Any hifi but simple line level stereo to mono converter?

[Fusion916]

Can use BJTs or Opamps, don't care. Just need something I can put together for a couple of weeks until I finish designing and building the next version of my amp.

 

[lineup]

some resistors and an OPamp fed by dual power supply would make a perfect mono converter.
somebody will post a schematic.

 

[sreten]

Hi,

Trivial just using two series resistors into an input.

rgds, sreten.

 

[DF96]

In many cases the source may already have the resistors, so just two bits of wire.

Any simpler solution?

 

[sreten]

In many cases the source may already have the resistors,
so just two bits of wire. Any simpler solution?

Hi,

No. Hardly ever. Very poor advice. Never short two outs into an input.
Most output resistors are to do with stability, way below current output.

rgds, sreten.

 

[DF96]

Very poor advice.

Really? This question crops up every few weeks and a simple short is often the agreed solution, provided the resistors are present. A few hundred ohms is plenty to avoid any damage, and this is the range of most 'stability' resistors. Shorting two outputs is fine when they are just L and R of the same stereo signal. There might be a bit of distortion, but mono isn't really hi-fi anyway.

 

[Fusion916]

Do you guys mean something like this?

 

[Ian Finch]

Exactly. You knew it all along, eh?

 

[Fusion916]

Exactly. You knew it all along, eh?

I've seen that circuit, I thought there may be a better hifi way that involves inverting summer opamps or something.

 

[Ian Finch]

If a buffer is also necessary, you could need such bells and whistles as you would find in an audio mixer but assuming your output is to a high, line impedance > 10k and you just want something for a couple of weeks, there's little point complicating the task.

This is all most stereo amps and subwoofers use to derive a single source.

 

[AndrewT]

Just listen to one channel until you have the second ready to hear.

 

[sreten]

Really? This question crops up every few weeks and a simple short is often
the agreed solution, provided the resistors are present. A few hundred ohms
is plenty to avoid any damage, and this is the range of most 'stability' resistors.
Shorting two outputs is fine when they are just L and R of the same stereo
signal. There might be a bit of distortion, but mono isn't really hi-fi anyway.

Hi,

Its still poor advice and will cause distortion even though destruction might
be unlikely, in some cases it isn't. There is no need for the outputs to service
the excessively high difference currents such an arrangement would cause.

A particularly bad case is deciding to use only one stereo input "as it ends
mono anyway", I'm sure you can work out the very poor consequences.

rgds, sreten.

 

[sbrads]

but mono isn't really hi-fi anyway.

Sacrilege!

 

[lineup]

You have not told us what is the source like
and what is the input where you will put signal.

 

[lineup]

Do you guys mean something like this?

I think you should use that method. With 2 resistors.
It is perfectly good enough.


I dont think you should bother to build this. See my diagram.
It is however an OP-based mixer for 2 channels.
It will keep level and phase of the signal.
The OPamp is one OPA2134 = a dual op.

 

[AndrewT]

Why have you chosen a pair of parallel 47k for R4/6 and yet a sole 22k for R1?

 

[MCSmith]

I know this thread is old...........

.........but here's hoping someone will help!

I just finished up a re-cap of a very early Heathkit. A little amplifier with a volume and tone control, the Model A-4 from 1950.

Obviously a MONO amplifier, I plan to fabricate a STEREO to MONO summing cable.

Could someone please suggest resister values that will serve me the best all around? Running typical CD players with UNbalanced outputs and the like.

I have also seen this cable done with a 3rd register to the ground shield. Is this necessary?

I am road testing my work using only one output from the CD player and it appears to be able to drive the little amp just fine.

I have very little understanding of electronics (mathematical) but can follow instructions, read a schematic and solder well.

Any suggestions will be well received!

Marshall

 

[tinitus]

make you can find split Y-adapter in PA connectors, if thats enough to do it

or you can build one using two female RCA

 

[picowallspeaker]

make you can find split Y-adapter in PA connectors, if thats enough to do it

or you can build one using two female RCA

That's why they insert 100 Ω resistors after the op-amps : to prevent
damage caused by things like this !

A pair of 27 kΩ resistors from the two channels, join ( maybe also a 27 kΩ resistor to Gnd ), and a 1uF capacitor.
I used also to feel some kind of electricity on the Cdp case when connecting
to a tube mono amp. A 250 V rated capacitor might be better

 

[MCSmith]

That's why they insert 100 Ω resistors after the op-amps : to prevent
damage caused by things like this !

A pair of 27 kΩ resistors from the two channels, join ( maybe also a 27 kΩ resistor to Gnd ), and a 1uF capacitor.
I used also to feel some kind of electricity on the Cdp case when connecting
to a tube mono amp. A 250 V rated capacitor might be better

Hello,
Are you suggesting a cap from the two resistors to the ground shield? 1uF or .1uF or .01uF?
That's an awfully large bulge on my cable! Could I put the cap in series with the amp's signal IN pin socket's resister to the amp's chassis ground (I think this is the amp's load/input resistance)? I have already installed a new safety "death" cap on the little amp when I did the power supply. I have not noticed any juice on the CD player's chassis; I will check with a meter.
Thank you,
Marshall