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    VTA M125 transformer heater filament rating

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    30 Ounce

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    Post by 30 Ounce on Sat Feb 01, 2020 10:22 am

    I am building an octal board for my VTA M125 and plan on using Shuguang CV181-t tubes in those positions. They need .9 amps @ 6.3v for their heater filaments. If I add all my heater values: 4x KT120 @ 1.95 each = 7.6 amps, Mullard GZ33 @ 3 amps, 2x Shuguang cv181-t @ .9 amps = 1.8 amps. Total 12.4 amps. Is the too much for these transformers? If so should I substitute a Weber WZ68 copper in place of the Mullard?
    Bob Latino
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    Post by Bob Latino on Sat Feb 01, 2020 11:12 am

    30 Ounce wrote:I am building an octal board for my VTA M125 and plan on using Shuguang CV181-t tubes in those positions.  They need .9 amps @ 6.3v for their  heater filaments.  If I add all my heater values: 4x KT120 @ 1.95 each = 7.6 amps, Mullard GZ33 @ 3 amps, 2x Shuguang cv181-t @ .9 amps  = 1.8 amps.  Total 12.4 amps.  Is the too much for these transformers?  If so should I substitute a Weber WZ68 copper in place of the Mullard?

    The two 6.3 volt AC lines are rated at 5 amps each so - 10 amps total for the two 6.3 volt lines

    The Mullard GZ33 is on a separate 5 volt @ 4 amp AC line.

    1. If you do use the octal board, I believe you are at 9.4 amps with the octal board (7.6 amps for the 4 X KT120 and 2.9 amps for 2 X 6SN7 type tubes) and you will be approaching the 10 amp "rating" of the two 6.3 volt AC lines.

    2. If you use the noval board with two 12AU7 type driver tubes (2 X 12AU7 = .6 amps) and your total current rating for the two 6.3 volt AC lines will drop to 7.6 amps and the amp will run noticeably cooler.

    Bob
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    BryceJ

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    Post by BryceJ on Sat Feb 01, 2020 5:31 pm

    30 Ounce wrote:I am building an octal board for my VTA M125 and plan on using Shuguang CV181-t tubes in those positions.

    I would be interested to know if you can get CV181-T tubes in both of those sockets. The sockets on the octal driver board are 1.7" apart according to Roy. The datasheet that I have seen for the Shuguang CV181-T indicates that the tubes are 50mm, or 1.9685",  in diameter. If that is accurate, you should not be able to plug two CV181-T tubes into the octal driver board.
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    30 Ounce

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    Post by 30 Ounce on Sat Feb 01, 2020 8:18 pm

    VTA M125 transformer heater filament rating D4676810

    It will be close, I was wondering the same thing...[url=https://servimg.com/view/20162508/1]


    Last edited by 30 Ounce on Fri Feb 14, 2020 10:35 am; edited 1 time in total (Reason for editing : double posted pictures)
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    Post by 30 Ounce on Sat Feb 01, 2020 8:20 pm

    VTA M125 transformer heater filament rating D4676810
    It will be close, I was wondering the same thing...[url=https://servimg.com/view/20162508/1][


    Last edited by 30 Ounce on Fri Feb 14, 2020 10:34 am; edited 1 time in total (Reason for editing : double posted pictures)
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    BryceJ

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    Post by BryceJ on Sun Feb 02, 2020 12:53 am

    That is about as close as you can get them! Very Happy
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    buchela

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    Post by buchela on Sun Feb 02, 2020 2:08 am

    So, given those those voltages approaching the 10 ampere rating, of the 6.3 V lines, are octal boards for the M-125, a bad idea ?.
    tubes4hifi
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    Post by tubes4hifi on Sun Feb 02, 2020 6:53 pm

    if you stick to more conventional tubes (KT88 1.5A, KT90 1.6A) then that totals 7.6A max for filaments using 6SN7 drivers
    even using KT120 (1.9A) gives you a max of 8.8A
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    buchela

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    Post by buchela on Mon Feb 03, 2020 7:04 pm

    Fair enough, it's always good to know the do's and don'ts. I only run KT120s, with novals, I will be trying the octals this week. By the way those octal boards are of very high quality, the assembled boards look awesome,
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    30 Ounce

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    Post by 30 Ounce on Thu Feb 06, 2020 11:11 am

    They do look awesome. The blue board with blue resistors look cool! Miflex caps make them look like pontoon boats though.VTA M125 transformer heater filament rating 2403aa10
    VTA M125 transformer heater filament rating 51de0410
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    buchela

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    Post by buchela on Thu Feb 06, 2020 11:32 am

    What's the word on those MIFLEX caps ?, those are huuuuge. They look like air compressor filters. Impressive.
    Do you have previous experience with those?, I'm intrigued
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    30 Ounce

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    Post by 30 Ounce on Thu Feb 06, 2020 12:03 pm

    Don Sachs built my preamp with Miflex caps in them and I was so impressed I thought I’d try them in my octal tube build. I should have this put back together this weekend.
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    30 Ounce

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    Post by 30 Ounce on Sat Feb 08, 2020 6:54 pm

    Got them back together. Thought I’d start with KT88’s and see how warm the transformer gets and try the KT120’s if they don’t get too hot.VTA M125 transformer heater filament rating 89446110
    VTA M125 transformer heater filament rating Dd93c310
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    buchela

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    Post by buchela on Sat Feb 08, 2020 7:36 pm

    Holy font,!!!!!!!! I understand now why you were so adamant about sitting those Chinese coke bottles on the driving seats, They look awesome !!!!!!! VTA 125 twin turbo
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    BryceJ

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    Post by BryceJ on Wed Feb 12, 2020 1:23 am

    Those amps look really nice all put together.
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    30 Ounce

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    Post by 30 Ounce on Wed Feb 12, 2020 10:17 am

    Thanks! I have about 15 hours on them now and everything seems fine as far as transformer heat goes. It sounds wonderful. I would highly recommend this combo of Miflex caps and Shuguang CV181-t if anyone is so inclined. It sounds so good I don’t want to put the KT120’s in!

    Here’s a picture after several hours of use...beautiful!VTA M125 transformer heater filament rating F9a92210
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    buchela

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    Post by buchela on Wed Feb 12, 2020 10:38 am

    30 Ounce I was waiting for your input before going that route..I see the cv181 closeness not much of an issue, they really look imposing. Have fun !!!!!
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    andyo

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    Post by andyo on Thu Feb 13, 2020 6:07 pm

    buchela wrote:What's the word on those MIFLEX caps ?, those are huuuuge. They look like air compressor filters. Impressive.
    Do you have previous experience with those?, I'm intrigued

    Miflex is a polish capacitor manufacturer (http://www.miflex.com.pl/en/products/audio-capacitors-and-filters ). These caps are KPCU-01 - with thick copper foil and are quite heavy. I have them in my Lampizator Golden Atlantic TRP. According to some people they are as good as Duelunds, except they are much cheaper and have no oil inside. Sonically, they are very musical, a bit on the warm side but don't emphasize any frequency. Check out http://www.humblehomemadehifi.com/Cap.html for a review of various audio caps.
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    buchela

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    Post by buchela on Thu Feb 13, 2020 7:53 pm

    Thanks andyo,the link was very helpful, I'm ordering those
    corndog71
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    Post by corndog71 on Thu Feb 13, 2020 10:56 pm

    I would save those CV’s for the voltage amplifier stage only. From my understanding the phase splitter is less affected by the tube. They do like very nice though and you can do whatever makes you happy.

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