Stereo to mono: is this schematic safe?

[stonemarten]

Dear experts,

after several and confusing searches due to the lack of my knowledge about how to merge two RCA channels in to one (I have one speaker per room, so I need both channels in both speakers), I've found this schematic

https://www.instructables.com/id/Simple-Way-to-Convert-Stereo-to-Mono/

Do you know if this works? Is it safe for the amplifier? Any suggestions?

Thanks to all!

Cheers

 

[rayma]

Where in the signal path do you plan to install them?
The resistor values shown are too low for most locations.

 

[stonemarten]

Dear Rayma,

thanks!

From a Pioneer DVD/CD player to the amp. What value do you recommend?

Thanks

Cheers

 

[rayma]

If the cables are a meter or less long, I'd use 10k resistors.
Thee may be some loss of gain level, but it should be ok.

 

[stonemarten]

Dear Rayma,

They are 50cm, so 10k should be fine. With that value I should be fine, with the same schematic?

Thanks!

Cheers

 

[MAAC0]

You even don't need the resistors, since nearly all op-amps have them protecting the output. I usually go with 4.7-10K for line level.

 

[rayma]

With that value I should be fine, with the same schematic?

Yes, just don't let anything short to anything else.

 

[stonemarten]

of course 🙂 thanks for the inputs!!

 

[russc]

So after mixing down to 1 RCA you are using a Y cable to connect to L & R amp input?

 

[stonemarten]

Dear Russc,

yes, this is the plan

thanks!

cheers

 

[Mark Tillotson]

You even don't need the resistors, since nearly all op-amps have them protecting the output. I usually go with 4.7-10K for line level.

The 100 ohms (typical) output resistors on opamps are to prevent oscillation into
a capacitive load, opamps are safe into a short-circuit by design (otherwise they'd be blowing up left, right and centre!!)


The vast majority of opamps can't drive 100 ohm loads without distorting, 2k--5k resistors are a good compromise (higher gives more noise and HF fall off, lower stresses the driving circuit more)

 

[stonemarten]

Thanks Mark!!