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Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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Dave_in_Va
Bob Latino
LeGrace
DavidR
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    12AU7 tubes and its Variants question

    DavidR
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    • Post n°1

    12AU7 tubes and its Variants question Empty 12AU7 tubes and its Variants question

    Post by DavidR Sat Sep 14, 2019 3:29 pm

    I have a VTA ST-120 amp and have been looking at the options for the driver tubes. I prefer NOS tubes vs todays tubes for driver tubes. For variants of the 12AU7/ECC82 I have the 12BH7, 6680, 6189, 5418, 5963 and the M8136. I run 12BH7A tubes in the center/amplifier driver section.

    I recently picked up a pair of NOS JAN 5814 tubes by Sylvania to use for phase inverter tubes. When I got them I went to test them on my Sencore TC136. I was surprised that the set-up for the Load was different than other 12AU7 tubes. The filament current is 175ma per section versus 150ma per section for a 12AU7. This is the same for the 5963 tube. All other 12AU7 tube variants have the same set-up parameters.

    Is there any issue running the 5814 and 5963 tubes in the ST-120?


    Last edited by DavidR on Sat Sep 14, 2019 6:08 pm; edited 1 time in total
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    LeGrace
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    • Post n°2

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by LeGrace Sat Sep 14, 2019 5:52 pm

    I have used 5963 in my VTA amps w/o incident.

    Edit: correct copy and paste error
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    DavidR
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    • Post n°3

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by DavidR Sat Sep 14, 2019 6:07 pm

    Thanks for the reply. What position(s) have you used them in?

    How is the SQ.

    I'm assuming that since they are possibly 'under driven' they should be longer lasting.
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    Bob Latino
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    • Post n°4

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by Bob Latino Sat Sep 14, 2019 6:51 pm

    DavidR wrote:I have a VTA ST-120 amp and have been looking at the options for the driver tubes. I prefer NOS tubes vs todays tubes for driver tubes. For variants of the 12AU7/ECC82 I have the 12BH7, 6680, 6189, 5418, 5963 and the M8136. I run 12BH7A tubes in the center/amplifier driver section.

    I recently picked up a pair of NOS JAN 5814 tubes by Sylvania to use for phase inverter tubes. When I got them I went to test them on my Sencore TC136. I was surprised that the set-up for the Load was different than other 12AU7 tubes. The filament current is 175ma per section versus 150ma per section for a 12AU7. This is the same for the 5963 tube. All other 12AU7 tube variants have the same set-up parameters.

    Is there any issue running the 5814 and 5963 tubes in the ST-120?

    There are no issues running any of the following driver tubes in any of the VTA amps built from April of 2012 to now.

    You CAN USE any 12AU7, 5963, 5814, 6189, 6680, CV4003 and ECC82. You can also use a 12BH7 which, although not a direct replacement for a 12AU7 type tube, is close enough and works well.

    The fact that the filament current may be slightly different from one tube to another is of no concern.

    Note that the earlier (Pre April of 2012 amps) used the older higher gain 12AT7 driver tubes.

    It is imperative that you NOT use 12AT7 or 12AX7 type tubes in these newer amps. If you try either of these two tubes, you could take out the LM334 IC which controls the CCS (constant current source) in the phase splitter/inverter section of the driver circuit.

    Bob
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    DavidR
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    • Post n°5

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by DavidR Sat Sep 14, 2019 7:18 pm

    Thanks Bob

    My amp was previously AudioBill's personal amp. I'm guessing post 2012 and it came with a 12BH7A in the center and 12AU7A for the phase inverter positions.

    The M8136 is the CV4003 tube.
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    Dave_in_Va
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    • Post n°6

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by Dave_in_Va Sat Sep 14, 2019 8:19 pm

    Don't forget the 7316. Really nice sounding tube (at least in my VTA ST 70).
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    DavidR
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    • Post n°7

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by DavidR Sat Sep 14, 2019 8:46 pm

    The 7316 seems to be strictly an Amperex ECC186 tube
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    HarryY
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    • Post n°8

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by HarryY Sun Sep 15, 2019 10:49 am

    What about the 12AV7 or the 5965A

    Any issues with using either one of those tubes?
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    Bob Latino
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    • Post n°9

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by Bob Latino Sun Sep 15, 2019 10:56 am

    HarryY wrote:What about the 12AV7 or the 5965A

    Any issues with using either one of those tubes?

    I honestly don't know if these two are acceptable? They do have about double the gain of a 12AU7 type tube and as such, I don't recommend their use in any VTA amp.

