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    GZ34 / GZ33 or GZ37



    Posts : 298
    Join date : 2010-11-10

    GZ34 / GZ33 or GZ37

    Post by mantha3 on Mon Dec 06, 2010 10:09 am

    GZ34 / GZ33 or GZ37

    I am running a new ST120. I have a cheaper Sovtek 34 that is working fine. I'd like to upgrade this rectifier tube and keep this Sovtek as a back up as rectifiers don't last long I hear. I know I could get a Webber Copper cap… I like the glow of the tubes and want to keep with a tube.

    I'm looking at Mullard.. I see some GZ33 and GZ37 out for sale. I think these are rated at a higer voltage then the 34. I'd like to get a more solid rectifier in my amp and I'm looking at doing a 33 or 37 as the price is a bit better.. Thoughts?

    What are the differences and would the options result in a different sound output?

    Lots of questions.. I feel like I should be paying people for responding to my posts. Thank you all.

    Bob Latino

    Posts : 2382
    Join date : 2008-11-26
    Location : Massachusetts

    Re: GZ34 / GZ33 or GZ37

    Post by Bob Latino on Mon Dec 06, 2010 11:34 am


    Rectifiers seldom make any significant difference in sound quality on the ST-120 UNLESS you play the amp loudly or have inefficient speakers. If you play the amp loud a lot OR your speakers are relatively inefficient (87 dB or lower) then I recommend the Weber WZ68 solid state rectifier which can flow more current than any tube rectifier.

    Re: GZ33 or GZ37 rectifier tubes vs. a GZ34. GZ33 or GZ37 rectifier tubes have some disadvantages.

    1. They are much more expensive than a GZ34
    2. There are few vendors for these tubes
    3. These tubes are taller (5 1/4" high) so that if you use a tube cage they won't fit under the stock ST-70/ST-120 tube cage.

    On the plus side both a GZ33 and a GZ37 with a choke input, as on the ST-120, can flow more current than a GZ34. I have two Mullard GZ33's that I have been swapping in and out with the Weber WZ68 SS rectifiers in the two prototype M-125 amps. I honestly can't hear any difference in the sound of either monoblock.

    There is a vendor on Ebay called "Langrex" who sells a NOS Mullard GZ33 for $78.60 + shipping from the UK. I bought two for the M-125's from him and they came quickly and were packed well. This is about the lowest price I have found for a NOS Mullard GZ** rectifier tube.



    Posts : 2
    Join date : 2010-11-26

    Re: GZ34 / GZ33 or GZ37

    Post by evilfij on Tue Dec 07, 2010 8:07 pm

    Take this for what it is worth, but I heard no difference in sound between a $125 mullard GZ34, a well used generic GZ34 and a mullard GZ33 on my dynaco mkiiis. What I run now are JJ GZ34s which at $16 per seems like a good deal. I only have a few hundred hours on them, but they did not blow unlike the 5ur4 which did manage to smoke and can be used as a substitute per dynaco but clearly has issues. Mullards are supposed to be the best, but i can buy 8 JJ for the price of one mullard gz34 or 5 for the price of one gz33 and they all sound the same to me.


    Posts : 298
    Join date : 2010-11-10

    Re: GZ34 / GZ33 or GZ37

    Post by mantha3 on Wed Dec 08, 2010 10:14 am

    I think I should have just stuck with a current production GZ34. I have a Sovtek that will now be my back up. I just dropped too much $$ on a NOS Sylvania Big Bottle GZ34. I paid about 60 bucks under what a Mullard would cost... But still more then what I would have spent. This tube rolling can get addiictive! Surprised

    I have my ST-120 all set with tubes... All around. The only area I may play around a bit now is the 12AT7's

    Has anyone purchased from - ?

    This is out of Ankara/Turkey?!?!?!

    They had the Sylvania Big Bottles at 60 bucks which is a bit better price wise then what I got mine for.

    About them -
    We are a hi-fi dealer located in Ankara/Turkey. We carry a huge stock of vintage electronic parts sourced mainly from military surplus of NATO member countries throughout Europe. So far, almost for a decade now we have been a wholesale supplier to the major tubes and parts dealers/resellers worldwide.

    I don't mean to sell these guys.. they have some interesting tubes

    Raytheon JAN CRP 12AT7WA Triple Mica Black Plates $18.00ea
    Tung-Sol JTL 12AT7WA 30.00 ea
    Many others...


    Posts : 298
    Join date : 2010-11-10

    Re: GZ34 / GZ33 or GZ37

    Post by mantha3 on Wed Dec 08, 2010 10:15 am

    PS - (Strange to respond to my own post) I was curious to see if anyone has any experience buying from this place.. Seems strange to order from Turkey for some reason...

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