both RCA and XLR on some (or all DIY) Class D modules

[hi30u]

I've noticed that Audiophonics uses a small circuit board marked "RCA/XLR SELECT" on many of its own-brand power amplifiers.

Is this just a switch? Or are there components (resistors, capacitors) involved?

Is there any risk of Crosstalk if both sources are On?

Is it possible to use the same kind of board for 3E Audio, Sylphaudio or other Amplifier Boards?

Too bad Audiophonics doesn't sell this "RCA/XLR SELECT".

I tried to read the following document but I am even more confused!

https://www.hypex.nl/media/c8/3d/26/1648383450/Application%20note%20Legacy%20pin%201%20problems.pdf

 

[dcibel]

Diagram is correct, 2 pole 2 throw switch.

 

[hi30u]

Diagram is correct, 2 pole 2 throw switch.

Which question did you answer?
For sure the diagram is correct, it's from the Hypex's document.
Is there a RC network (100nF, 100 ohms) on the Audiphonics small "RCA/XLR SELECT" board?

 

[DVDdoug]

There's more than one way to do it. A lot of amplifiers or active speakers/monitors don't have a switch and you just plug-in whichever one you want to use.

But you shouldn't use both at the same time. Of course the switch prevents that possibility.

 

[dcibel]

Which question did you answer?
For sure the diagram is correct, it's from the Hypex's document.
Is there a RC network (100nF, 100 ohms) on the Audiphonics small "RCA/XLR SELECT" board?

Unable to determine from your image, it looks like "no". Easy to determine for yourself if you have the equipment in front of you. Optional (but recommended) components if you read the Hypex doc.

"The only reason why one should consider including an RC combination is to keep the signal within the common mode range of the input circuit (remember that the source may be floating) and to keep RFI that’s been picked up by the RCA cable out of the box."

Other question on connecting 2 sources. As DVDdoug mentions, some manufacturers don't include any switch, expectation is that the end user is conscious enough to know not to connect both RCA and XLR inputs simultaneously, it's one or the other in this case, never both. The switch adds some functionality as a simple input switch if you did want to connect 2 different sources and switch between them, and helps to prevent general stupidity of the end user.

 

[NTK]

It looks like it is just a switch. Also, from the spec in the Audiophonics site, the amp's sensitivity does not change with either input connector, which is another indicator that there is no active component in the circuit.

The Hypex app notes also says that the RC circuit is optional for devices for consumer use. They don't seem to be in Audiophonics' circuit.

[Edit]
Please also note that Hypex recommends using an RCA to XLR adapter cable to connect to single-ended sources, not a passively adapted RCA connector on the amplifier.

 

[hi30u]

There's more than one way to do it. A lot of amplifiers or active speakers/monitors don't have a switch and you just plug-in whichever one you want to use.

But you shouldn't use both at the same time. Of course the switch prevents that possibility.

Yes, and this board looks like it is the cheapest way to create an HT Bypass function as mentioned here:

Same power amp for AVR and Stereo Preamp

That's why I was wondering if there were any drawback.

 

[hi30u]

It looks like it is just a switch. Also, from the spec in the Audiophonics site, the amp's sensitivity does not change with either input connector, which is another indicator that there is no active component in the circuit.

The Hypex app notes also says that the RC circuit is optional for devices for consumer use. They don't seem to be in Audiophonics' circuit.
View attachment 362500

[Edit]
Please also note that Hypex recommends using an RCA to XLR adapter cable to connect to single-ended sources, not a passively adapted RCA connector on the amplifier.
View attachment 362506

Thanks for the good picture.
Ok no RC.

ALSO, very important Warning information that I found afterwards:
Application note Amplifier signal wiring
If you think that you are going to use RCA, you cannot connect chassis to safety earth. And you need to implement double insulation safety standards.

 

[hi30u]

RCA output voltage goes up to 2V while XLR can be 4V or 5V on some DAC.
How is the Audiophonics / Hypex Class D amp dealing with the difference?
Will using RCA instead of XLR reduce its power by half?

 

[NTK]

Assuming the amplifiers you are thinking about are based on the Hypex NCxxxMP series, it will depend on which Hypex amplifier module is used:

Amplifier Module	Input Voltage Required to Reach Maximum Rated Output
NC122MP	1.17 Vrms
NC250MP/NC252MP	1.66 Vrms
NC500MP/NC502MP	2.35 Vrms

Therefore, with the standard RCA output voltage, you will only not be able to reach full output power with the NC500MP or NC502MP based amplifier.