AVA Super 70 PC Board

Discussion in 'Audio by Van Alstine' started by reed338, Sep 27, 2015.

  1. reed338

    reed338 New Member

    Messages:
    33
    Hi,

    Anyone out there have an AVA super 70i pc board you can part with? I would prefer the older version you see from the 80s with an opaque white board material.

    PM me.

    Thanks!
     

     

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  2. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    We never made a Super 70i board from opaque white board material.

    Note that a complete Ultimate 70 rebuild kit is $449 and it builds a much better amplifier than the original Super 70i.

    Note too that the original version of the 70i board used 7199 tubes. Later versions and current U70 amplifiers use more available 6GH8A tubes. Same tube, different and non-interchangeable pin out.

    Frank
     
  3. reed338

    reed338 New Member

    Messages:
    33
    Hi Frank,


    Thanks for the info :)

    I have seen the attached type board floating around in the past. Was looking for one to use...in a low budget build. I am guessing this would have been a home brew version?
     

    Attached Files:

  4. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    That is our board but not our parts, obviously from a do it yourself plans and bare board we supplied long ago.

    The board is green, not white. Bad color balance in the photo.

    Without seeing the foil side I can't tell if this board is pinned out for 7199 or 6GH8a tubes.
     
  5. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Frank,

    When you switched from the 7199 to the 6GH8A, did you need to adjust the associated resistor values? In other words, in the different versions of your Stereo 70 modification over the years, would the 7199 and 6GH8A use the same or different value resistors off of their respective plates, cathodes, grid, in order to establish their operating parameters? I understand that the pin-outs are different.

    Thank you.
    Peter
     
  6. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    The 7199 and 6GH8A are the same tubes, just different pin out, so parts values remained the same.

    Frank
     

     

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  7. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Thank you for your response, Frank. So, then, if someone had a mind to do so, it would be possible to take your currently available Ultimate 70 rebuild kit, cut certain traces and add jumpers in just the right places so that a 7199 could be used? And, the 7199 would work just as well in your Ultimate 70 as the 6GH8A now does, without making any changes to associated parts values, whether resistors or the coupling capacitors?

    Thank you.
    Peter
     
    Last edited: Oct 10, 2015
  8. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    The Ultimate 70 rebuild kit ($449) comes with a set of 6GH8A single tubes so ther is no need to change its circuit board.

    Frank
     
  9. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    If I were to purchase the kit, I may nevertheless wish to make the changes I described, as I have several 7199 tubes that I'd like to make use of. In fact, it was in your own Audio Basics newsletter of July 1990 that you described a procedure for altering the Stereo 70 circuit board to accept the 6GH8A by cutting traces and adding appropriate jumpers. When you have a moment, I'd appreciate a specific response to my question in post # 7. Thank you.
    Peter
     
    Last edited: Oct 11, 2015
  10. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    I will research this for you when I have time. I am not sure that it is easily possible with the Ultimate 70 board which has a full ground plain, not a simple one sided board like the old Super 70i.

    Frank
     
  11. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Thank you. No rush.
     

     

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  12. avahifi

    avahifi AK Member

    Messages:
    39
    Location:
    Woodbury, Minnesota
    Due to its double sided construction with a bottom ground plain and plated through holes, our newest PC-1104 Ultimate 70 mother board is not a candidate for conversion to use 7199 tubes.

    So your choice is to invest in hacking up an original Super 70i board to use 7199 boards or simply going for the day and night better sounding Ultimate 70 board and suffer along with 6GH8A tubes.

    If the $449 cost of the Ultimate 70 rebuild kit is too much for you, note that the bare PC board and complete rebuild plans are available for $149.

    Frank
     
  13. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Thanks. I'll mull it over.
     
  14. keith dobbs

    keith dobbs New Member

    Messages:
    4
    Frank, Peter,
    You can always use a tube adaptor in case of 'must use' a specific tube.
    Plenty are sold on Ebay.
     
  15. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Keith, I've seen plenty of adapters to use the 6GH8A in place of the 7199 and have wondered if this same adapter can be used the other way around. If not, I don't recall seeing adapters specifically for using 7199 in place of 6GH8A? Or, did I just miss them?

    Referring to the previous post about modifying the PCB, as far as the ground plane and plated-through holes on the PC board, as long as the board is just two-sided with no internal layers, I would think it should be possible to make orderly cuts and jumps in the foil so that 7199 can be used directly with no adapter, if desired.

    I was primarily concerned about differences in related component values, especially the resistors, in switching between 6GH8A and 7199. For example, Dave Gillespie uses different resistor values for his drop-in replacement board for the SCA-35, the reason being his board uses 6GH8A in place of the 7199. Note the description of the PC-10A Output Board Set here: http://www.audioregenesis.com/ Have been wondering if something similar might apply if swapping these tubes around in the Stereo 70 or its variants like the AVA Ultimate 70 / Ultravalve.
     
    Last edited: Mar 12, 2016
  16. keith dobbs

    keith dobbs New Member

    Messages:
    4
    Peter,
    These adaptors are use specific- 7199 bottom + 6gh etc top
    Have seen plenty on Ebay.
    Just send an email to any adaptor advertiser and they will make what you want to order..
     

     

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  17. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Thanks for the info!
     
  18. shoown

    shoown New Member

    Messages:
    4
    http://hardware.ui3g.com/ You can find some pcb manufacturer on this website. I think this website is very useful for electronic engineers.
     
  19. petercapo

    petercapo AK Subscriber Subscriber

    Messages:
    854
    Thank you.
     

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