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RCA Audio Switch Silent 2(1)-in-1(2)-Out Stereo RCA Switch Selector review

pma

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RCA Audio Switch Silent 2(1)-in-1(2)-Out Stereo RCA Switch Selector for Soundbar TV Speaker Headphones PC Game Consoles

I needed a 1 IN – 2 OUT RCA selector switch for my small lab so after a short hesitation if to solder something myself or to buy some cheap product I have decided to order this:

https://www.amazon.de/dp/B09Q85BGN9/ref=pe_27091401_487024491_TE_item

mostly for the reason I was lazy to make a box and also for price reason, as the cost is as low as it does not make sense to waste my time by hand-making something similar.

The little box has arrived today. It is small and cute, built in a sturdy metal box.

RCA-switch_topview.JPG


There are 2 pairs of RCA-CINCH on one side and one pair of the same connectors at the opposite side, call it front and back panel if you wish. On the top there are two switches, one of them switches between channels 1 and 2 and the second one is a mute switch. There is also a volume potentiometer knob between the switches. Unfortunately there are no rubber pads at the bottom, so the little box happily slides on the surface where it has been placed. I have fixed it by attaching of 4 self-adhesive small rubber boots to the bottom panel.

There is also a 140cm long RCA to RCA stereo signal cable supplied with the box (comments later).

What is inside

I have opened the box and made some reverse engineering as I wanted to know the schematic diagram of the switch box.

RCA-switch_open.JPG


RCA-switch_pcbtopview2.JPG


RCA-switch_pcbbottomview.JPG


Function

The circuit is simple and is connected like this

RCA-switch_schematics.png


It is advertised as bi-directional switch, it means it may have

a) 2 inputs and 1 output
or
b) 1 input and 2 outputs

Case (a) is OK, we have 2 switchable input channels with volume pot of 5 kohm resistance. It will switch 2 sound sources into one device like amplifier.

Case (b) may make a problem. It will switch 1 sound source into 2 devices like 2 different amplifiers. But, if the volume pot is turned full left, then the input impedance of this switch was measured only 12 ohm (10 ohm fixed resistor + residual resistance of the pot) and this may make a trouble to the sound source, loading it with very low impedance of 12 ohm. I would recommend to use this switch in case (b) only with volume pot turned full right, then it will load the source by 5 kohm.

Some measurements

I have quickly measured the RCA switch with RMAA and REW software. I used the 140cm RCA link cable supplied with the switch (called “Supplied cable” here) and the 100cm cable that was in the past supplied with some CD player (called “Generic cable”). As a sound source I used Topping D10s DAC connected to PC via OLIMEX USB-ISO adapter (to avoid signal ground loop) and the measurement behind the switch box was done by modified Creative USB X-Fi HD. The volume pot setting was close to 50%.

Here is the RMAA result

Generic_vs_Supplied cable.png

We can see the significant difference in crosstalk, the supplied cable is much worse. The reason is that it is not shielded, just 2 parallel wires per channel inside the plastic tube. Such is the construction of the cheapest cables, resulting in capacitive crosstalk between the closely spaced wires and thus worsening of crosstalk.

ct.png

Crosstalk measurement with 2 different input cables

We can also see higher 50Hz mains component and additive spectrum spuriae with the supplied cable. My recommendation is not to use it, it is a piece of junk. The difference is not because of 100cm x 140cm length difference, the reason is shielded x unshielded cable.

RCA-switch_generic vs_supplied.png

The harmonic distortion seen is a behaviour of the X-Fi HD soundcard. Differences below 1kHz are because of different cables construction.

The pot's impedance matching is surprisingly acceptable.

Conclusion

I have mixed feeling of this switch. If used to connect 2 sound sources to 1 amplifier, it may be quite acceptable. In case it is used to split 1 sound source into 2 amplifiers, great care should be taken because it will load the source by a mere 12 ohm if the pot is turned full left. Another not very good feature is that grounds of both switched channels are directly interconnected by a PCB groundplane. So be aware of possible signal groundloops. Also the absence of rubber pads on the bottom makes the device sliding on the surface, so better to add the rubber pads or boots. I appreciate the sturdy metal box and gold plated RCA jacks. Considering the low price about 20 EUR, the switch might be acceptable if is needed.
 
