Custom OT

Discussion in 'DIY' started by m17xr2b, Apr 13, 2019.

  1. m17xr2b

    m17xr2b Friend

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    I'm looking to upgrade the output transformer of a 300B amp and couldn't find any for my requirement.
    Are there any companies that make custom high quality output transformers that will be a noticeable upgrade to say the woo ones?

    Am I mad to request this?
    Primary 2.5K,3.5K,5K
    Secondary 8Ω, 110Ω
    100+mA

    The Tango XE20S might fit the bill but it doesn't have the high impedance secondary and I've come to appreciate with senns and still on the fence if I should drop it.
    The different primaries are for me to experiment and hear for myself what impact it has on sound with different biases.
     
  2. gridmaster

    gridmaster Rando

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    Pretty expensive and long wait times, but http://www.monolithmagnetics.com/ makes high quality custom transformers.

    I called them once, the technician was very open about discussing the topic of a custom I wanted, gave really good advice.

    Edit: I also believe http://www.tribute-audio.nl/ does customs.
     
    Last edited: Apr 13, 2019
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  3. MisterRogers

    MisterRogers Friend

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    Also, SACThiland / Silk transformers are custom wound. I'm using them in my DG300B, and they're top notch.
     
  4. Hrodulf

    Hrodulf MOT - Sonarworks

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  5. Zampotech

    Zampotech Wow, I made it this far without being a friend?

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    in Moscow there is a firm which makes fine transformers according to the specification of the customer. They have very good transformer steel.

    http://www.audioalt.ru
     
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  6. k4rstar

    k4rstar Sad on the inside

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    Do you know if their sales team speaks English or if they ship outside of Russia? They have some very cool looking amplifiers available.
     
  7. purr1n

    purr1n Finding his inner redneck

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    You can still experiment with different biases (within limits) if you go with just 3.5k primaries. Bias is a matter of taste. Almost anything is an upgrade to the Woo OPTs. You don't need a 100ohm secondary - might as well go OTL. Something like a 3.5kΩ to 8Ω would be about right for a 300B or 2A3 into a headphone. Plate impedance of those DHTs is about 1kΩ. x3.5 is the sweet spot. 5k may yield a better damping factor but less power transfer. 2.5k is too low. Don't try to be special or reinvent the wheel.

    Not sure if you can get the Tangos anymore. Even if you can, a colossal waste of money.

    Check out the S-7. 3k3 primary and 4/8 secondary:
    http://www.monolithmagnetics.com/products?q=node/97

    Available in amorphous core too for an additional price.

    Mable audio has an "advanced 300B" transformer which was the basis of the SJR's OPTs. This is the best one I've heard that isn't boutique priced - great bandwidth and even more importantly sounds just right*. Running without feedback, it's less bloated than most 300B OPTs, still has a bit of that rolloff, but immensely powerful and slammin' down low - none of that soft squishy stuff. It reminds me of a bit of the DNA Stellaris; sound. For a China product, not cheap, but better than the double C-core Lundahl I have in my custom 45 and any ElectraPrint.
     
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  8. restrav3

    restrav3 Likes Audio-GD

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    The descriptions and the specs for their Amps are some of the weirdest I've ever seen.
     
    Last edited: Apr 14, 2019
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  9. m17xr2b

    m17xr2b Friend

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    Is a 45 happy with that primary? Sounds like I'd have to source a 3.5/5 primary to run all three. My end goal is to run the trifecta of DHT.
    Am I asking too much and should just stick with 2A3/300B where the 45 would never run to its full potential without compromises for the other two?
     
    Last edited: Apr 14, 2019
  10. Zampotech

    Zampotech Wow, I made it this far without being a friend?

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    I know they work with international shipping. Postal transportation has a simplified customs.

    Write them. The owner's name is Roman.


    Yes, unusual. They produce unusual DACs. With a discrete implementation of the algorithm PCM53 DAC:eek:
     
    Last edited: Apr 14, 2019
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  11. purr1n

    purr1n Finding his inner redneck

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    45 tube will need 5k.

    Going with a 5k primary might be easier. Would work with 300B, 2A3, and 45. Not really a huge downside with 300B or 2A3. Maybe less power, but benefit of lower output impedance. You could still go with 3.5k primary though if headphones with higher impedance, just miss goodbye to speakers.

    Keep in mind there is really no such thing as a static 2.5k or 5k primary impedance. It's all ratios and dependent upon the speaker or headphone load.

    Don't forget heater voltages. 300B is 5V. 2A3 is 2.5V, but draws significant current.

    I would advise narrowing the scope. The one thing that does them all usually results in more permutations to try and spread out effort, ending up witu the one thing that does them all in a mediocre way.
     
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  12. m17xr2b

    m17xr2b Friend

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    Gold advice, thank you.
     

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