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poor output transformers

Discussion in 'Amp Tech Center' started by bmc496, May 14, 2018.

  1. bmc496

    bmc496 NEW MEMBER!

    Age:
    60
    1
    May 14, 2018
    Riverview, Mi.
    Hello, I am not an expert in this area but do have some knowledge. Built 1,500 and 2,000 watt rf amplifiers from a kit. Been into ham radio since 1972, got extra license in 1989. Also play drums and guitar. Just purchased an Egnater tweaker 88, price was 50% off. I found tubes are Chinese, they will be replaced, my question is the output transformer also Chinese. If yes, should I replace it with a made in US? Bought a Vox NT2H first thing I did was replace preamp tubes with nos matched pair Mullard 12at7's and replaced output transformer. New transformer was $38 with shipping. Could not believe the difference it made, for the better. Take it easy on me, lol, this is my first post, I'm a newb. James
     

  2. VintageSG

    VintageSG Tele-Afflicted Ad Free Member

    Mar 31, 2016
    Yorkshire
    If the amp was built in China, the transformers will be too. Commercially, it makes little to no sense to ship a transformer from the US or Europe, have it fitted, then ship the completed item back.
    There is nothing wrong with a Chinese transformer, if it is built to spec, and Egnator have bitten on the behind with regard to this, though I think it was non-resettable thermal fuses in the power transformer. The sorry tale is readily available on the Internet should you wish to explore it.
    Try it first. Try it with replacement valves if the stock valves don't cut it for you. What would a different transformer do for you?. What is the limiting factor with the stock transformer.
    Sometimes, a marginal output transformer contributes to the sound for some people. The compression it can bring to some ears can be quite pleasant.
    What was wrong with the Vox after the new valves that prompted a transformer swapout?. What changes did it bring, and were those changes due in part to exchanging AX valves with AT.

    Play it first, change inexpensive, easy to revert items.

    ps.Welcome!
     
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  3. SSL9000J

    SSL9000J TDPRI Member

    Age:
    46
    53
    Dec 18, 2016
    North of Atlanta, GA
    If I understand correctly, all vacuum tubes currently in production are made in either China or Russia. New old stock, (NOS,) is a different story, of course.
     

  4. wanderin kind

    wanderin kind TDPRI Member

    Age:
    63
    53
    Apr 24, 2018
    Olympia WA
    an offshore transformer might sound OK, or not,

    it might break, or not,

    QC seems to be highly variable.

    laminations will be cheaper, wire will have less copper, winders will be under stress to deliver,

    i have taken apart some of the offshore output transformers and was sorry to see what a rushed job they did.

    you can buy a new transformer but where will it come from?

    WA6LSI
     

  5. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    Slightly off topic, but JJ are made in eastern Europe. Can't recall offhand whether Czech or Slovak Republic, though.
     

  6. flyswatter

    flyswatter Friend of Leo's

    Jan 12, 2013
    Quebec
    Slovakia.
     

  7. Nickfl

    Nickfl Tele-Holic

    888
    May 24, 2016
    Florida
    I wouldn't. The OT for a 2xKT88 amp is going to cost a lot more than the tiny little one for that vox did. Same with the tubes. There is nothing wrong with Chinese tubes per se, maybe not the best but what are you going to replace them with... a pair of NOS KT88 would probably be worth more than the amp! FWIW amps like this are designed with new production tubes in mind and I've heard it said that they therefore may sound better with the cheap Chinese tubes than with $$$ NOS...

    Even if you for sure knew that the amp would sound better with new tubes and a new transformer (thats a big if), would it be enough of an improvement to justify spending probably $200+ (more if you want NOS tubes) on a Chinese made PCB amp. Certainly not money you'd ever see again in resale value if that is a concern...
     

  8. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

    Age:
    65
    Mar 2, 2003
    Lawndale CA
    No. because - why? You don't just replace parts because of were they are made. That's just throwing dollars away. Only replace it IF there is solid evidence that the replacement pro ides a significant improvement in tone. Don't worry about power - it's irrelevant. Just concentrate on tone.

    Not true. Also Slovakia and several other locations - but so what? Many are excellent tubes. Some aren't. Voicing and gain varies among preamp tubes and there are all sorts of variations in power tubes.

    But "location" alone isn't a qualifier OR disqualifier. NOS tubes, OTOH, have to be bought very carefully from only a few reputable sources. And not all of them are so different that the dollar-for-dollar difference is justified.

    Many players replace both preamp and power tubes FAR too often. With few exceptions they just don't wear out in a year or two...or five. Far more attention needs to be paid to normal service items like filter and bias capacitors (good for around 15 years max) and replacing crappy original (cheap) speakers than tubes.
     
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