Balanced to single-ended converter (XLR to RCA / BAL to SE)

Discussion in 'DIY' started by purr1n, Jun 27, 2020.

  1. Baten

    Baten Friend

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    I have jensen transformers in an audial AYAII build that provide "pseudo" balanced XLR outputs to this TDA1541A DAC. I was wondering, can I safely short this transformer-coupled output with XLR to RCA adapters? I am pretty sure that yes, this is not an issue and have been using it like so, but I'm just wondering. With a traditional differential build this could seriously hurt performance but with transformers I believe it is safe. But, I wouldn't want issues long-term...

    Thank you for your thoughts :) on a DAC like the Yggdrasil I am aware that a balanced to single-ended converter is needed to get a high-performance 1:1 conversion, but in my use case it is not really balanced and using adapters should provide the exact same voltage output, if I got this correct.
     
  2. Andre Y

    Andre Y Friend

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    It's safe, and a transformer is true balanced. Nothing pseudo about it.
     
  3. Elmer Danilovich

    Elmer Danilovich MOT:Earmen, HeadAmp, Bricasti; AKA:MShenay

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    Pi 2XR is the 1:1 I believe, as the PC 2XR is advertised as the +4 to -10 unit

    That said I've a Modius inbound and I'm happy to say I've finally order myself the PI 2XR after eye balling it for a while now!
     
  4. MisterRogers

    MisterRogers Ethernet Nervosa

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    I also have a bunch of PCB’s bal to se (chip based) I put together years ago. Don’t want to derail the thread, but you can message me if you need one (friends and contributors).
     
  5. ogodei

    ogodei MOT: Austin AudioWorks

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    I have had both, this is accurate.
     
  6. skem

    skem Friend

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    I hooked some transformers up per Marv’s diagram and got tons of buzz, even though my unbalanced/SE cable run was only 4 inches. I then saw that Bill Whitlock of Jensen recommends tying XLR 1 (shield) to SE shield, and this also appears in @m17xr2b’s board traces (I think). Anyway, that fixed the problem. Perhaps a useful note for others.

    This is the best technical reference I’ve found on transformers
    https://www.jensen-transformers.com/wp-content/uploads/2014/08/Audio-Transformers-Chapter.pdf

    This is the best guide I’ve found for doing these connections without a transformer:
    https://crookwood.com/blog/dealing-with-unbalanced-gear-in-the-studio

    EDIT: In my case, the amplifier was the Pioneer M22, which being old is not tied to earth ground and therefore no ground loop.
     
    Last edited: Jul 9, 2020
  7. m17xr2b

    m17xr2b Friend

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    XLR1 is left unconnected by default on my setup but did add a pin for it in case it needs to be grounded. Jensen have small switches on PC2XR to float the ground or not. I can immagine this is needed for an amp with a floating ground.
    You may have a reason for grounding XLR1 and a valid one. You usually don't want to ground it as there's a chance for ground loops.

    Look at what the cat dragged in:
    [​IMG]
     
    Last edited: Jul 9, 2020
  8. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    I would connect the PIN1 to the device enclosure and transformer enclosure, if there's a pin on the trafo that allows for it. On the SE end I'd leave audio ground connected only to the RCA. This way you get some shielding from the BAL device and there isn't really a chance to get a ground loop, as the SE side is only connected to the coil.
     
  9. Riotvan

    Riotvan Snoofer in the Woofer

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    Did this once with a pair of higher end Lundahl’s was really nice. Thinking of doing it again and putting a nice selector switch on the xlr side so i can use the better xlr outs from my Yggdrasil for my headphone amp as well. The se out sounds like too dry bs to me.
     
  10. m17xr2b

    m17xr2b Friend

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    With soldered connectors. At this point there are two options
    1. Use the PCB version of the Sowter 3575, solder and have a clean look without wires
    2. Use the grommet or side leads option and attach the leads using the push connector without needing to solder.
    The Cinemag grommet ones are designed to fit as well.
    [​IMG]

    Since my sowter PCB order is still weeks away I pulled out the one from my amp to install, who has the pacience to not test a new toy?
    The original printed support:
    [​IMG]

    All hooked up with the wires routed though the auxiliary hole for this purpose. No soldering.
    [​IMG]

    Also ditched the latch for the XLR connector, I really see no point for a consumer application
    [​IMG]

    Worked like a charm from the first go:
    [​IMG]

    Sounds pretty much the same, just a tad more rounded but not unexpected considering I'm using an additional different cable now. Ideally both cables should be the same.

