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Thread: Any decent 12AU7 recomendations?

  1. #1
    Join Date: Apr 2017

    Location: Bristol

    Posts: 70
    I'm Tony.

    Default Any decent 12AU7 recomendations?

    I'm tube rolling my Yaqin MC13s which has two 12AX7s in V1 & V4 and two 12AU7s in V2 & V3.

    So far I've tried Svetlana Winged C 12AX7s and Mullard 12AU7S. I found the Mullards to be really disappointing with a closed in muffled sound.

    However, when I put the Svetlana's into V2 & V3 and used the old chinese 12AX7s in V1 & V2 I got a really nice sound, open, smooth and detailed.

    I would stick with this but I'm concerned that using a 12AX7 in place of a 12AU7 may harm the amp?

    So can I ask if it is OK to keep using Svetlana's in this way. Any concerns?

    If not any recommendations for a decent 12AU7?
    VPI Scout 1.1, Ortofon Quintet Bronze, Trigon Vanguard I, SB Touch, Beresford Caiman SEG, Yaquin MC13S and Rega RS3

  2. #2
    Join Date: Sep 2014

    Location: Northern Ireland

    Posts: 595
    I'm John.

    Default

    Quote Originally Posted by Intenso View Post
    I'm tube rolling my Yaqin MC13s which has two 12AX7s in V1 & V4 and two 12AU7s in V2 & V3.

    So far I've tried Svetlana Winged C 12AX7s and Mullard 12AU7S. I found the Mullards to be really disappointing with a closed in muffled sound.

    However, when I put the Svetlana's into V2 & V3 and used the old chinese 12AX7s in V1 & V2 I got a really nice sound, open, smooth and detailed.

    I would stick with this but I'm concerned that using a 12AX7 in place of a 12AU7 may harm the amp?

    So can I ask if it is OK to keep using Svetlana's in this way. Any concerns?

    If not any recommendations for a decent 12AU7?
    I have a pair of these in my power amp. Really ballsy, rhythmic full sound, great for rock and blues. Mullards much more polite IMHO.

    https://www.upscaleaudio.com/product...que-12au7-6189

  3. #3
    Join Date: Oct 2016

    Location: Bolton, England

    Posts: 666
    I'm Andrew.

    Default

    Quote Originally Posted by Intenso View Post
    I'm concerned that using a 12AX7 in place of a 12AU7 may harm the amp?

    So can I ask if it is OK to keep using Svetlana's in this way. Any concerns?
    Without seeing a circuit diagram it's difficult to say exactly what will happen when using 12AX7s instead of 12AU7s but generally valve amps are pretty robust and there's a good chance that no harm will come of it. Worst case scenario is that there will be more power dissipation in a valve or a resistor than they're designed for and they'll either slowly cook or burn out pretty rapidly. Also, a voltage across a capacitor could rise too high and cause failure. However, more likely than not, no harm will be done.
    Bear in mind that the operating points for the amplifier will be different and distortion might be worse, maximum power output might be reduced etc. Best to just stick with a 12AU7 where the circuit is designed for a 12AU7 imho.

  4. #4
    Join Date: Oct 2008

    Location: Glasgowshire

    Posts: 6,124
    I'm availableforweddingsAndBarmitzvas.

    Default

    Always liked NOS Tung Sol "D-Getter" tubes, the new issue ones are also well thought of?
    http://www.musiciansfriend.com/acces...sol-12ax7-tube
    I have hifi 'n stuff.


  5. #5
    Join Date: Oct 2012

    Location: NE England

    Posts: 4,598
    I'm Jez.

    Default

    Quote Originally Posted by RothwellAudio View Post
    Without seeing a circuit diagram it's difficult to say exactly what will happen when using 12AX7s instead of 12AU7s but generally valve amps are pretty robust and there's a good chance that no harm will come of it. Worst case scenario is that there will be more power dissipation in a valve or a resistor than they're designed for and they'll either slowly cook or burn out pretty rapidly. Also, a voltage across a capacitor could rise too high and cause failure. However, more likely than not, no harm will be done.
    Bear in mind that the operating points for the amplifier will be different and distortion might be worse, maximum power output might be reduced etc. Best to just stick with a 12AU7 where the circuit is designed for a 12AU7 imho.
    ^ Good advice. +1
    Arkless Electronics-Engineered to be better. Tel. 01670 530674 (after 1pm)

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  6. #6
    Join Date: Jul 2017

    Location: Oklahoma, USA

    Posts: 7
    I'm Darius.

    Default

    I have quite a collection of old 12au7s. You cannot go wrong with RCA cleartops and Sylvania long plates. Both cheap and plentiful on ebay.

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