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

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

  1. Clemmaster

    Clemmaster Friend

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    Do you need a transformer with the B2? I think you can just use XLR to RCA cables (per the manual).
    You can adjust the gain to tune the distortion profile.
     
  2. Josh Schor

    Josh Schor Friend

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    wow Pancakes thank you, I will PM you in a few weeks
     
  3. Josh Schor

    Josh Schor Friend

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    Clemmaster, Im a nooob with tech stuff was not clear when looking at the manual about xlr to rca, which cable would I need is this balanced to rca? I do not want to fry the dac if I get one, would be using it with the EC studio b. appreciate your help with this
     
  4. Armaegis

    Armaegis Friend

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    Maybe I'm reading a different manual... but I don't see anything about using an adapter cable to get single ended outputs in the manual.

    Granted, most pro gear tends to be fairly robust and can tolerate having one of the legs grounded. Some gear (like Prism, and I think RME) will have circuits which auto adjust when they detect a single ended adapter on their balanced outputs. You could maybe float pin3 in a cable adapter, but all of these are not good practice.
     
  5. Josh Schor

    Josh Schor Friend

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    Those with the knowledge which outputs would be used on the burl b2 to go to the cinimag transformer im getting built. AES out? xlr to xlr in at transformer? Been looking at info I can find on using the burl and I am still confused. I would appreciate any help from those in the know.
     
  6. Pancakes

    Pancakes Friend

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    This.
     
  7. Josh Schor

    Josh Schor Friend

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    excellent thanks Pancakes, I will PM in a few weeks
    best
     
  8. ogodei

    ogodei Friend

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    Last edited: Feb 7, 2022
  9. Josh Schor

    Josh Schor Friend

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    If you need to order Cinemag CMLI-15/15B go direct to the company they have in stock and much cheaper than ebay. $60 including shipping to Michigan from CA compared to $90 on ebay
     
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  10. cbarth

    cbarth New

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    Hi,
    I have followed this thread with great interest and thus bought ISO-MAX PO-2XR. I have XLR input on my amp, but it sounds sooo much better with this transformer and connected with RCA. But I have an issue with gain. The signal is too high on the single ended input.
    Signal is about 5V and input impedance on amplifier is specified to 40k ohms. Source has extremely low output impedance and gobs of current capability.
    So I was wondering if anybody had a tip for resistor loading to get the level down a bit?
     
  11. mitochondrium

    mitochondrium Friend

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  12. peef

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    A quick word of warning for anyone using these transformer boxes with DC-coupled sources: make sure your source is free of DC offset. I tested the LL1544A in SE -> Bal, and Bal -> Bal. The latter sounded broken, with the bass sounding much less impactful.

    So, I took some measurements, and found that my source had 0.3mV of DC offset on the SE output, and 1-2mV on the balanced output. 0.3mV is fine, >1mV, no so much.

    Here's a distortion plot taken at -17dBU, with about 1mV on the primary. This is my normal listening level, and well below the maximum recommended level of +20dBU for this transformer. It's being used as the IPT of an amp, so this is probably why the third harmonic dominates and does not change between measurements-- if there's interest, I can measure just the transformers at a few different levels, and compare to a Cinemag 15/15b.

    [​IMG]

    And the same with a 10uF film cap to block DC on the transformer primary. You don't heard this often, but it sounded far, far better with the cap in place.

    [​IMG]

    It's subtle, but with DC, distortion goes up significantly. H2 doubles at 100Hz, and higher order distortion products go up as well.

    What's troubling is that the DAC I am using is a piece of commercial gear with audio op amps on the outputs. The datasheet specifies an input offset of 3mV, so if you are using two in a balanced configuration, that goes up to 6mV-- good enough to plug into powered monitors, but troublesome for amorphous cores. So, if you're disappointed with how your transformers (or transformer-coupled gear) sounds, consider checking the outputs for DC.
     
  13. Baten

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    So.. for science, what DAC was it that showed this DC offset?
     
  14. peef

    peef Friend

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    I hate to pick on a specific piece of gear-- it's a fault of op amp output stages in general, which are as ubiquitous as they are terrible.

    The DAC is a MOTU M4. I've since measured similar or worse on an Analog Devices DSP evaluation board and on the output of an SVS sub. Super high DC accuracy really doesn't matter until you reach for esoteric parts like we're doing here.

    Edit: I've since tested a Convert-2. It's the worst of the bunch, with about 5mV of DC offset.
     
    Last edited: Mar 23, 2022
  15. Josh Schor

    Josh Schor Friend

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    Writing to ask if there is anyone in the states who could build a xlr/balanced to SE box for me. I have all of the parts, hammond aluminum box, xlr and rca chasse connectors and two cinamag transformers. Any skilled help much appreciated, Im a noob with DIY stuff. Pancakes had offered and he is really busy now.
    best,
    josh
     
  16. Armaegis

    Armaegis Friend

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    Do you know how to solder?
    Do you have a drill (or drill press) with appropriately sized bits?

    As far as DIY projects go, this is super straightforward. Prepping the case is arguably more work than the soldering. Heck, if you got crimp style connectors you wouldn't even need solder.
     
  17. Josh Schor

    Josh Schor Friend

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    Not good at soldering, no drill press, I think its easy if you know what your doing
    best
     
  18. Wobbletits

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    So I'm not concerned with the building of any of it but is it crazy to make a passive pre with 4 transformers to do se -> bal and vice versa as long as I keep the output wiring short? I'll probably make it anyhow but is there some reason I'm an idiot for doing that instead of making 3 separate boxes?

    I actually already intended to put in 2 rotary 6p3t switches so one would toggle input (of the attenuator) between xlr / se / se + transformer, and then one to toggle the outputs between (xlr out always wired up) rca out disconnected, rca out wired for just se pass through, and rca out using the transformers. Technically the rca jacks would always be wired to either the primary or secondary of the transformers depending on input/output side and the switches would just route things a little differently.
    Is there basically no chance of it driving something if I were to have both transformers and the attenuator in the circuit (though I'm not sure why I would se -> bal -> se but whatever)
     
  19. TheloniuSnoop

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    Hopefully someone here will read this who knows what's going on. (Yah, I know, goofy intro.)

    Here's my dilemma. Last month I emailed Cinemag to see if they had the CML 15's in stock. David got right back to me to say that they did, along with the mounting types and prices. I replied with the ones I wanted, and he sent me a Paypal invoice, which I promptly paid. That was on March 2nd and then they went silent. I've asked if my order has shipped three times, but still silence. No explanation, no kiss my arse, nothing.

    Are they still in business? Has Covid hit them? Alien abduction? I've done biz with them once before with no issues, so I'm a bit concerned and a lot peeved, especially since they took my cash right away, then darkness.
     
  20. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    I bought a pair of 600's from them recently. It only works to call them, email communication isn't reliable. I emailed and waited forever too, then I called and they picked right away and were very very kind.
     

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