Balanced to RCA

+1 re. "You need an adapter"

I had to do this for my fully balanced Preamp to SE SET amp.

You will have to ground one of the pins. Important because it is protective. Find out which one, based on your output component (XLR side)?

I went with Cardas. They offer two levels of XLR to RCA adaptors. When compared directly, I found easily heard differences in sound between the two.

Cardas will custom spec their adaptor, if your ground needs require something different than their standard/stock offering.

I defer to @gdnrbob on the transformer approach as I chose not to go that route. Reach out to Bob for more on that and whether it will be superior to adaptors for your application.

I agree that the transformer approach is superior to simple adapters, especially when going from balanced output to unbalanced input. It allows you to use the whole signal (rather than half of it) and is less likely to cause hum issues. Whether the improvement will be significant is situation dependent, but it's the best approach, IMO.
Adapters from unbal to bal sometimes ground one of the active pins (2 or 3 of XLR), but that is not advisable going from bal to unbal, as you would be grounding one output of your source component, which could damage it.

@mike_in_nc   I'm unsure regarding your comment below. Can you elaborate?

I was very concerned about this very issue and a number of folks helped me out. Al ( @almarg ) was a primary advisor on this. Perhaps he can comment and add his usual dose of clarity to the discussion?

I also reached out to the designer and manufacturer of both the Preamp and Amp. Both verified that the approach @almarg and others recommended was safe. I also verified with Richard Gray who is local to me, before moving forward. 

Thanks.

Adapters from unbal to bal sometimes ground one of the active pins (2 or 3 of XLR), but that is not advisable going from bal to unbal, as you would be grounding one output of your source component, which could damage it.

For a definitive answer, I’d go with the recommendation of the manufacturer of the balanced-output source component. (Some manufacturers even provide wiring diagrams for their recommended method of going from balanced to unbalanced.)

It makes me uneasy to short any output to ground, but I’m not an EE nor a circuit designer, so there’s a lot I don’t know.

@david_ten

Thanks for the mention, David. Most (but not all) XLR-to-RCA adapters ground the signal on XLR pin 3, i.e., they connect pin 3 to pin 1, which is the ground pin. In the case of most (but not all) components providing XLR outputs that kind of adapter should not be used, for the reason @mike_in_nc stated. And the same considerations apply in the case of an XLR-to-RCA cable.

Following is an excerpt from what I had said when we discussed this issue via PM in November 2018:

An adapter that shorts pin 3 to pin 1 would be appropriate when adapting an RCA output to an XLR input, and would be appropriate and sometimes even necessary with **some** designs (especially some tube-based designs having transformer coupled outputs) when adapting an XLR output to an RCA input. However in many cases, especially cases involving solid state designs having low output impedances, such a short could cause adverse sonic effects, buzzing, or even damage, eventually if not sooner. I once diagnosed a severe buzzing problem that occurred with a member’s CD player which was caused in exactly that manner. When he went to an adapter cable which left pin 3 open everything worked fine.

You subsequently received a response from the designer of your Grandinote preamp stating that pin 3 should be left open (unconnected) when adapting its output to an RCA input.

And chances are that would also apply to the OP’s situation, but not necessarily. For a firm conclusion to be reached he should either ask the manufacturer of the component providing the balanced output (as I see Mike suggested just above), or let us know the specific make and model of the component and we may be able to determine the answer.

Best regards,
-- Al