    Bob
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    Dave_in_Va
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    • Post n°10

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by Dave_in_Va Sun Sep 15, 2019 11:29 am

    "The 7316 seems to be strictly an Amperex ECC186 tube"

    Yes, it's a high quality 12AU7 variant. It was used in computers and medical/aircraft equipment.
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    HarryY
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    • Post n°11

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by HarryY Sun Sep 15, 2019 12:05 pm

    Bob Latino wrote:
    HarryY wrote:What about the 12AV7 or the 5965A

    Any issues with using either one of those tubes?

    I honestly don't know if these two are acceptable? They do have about double the gain of a 12AU7 type tube and as such, I don't recommend their use in any VTA amp.

    Bob



    Thank you

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    irishsgd
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    • Post n°12

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by irishsgd Thu Sep 19, 2019 9:54 am

    With regard to 12AU7 variants: after rolling through
    - NOS 1960's RCA 12AU7 Clear-Top (as center alone, as inverters alone, and in all 3 positions)
    - NOS 1950's TELEFUNKEN 12AU7
    - Brimar 12BH7 (as center alone, as inverters alone)
    - Sylvania 6189 GB (as center)
    - Hammond 12BH7A (as center)
    - RCA 5963 (as center)
    - Sylvania 12BH7A yellow label (as center alone)

    I have finally dialed in (to my deep satisfaction) the VTA ST-70 amp with my system using the following:

    Center/Amplifier: NOS 1950's RCA 12BH7 Black Plates
    Phase Inverters: NOS 1950's RCA 5814 Triple-Mica (matched)

    Rectifier: NOS 1960's MULLARD 5AR4
    Power: NOS 1960's GE 6L6-GC (matched)

    Qobuz Hi-Res streaming and local AIF files
    played through Amarra Luxe (on MacMini 2014, with all processing disabled; i.e. "flat")
    through Mytek Liberty DAC (pass-through volume)
    to ST-70 in Triode Mode (volume by ST-70 attenuator)
    driving KLH Model Six speakers (all original).

    All NOS tubes from Vintage Tube Services. A+ service.
    All others were eBay purchases (trial and error!)
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    MechEngVic
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    • Post n°13

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by MechEngVic Thu Sep 19, 2019 1:59 pm

    DavidR wrote: I prefer NOS tubes vs todays tubes for driver tubes.

    I have a pile of NOS tubes sitting in their boxes instead of in my amp or pre. The only NOS tubes that I liked were the Mullard's. I'm using 6GH8A's and 12AX7's but my point is this: With the exception the Mullard's, new tubes have out-performed the NOS ones. The new Tung-Sol's and JJ's sound fantastic. Tube makers today are using yesterday's designs and making on-the-fly improvements that were just not possible before. Plus, tubes today are made almost exclusively for sound reproduction so the focus is on sound quality.
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    LeGrace
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    • Post n°14

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by LeGrace Fri Sep 20, 2019 2:42 pm

    What is difference between 12AU7 and 12AU7A?
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    10-E-C
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    • Post n°15

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by 10-E-C Fri Sep 20, 2019 3:59 pm

    LeGrace wrote:What is difference between 12AU7 and 12AU7A?

    From google,


    The only difference between the 12AU7 and the 12AU7A is the "A" version can be used in series string filament circuits due to it's controlled warm-up cathode. Otherwise, there is no difference.
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    LeGrace
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    • Post n°16

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by LeGrace Fri Sep 20, 2019 4:37 pm

    10-E-C wrote:
    LeGrace wrote:What is difference between 12AU7 and 12AU7A?

    From google,


    The only difference between the 12AU7 and the 12AU7A is the "A" version can be used in series string filament circuits due to it's controlled warm-up cathode. Otherwise, there is no difference.

    Thanks!
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    DavidR
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    • Post n°17

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by DavidR Wed Dec 04, 2019 8:22 pm

    Is a 6350 vacuum tube in the 12AU7 family?
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    Dave_in_Va
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    • Post n°18

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by Dave_in_Va Wed Dec 04, 2019 10:50 pm

    Nothing I could find on the 6350 showed it as a sub for a 12AU7.
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    DavidR
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    • Post n°19

    12AU7 tubes and its Variants question Empty Re: 12AU7 tubes and its Variants question

    Post by DavidR Wed Dec 04, 2019 11:04 pm

    They look very much like a 12BH7 which is not really in the 12AU7 family but I found this:

    6350: This tube was mainly manufactured for IBM and other computers in the late 1950s to mid 1960s. Sylvania and GE blackplates are considered the best of all with this tube. The only difference is the pins that correspond to the grid and plate of each triode are reversed from the 12AU7 connections, so you will either need to rewire your sockets to take this tube, or consult with the manufacturer of your unit to see if this tube can be used as a sub for the 12AU7. It has a mu or gain factor of 18 so is very close to the 12AU7. These were made to tight specs and carefully quality checked, since replacement in a computer of the day was difficult and costly, and the tubes were expected to operate 24-7. These make impressive upgrades to the standard 12AU7!
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