    Now even with the PCB version the push connector is still very usefull, dare I say it it can be used for another set of outputs, testing grounding issues, using it inside an amp etc.

    [​IMG]

    I'll need to design and print a bespoke case and that will be that.
     
  11. Walderstorn

    Walderstorn Friend

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    Visually, the result is even better than i had visualized. I think the push connector is great for people, like me, that would kill themselves with an iron.
     
  12. m17xr2b

    m17xr2b Friend

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    The push connector, from CUI devices has several advantages IMO in this setup and why I chose it after thorough research:
    1. Solder free install of a grommet/compatible side lead input transformer
    2. Easy way of swapping an input transformer without soldering. It's easy to have perfect soldering the first time, each solder job on the same area degrades quality IMO.
    3. Cinemag and Sowter transformers already have stripped leads. In theory one can buy new input transformers and this pre-assembled board, screw in a couple of screws after pushing in the leads and it's ready to go.
    4. More on my side, I'd prefer transformer factory setup hence keeping the resell value of input transformer to the max(no need to trim leads).

    Pushing the text print quality of my cheap and cheerful printer, the backside of the first converter:
    [​IMG]

    With the top and bottom layers assembled on standoffs as designed. I do love flush colour matched screws.
    [​IMG]

    The finished prototype, not too bad if I say so myself. With Wywires platinum XLR and silver RCA ICs I can't hear a difference from memory of the hardwired solution. For a true finished product I'd have to go trough several case iteration just like the PCB which is at version 7 in this product.
    Apologies for the bad lighting.
    [​IMG]
    [​IMG]


    Printed with 2.5mm walls which is almost overbuilt from my experience and how it should be. 3mm walls increases the print time, filament requirement to almost absurd levels yet even if 2mm is more than enough I like to be extra sure and have that sturdy weighty feeling.

    The PCB itself could be sold yet I'd rather offer a complete solution for fellow members, soldered PCB with connectors and 3D printed case with all screws. Basically get preferred transformers and this kit for the best DIY solution possible. For the purist in mind the push connectors is a nuisance and not perfect yet those persons can DIY so I can't see the downside.

    If there is enough interest I can offer the kit without transformers and I have a few available. The ultimate goal is to sell finished XLR to RCA converters. Would be a lot easier if Sowter wouldn't be swamped at the moment with 8 to 12 weeks lead times. Cinemag isn't that hard to get but the additional fees to get in into Europe might dissuade some hence the kit offer.

    While prototyping the case I've been using SE from Pavane to my now upgraded DIY amp, still a great sound but something is missing. Installing the finished product I can breath easier again yet a question ponders: sowter vs audio note input transformers...

    [​IMG]
     
    Last edited: Jul 13, 2020
  13. purr1n

    purr1n Desire for betterer is endless.

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    If the input impedance of the amp or preamp is greater than 10k, you may want to load the CMLI-15 with a 10k resistor to shave off a few 0.001% THD in the lows if the outputs from the source is hot.
     
  14. dasman66

    dasman66 Self proclaimed lazy ass - friend

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  15. purr1n

    purr1n Desire for betterer is endless.

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  16. monacelli

    monacelli Friend

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    That's what I thought too, @purr1n. Apparently the J-Iso uses the JT-11-YMPC, which is 1:1 but with bifilar windings, slightly different from the JT-11P-1. It looks like the attenuation on the J-Iso comes from an in-line potentiometer, which I would probably also prefer to avoid in this type of product.

    https://www.radialeng.com/product/j-iso/specifications
     
  17. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    then which one of their products does 1:1 XLR to SE? The amazon link in your post is to the Twin-ISO, which appears to be XLR to XLR... I tried going thru Radial products, but I couldn't seem to find anything other than the J-ISO...
     
  18. purr1n

    purr1n Desire for betterer is endless.

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  19. Melvillian

    Melvillian Friend

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    Thought this would be a fun and quick project. Bought the parts, but haven't had time to put it all together. I think the Hammond box I bought is a little too big.

    When It's done I can send this out on a loaner tour along with a 4:1 Jensen IsoMax if people are interested.

    [​IMG]


    Transformers were $75 each brand new on ebay. All parts together come out to around $180, which isn't bad if it's a good solution for higher end DACs. Like Marv said, not worth doing this for a Modius or other affordable dacs.

    Btw if you're cheap and want a box, you can probably use an electrical junction box from home depot. They're like $3
     
    Last edited: Jul 19, 2020
  20. dasman66

    dasman66 Self proclaimed lazy ass - friend

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