Upgrade Tubes for Meixing Mc-7r Preamp

Discussion in 'Hi-Fi and General Audio' started by pidge22, Mar 20, 2005.

  1. pidge22

    pidge22

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    Upgrade Tubes for Ming-Da Mc-7r Preamp

    Hi new to this Forum...I recently purchased a Ming-Da Mc-7r preamp to go between my Cd Player (Njoe-Tjoeb 4000 with u/s) and the power amp of my av processor...a Pioneer ax10i

    I have read on one or two reviews that upgrading the Stock Chinese tubes that came with the amp can make a difference.

    Has anyone done this and if so did it improve the sound...suggestions of what make of tubes would be appreciated.

    I will require 1 pr of Ecc83/12ax7 & 1 pr of Ecc82/12au7.

    Thanks Pidge22
     
    Last edited by a moderator: Mar 20, 2005
    pidge22, Mar 20, 2005
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  2. pidge22

    bottleneck talks a load of rubbish

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    well, those valves are inexpensive so upgrading them won't cost much.

    My advice - make sure the valves you get are tested on a valve tester (for microphony). Get them level matched if possible. The level matching is more important for power tubes, but I'd get it done anyway, to avoid discrepancies between channels.

    Getting a valve that measures well is more important than who made it or where.

    If you want clean, quick, bright kind of sound go for an american valve, like a philips. If you want to save money get something from russia. If you want classic british tone go for a british valve like a nos mullard. There are some great valves coming out of China now, and a lot of negativity about Chinese valves. The trick is to seperate the quality from the dross.

    Shop at a place that spends the time to test and match your valves for you, and you can't go too far wrong.
     
    bottleneck, Mar 20, 2005
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  3. pidge22

    lordsummit moderate mod

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    How do you install the new valves, are they just plug and play, or is there something else to do as well?
     
    lordsummit, Mar 20, 2005
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  4. pidge22

    pidge22

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    Thanks Bottleneck I wil probably go for Philips..although I listen to a lot of Jazz,Vocals and Classical so I don't know if they will be too bright? compared with Mullard.
    I upgraded my Cd Player valves to Amperex Bugle Boys from Philips but preferred the Philips and went back to these I found the bugle Boys just a bit too sharp for my taste.
    Lordsummit yes it is just a cse of Plug and Play.
    Pidge22
     
    pidge22, Mar 20, 2005
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  5. pidge22

    bottleneck talks a load of rubbish

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    hiya

    pre-amp tubes are plug and play.

    power amp tubes it depends on whether the amp is auto-bias or fixed bias. Fixed bias you need to get it to a tv repair place/hifi repair/guitar amp repair type chap - or have a go yourself with a voltmeter if you're good with eletrics.
     
    bottleneck, Mar 20, 2005
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  6. pidge22

    lordsummit moderate mod

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    Mines fixed bias, so I'd need to get it checked. Will the TV engineer know what the settings should be, or do I need to find it out? Sorry for the thread hijack by the way
     
    lordsummit, Mar 20, 2005
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  7. pidge22

    Tenson Moderator

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    I have the same pre-amp and changed the front tubes (I forget which they are) too some gold pin Electro Harmonix ones... 59..somethings.. They were not the exact same tubes but ones developed by the military which are far less susceptible to microphonics though have a slightly lower gain. I'm sure someone here can tell you what they were.. if not I'll post when I get back home.

    They did improve things a bit. Better soundstageing and tighter bass, everything integrated a bit better.
     
    Tenson, Mar 20, 2005
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  8. pidge22

    pidge22

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    Hi Tenson,
    thanks for the feedback I would appreciate knowing which spec the tubes were...so you definitely feel upgrading the tubes is worthwhile?
    Pidge22
     
    pidge22, Mar 20, 2005
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  9. pidge22

    Tenson Moderator

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    For the £25 or so I paid, yes. I did only change the front pair, I imagine there are yet more gains to be had by changing the others as well.
     
    Tenson, Mar 20, 2005
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  10. pidge22

    T-bone Sanchez

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    What do you think of the preamp with the AX10i? My mate has the same amp and we keep wondering about the possibility of putting a valve pre with the pioneer.
     
    T-bone Sanchez, Mar 21, 2005
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  11. pidge22

    Tenson Moderator

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    I replaced the front vales with Electro Harmonix 5751's. They are pin to pin compatible and I can't say I noticed a drop in gain. I think I should get some proper tube dampers, at the moment I just have blue-tack stuck round them in a ring shape!
     
    Tenson, Mar 21, 2005
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  12. pidge22

    pidge22

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    T Bone,
    With regard to the Preamp with the Ax10! it works very well and gets me closer to a system that combines both good Av and 2 channel reproduction.
    I have a Njoe Tjoub 4000 cd player with unsampler and putting the Ming Da Valve Preamp between this and the Ax10i directly into the poweramp section definitely improved things further in terms of Midrange and Detail as well as a tighter bass. ...
    I am now going to upgrade the Output tubes to Mullards 83's and 82's so am looking for further improvement.
    I will report back how it goes
    Tensen thanks for coming back to me on the Electro Harmonix but felt that Mullards would be more suiable to what I listen to...Jazz,Vocals and Classical as to if i have done the right thing I am about to find out!!!
    Can anyone tell me is there any merit in upgrading the rectifier from the Stock Chinese one that came with the Preamp?.
    Pidge22
     
    pidge22, Mar 21, 2005
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  13. pidge22

    T-bone Sanchez

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    If you want tube dampers check out this months hi-fi world, theres an article about making some tube dampers for about £3, I made some and they do make abit of a difference.
     
    T-bone Sanchez, Mar 22, 2005
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  14. pidge22

    pidge22

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    T Bone,
    is that in April's (the current edition) Hi Fi world.
    Pidge22
     
    pidge22, Mar 22, 2005
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  15. pidge22

    Tenson Moderator

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    Damn, and I bought Hi-Fi News....

    I have seen some dampers which are solid metal, I think they would be pretty good.. at least better than my blue-tac.
     
    Tenson, Mar 22, 2005
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  16. pidge22

    T-bone Sanchez

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    It certainly is, if your struggling to get a copy and can scan easily enough.
     
    T-bone Sanchez, Mar 23, 2005
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  17. pidge22

    bottleneck talks a load of rubbish

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    I read on this forum once that you can use rubber O rings if you buy ones with a high enough melting point.
     
    bottleneck, Mar 23, 2005
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  18. pidge22

    pidge22

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    Hi T-bone..I have got this months edition of Hifi World I have had a look and seen the article concerned..I will have a go thanks for the offer of scanning your copy.
    Pidge22
     
    pidge22, Mar 23, 2005
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  19. pidge22

    jonjin

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    Errr... would appreciate a copy.

    I am also thinking of changing the 12AX7 on my amp (it's the driver tube on my power amp actually). At the moment it is a Electro Harmonix and the sound is a little on the bright side for my tastes. I've recently got my hands on a Mullard so will hopefully be able to share my experience here. I'm not sure how much of a difference it can make.

    JJ
     
    jonjin, Mar 23, 2005
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  20. pidge22

    T-bone Sanchez

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    No worries I'll scan it later and send it to you. The EH are well known for being on the bright side, as are many US tubes, The mullards will make a difference.
     
    T-bone Sanchez, Mar 24, 2005
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