had a love for the 6V6,but I just don't have any speakers efficient enough to do them justice. And no,I will not be buying any more speakers,efficient or otherwise,as I already need a bigger house as it is:(

    Just a thought: If someone is running a CD player or other higher-output source,what about skipping the input stage entirely and running directly into a split load inverter? Probably not enough gain to support a feedback loop,but maybe do away with that as well.....hmm,this :idea: or this :crazy:
     
  13. battradio

    battradio Electron trainer Subscriber

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    If i went with 6V6's , would most likely go with a 6SF5 and 6J5 to drive them with the split load inverter , though i do have a lot of NOS 6SL7's and 6SN7's

    https://frank.pocnet.net/sheets/049/6/6SF5.pdf , i have more octal tubes than 9 pin tubes
     
  14. battradio

    battradio Electron trainer Subscriber

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    I have Klipsch Cornwalls in the living room and KEF Corelli's at my desk , both are happy with 3 watts or more .
     
  15. whoaru99

    whoaru99 Epic Member

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    I have an amp based on this, but the back bias was modified/eliminated and is using EFB circuit to provide bias.

    It sounds quite nice to me.

    Screenshot_2017-10-09-11-07-54.png

    20151204_083852.jpg

    At top of the stack:

    20160118_135324.jpg
     
  16. primosounds

    primosounds AK Subscriber Subscriber

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    Classic 40s to 50s amplifier. Similar to Grommes LJ.
     
  17. Pio1980

    Pio1980 AK Member Subscriber

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    The 6BQ5 has an easy drive characteristic, a dc coupled cathodyne driver would yield the most direct signal path.
    Simplicity!
     
  18. AmadeusMozart

    AmadeusMozart Member

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    Increased front end gain does not need to be a bad thing - if you are driving the amplifier directly from a CD/DVD player then you might find that the balance between the two channels on older / remastered CD's might need adjustment. Elliot Sound Products has a schematic that a contributer (Bernd Ludwig) supplied and which works wonders. (Yes, there are those who will not have an amplifier without a balance control.....)

    http://sound.whsites.net/project01.htm (bottom of the page)

    Enjoy!
     
  19. battradio

    battradio Electron trainer Subscriber

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    I have not had the need for a balance control on any of the amps i have rebuilt , correct grounding and 1 percent parts in the feedback loop , have served me well .
     
  20. AmadeusMozart

    AmadeusMozart Member

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    If the recording is perfect then a balance control -should- not be necessary but speakers can easily have half a dB or more difference between them, even two or three dB difference between speakers are not unheard off.

    I am using foobar2000 with Mathaudio equalizer which uses a microphone to adjust the equalizer automatically. Mathaudio can also compensate for any volume differences between the speakers. Not to forget room asymmetry and furnishings may also have an effect on the propagation of sound and hence require some adjustment. In the past I have wanted a balance control for adjustment (when using a CD player) but all I need now is volume control (and even that can be controlled from the computer).
     
    Last edited: Oct 11, 2017

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