OP
pma

pma

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The "Generic" cable and the "Supplied" cable that were tested with the switch. They look pretty same, right? But they are quite different :).

cables_tested.png
 

DDF

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@pma
Hi Pavel,
I make my own switch boxes and switch the ground along with hot (make before break) so only the one input hot and ground connect to the circuit. Depending on the situation, it can drop system noise getting rid of all those extra antenna feeding into the box, and can significantly reduce the risk of ground loops

I used to make a nice dual mono passive pre with switched ground inputs and 10 turn lab grade pots (no carbon tracks, no issue with deformation @ high load current etc) with verniers, infinite balance adjustment
 
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pma

pma

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Joined
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Location
Prague
Hi Pavel,
I make my own switch boxes and switch the ground along with hot (make before break) so only the one input hot and ground connect to the circuit.
Hi Dave,
I agree, for serious purposes I would do the same. This one only sends the music signal between two "background music" amplifiers that are not class I devices.
 

nathan

Active Member
Joined
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RCA Audio Switch Silent 2(1)-in-1(2)-Out Stereo RCA Switch Selector for Soundbar TV Speaker Headphones PC Game Consoles

I needed a 1 IN – 2 OUT RCA selector switch for my small lab so after a short hesitation if to solder something myself or to buy some cheap product I have decided to order this:

https://www.amazon.de/dp/B09Q85BGN9/ref=pe_27091401_487024491_TE_item

mostly for the reason I was lazy to make a box and also for price reason, as the cost is as low as it does not make sense to waste my time by hand-making something similar.

The little box has arrived today. It is small and cute, built in a sturdy metal box.

View attachment 202263

There are 2 pairs of RCA-CINCH on one side and one pair of the same connectors at the opposite side, call it front and back panel if you wish. On the top there are two switches, one of them switches between channels 1 and 2 and the second one is a mute switch. There is also a volume potentiometer knob between the switches. Unfortunately there are no rubber pads at the bottom, so the little box happily slides on the surface where it has been placed. I have fixed it by attaching of 4 self-adhesive small rubber boots to the bottom panel.

There is also a 140cm long RCA to RCA stereo signal cable supplied with the box (comments later).

What is inside

I have opened the box and made some reverse engineering as I wanted to know the schematic diagram of the switch box.

View attachment 202265

View attachment 202266

View attachment 202267

Function

The circuit is simple and is connected like this

View attachment 202268

It is advertised as bi-directional switch, it means it may have

a) 2 inputs and 1 output
or
b) 1 input and 2 outputs

Case (a) is OK, we have 2 switchable input channels with volume pot of 5 kohm resistance. It will switch 2 sound sources into one device like amplifier.

Case (b) may make a problem. It will switch 1 sound source into 2 devices like 2 different amplifiers. But, if the volume pot is turned full left, then the input impedance of this switch was measured only 12 ohm (10 ohm fixed resistor + residual resistance of the pot) and this may make a trouble to the sound source, loading it with very low impedance of 12 ohm. I would recommend to use this switch in case (b) only with volume pot turned full right, then it will load the source by 5 kohm.

Some measurements

I have quickly measured the RCA switch with RMAA and REW software. I used the 140cm RCA link cable supplied with the switch (called “Supplied cable” here) and the 100cm cable that was in the past supplied with some CD player (called “Generic cable”). As a sound source I used Topping D10s DAC connected to PC via OLIMEX USB-ISO adapter (to avoid signal ground loop) and the measurement behind the switch box was done by modified Creative USB X-Fi HD. The volume pot setting was close to 50%.

Here is the RMAA result

View attachment 202269
We can see the significant difference in crosstalk, the supplied cable is much worse. The reason is that it is not shielded, just 2 parallel wires per channel inside the plastic tube. Such is the construction of the cheapest cables, resulting in capacitive crosstalk between the closely spaced wires and thus worsening of crosstalk.

View attachment 202271
Crosstalk measurement with 2 different input cables

We can also see higher 50Hz mains component and additive spectrum spuriae with the supplied cable. My recommendation is not to use it, it is a piece of junk. The difference is not because of 100cm x 140cm length difference, the reason is shielded x unshielded cable.

View attachment 202270
The harmonic distortion seen is a behaviour of the X-Fi HD soundcard. Differences below 1kHz are because of different cables construction.

The pot's impedance matching is surprisingly acceptable.

Conclusion

I have mixed feeling of this switch. If used to connect 2 sound sources to 1 amplifier, it may be quite acceptable. In case it is used to split 1 sound source into 2 amplifiers, great care should be taken because it will load the source by a mere 12 ohm if the pot is turned full left. Another not very good feature is that grounds of both switched channels are directly interconnected by a PCB groundplane. So be aware of possible signal groundloops. Also the absence of rubber pads on the bottom makes the device sliding on the surface, so better to add the rubber pads or boots. I appreciate the sturdy metal box and gold plated RCA jacks. Considering the low price about 20 EUR, the switch might be acceptable if is needed.
Thanks for posting this. These don't appear to be available in North America but it gives me hope I can pick up something "cheap" and it might be reasonably transparent.
 
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