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Old 1st October 2013, 02:36 AM   #471
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Quote:
Originally Posted by TNT View Post
But you don't like whats going on at the secondary side?

//
I am not very familiar with balanced outputs but your connections don't look correct. Aren't you supposed to connect the secondaries in series and reference one pin on the XLR output connector to ground?

I am sure somebody here with more experience with balanced outputs will chip in.
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Old 1st October 2013, 03:04 AM   #472
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Originally Posted by ihear21khz View Post
I am not very familiar with balanced outputs but your connections don't look correct...
In fact, the centre of the secondary need not be grounded to chassis or even to Pin 1. In fact, it may well be advantageous NOT to ground it at all.

What then determines whether it is balanced is the receiving end. If the receiving end grounds the bottom (or one side) of the secondary, it then becomes unbalanced. On the other hand, if the input on the receiving end is truly balanced, then signal will appear on both Pin 2 and 3. But the signal that gets processed is the difference between Pin 2 and 3, and not with any reference to ground. The ground reference is not the reference to the signal and that is a good thing. Hence best not to ground the secondary at all.

The receiving ends sees the difference between Pin 2 and 3, that is all. Hence, perhaps the better description is that it is differential rather than balanced, since signals at Pin 2 and Pin 3 may not be exactly balanced or exactly the same amplitude anyway.

Is that clear as mud?

There are other advantages to a gloating secondary, galvanic isolation. This is an advantage peculiar to transformers as they can be used as isolators.

Cheers, Joe

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Old 1st October 2013, 01:50 PM   #473
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In the case of a balanced interconnect, the XLR pin #1 is not part of the audio circuit ground. The XLR pin #1 is only a shield and should be connected to the chassis very near the connector. Occasionally at the receive end of the cable, the shield is not connected at all or connected through a capacitor. But this modification should be done inside the cable connector not inside the chassis.
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Old 2nd October 2013, 03:06 AM   #474
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Yes, interconnect shield to chassis ground. The outputs of the transformer (signal) should not be referenced to ground.
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Old 3rd October 2013, 03:06 PM   #475
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Originally Posted by Joe Rasmussen View Post

There are other advantages to a gloating secondary ...
Smug bastards!
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Old 3rd October 2013, 03:21 PM   #476
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Originally Posted by tubesguy View Post
Smug bastards!
Very sharp... OK... correction... "floating secondary".
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Old 6th October 2013, 06:31 PM   #477
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I'm ready to give this a shot, but can anyone tell me if there is any significant difference, aside from the DCR of the windings, between a "600:600" transformer and a "10k:10k" transformer in either the voltage out or the current out configurations suggested in this thread? I'm looking at the Lundahl 1527 for the former or the Jensen 11p1 for the latter. TIA - Pat

Last edited by tubesguy; 6th October 2013 at 06:34 PM.
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Old 6th October 2013, 10:43 PM   #478
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Originally Posted by tubesguy View Post
I'm ready to give this a shot, but can anyone tell me if there is any significant difference, aside from the DCR of the windings, between a "600:600" transformer and a "10k:10k" transformer...
LL1527 is Lundah's general purpose 1:1 transformer.

I am sure others will give more complex explanations, but when I see a transformer with reasonably low DCR and reasonably low insertion loss, the main thing I look at is the ratio of the transformer.

But there are other factors to consider, the max level of signal and the current loads and the magnetics to support it, frequency response under those conditions and so on. But with 1:1 transformers and 43R DCR per winding, for our use here, a well designed transformer should do the job. Try it and see if you like what that one does for you.

Yes, I would try LL1527, if I had one on hand to try. The specs are quite good, 0./1% distortion at +6dBu (1.5V), <1% at +16dBu (5V).

Cheers, Joe
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Last edited by Joe Rasmussen; 6th October 2013 at 10:50 PM.
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Old 7th October 2013, 02:33 PM   #479
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Thanks, Joe, got a quote from Kevin at K&K. Just need to find someone to do the assembly and SMD soldering for me on my Acko isolator/reclocker, and I'll be good to go. (Digikey sent me some envelopes with what they claimed to be 0603 components (or perhaps caraway seeds) but I'm 63 and my eyes are not that good anymore, and my hands are so shaky that the only way to stop them is to drink to excess, and that makes my eyesight just that much worse.) ;-)

Last edited by tubesguy; 7th October 2013 at 02:46 PM.
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Old 7th October 2013, 09:32 PM   #480
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Sorry to be OT, but that last post from tubesguy almost caused me to spit out my cocoa.
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