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ECC 83 / 12AX7A Valve question

Discussion in 'audio' started by kjb, Jan 12, 2022.

  1. kjb

    kjb pfm Member

    I'm thinking of switching out the two 12AX7A(Sovtek) in my Leben 300XS amp. I've already changed the EL84s to positive effect.

    I've very little knowledge of valves and swapping them around apart from what I've picked up here so a few questions:

    Is it worth it?
    What are the pros and cons of ECC83 over 12AX7A?
    What brands are recommended to seek out or avoid?
    Any recommended UK suppliers?

    Most comparisons I can find online seem to be focused on guitar amps and gain/distortion rather than hi fi. I assume what is best for one may not necessarily be the preferred option for the other.

    Thanks in advance

  2. chartz

    chartz If it’s broke fix it!

    Hi Kevin,
    They are the same. Try to find NOS 80’s Philips/RTC ones, they are excellent and last forever.
    Don’t expect any big sound quality change though.
    I have tested many over 35 years, mostly in phono preamps.
    Vinny likes this.
  3. Mike P

    Mike P pfm Member

    I've found the Sovtek 12AX7LPS to be a very decent current production valve which holds its own admirably against much more expensive vintage valves.

    Honestly, the difference between something like the 12AX7LPS and the most desirable of vintage NOS valves is often wildly exaggerated.
  4. early

    early pfm Member

    You could try 5751's . If you want some nice ones contact "The Bish" he's a lovely fella and has a stash of these .
  5. brab

    brab pfm Member

    5751s are not the same as AT7s
  6. gavreid

    gavreid pfm Member

    The long plate (LPS) version has a reputation for being more microphonic though - in the guitar amp community anyway.
  7. coltrane

    coltrane electrobaroCKjazzer

    absolutely seconded, IME mostly in the ol' Audio Innovations and Audio Note amps
    Rockmeister and Vinny like this.
  8. Bairnstorm

    Bairnstorm pfm Member

    I have old shield Mullard ECC83's in my phono stage and some Mazda's as back up. I can't tell the difference between them.

    They replaced JJ's which sounded slightly wiry and less fleshed out. It is not a huge difference.

    We all go chasing small improvements and these are small improvements.

    When the Mullards and Mazdas die, I will replace with whatever is around but certainly won't pay the current silly prices for NOS.

    Watford Valves and Hotrox are good places to look as they will be genuine.

    Ebay is a lottery but have bought valves happily. Some have been great some not so great.

    Final place Tonbridge Vintage show. They are all as mad as us and frequently madder. Your valves aren't that bad anyway.
  9. Vinny

    Vinny pfm Member

    Mazda is a brand that is/was owned by GE USA and licensed to various manufacturers in Europe (though mostly Thorn-EMI who also sold valves under Brimar and various other brands and also sourced a lot of their valves from Tungsram (et al)), the valves with the Mazda brand on them could be from any one of several manufacturers/designs. Numerous brands could be Thorn-EMI/Mazda valves.

    Pre-amp valves have almsot infinite lives.

    Any differences are mostly very subtle - on extended listening in Croft pre's, I prefer Philips Heerlen to Blackburn and also like some of the E European and Toshiba, and RCA valves. (Japanese valves were very largely made on European machines to European designs, especially Philips, as Japanese industry was often tooled by European companies after WW2.)

    If you search online, valves that were slated 5 years ago are now the dog's bits as they are now the only NOS valves available. Strange!!! (Not)
  10. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Differences between valves of the same type but different maker are fairly subtle. Differences between valves which are worn out or damaged and new ones not so subtle....
    Mike P and chartz like this.
  11. G T Audio

    G T Audio Trade: Manufacturer and Distributor

    5751's are not the equivalent of a 12AX7 or an ECC83. They are more like a 12AT7 or 6072. They have less gain than a 12AX7 and should certainly not be used as a replacement for a 12AX7, especially in a RIAA circuit.
    Arkless Electronics and chartz like this.
  12. Euan

    Euan pfm Member

    I found this thread where someone asked the question of Leben themselves. Answer is in the final post.
  13. kjb

    kjb pfm Member

    Thanks all

    Sounds like the money may be better spent on more unreasonably priced vinyl :D
    Rockmeister likes this.
  14. gints

    gints pfm Member

    Some sellers suggesting them as replacement for hifi and guitar amps with less gain as benefit. Are they wrong?
    Probably nobody wants less gain in phono amps anyway.
  15. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Only fit the valve type the equipment was designed for. In guitar amps they WANT distortion and odd euphonic effects! In a phono stage it could very well put the tonal balance way out.
    gavreid, G T Audio and Mike P like this.
  16. chartz

    chartz If it’s broke fix it!

    In final cathode follower stages with no gain it’s okay to use ECC82 for instance.
    However I find it rather dull sounding.
  17. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Even then it's a bad idea! 100% NFB lets you "get away with murder" but the ECC81/82 operate at way different optimum current to the ECC83.

    I've also found pre amps that consist of an ECC82 cathode follower of the bog standard text book variety to sound poor.
  18. oceanobsession

    oceanobsession pfm Member

    These small signal valves aint cheap any more , i managed to buy a few different types 10 years back cheaper then , i personally like the American valves
    tungsol rca sylvania original types , some are great valves packaged under a different name baldwin adzam zairex etc . phil.
  19. Mat C

    Mat C Active Member

    Try NOS Philips/Valvo/Siemens they are wonderful.
  20. kjb

    kjb pfm Member

    A final question after reading more about these valves following your comments.

    Is higher or lower gain better for hi fi? I tend to go higher gain in guitar pedals /amps to get more dynamism. Is there a preference for valves in hi fi amps? Is one purer or is there a payoff of purity v dynamics?

    The Watford valve blurb on the GE ECC83/ 5751 says "The valve has a lower amplification of 70 mu as opposed to a 100 mu of a ECC83/12AX7. This makes it harder for the valve to distort and therefore an ideal choice when the best clean sound is required." Is lower distortion better?

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